Manual of Multistorey Timber Construction 9783955533953

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HERMANN KAUFMANN STEFAN KRÖTSCH STEFAN WINTER

Edition ∂

MANUAL

of Multi-Storey Timber Construction

HERMANN KAUFMANN STEFAN KRÖTSCH STEFAN WINTER

Edition ∂

MANUAL

of Multi-Storey Timber Construction

The authors Univ.- Prof. DI Architect Hermann Kaufmann Technical University of Munich, Department of Architecture, Professorship of Architectural Design and Timber Construction Jun.- Prof. Dipl.-Ing. Architect Stefan Krötsch Technical University of Kaiserslautern, Faculty of Architecture, Department of Tectonics in Timber Construction Univ.- Prof. Dr.-Ing. Stefan Winter Technical University of Munich, Department of Civil, Geo and Environmental Engineering, Chair of Timber Structures and Building Construction

This book was compiled under the direction of the Professorship of Architectural Design and Timber Construction at the Technical University of Munich, Department of Architecture, www.holz.ar.tum.de Co-authors: Dipl.-Ing. Architect Anne Niemann (Project Manager) Dipl.-Ing. Architect Maren Kohaus Dipl.-Ing. FH MAS ETH MA Lutz Müller Dipl.-Ing. Architect Christian Schühle M. Eng. Dipl.-Ing. Architect Manfred Stieglmeier Research assistants: Dipl.-Ing. Architect David Wolfertstetter M.Sc. Claudia Köhler Student assistants from the Technical University of Munich Tobias Müller, Moritz Rieke, Konstanze Spatzenegger, Fabia Stieglmeier Student assistants from the University of Kaiserslautern Sandra Gressung, Maren Richter, Sascha Ritschel

With specialist contributions from: DI Heinz Ferk Graz University of Technology, Faculty of Civil Engineering, Laboratory for Building Science (LFB) at the Laboratory for Structural Engineering (LKI) Dipl.-Ing. Sonja Geier Lucerne University of Applied Sciences and Arts – Engineering and Architecture, Competence Center Typology & Planning in Architecture (CCTP) Prof. Dr.-Ing. Architect Annette Hafner Ruhr University Bochum, Department of Civil and Environmental Engineering, Chair of Resource-Efficient Building Prof. Dipl.-Ing. Architect Wolfgang Huß Augsburg University of Applied Sciences, Faculty of Architecture and Civil Engineering, Industrialised Construction and Production Technology Dipl.-Ing. Architect Holger König Dipl.-Ing. Architect Frank Lattke BDA DI Daniel Rüdisser Graz University of Technology, Faculty of Civil Engineering, Laboratory for Building Science (LFB) at the Laboratory for Structural Engineering (LKI) DI Dr. techn. Martin Teibinger Univ.- Prof. Dr. Dr. habil. Drs. h.c. Gerd Wegener TUM Emeritus of Excellence

Editorial services Editing, copy-editing (German edition): Steffi Lenzen (Project Manager), Jana Rackwitz, Daniel Reisch, Eva Schönbrunner, Sophie Karst, Sonja Ratz, Carola Jacob-Ritz Drawings: Ralph Donhauser, Marion Griese, Martin Hämmel, Simon Kramer, Dilara Orujzade, Janele Suntinger Translation into English and copy-editing (English edition): Christina McKenna, Douglas Fox and Meriel Clemett for keiki communication, Berlin Proofreading (English edition): Stefan Widdess, Berlin Production and DTP: Roswitha Siegler, Simone Soesters Reproduction: ludwig:media, Zell am See Printing and binding: Grafisches Centrum Cuno GmbH & Co. KG, Calbe Publisher: Detail Business Information GmbH, Munich www.detail-online.com © 2018 English translation of the 1st German edition ISBN: 978-3-95553-394-6 (Print) ISBN: 978-3-95553-395-3 (E-Book) ISBN: 978-3-95553-396-0 (Bundle)

4

Bibliographic information published by the German National Library. The German National Library lists this publication in the Deutsche Nationalbibliografie (German National Bibliography); detailed bibliographic data are available on the Internet at http://dnb.d-nb.de. This work is subject to copyright. All rights reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, recitation, reuse of illustrations and tables, broadcasting, reproduction on microfilm or in other ways and storage in data processing systems. Reproduction of any part of this work in individual cases, too, is only permitted within the limits of the provisions of the valid edition of the copyright law. A charge will be levied. Infringements will be subject to the penalty clauses of the copyright law. This textbook uses terms applicable at the time of writing and is based on the current state of art, to the best of the author’s and editor’s knowledge and belief. All drawings in this book were made specifically by the publisher. No legal claims can be derived from the contents of this book. This book is also available in a German-language edition (ISBN 978-3-95553-353-3)

Contents

7 Foreword

Part A 1 2 3 4 5

Introduction

The development of multi-storey timber construction Wood as a resource Solid wood and wood-based products Life-cycle assessment Interior air quality – the influence of timber construction

Part B

Support structures

1 Structures and support structures 2 Structural components and elements

Part C 1 2 3 4 5

1 2 3 4

72 88 92 114 122

Process

Planning Production Prefabrication Solutions for modernising buildings

Part E

38 50

Construction

Protective functions Thermal insulation for summer The layer structure of building envelopes The layer structure of interior structural components Building technology – some special features of timber construction

Part D

10 14 18 24 30

130 138 142 150

Examples of buildings in detail

Joints in detail Project examples 1– 22

160 166

Appendix Authors Glossary DIN standards Literature Image credits Index Supporters / Sponsors

258 260 264 266 268 270 272

5

6

Foreword

Fig.

Timber construction has undergone intensive development in recent years. The quantum leap it has made lately is demonstrated by the fact that a growing number of higher buildings are being built with timber. This classic building material, one that modernity seemed almost to have forgotten, is undergoing a renaissance for various reasons. Climate change is leading to an increasing interest both in the wider public and among architects and their clients in sustainable and bio-based construction solutions that use resources efficiently. Timber construction offers a better response to this interest than other construction methods. Wood’s special tactile, visual and olfactory qualities as a natural building material and its outstanding strength-to-weight ratio make timber construction increasingly attractive in modern construction, although the primary costs compared with common standard solutions can be somewhat higher than those for conventional structures, depending on the type of project. In terms of overall economic efficiency however, modern timber construction can already give conventional construction a run for its money. This Manual of Multi-Storey Timber Construction is specifically not a continuation or revised version of the Timber Construction Atlas published in 2003. That book focused on timber structural engineering because of the situation that prevailed when it was published. At that time, few multi-storey timber buildings had been built. The new manual is being published in response to a very different situation. While the use of timber in single detached houses and agricultural construction has been steadily increasing for a long time, it had until recently almost entirely disappeared from cities. This is beginning to change. Initiated by committed housing cooperatives, housing societies and some joint venture residential building projects with a growing awareness of environmental concerns, new multi-storey timber buildings are being built that are making this oldest of natural building materials available for many more people to experience. Timber construction has also begun to make a comeback in cities because it is very suitable for conversion and densification measures in populous urban areas and for

added storeys, extensions and alterations. Wood is light and easy to work with, can be efficiently transported, and prefabricated elements can make it possible to build quickly with a minimum of disruption. The many interesting examples of timber buildings in this manual clearly demonstrate the ways in which they have enriched architecture in urban settings. Many of them are in fact hybrid structures, which is by no means a retrograde step for timber construction. On the contrary, skilfully combining the proven building materials and construction methods that are readily available on the market to build efficient and profitable buildings in keeping with the performance, availability, price and design potential required is both consistent and logical. This approach has long been typical of construction in urban spaces, if we consider the mixture of construction methods used in the Middle Ages, where combinations of timber and stone made it possible to build impressive half-timbered structures, or Wilhelminian buildings, which from the outside seem to be made of solid masonry, but in fact contain a high proportion of timber in horizontal structural elements such as slabs and roofs. It is this wide range of possibilities modern construction offers that has inspired us to question and expand the conventional and very narrow categorisation of timber structures into timber frame and panel construction and solid timber construction. Drawing on standard practice, this book shows the many options for combining horizontal and vertical elements that can make building with timber such a fascinating and creative process. Together with modern shell structures, this is resulting in an almost explosive expansion in the potential applications of this renewable raw material. Using wood as a construction material also stores carbon for the long term, creating a carbon sink and making a positive contribution to combating global warming. Climate change will however impact wood and wood supplies. In future, wood as a natural building material will be available to us in a different mix from that currently prevailing. Supplies of hardwood will probably grow in future, while softwood stocks will simultaneously decline. This will result in new and further developments

Zollfreilager residential buildings, Zurich (CH) 2016, Rolf Mühlethaler

in wood-based materials and a much larger proportion of hardwood-based materials in multi-storey timber buildings than has hitherto been the case, with positive consequences. Many hardwoods have much better strength and stiffness properties, which can allow planners to work with much thinner and lighter structural components and open up entirely new design possibilities. Europe’s forestry industry, sustainably practised for centuries, shows that despite intensive use of this raw material, a vigorous forest can be maintained that also continues to fulfil its other functions, ranging from air purification through water storage up to serving as a recreational space. Europe currently grows more wood than it uses. In Germany, Austria and Switzerland it would be theoretically possible to build all new buildings with timber using about a third of the annual wood supply. This manual is designed to provide interested planners and developers who have no or little experience of timber construction with targeted information and to help alleviate their scepticism about a material that is still largely unfamiliar when it comes to constructing multi-storey buildings and subject to various misconceptions. Potential design options are presented and explained based on a new systematisation of construction methods that has been developed based on practical reality. The range of possibilities available shows that building with timber is no more difficult than building with other materials. It is high time to make more use of this readily available natural resource as a material and integrate it more into people’s living and working environments. We would like to thank everyone who contributed to the creation of this book; the publishers for their confidence in us, the authors for their knowledgeable contributions, the sponsors for their generous support, and our project manager Anne Niemann for her untiring commitment. Munich, May 2017

Hermann Kaufmann Stefan Krötsch Stefan Winter

7

Part A

Introduction

1 The development of multi-storey timber construction Antiquity and the Middle Ages in Eastern Asia The Middle Ages in Europe The modern era 2

10 11 12 14 14 15 15 16 17

3 Solid wood and wood-based products

18

4

24

5

Fig. A

Wood as a resource Forestry and timber The forestry and timber industry: partners in timber construction The timber resource situation and its prospects Deciduous woods: another option in timber construction Conclusion

10

Life-cycle assessment Timber buildings can contribute to environmental protection Carbon sequestration and substitution Carbon sequestration versus an efficient use of resources in construction CO2-efficient timber construction Comparative evaluations of conventional and timber buildings based on life-cycle assessments Conclusion Interior air quality – the influence of timber construction A healthy indoor climate Emissions in interior air The influence of natural wood on interior air The impact of glued construction timber on interior air The influence of wood-based materials on interior air Strategies for managing emissions Conclusion

24 25 25 26

27 28

30 30 30 33 33 33 35 35

Illwerke Zentrum Montafon, Vandans (AT) 2013, Architekten Hermann Kaufmann

9

The development of multistorey timber construction Stefan Krötsch, Lutz Müller

A 1.1

Since the advent of fortified cities and villages, developments in construction have focused on building high, multi-storey buildings, sometimes due to a lack of space inside fortifications but also for reasons of prestige. In regions where wood was the predominant building material, the knowledge and manual skills for building durable, multi-storey timber buildings have been established since antiquity. Even log construction, one of the oldest methods of timber construction and one practised since the Neolithic Age, made it possible to build buildings with several storeys. This method was common in densely forested regions of Asia and Europe well into modern times and is still used in some areas. Closed, windproof insulating walls are created by stacking blocks or logs and by dovetailing, lapping or notching corners and bracing interior walls. Although tall buildings made of horizontally stacked logs can settle signifiA 1.1 A 1.2 A 1.3 A 1.4 A 1.5 A 1.6

10

cantly, buildings of surprising height were built in areas with highly skilled craftsmen, as demonstrated by the example of a fivestorey residential building in the Swiss canton of Valais (Fig. A 1.2).

Antiquity and the Middle Ages in Eastern Asia

Competition design for the Langelinie Pavilion, Copenhagen (DK) 1953, Jørn Utzon Five-storey building in Evolène, Valais (CH) 1958, Follonier brothers Tō-ji Temple, Kyoto (JP) 9th century (the pagoda was rebuilt after being destroyed in 1644) Pura Besakih Temple, Bali (ID) 8th century Himeji Castle, Himeji (JP) 17th century “Alter Bau” granary, Geislingen an der Steige (DE) 1445

Influenced by the Chinese, highly-developed woodworking techniques emerged in Japan in the 6th century, the protagonists of which were referred to as “master builders” and “great craftsmen” and were held in high regard. During the Asuka and Nara periods, the method of frame construction developed and it was to remain the mainstay of Japanese architecture well into the modern era. A roof structure secured against the effects of wind with a heavy weight is held up by pillars attached to notched beams to form a load-bearing frame. The entire structure sits loosely on base blocks without further reinforcement. Its solid, continuous pillars can withstand very heavy loads, while the ductility (ability to deform without failing) of the frame and base connections ensures very good protection from earthquakes. As long ago as 725, the pagoda of the Buddhist Kōfuku-ji Temple in Nara, the capital of

A 1.2

A 1.3

The development of multi-storey timber construction

Japan at that time, was constructed with five storeys and a height of more than 50 metres. The main hall of the world’s largest building entirely of wood, the Buddhist temple of Tōdai-ji in Nara, is 57.01 metres wide, 50.48 metres deep and 48.74 metres high and was built in 745. The five-storey, 57-metre high pagoda of the Tō-ji Temple in Kyoto, built in the 9th century, was Japan’s tallest building at the time (Fig. A 1.3). The buildings of the 8th-century Pura Besakih Temple on Bali are up to 44 metres high (Fig. A 1.4). Each of their eleven storeys houses a single room that is used as a shrine for religious rituals. Their slender towers are braced by elaborate framework connections between the pillars and beams using a technique similar to that employed in the Japanese structures described above. The palaces of Beijing’s Forbidden City were built over less than two decades in the early 15th century. At the ceremonial centre of this gigantic building complex is the “Hall of Supreme Harmony”, which is 35 metres high and has a floor area of 2,400 m2. The 17th-century Himeji Castle in Japan, six storeys and 31.50 metres high, was one of the biggest multi-storey timber buildings of its day (Fig. A 1.5). Frame construction and the accompanying undefined utilisation and spatial system

A 1.4

remained unchanged in China and Japan for a long period. It was not until the modern era that this millennia-old tradition ended abruptly, with timber being completely replaced as the primary construction material in buildings of more than two storeys by new building materials such as steel and concrete.

The Middle Ages in Europe Half-timbered construction was the main method used to build buildings in central European cities from the Middle Ages until well into the 19th century, but it follows a fundamentally different construction approach. Despite their frame-like appearance, the posts and beams interact with the bottom plates and wall plates and function more like braced wall slabs than a frame construction. These wall slabs (interior and exterior walls) brace the building without significantly activating the ceiling slab. Ceiling joists are laid on the walls, often following their own rhythm without regard to the spacing of posts. In contrast to Asian frame constructions, supporting pillars do not run through the storeys but are intercepted by the bottom plate, ceiling joists and wall plates and are sometimes slightly offset on each storey. This overhang clamps the ceiling joists between the walls,

A 1.5

making it possible to build larger ceiling spans and improve the roof’s vibration characteristics. An overhang also protects the facade below it from the weather. Post-in-ground and post-and-beam structures were the precursors of half-timbered buildings. Post-in-ground is a framed construction method using posts driven metres deep into the earth and dug in, to serve as supports that brace the building. The bases of the pillars usually rot through in 20 to 30 years and the building must then be replaced. Postand-beam buildings dealt with this problem by replacing the posts with building-high pillars that were no longer driven into the earth but laid dry on a horizontal bottom plate, which greatly prolonged the lifespan of buildings. This technique could also be used to build buildings several storeys high, but the height of individual structures was generally limited by the length of tree trunks available. Loadbearing pillars could only be replaced at great expense. The advent of half-timbered construction represented a revolution in construction. It was now possible to build timber structures which would last several hundred years because individual load-bearing elements could be replaced without jeopardising the entire structure. Half-timbered construction also resulted in the development of a great

A 1.6

11

The development of multi-storey timber construction

Tō-ji Temple Japan, 888

Pura Besakih Temple Bali, 8th century

Hopperstad stave church Norway, 1130

Qigu Tan China, 1420

“Alter Bau” granary Germany, 1445

57 metres 5 storeys

44 metres 11 storeys

27 metres 4 storeys

25 metres 3 storeys

21 metres 7 storeys

90 m 80 m 70 m 60 m 50 m 40 m 30 m 20 m 10 m

deal of knowledge and skill involving constructional timber preservation that is still in use today. The lengthening of buildings’ lifespans and structures comprising stacked, well-braced storeys facilitated the construction of multistorey buildings. The seven-storey former granary (Alter Bau) in Geislingen an der Steige dates from 1445 and is built from timber resting on a masonry basement storey, proof of this construction method’s effectiveness and durability (Fig. A 1.6, p. 11).

The modern era Concrete and steel dominated the material canon of classic modernism. Initially, timber as a material for building bearing structures no longer played any significant role. Competition from suddenly widely available, nonflammable materials relegated timber to a

A 1.7

12

building material for lower, sometimes temporary buildings. Only since the turn of the millennium has timber construction taken a fundamental new direction, thanks to a series of technical innovations. In the context of a worldwide political rethink in the face of global environmental development, especially global warming, there has once again been an increased focus on using timber for multi-storey construction in central and northern Europe. In a wide-ranging model project in Bavaria [1] and following new developments in Austria, a number of three-storey timber apartment houses were built in the 1990s (Fig. A 1.7). Initially partly oriented towards North American building methods, these model projects established various construction methods that meet central European requirements. An evaluation of the results of these projects created an impetus for more advanced research by

A 1.8

research institutes and timber construction companies [2]. Technical advances and a continuously improving legislative environment have since resulted in new height records for timber buildings at increasingly short intervals. The sevenstorey e3 apartment building (Fig. A 1.8), built in Berlin in 2008, features elements such as timber-concrete composite slabs and an external steel-reinforced concrete staircase that ensure that it meets fire safety requirements. Eight-storey buildings such as H8 in Bad Aibling (Fig. A 1.9) and the LifeCycle Tower One in Dornbirn followed in 2011 and 2012. The first timber building taller than eight storeys, the nine-storey Murray Grove Tower, was built in London in 2008 (Fig. A 1.11). A ten-storey apartment building, Forté Tower, opened in Melbourne in 2012. The Via Cenni residential complex in Milan, completed in 2013, (p. 174ff.) is “only” nine storeys high but consists of four residential towers linked by a two-storey plinth

A 1.9

The development of multi-storey timber construction

Damaschke housing estate Germany, 1996

H8 Germany, 2012

Forté Tower Australia, 2012

Student residence Canada, 2017

HoHo timber high-rise building Austria, in the planning stage

9 metres 3 storeys

25 metres 8 storeys

32 metres 10 storeys

63 metres 18 storeys

84 metres 24 storeys

Architects: Fink + Jocher

Architects: Schankula Architekten

Architects: Lendlease

Architects: Acton Ostry Architects

Architects: RLP Rüdiger Lainer + Partner 90 m 80 m 70 m 60 m 50 m 40 m 30 m 20 m 10 m Time A 1.10

structure the size of a city block. In the UK, Australia and Italy, the flammability of the bearing structure of high-rise buildings is not specifically regulated (as long as an adequate period of fire resistance is ensured), so buildings may be built of enclosed cross laminated timber panels. A 14-storey building with a glued laminated timber frame, into which prefabricated modular rooms were set, was built in Bergen in Norway in 2015 (Fig. A 1.12). Canada is currently home to the world’s tallest timber building, a student residence in Vancouver completed in 2017 (p. 166ff.). It comprises a glued laminated timber frame with 18 storeys over its 63-metre height. This record will however not stand for long because the HoHo, an 84-metre-high timber-concrete hybrid high-rise building with 24 storeys is currently being built in Vienna (Fig. A 1.13). There seems to be no end in sight to these constantly accelerating developments, raising

the question of whether the increasing effort involved makes it worth further pushing the limits. What is certain is that timber meets the demands made on a modern building material in all respects. The examples from recent years outlined above show that timber’s flammability has long been overstated and is no longer an obstacle to the construction of multi-storey buildings. Timber now seems to have taken its place in the material canon of current construction and could in future continue its long tradition as a building material for tall and urban buildings.

A 1.11

A 1.12

A 1.7 A 1.8 A 1.9 A 1.10 A 1.11 A 1.12 A 1.13

Apartment building – Bavarian model project, Regensburg (DE) 1996, Fink + Jocher e 3 high-rise apartment block, Berlin (DE) 2008, Kaden Klingbeil Architekten H 8 high-rise apartment block, Bad Aibling (DE) 2011, Schankula Architekten Increases in the heights of multi-storey timber buildings Murray Grove Tower, London (GB) 2008, Waugh Thistleton Architects High-rise apartment block, Bergen (NO) 2015, Artec Arkitekter / Ingeniører HoHo timber high-rise building, Vienna (AT) under construction, RLP Rüdiger Lainer + Partner

Notes: [1] Bavarian Ministry of the Interior – Supreme Building Authority (Pub.): Wohnmodelle Bayern – Wohnungen in Holzbauweise. Munich, 2002 [2] For example, see section 1, May – June 2001, Wohnen im Holzstock

A 1.13

13

Wood as a resource Gerd Wegener

A 2.1

Throughout human history and until well into the 19th century, wood was indispensable as a raw material and building material and part of our cultural heritage. It has been used to build buildings and ships and as a basic material for making tools, weapons and works of art. Until the late 19th century, wood was the most important fuel, was used to produce a wide range of basic chemical materials and was the main raw material used to make charcoal and potash for iron and glass production. Its diversity of applications meant that wood was more familiar to people than any other material, but overuse of timber resources in the 17th and 18th centuries led to a shortage of wood and to deforestation in Europe [1]. In response to these abuses, Hans Carl von Carlowitz formulated his fundamental principle on sustainable forest use in 1713 – “Do not cut more wood than will regrow” [2]. By the late 19th and into the 20th century, wood was largely supplemented by other materials (steel, concrete, steel-reinforced concrete, plastics) and new sources of energy (coal, oil, gas, nuclear energy) and in many areas was replaced entirely. Looking back over the highlights of various cultural epochs in the context of building with timber, the millennial significance of this building material becomes clear. Stone Age houses and those of the Celts built before the common or current era, then the houses of the Vikings, stave churches and medieval halftimbered buildings (Fig. A 2.2) demonstrate its importance, as do the mid-19th century entrance hall of Munich’s main railway station (Fig. A 2.3) and the 163-metre-high early 20th century Ismaning radio transmission tower (Fig. A 2.4). Timber became less important as a construction material in the first decades after the A 2.1 A 2.2 A 2.3 A 2.4 A 2.5 A 2.6

14

Mixed forest Medieval half-timbered buildings in Einbeck (DE) Railway station building, Munich (DE) built around 1850 (demolished in the 1870s) Broadcasting tower in Ismaning near Munich (DE) built in 1932 (demolished in 1983) Comparison of annual consumption of different materials EU-wide wood stocks by country

Second World War, apart from classical applications in roof trusses, stairs and floors. In the past 20 – 30 years, timber construction has enjoyed renewed popularity and this period could be described as the dawn of a new era in building with timber. This development is on the one hand due to the ecological advantages of this renewable building material, on the other hand to the enormous diversity of new, highperformance wood-based and composite materials, innovative means of joining elements and powerful adhesives that have become available. Current engineering services, computer-based planning and industrial prefabrication have also decisively contributed to enabling architecturally sophisticated construction with timber in urban and rural areas that is now reaching new dimensions. This type of construction can be fast, dry and competitive and be used to create high-quality structures, renovate existing buildings and to build new housing, kindergartens, schools and office and commercial buildings up to a height of eight storeys and more.

Forestry and timber Resources issues in a globalised world require us to take a local, regional and a global view of forests and wood. Around 30 % of the Earth’s land surface, 4 billion hectares, is currently covered with forest. Global forest cover has however been shrinking for decades due to slash-and-burn farming, conversion into agricultural land and illegal logging. The rate of forest disappearance did however slow between 2010 and 2015. Despite 4.3 million hectares of plantation forestry planted annually, 3.3 million hectares of forest is now lost every year [3]. Tropical, subtropical, boreal and temperatezone forests are the most important forests supplying useful timber, with natural and virgin forest playing only a subordinate role. In cultivating forests of the type almost exclusively found in Europe there is a focus on multifunctional, sustainable forest management, which as well as supplying timber has a wide range of protective and recreational functions

Wood as a resource

A 2.3

A 2.2

[Billions of m3]

and maintains biodiversity. In contrast, the global plantation industry (about 7 % of all forested area) mainly grows eucalyptus and fast-growing pine species in monocultures for the production of timber and biomass for specific purposes such as energy generation and the manufacture of cellulose, paper, woodbased materials and lower-quality types of construction timber. The Earth’s forests provide 3.7 billion m3 (= 2.2 billion tonnes) of logs annually, 1.3 billion m3 of softwood and 2.4 billion m3 of hardwood. Half of this is used to generate energy (51 %), while 49 % of logs are made into products (timber). Wood is therefore still one of the most important renewable raw materials on Earth and one of the three most commonly used materials. Figure A 2.5 shows strikingly that a world without wood as a raw and construction material and source of energy is inconceivable [4]. In the area of non-energy uses, 1.8 billion m3 of timber is turned into 440 million m3 of sawn lumber and 390 million m3 into wood-based materials for building and residential pur-

A 2.4

poses (construction, equipment and furniture). 400 million tonnes are used to produce paper and wood pulp products [5]. By-products and waste materials from manufacturing are put to good use as raw materials or energy sources (e.g. pellets).

struction, carpentry, joiners, cabinetmakers and the furniture industry) include the forestry, sawmilling and wood-based products industries and the sawn lumber, woodbased products and wooden component trades [6].

The forestry and timber industry: partners in timber construction

The timber resource situation and its prospects

In Europe timber construction is part of the diverse and powerful forestry and timber industry that form a complex value chain extending from the forestry sector through the timber industry and down to printing and publishing. With turnover of EUR 180 billion and 1.1 million employees in Germany, the sector is a heavyweight in terms of social, resources and environmental policies as well as the national economy. The timber industry is divided into the wood industry, woodworking trades and lumber trade. Further partners in timber construction (prefabricated timber construction, industrial timber con-

For centuries, Europe’s forests have been cultivated and commercial forests created by people to supply the lumber and timber construction industries with home-grown timber. The 28 EU member states have 180 million hectares of forests covering 41 % of their land area. Remarkably, forested area increased by 5 % from 1990 to 2010 and in Germany by 48,000 hectares from 2002 to 2012. These forests harbour impressive supplies of wood, with 3.7 billion m3 in Germany and 22.5 billion m3 in the EU as a whole (Fig. A 2.6). Germany has the biggest reserves of wood in the EU after Switzerland and Austria,

6

Wood stocks in billions of m3 Germany 3.700

5

5 Sweden 2.651 France 2.453

4

Poland 2.092 3.7

Finland 2.024 Italy 1.285

3

Austria 1.106 Czech Rep. 0.738

2 1.8

Slovakia 0.478 Slovenia 0.390

1 0.21

0.28

Croatia 0.334 0.02

0 Concrete

Logs, of which lumber

Steel

Plastics

Aluminium A 2.5

Hungary 0.259 Proportion of forest of all land A 2.6

15

Wood as a resource

A 2.7

with an average of 336 m3/hectares. In Germany 120 million m3 of surface wood biomass regrows annually, about 80 million m3 of which is used in the form of raw logs (Fig. A 2.9). These figures show that Germany’s stocks of this raw material are replete for the long term and even growing [7]. A model calculation came to the surprising conclusion that all the new buildings built in Germany could be built with a third of the country’s average sustainable timber harvest (Fig. A 2.9) [8]. Sustainable timber use also presupposes an interest in maintaining and rejuvenating forests. Combined mixed forests adapted to their specific locations and the climate will be near-nat-

A 2.8

ural, stable forests characterised by biodiversity (with over 50 types of trees) that produce more hardwood and increasing proportions of dead and decaying wood. Germany’s current forest development and timber resource modelling (Waldentwicklungsund Holzaufkommensmodellierung – WEHAM) [9] has forecast a potential supply of around 80 million m3 of raw logs per year for the next 40 years, so timber stocks in German forests will grow to 3.9 billion m3. Potential supplies of raw spruce logs, the most important construction timber, which now makes up 44 % of the raw log supply, are forecast to decline by 2027 to around 35 %, while the proportion

There is 3.7 billion m3 of timber stock in Germany Annual wood growth in Germany is around 80 million m3. 10 million m3 remains in the forest and 70 million m3 is harvested. Of this, 45 million m3 of timber construction products could theoretically be made annually.

Around 100 million m3 of new housing (31 million m2 of residential space) and 190 million m3 of new non-residential buildings is built annually In Germany. 0.08 m3 of wood in the form of timber construction products is required on average to build each m3 of residential buildings and 0.05 m3 of timber for each m3 of non-residential buildings.

Just over a third of Germany’s annual wood harvest would be enough to build the country’s entire annual volume of new buildings with timber.

A 2.9

16

of alternative softwood types such as pine and Douglas fir will greatly increase. Beech (+59 %) and oak (+97 %) will also record considerable increases. There are no figures available for Europe, but it has been predicted that deciduous and mixed forests will play a greater role in supplying timber due to climate change.

Deciduous woods: another option in timber construction Since the severe windthrow due to storms “Vivian” and “Wiebke” (1990) and the setting of the forestry policy goal of restructuring forests from purely conifers to near-natural mixed forests adapted to their specific locations at that time, the area of mixed forest has increased to 76 % and the area of deciduous forest to 43 % in Germany. All over Europe too, the proportion of deciduous forest has grown in recent years by 2.5 %. As well as preserving ecological diversity, this should help to ameliorate storm damage and the effects of climate change. Beech is one of the most commonly used woods and makes up 45 % of total deciduous timber stocks in Germany. Beech has long been a classic firewood and has been used for wood-based materials, veneers, parquetry and stairs, furniture and interior fittings and much more. Despite its good strength and rigidity, it has been surprisingly little used as a construction timber, with the exception of the glued laminated beech timber used in special projects in Switzerland since the 1970s. As a result of the forest resource situation described above, interest in and scientific examination of new options for using deciduous woods in construction – including beech, oak and ash as well as maple, black locust and other woods – have considerably increased in the past few years. A current study of research and development (R & D) activities involving “Deciduous woods for load-bearing structures” [10] found that in German-speaking countries, since 2000, over 50 R & D projects have worked on or are working on sorting, strength properties, bonding and the development of new wood building products. Innovative deciduous timber building products

Wood as a resource

A 2.10

include glued laminated timber (Fig. A 2.7), laminated hybrid timber (beech / spruce), and laminated veneer lumber (Fig. A 2.8). These products have been widely approved by building inspection authorities and their use in timber construction has expanded. Deciduous wood is 1.5 to 3 times stronger than spruce wood, so products made with it enable engineers and architects to plan structures with much more slender dimensions. Although these are currently still new, niche products and used mainly in innovative construction projects (Fig. A 2.10), given the resource situation of deciduous wood that can be expected in coming years as a result of forestry restructuring and climate change, they may have great potential. Targeted marketing activities and a growing number of completed construction projects will further promote the use of deciduous wood products in building.

Conclusion People have tended to and shaped our cultivated and commercial forests for centuries, making them cultivated ecosystems. Given the challenges of sustainability, climate protection and the transition to the use of more ecologically responsible energy and materials, forests will become increasingly important as a habitat, an economic resource and as repositories and suppliers of raw materials, energy and carbon. Together with the resource-saving and energyefficient use of wood, as exemplified in building with timber, the value-added chain from the forest to timber products and timber buildings represents a unique symbiosis of nature, technology and culture. When society and policy makers take the transition to an economy based on sustainable and renewable resources seriously, wood will play a major role in it as a raw material and a building material. Sustainable forestry ensures a long-term, ecologically compatible supply of this unique natural material. Only maintenance of woodlands and the use of timber will preserve our forests as cultivated ecosystems, as stores of carbon und energy and not least as sources of raw materials in the long term.

Notes: [1] Radkau, Joachim: Holz. Wie ein Naturstoff Geschichte schreibt. Munich, 2012 [2] Carlowitz, Hans Carl von: Sylvicultura oeconomica. Munich, 2013 [3] FAO (Pub.): State of the World’s Forests. Rome, 2014 [4] FAO (Pub.): Yearbook Forest Products 2013. Rome, 2015 The European Cement Association: CEMBUREAU, Cement & Concrete: Key facts & figures 2014 World Steel Association: Steel Statistical Yearbook 2015 Plastics Europe: Plastics – the Facts 2015 The International Aluminum Institute: Historical Aluminium Inventories (1973 –2014). 2014 [5] FAO (Pub.): Yearbook Forest Products 2013. Rome, 2015 [6] Becher, Gerhard: Clusterstatistik Forst und Holz. Tabellen für das Bundesgebiet und die Länder. 2000 to 2012. Thünen Working Paper 32, November 2014 [7] EUROSTAT: Forestry Statistics 2015 [8] EUROSTAT: Forestry Statistics 2015 Federal Ministry of Food and Agriculture (Pub.) The Forests in Germany. Selected Results of the Third National Forest Inventory, Berlin 2014 [9] Thünen scientists have calculated the amount of timber forests will supply in the next forty years, Thünen Institute. https://www.thuenen.de/de/infothek/ presse/pressearchiv/pressemitteilungen-2015/ thuenen-wissenschaftler-berechnen-das-holzangebot-der-waelder-in-den-kommenden-vierzig-jahren/ Press release, 29.06.2015 [10] Wehrmann, Wiebke; Torno, Stefan: Laubholz für tragende Konstruktionen. Cluster-Initiative Forst und Holz in Bayern GmbH (Pub.) http://www.cluster-forstholzbayern.de/images/ Laubholzinnovationsverbund/Ergebnisse/Broschre_ Laubholz_tragende-Konstruktionen_2015_07.pdf

A 2.7

Beech glued laminated timber left: no heartwood colouring, right: with heartwood colouring A 2.8 Baubuche Pollmeier beech laminated veneer lumber left: S board, right: S/Q board A 2.9 Timber stocks, annual increase and wood required to build the entire annual volume of new buildings in timber A 2.10 Factory hall, Probstzella (DE) 2016, F 64 Architekten

17

Solid wood and wood-based products Anne Niemann

Many new solid wood products and woodbased materials have been developed as a result of the industrialisation of timber processing. This chapter offers an overview of the most important properties of the timber products currently most commonly used. Solid wood products The use of wood has a long history in construction. Finger jointing and gluing individual lengths of timber can extend their spans and increase their load-bearing capacity. Drying timber reduces its subsequent shrinkage and the risk of fungal infestations. Wood-based materials Wood-based materials are made by bonding wood (in the form of planks, sheets, chips or fibres) in a wet or dry process, often with the help of adhesives. In so doing, the beneficial properties of wood can be selectively enhanced. The development of stress-resistant products has made a significant contribution to the construction of modern multi-storey buildings using wood. Technical rules The EU construction product standards allow only products whose usability has been proven. This is especially significant for those considering the use of wood-based materials, because their appropriateness is not easy to determine due to the wide range of products available. Product properties are described in EN product standards, while ETAs, European Technical Assessments, prescribe more detailed requirements. Products that are not authorised and verified for use require a separate specific proof of serviceability. Types of wood Softwoods and hardwoods have very different structures so are used for different purposes. Climate change is leading to an increased use of other types of woods and hardwoods from deciduous trees in timber construction (see “Wood as a resource”, p. 14ff.). Adhesives, bonding agents, additives Bonding agents can be used to help press sheets, chips or fibres together to form woodbased materials. Adding other substances can influence the materials’ performance when exposed to fire and moisture and modify their load-bearing capacity. Bonding agents made of renewable raw materials are currently being developed but do not yet play any notable role in the wood-based materials industry (see “Interior air quality – the influence of timber construction”, p. 30ff.). Bulk density /specific weight [kg/m3] A timber’s essential technological properties such as strength, thermal conductivity or hardness depend on its bulk density. Wood’s bulk

18

density is determined by its moisture content (changes to its mass and volume due to swelling and shrinkage) and the position the wood came from in the log. Fire performance The European fire performance classes developed out of decisions made by the European Commission when establishing fire performance classes for specific construction products and charring rates in accordance with DIN EN 1995-1-2 (Eurocode 5). Bending or flexural strength fm, k [N/mm2] Wood’s bending strength is a measure of its resistance to a force bending it. Wood with higher bulk density will have greater bending strength and wood with higher moisture content has less bending strength. Water vapour diffusion resistance – μ Porous materials usually have a lower μ-value than dense ones. The lower the μ-value, the lower a building material’s water vapour diffusion resistance will be and the higher the μ-value the more resistant to vapour the material will be. Vapour diffusion-regulating layers required in construction can be made by using a wood-based material containing a high proportion of adhesive (Fig. C 3.3, p. 93). Thermal conductivity [W/mK] Wood’s thermal conductivity depends mainly on its bulk density, moisture content and grain direction. Simplified calculation values as prescribed in DIN 4108 must be used in establishing a practical verification of thermal insulation. Carbon content [kg/m3] The amount of carbon stored in timber products is converted into a CO2 content figure as per DIN EN 16 449. The higher the figure, the more carbon is stored in the structural component, which helps to alleviate its impact on the global climate. When the structural component is used to produce energy, the carbon is released. A cascading or multiple use of wood in several steps delays this process (see “Renewable raw materials and carbon sequestration”, p. 25). Global warming potential (GWP) [kg CO2 eq.] Greenhouse gas emissions are currently the most important indicator in the climate debate. Global warming potential measures the potential contribution of a material to warming layers of air near the ground, i.e. its impact on the greenhouse effect. The figure is specified relative to the global warming potential of carbon dioxide (CO2). The lower the CO2-equivalent figure is, the lower its potential effect on global warming and related environmental effects will be. The figure specified refers to the production of the timber product (see “Life-cycle assessment”, p. 24).

Solid wood and wood-based products

A 3.1

a

b

c

Common solid wood products and wood-based materials a Solid wood, sawn softwood / sawn hardwood b Finger-jointed solid timber / solid construction timber c Double and triple laminate beams d Glued laminated timber e Lightweight timber beams / supports f Cross laminated timber g Three-ply laminate sheeting h Single-ply sheeting i Veneered plywood

d

j Beech veneer plywood k Laminated veneer lumber (LVL) l Medium-density fibreboard (MDF) m Porous wood fibreboard n Cement-bonded particle board, chipboard o Chipboard, particle board p OSB board q Long span lumber (LSL) r Lightweight wood wool construction board (WW) A 3.2 Comparison of common solid wood products and wood-based materials showing aspects relevant to use

e

g

h

i

j

k

l

m

n

o

p

q

r

f

A 3.1

19

Solid wood and wood-based products

Components

Name

Technical rules

Wood types

Main application(s)

Other applications

Solid wood – bar-shaped materials

Solid wood

Solid softwood timber

DIN EN 14 081-1, strength grading of wood according to DIN 4074-1 and DIN EN 1912, strength classes in DIN EN 338, grading by appearance in DIN EN 1611-1

Spruce, fir, pine, larch, Douglas fir

Load-bearing structures, formwork, cladding, ceilings, walls, roofs, framing

Civil engineering, timber structural engineering

Solid hardwood timber

DIN EN 14 081-1, strength grading of wood according to DIN 4074-5 and DIN EN 1912, strength classes in DIN EN 338, grading by appearance in DIN EN 975-1

Beech, oak, more rarely poplar, maple, alder, birch, cedar, ash, eucalyptus

Structural reinforcement for interiors, superior visual qualities

Timber structural engineering

Fingerjointed solid wood

Construction timber

DIN EN 15 497 and application standard DIN 20 000-7; maximum moisture content 18 %, dimensional accuracy and stability, appearance, surface qualities, taking preferred cross sections and lengths into account

Spruce, fir, pine, larch, Douglas fir

Load-bearing cross sections for ceilings, walls, roofs and framing sections

Stacked element

Laminated beams

Double / triple laminated beams

Strength grading as for sawn lumber, DIN EN 14 080 or proof of appropriateness according to approval Z-9.1-440

Spruce, fir, pine, larch, Douglas fir, poplar

Visible wall, ceiling and roof structures with large cross sections

–

Glued laminated timber

Strength grading as for sawn lumber, DIN EN 14 080 and application standard DIN 20 000-3

Spruce, fir, pine, larch, Douglas fir, western hemlock, cedar

Universal applications for all bar-shaped structural components, ceiling elements, long-span structural components subject to heavy loads

Straight and curved beams with very stable forms and high visual quality

Wood-based materials

Solid wood products

Material

20

Mixed product

Composite beams

Lightweight timber beams / supports

According to ETAG 011

Flanges: mainly construction timber sorted according to strength, glued laminated timber or laminated veneer lumber; webs: mainly OSB or hard wood fibreboard

Wall supports, ceiling and roof beams, framing with high thermal insulation requirements

Supports for concrete formwork

Laminated materials

Planks

Cross laminated timber

According to approval

Spruce, fir; more rarely pine, larch, Douglas fir

Non-load-bearing and load-bearing structural elements, sheeting or panel elements, walls, ceilings and roofs

Non-loadbearing walls

Three-ply sheeting (SWP-L3)

DIN EN 13 353 DIN EN 13 986 According to approval

Softwoods, esp. spruce, Douglas fir

Non-load-bearing, loadbearing and reinforcing planking for walls, ceilings, roofs, box elements and facade cladding

Formwork, interiors, furniture

Single-ply sheeting (SWP-L1)

DIN EN 13 353 DIN EN 13 986 According to approval

Softwoods, esp. spruce, Douglas fir; more rarely hardwoods: maple, beech, oak, alder

Furniture and interiors, visible surfaces

–

Solid wood and wood-based products

Proportion Adhesive, bonding of additives agent, aggregate [kg/m3]

Bulk density / specific weight [kg/m3]

Fire performance

Bending strength fm, k [N/mm2]

Water vapour diffusion resistance μ (dry / damp) 1)

Thermal conductivity  [W/mK] 2)

Carbon content [kg/m3]

GWP [kg CO2-eqv/m3] A1 to A3 3)

–

None

Based on DIN EN 350: Spruce 440 – 470 Fir 440 – 480 Pine 500 – 540 Larch 470 – 650 Douglas fir 470 – 550 Cedar 450 – 600 Calculated bulk density from DIN EN 338 for dimensioning and design and from DIN EN 1991 for loading assumptions

D-s2, d0

Strength and rigidity values as per DIN EN 14 081-1 and strength class C14 – C 50 as per DIN EN 338

50/20

Spruce 0.09 – 0.12 Fir 0.10 – 0.13 Pine 0.12 – 0.14 Larch 0.11– 0.13 Douglas fir 0.12 Cedar 0.09

216.3

-735

–

None

Based on DIN EN 350: Beech 690 –750 Oak 650 –760 Poplar 420 – 480 Maple 610 – 680 Alder 500 – 550 Birch 550 –740 Ash 680 –750 Eucalyptus 540 – 900 calculated bulk density from DIN EN 338 for dimensioning and design and from DIN EN 1991 for loading assumptions

D-s2, d0

Strength and rigidity values as per DIN EN 14 081-1 and strength class D 18 – D 80 as per DIN EN 338

50/20

Beech 0.15 – 0.17 Oak 0.13 – 0.17 Poplar 0.12 – 0.13 Maple 0.15 Alder 0.15 – 0.17 Birch 0.14 Ash 0.15 – 0.17 Eucalyptus 0.13 – 0.24

340

-1,120 4)

0.5

Polyurethane adhesive (PUR) or melamine-ureaformaldehyde (MUF) resin + curing agent; rarely: phenol-resorcinolformaldehyde (PRF) adhesive

Depending on the type of wood

D-s2, d0

Strength and rigidity values as per DIN EN 14 081-1 and strength class C 14 – C 50 from DIN EN 338

50/20

0.13 (average) depending on the type of wood and its bulk density

219.83

-712

5

Melamine-urea-formaldehyde (MUF) resin + curing agent or polyurethane (PUR); rarely: phenol-resorcinol-formaldehyde (PRF) resin or emulsion-polymer-isocyanates (EPI)

Depending on the type of wood

D-s2, d0

Characteristic grainparallel bending strengths as per DIN EN 14 080 between 20 and 32 N/mm2

50/20

0.13 (average) depending on the type of wood and its bulk density

221.14

-674

8.8

Melamine-urea-formaldehyde (MUF) resin + curing agent or polyurethane (PUR); rarely: phenolresorcinol-formaldehyde (PRF) or emulsion-polymer-isocyanates (EPI)

Depending on the type of wood

D-s2, d0

Characteristic grainparallel bending strengths as per DIN EN 14 080 between 20 and 32 N/mm2

50/20

0.13 (average) depending on the type of wood and its bulk density

222.46

-650

–

Adhesive as specified in DIN EN 301 and DIN EN 15 425

Depending on the type of wood and its constituents

Determined by materials, usually D-s2, d0

According to approval

50/20

From EN 13 986 0.13

n. d.

n. d.

7.5

Polyurethane (PUR) or melamine-urea-formaldehyde (MUF) resin + curing agent; rarely: emulsion-polymer-isocyanates (EPI)

Depending on the type of wood

D-s2, d0

According to approval

50/20

0.13 (average) depending on the type of wood and its bulk density

215.12

-632

17.8

Melamine-urea-formaldehyde (MUF) resin

400 – 500

D-s2, d0

Parallel to the surface grain 12 – 35, perpendicular to the surface grain 5 – 9

50/20

0.09 – 0.13 depending on bulk density

221.9

-642

1.5

Melamine-urea-formaldehyde (MUF) resin

400 – 500 (figures for hardwoods vary)

D-s2, d0

DIN EN 13 353: parallel to the grain 40 (figures for hardwoods vary)

50/20 (figures for hardwoods vary)

0.09 – 0.13 Depending on class (figures for hardwoods vary)

220 (figures for hardwoods vary)

-712 (figures for hardwoods vary) A 3.2

21

Solid wood and wood-based products

Wood-based materials

Material

Strand, chip and fibre-based materials

Fibre-based materials – fibres

Wood wool

1)

Components

Name

Technical rules

Wood types

Main application(s)

Other applications

Veneers

Veneered plywood

DIN EN 636 DIN EN 13 986 According to approval DIN EN 635-3

Spruce, pine, Aleppo pine, Douglas fir, hemlock, mahogany, African cherry

Load-bearing ceilings and walls, load-bearing and bracing planking for walls, ceilings and roofs

Weather-proof cladding, formwork, scaffolding, interiors, furniture

Beech veneer plywood

DIN EN 636 DIN EN 13 986 According to approval DIN EN 635-2

Beech

Load-bearing ceilings and walls, load-bearing and bracing planking for walls, ceilings and roofs, very high strength

Weather-proof cladding, formwork, scaffolding, interiors, furniture

Laminated veneer lumber (LVL)

DIN EN 14 279 DIN EN 14 374 According to approval

Spruce, beech, pine, Douglas fir

Load-bearing structures, beams, supports, flanges and struts of truss beams and spatial trusses, support structures for large halls

Interiors, furniture

Parallel strand lumber (PSL)

According to approval

Poplar, Douglas fir, pine

Applications with extreme structural requirements e.g. bottom plates, edging boards or lintel areas, wall, roof and ceiling plates, supports and beams

Floor and ceiling panels

Oriented strand board (OSB)

DIN EN 13 986 DIN EN 300 DIN EN 12 369-1 According to approval

Pine, Aleppo pine, Douglas fir, alder, poplar

Load-bearing walls, load-bearing and bracing planking for floors, walls, ceilings, box elements and roofs (outside with weather protection), webs of Å-beams

Mounting panels for flooring, concrete formwork, interiors, furniture

Chipboard

DIN EN 13 986 DIN EN 312 DIN EN 12 369-1 According to approval

Pine, spruce, beech, birch, alder, ash, oak, poplar, chestnut

Can be universally used for non-load-bearing, loadbearing and bracing planking and as filling panels in timber frame construction

Interiors, furniture

Cement-bonded chipboard

DIN EN 13 986 DIN EN 634 According to approval

Spruce, fir, softwood chips bonded in cement

Fire-resistant panels, load-bearing and bracing planking for interiors and exteriors, facade cladding

Non-loadbearing interior walls, sound and thermal insulation

Medium density fibreboard (MDF)

DIN EN 622-5 DIN EN 13 986 DIN EN 316 According to approval

Spruce, pine, fir, beech, birch, poplar, eucalyptus

Interiors, acoustic elements, furniture

Limited use as load-bearing and bracing planking and to make wall, ceiling and roof panels

Porous panels

DIN EN 13 171 DIN EN 622-4 DIN EN 13 986 DIN EN 316 According to approval

Spruce, fir, pine, beech, birch, poplar, eucalyptus

Insulation inside and out and between frames and rafters of walls and roofs, insulation of partition walls, footfall sound insulation

Underlay boards for roofs or to make the building envelope more windproof

Lightweight wood wool board (WW)

DIN EN 13 168

Spruce, pine, mainly softwoods

Plaster base for ceilings and soffits, acoustic panels for soundproofing

Interior and exterior planking, thermal insulation in summer

Strands

Fibres

Wood wool

Figures from DIN EN ISO 10 456 2) for a 15 % moisture content, perpendicular to the grain / board direction The biogenic carbon stored in the product is contained in Module A1– A3. The amount of stored carbon is eliminated from the system when a product in Module C 3 is disposed of, either as CO2 (use in generating energy) or still bound into the old wood. All modules must be considered in an ecological life-cycle assessment. 4) 1 m3 of hardwood contains about 1.5 times as much biogenic carbon as softwood, so the GWP (A1– A3) figure for hardwood is much higher than it is for softwood mainly for this reason. Considering the wood over its entire life cycle qualifies this figure somewhat. Hardwood processing uses much more primary energy so it produces more greenhouse gas emissions. 3)

22

Solid wood and wood-based products

Proportion Adhesive, bonding of additives agent, aggregate [kg/m3]

Bulk density / specific weight [kg/m3]

Fire performance

Bending strength fm, k [N/mm2]

Water vapour diffusion resistance μ (dry / damp) 1)

Thermal conductivity  [W/mK] 2)

Carbon content [kg/m3]

GWP [kg CO2-eqv/m3] A1 to A3 3)

89.5

Melamine-urea-formaldehyde (MUF) resin or phenol-formaldehyde (PF) resin

450 – 580

D-s2, d0

Depending on the class 5 –120

200/70

0.11– 0.15, depending on bulk density

340

-350.9

89.5

Melamine-urea-formaldehyde (MUF) resin or phenol-formaldehyde (PF) resin

720 –780

D-s2, d0

Depending on the class 5 –120

220/90

0.14 – 0.18, depending on bulk density

340

-350.9

56.8

Melamine-urea-formaldehyde (MUF) resin or phenol-formaldehyde (PF) resin

480 – 580

D-s2, d0

DIN EN 14 374 or according to approval

200/70

From DIN EN 13 986 0.09 – 0.17, depending on bulk density

180

-350.9

58

Polymeric diphenylmethane diisocyanate (PMDI)

600 –700

D-s2, d0

According to approval

50/15

0.13

268.83

-768

42.1

Phenol-formaldehyde (PF) or melamine-ureaformaldehyde (MUF) resin or polymeric diphenylmethane diisocyanate (PMDI)

550 – 650

D-s2, d0

Depends on application and thickness, as per DIN EN 300 depending on board types 1– 4, main axes 14 – 30, minor axes 7–16

50 / 30

From DIN EN 13 986 0.13

265.43

-565

58

Urea-formaldehyde (UF), phenol-formaldehyde (PF) or melamine-ureaformaldehyde (MUF) resin or polymeric diphenylmethane diisocyanate (PMDI), paraffin sometimes added

DIN EN 13 986 300 – 900

D-s2, d0 D-s2, d2

5.8 –18.3 from DIN EN 12 369-1 depending on application and thickness acc. to DIN EN 312

50/10-20

From DIN EN 13 986 0.07– 0.18, depending on bulk density

268.83

-768

862

Portland cement, foamed clay granulate, foamed glass granulate, alkaliresistant glass fibre mesh

1,000 –1,500

B-s1, d0

9 (for all thicknesses) from DIN EN 634-2

50 / 30

From DIN EN 13 986 0.23

298.75

357

100.3

Urea-formaldehyde (UF) or melamine-ureaformaldehyde (MUF) resin, phenol-formaldehyde (PF) or polymeric diphenylmethane diisocyanate (PMDI)

760 –790

E to D-s2, d0

5.1– 20 from DIN EN 622-5 depending on the application and thickness range

30/20

From DIN EN 13 986 0.08 – 0.14, depending on bulk density 7)

295.3

-668.6

1.5

Natural tree resin, alum or hydrophobic materials such as bitumen, paraffin, latex or polyurethane (PUR), fire retardants may be added

40 – 230 5)

E

0.8 –1.3 from DIN EN 622-4 depending on the application and thickness range

5/3

0.039 – 0.045 7)

88.5 5)

-164

54

Portland cement or magnesite-bonded

350 – 570

A2 – s1, d0 to B-s1, d0

depending on the application and thickness range, DIN EN 13 168

5/3

0.08 – 0.11 6)

133.74 6)

136.3

5)

dataholz.com – catalogue of structural ecologically certified timber structural components, partly converted Manufacturer EPD; partly converted Informationsdienst Holz, Faserdämmstoffe (fibre insulating materials) Source: Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-Basisdaten für Bauprodukte aus Holz. Arbeitsbericht aus dem Institut für Holztechnologie, No. 2012/1; Published by Johann Heinrich von Thünen-Institut. Hamburg 2012

6) 7)

A 3.2

23

Life-cycle assessment Annette Hafner, Holger König

A 4.1

Passive house, Samer Mösl housing estate, Salzburg (AT) 2006, sps-architekten A 4.2 Amount of carbon (C) and its conversion into CO2-equivalent shown for examples of specific buildings

24

The construction sector is responsible for a large proportion of our consumption of resources as well as for our greenhouse gas emissions, with the construction of buildings consuming around 40 % of all of energy and materials. This sector also produces 36 % of all greenhouse gases and 33 % of all waste. [1] This creates a need for planners to increasingly focus on environmental aspects in designing and planning buildings. Using buildings in more energy-efficient ways will not be enough to achieve the targets for reducing greenhouse gas emissions, so the choice of building materials will play an increasingly important role in reaching these targets. More use of wood and wood-based materials could contribute significantly towards reducing the construction sector’s carbon (CO2) emissions in the long term. The amount of CO2 in the atmosphere can be reduced in two ways: either by reducing CO2 emissions or by extracting CO2 from the atmosphere and storing the carbon. Wood has the unique ability to contribute to both of these possible reduction methods. Life-cycle assessments (LCAs) are an established method of quantifying a product’s environmental impact and make it possible to compare the environmental impacts of different products and the environmental parameters of buildings built in different ways. The information they yield is key in demonstrating wood’s positive effects on the climate and can be used to help make decisions for or against using this material. A life-cycle assessment of a building consists of two parts: firstly, a materials flow and energy balance plus verification of the resources (including lists of materials) and renewable and non-renewable primary energy used, and secondly, an impact assessment based on various indicators such as greenhouse gas emissions for energetic use, ozone depletion and the potential for summer smog, acidification and eutrophication. Based on this data, the proportion of renewable raw materials in the building product is ascertained and the amount of carbon (C) stored and thus the extent to which the materials temporarily sequester CO2 is calculated. Impact assessments can be drawn up by linking the mass of the building products used with data from the life-cycle assessment. System boundaries, functional equivalents and the data sources on construction products included in the calculations are highly relevant in calculating and comparing the entire life-cycle assessment of buildings. DIN EN 15 978 (Assessment of the environmental performance of buildings) and, at the product level, DIN EN 15 804 (Environmental product declarations) now provide a consistent basis for evaluating building lifecycle assessments. The standards offer clear rules for adequately representing the special features of timber construction. The most upto-date data sets for timber construction products and building with wood are available from the Thünen Institute of Wood Research [2]. The impact of global warming potential (GWP)

is also often referred to as an ecological or carbon “footprint”. It measures the anthropogenic proportion of global warming and is specified as a CO2-equivalent. To ensure that calculations include the retention period of greenhouse gases in the atmosphere, a carbon footprint always includes an integration period, usually GWP 100, a period of 100 years. Accurate statements on the amount of CO2 stored through the use of renewable building materials in a building during its use stage cannot be made based on the indicator of greenhouse emissions alone, because the carbon sequestered by the materials is burnt at the end of its life cycle so the sequestration effect is lost.

Timber buildings can contribute to environmental protection Timber components in buildings store carbon and delay its release until the component is disposed of. However, carbon is released during disposal if the wood is burnt to generate energy. The longer timber is used as a material, the longer this storage effect is maintained, so a timber building temporarily sequesters carbon. Carbon sequestration can play an important role in improving the effectiveness of forests in reducing CO2 levels. In the 1997 Kyoto Protocol the delayed emissions from timber products that sequester carbon were not taken into account in the first commitment period’s inventory rules. After negotiations at the Durban Climate Change Conference in 2011, the agreements reached under the Kyoto Protocol were extended and some of the rules on the inventory and quantifying of the forestry and timber industry were amended. Since then, the reporting and inclusion of forestry management has been introduced as obligatory and any temporary, dynamic changes in the carbon pool of wood harvested and used must be explicitly taken into account [3]. Under the Kyoto Protocol and agreements reached at the Durban Climate Change Conference, from early 2013 the use of wood products as material was credited in the second commitment period until 2020, although the credits were provided only at the national level and only for domestic timber. Every increase in the use of wood as a material and especially for more use of domestic timbers in construction has a positive effect on the CO2 balance. Germany identifies this effect based on a set reference (reference level for forestry management) at the end of the commitment period. Quantifying the expected impact of an increased use of wood as a material on the climate is also very important at a national level and can help to enhance the sink effect of forests. The amount of carbon in the wood used is estimated based on amounts of sawn timber and wood-based materials used and on paper consumption. Wood used in the construction sector is comprehensively considered in this survey [4].

Life-cycle assessment

Holztechnikum Kuchl college Samer Mösl housing estate Ludesch community centre Garmisch-Partenkirchen tax office Lebenshilfe workshops, Lindenberg New replacement building, Fernpaßstraße housing development, Munich Housing in Erlangen Munich-Hadern youth centre Modernising of Fernpaßstraße housing development, Munich Modernising of Grüntenstraße housing development, Augsburg Modernising of Gundelfingen primary school 0

200

400

600

800

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Absolute figures for carbon and CO2 sequestration in building [t C /CO2] A 4.1

To demonstrate the effects of the climate neutrality of wood that is taken as a basis in assessing the CO2 balance of forests, only wood from domestic forests is taken into account as contributing to timber products’ carbon sequestration. Article 3.4 of the Kyoto Protocol requires that it be inventoried in advance. This means that wood harvested from logging is excluded from this balance. For this reason, certification systems for buildings in Germany require proof that the wood used has a FSC (Forest Stewardship Council) or PEFC (Programme for the Endorsement of Forest Certification Schemes) certificate. However, these certificates do not provide any information as to whether the sustainability of forests and CO2 neutrality of the timber is ensured in each nation. To assess the impact of timber buildings on the environment, the carbon they sequester must be separately recorded in groups of materials. Substitution factors for buildings can also be determined if they are built with timber instead of mineral building materials. Life-cycle assessments make it possible to develop these determinations.

a building is verified and offset in the production stage (with a minus symbol) in a life-cycle assessment. When the building or parts of it are disposed of, the carbon is released and the greenhouse gas emissions for incineration are calculated, so the negative offset in production and calculation of greenhouse gas emissions from disposal compensate each other, which is often somewhat simplistically referred to as the “climate neutrality” of renewable raw materials. The Intergovernmental Panel on Climate Change (IPCC) has published lists of the quantities of carbon stored in various timber products. It is assumed that there is 225 kg of carbon in each m3 of timber (that has a bulk density of 450 kg and is absolutely dry). DIN EN 16 449 prescribes the conversion of stored carbon into CO2. Based on this approach to the balance, the carbon sequestration effects of various material-specific structures in the building sector can be determined, calculated, assessed and compared. Figure A 4.2 shows examples of different buildings and their absolute amounts of carbon resulting from the use of products made of renewable raw materials in buildings and their conversion into carbon dioxide in tons [5].

Carbon sequestration and substitution Two aspects are of particular interest in assessing the impact on the environment of wood and timber products in construction: • The carbon sequestered by the building • The substitution of finite raw materials Renewable raw materials and carbon sequestration

CO2 balancing of forestry management was included in the amended Kyoto Protocol rules for the second commitment period. This creates a basis for including the effects of the carbon sequestration of wood products in determining a building’s environmental impact. For this reason, the amount of carbon tied into

1200 C

1400 CO2 A 4.2

indicator “greenhouse gas” (CO2-equivalent or CO2-eq.) is shown as an example here. The substitution effect that can be achieved by using products made of renewable raw materials can vary greatly depending on the choice of materials used in the primary structure and for fittings (windows / doors, floors and facade cladding). The literature on this topic usually currently draws on the metastudy by Sathre & O’Connor, which identified an average substitution factor of 3.9 t CO2-eq. per tonne of timber used [6]. However, these figures do not take current standards into account and contain possible credits. Ongoing research projects show that these factors have to be reviewed and recalculated [7]. The figure for wood can be estimated at between 1.6 and 2.6 kg CO2-eq. of fossil-derived greenhouse gas emissions per kilogram of timber used in an average detached house. Depending on the part of the building to be substituted pursuant to DIN EN 15 978, it includes Modules A and C for the primary structure and fittings, but not the credits from the extra benefits in Module D. These can be accounted for separately [8].

Potential savings from substitution

Carbon sequestration versus an efficient use of resources in construction

As well as temporarily storing biogenic carbon, construction products made of renewable materials can replace or substitute components made of finite resources such as plastics, metals and minerals. A fundamental precondition for estimating the potential savings resulting from the use of construction products made of renewable materials is the application of the same functional equivalents. This precondition is fulfilled by surveys of each cubic metre of a particular structural element or of the same part of the building with the same energy consumption. Substitution potential varies for each environmental indicator. The potential for the

If extensive carbon sequestration contributes to the achieving of climate protection goals, it would seem to be advisable to use wood as a building material wherever possible. Yet if we want to use material resources efficiently and timber structures appropriately, we should not necessarily leap to this conclusion too quickly. Efforts to use more wood as a material, especially in competition with the use of wood to generate energy, must be balanced to ensure that enough renewable raw materials remain available. The potential effects of extensive carbon sequestration and the efficient use of

25

Renewable raw materials [kg/m2WF]

Life-cycle assessment

250

Timber construction

Hybrid

204

200

189

188

186 170

150

128

119 100

50

163

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136 118 98

91

96

GF + 4/6 FS

GF + 5 FS

GF + 3 FS

GF + 3 FS (Var. 1)

GF + 3 FS (Var. 2)

EGF + 3 FS (Var. 3)

GF + 3 FS (Var. 4)

GF + 3 FS (Var. 5)

GF + 2 FS

GF + 7 FS

GF + 7 FS (Var. 1)

GF + 5 FS

GF + 3 FS

GF + 3 FS

EW: TFC, solid wood CS: Woodconcrete composite

EW: TFC

EW: TFC

EW: TFC

EW: TFC

EW: TFC

EW: TFC

EW: TFC

EW: TFC

EW: TFC

EW: Solid wood

EW: TFC

CS: Woodconcrete composite

CS: Timber beams

CS: Woodconcrete composite

CS: Timber beams

CS: Solid wood

CS: Timber I beams

CS: Timber beams

CS: Solid wood

CS: Solid wood

CS: Solid wood

EW: TFC / Solid wood CS: Solid wood

CS: Solid wood

EW: Solid wood CS: Solid wood

IW: Timber studs

IW: Timber studs

IW: Timber studs

IW: Solid wood

IW: Timber studs, SRC

IW: Solid wood

IW: Solid wood

IW: Solid wood

IW: Solid wood

IW: Timber studs

RS: Timber I beams

RS: Timber I beams

RS: Timber I beams

RS: Timber beams

RS: Solid wood

RS: Solid wood

RS: Solid wood

RS: Timber I beams

RS: Solid wood

RS: Timber I beams

SC: SRC

SC: SRC

SC: SRC

SC: SRC

SC: SRC

SC: SRC

SC: SRC

SC: SRC

SC: SRC

SC: Steel

43

0 GF + 4 FS EW: TFC CS: Stb Wooden floorboards IW: SRC RS: SRC Wooden floorboards SC: SRC and steel

IW: SRC (GF) IW: SRC and Solid wood (UF) Timber studs

IW: Timber studs

IW: Timber studs

RS: Solid wood

RS: Timber beams

RS: Timber beams

RS: Timber I beams

SC: SRC

SC: SRC

SC: SRC

SC: SRC and steel

A 4.3

wood as a resource and a material should be considered individually for each building task. Optimising buildings in terms of structural, fire safety, energy use, economic and interior climatic criteria will always involve compromise and every type of construction will result in a different optimum. Buildings’ support structures require large quantities of materials to build them, so they can extensively sequester carbon. Facades, on the other hand, need to be well insulated and as thin as possible, so the large quantities of insulating materials they require mean that less timber is used in their construction and less carbon is stored in that way. Visible interior walls and solid timber ceilings offer potential for extensive carbon sequestration, but it may be preferable for soundproofing or fire safety reasons to build these structures in other ways. Individual areas must be considered in each case. A German Federal Environmental Foundation (Deutsche Bundesstiftung Umwelt – DBU) research project compared various timber buildings with each other and analysed the differences in amounts of renewable raw materials used in buildings and their carbon sequestration and greenhouse gas emissions [9]. Fig. A 4.3 shows the amounts of renewable raw materials in timber apartment buildings, which are classified as hybrid buildings (with a certain proportion of timber in exterior walls), timber-frame structures or solid timber structures (with cross laminated timber load-bearing structures). Related superstructures and fittings are also shown. Appropriate government funding and support programmes are also important in helping to establish timber construction. The City of Munich, for example, has a funding programme that supports the construction of environmentally-friendly timber buildings and pays a subsidy for every kilogram of carbon stored under certain conditions, as long as timber from sustainable forestry is used.

26

CO2-efficient timber construction If construction is to be as CO2-efficient as possible, contractors and clients must take decisions to pursue this type of construction and set precise goals at the outset of planning. Planning CO2-efficient buildings

Target values based on the following assumptions should be set in the preliminary design phase: • Use of timber in the primary support structure, which has a major influence on the results of the life-cycle assessment. • Keeping energy consumption to a minimum during the use stage. • The fixing of maintenance cycles for individual structural components. They influence construction and create specifications for construction quality. • Formulation of disposal scenarios for the entire structure and for any dismantling into individual parts with options for reusing timber elements. The connection between the construction and use stages

Efforts to optimise buildings have so far concentrated on the lowest possible energy consumption and keeping CO2 emissions low during the use stage. With the introduction of the passive house standard, almost-zero energy and plus-energy buildings, there is an increasing focus on the potential savings that the construction and maintenance of buildings can offer. Figure A 4.4 shows a comparison of the primary energy requirements of a multi-storey building according to the EnEV 2009 standard (70 kWh/m2a) and those built to a passive house standard (15 kWh/m2a), with the energy required for construction, maintenance and energy supply shown for a period of 50 years.

It clearly demonstrates that the overall energy consumption of buildings with highly efficient energy standards is lower over the building’s life cycle. At the same time, the percentage distribution between buildings (construction) and energy supply shifts in the use stage, so primary energy consumption assumes vital importance in buildings with high energy consumption standards. More than 50 % of primary energy requirements and greenhouse gas emissions generated by passive house buildings are produced by the building’s construction and maintenance, so there is an increasing focus on the overall material concept and on individual construction products. The better a building’s energy use standard is and the less energy it consumes, the more influence its construction will have on its overall life-cycle assessment. Dismantling and disposal

The EU’s Waste Framework Directive establishes a waste hierarchy and prescribes that, in Europe, as much material as possible should be re-used or recycled [10]. In a second step, material is also regarded as an energy resource. If wood is to be reused as a material, it must be classified as waste wood [11]. Only timber that is not contaminated with hazardous substances can be reused, so timber that has been treated with chemical timber preservatives cannot be reused, but must be used to generate energy. Better reuse of untreated, reclaimed timber can help to stabilise the amounts of timber available at a reasonable cost in the long term. Solid wood should generally be first used as construction timber, with the next step being the use of weak wood and wood cut during thinning in wood-based materials. The third and last option is to use wood in thermal energy recovery. This approach greatly extends and expands the extent of carbon sequestration.

Life-cycle assessment

Apartment building Passive house standard (15 kWh/m2a)

Apartment building EnEV 2009 standard (70 kWh/m2a)

25%

A 4.3

A 4.4

Amounts of renewable raw materials in kg/m2 of living space for various timber and hybrid apartment blocks Ground floor (GF), upper floor (UF), full storeys (FS), exterior walls (EW), timber frame construction (TFC), ceiling structure (CS), steel-reinforced concrete (SRC), inner walls (IW), roof structure (RS), staircase (SC) Correlation between primary energy consumption used to build buildings with different energy use standards and their primary energy consumption over 50 years

36%

6% 69%

Construction Maintenance Building services over 50 years

47%

17%

A 4.4

Long transport routes have a negative effect on environmental assessments and the fossil fuels used to achieve them reduce primary energy efficiency, so the wood for buildings should be sourced from the region in which it is processed and used and then reused in thermal energy recovery as far as possible. Cascading use of raw materials

A targeted extension of the material life cycle of solid wood products and the consistent application of “cascading use” (multiple reuse of a raw material) can open up sources of raw materials for new products. Keeping contaminants to a minimum and intelligent dismantling concepts (reuse or recycling of valuable materials) can make it possible to greatly reduce the amounts of raw materials used in thermal energy recovery. In the wood-processing sector, the potential of efficient cascading use is only fully exploited in horizontal reprocessing and recovery (e.g. simultaneous use of wood, bark and shavings) and remains otherwise largely unused. Vertical integration of this kind of use over the whole life cycle of materials could be expanded. Every structure is built in layers. The layers and their sequences are closely connected with the total service life of the structural element and must be designed and optimised with maintenance, dismantling and recycling scenarios during the planning stage. When the interaction of layers is well planned, structural elements and components can be better demarcated from each other and joints designed with a view to subsequent dismantling, with a focus on detachable connections in structures (e.g. screws instead of adhesives). The carbon footprint of timber in buildings

Some general guidelines must be considered when using timber to sequester carbon in buildings:

• To build carbon-efficient buildings, specifications on the structure’s carbon footprint, primary energy consumption (in the form of material and energy) and the amount of renewable raw materials used in it must be established in the planning phase. • The intensive energy use of mineral building materials means that parts of buildings such as cellars and foundations have a major impact on buildings’ carbon footprints. The extent of the effect will depend on the size of cellar and type of foundation. The taller a building is, the lower their percentage ratio will be. • The wood used must come from sustainable forestry management. • The extent of carbon sequestration increases with the amount of wood or wood-based materials used. Support structures require large amounts of materials. Another factor that may increase carbon sequestration is the use of planar solid wood structural components in walls, ceilings and roofs. • The amount of timber used must be considered in relation to a resource-saving use of timber stocks, so the advantages of maximum carbon sequestration must be weighed up against an economical use of timber. • Local government authorities should establish sustainable contract award practices by prescribing maximum carbon footprint specifications for the construction phases of different types of buildings. These could be anchored in development plans.

Comparative evaluations of conventional and timber buildings based on life-cycle assessments Comparisons made between buildings built using conventional (mineral) materials and methods involving construction products made of finite resources and buildings containing

high proportions of products made of renewable raw materials reveal the significant potential environmental benefits that timber buildings can offer the ecosystem. One example of this are the comparative life-cycle assessments published in the catalogue for the “Bauen mit Holz – Wege in die Zukunft” (“Building with wood – paths into the future”) exhibition [12], that analyse eight examples of buildings in which many structural components made of renewable raw materials were used. The life-cycle assessments carried out make use of the ÖKOBAUDAT database (oekobaudat.de; 2011– 2013 version) as basic information. LEGEP software was used to model and calculate objects. Each building was compared with a model of a standard version with conventional construction products made largely of non-renewable, i.e. mineral, metallic and synthetic raw materials. This version was identical with the actual building in its space, area and design and met the same energy targets. The structural components were taken from the LEGEP database element catalogue and had the same structure and choice of materials as those built into many buildings already assessed. The modelling of these “non-identical twins” clearly shows the difference between various construction methods. In the following life-cycle assessments, the buildings were surveyed from the lower edge of their ground floor slabs. Cellars and foundation elements (with cellars under some or all of the floor space and foundations) were not included in the assessments because they would have tended to distort the results in terms of the building’s function and its material quality. Only buildings with timber primary support structures were taken into account. The various building materials were grouped into non-renewable (mineral, metallic, synthetic) and renewable raw materials (wood, plant and

27

Life-cycle assessment

animal fibres) for the purposes of evaluation. To facilitate comparisons of objects, the reference value was 1 m2 of gross floor area only above ground, and the kilogram was used as a unit of weight. The comparison shows that buildings made of renewable raw materials had about 50 – 65 % the weight of conventional buildings. The results also showed a very low proportion of renewable raw materials of just 0.5 – 1 % of the total weight of conventional buildings. In buildings containing high proportions of renewable raw materials, they accounted for up to 18 % of the total weight. The low percentage of their share of the weight – despite an almost exclusive use of wood – was due to the heavy weight of the mineral building materials used. A concrete floor slab in a timber building weighs about as much as two timber slabs plus the flooring. Most of the buildings surveyed had two storeys. The influence of a mineral floor slab only decreases significantly in multi-storey timber buildings. Figure A 4.5 shows the results of such a comparison of buildings, based on the example of the Fernpaßstraße housing development in Munich [13]. The results of this study will have to be recalculated to take into account the current DIN EN 15 978 standard and adjusted ÖKOBAUDAT from 2015. Credits (Module D) for the incineration of building products at the end of their life cycles to generate energy will no longer be included in the calculations, so that the advantageousness of the global warming potential indicator levels off at up to 50 % [14].

Conclusion The construction sector offers considerable opportunities for greatly reducing greenhouse gas emissions. New buildings are always more energy-efficient to operate, so interest in the carbon footprint of building materials is increasing. The advantages of using timber from an ecological point of view

A 4.5

A 4.6

28

Comparison of selected indicators in life-cycle assessments (calculated with ÖKOBAUDAT 2011– 2013) made between timber buildings in the Fernpaßstraße housing development in Munich (DE) 2012, (Architekten Hermann Kaufmann / Lichtblau Architekten) and buildings built with conventional materials. Period under review – 50 years Fernpaßstraße housing development

Timber products offer a number of significant advantages from a climate protection point of view: • Wood used as a construction product can have a double climate protection advantage. Compared with other building materials, it produces only low CO2 emissions from fossil sources and it can store CO2 and remove it temporarily from the atmosphere. • The best ways to take advantage of the potential savings of CO2 that wood offers for the building sector are to use a high proportion of timber products, to use wood products that are as durable as possible, and to replace energy-intensive materials with wood and wood-based products. • Specific national factors significantly influence the carbon footprint of construction

products and buildings, because the different energy sources in the electricity mix of various countries can mean that similar production processes may have different carbon footprints. These factors must be properly considered when assessing products. • To avoid negative effects on the carbon sink effect of forests, wood must come from sustainably managed forests. • Wood and wood-based building materials can be reused, recycled as a material and then be used to generate energy in cascading use, which can extend the period for which atmospheric carbon is stored many times over. A cascading use of wood not only makes it possible to use this resource efficiently, it also allows for multiple substitution effects due to the use of more energy-intensive materials and /or of fossil energy sources in energy recovery. The carbon footprint of structural components in timber buildings

Building with timber, which can temporarily sequester carbon and replace non-renewable materials, can make a major contribution to achieving climate protection goals, as long as the wood comes from sustainable forestry. The following factors should also be taken into account: • Foundations and cellars have the biggest influence on the carbon footprints of buildings. The extent of their influence depends on the size of cellar and type of foundation. The taller the building, the lower the ratio of their influence will be. • The extent of carbon sequestration increases with the amount of timber from sustainable forestry used in a building. • Most of the carbon in a building is stored in its support structure because it requires the largest amount of timber. Solid wood structures use a great deal of timber so they store a large quantity of carbon. The amount of timber used must, however, be proportionate to the use of timber in a way that preserves it as a resource, so the advantages of maximum carbon sequestration must always be weighed up against an economic use of timber. • A building’s fittings (floor coverings, windows, doors and any wooden facade cladding), regardless of the material used for the support structure, can influence carbon sequestration in the long term, particularly since fittings may be replaced several times over a building’s life cycle [15]. • The carbon footprint of assembly on a building site is minor compared with that resulting from the manufacture of building materials. • Maintenance of structural components (e.g. by providing the wood with structural protection) is essential for optimising the durability of building products beyond the building’s life cycle and thus its carbon footprint.

Life-cycle assessment

Timber Standard

0

5

10

15

20 2

Comparison of greenhouse potential [in kg CO2-equivalent to each m of net floor space and year]

Timber Standard

0

0.02

0.04

0.06

0.08

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2

Comparison of abiotic resource potential [in kg of antimony-equivalent to each m of net floor space and year]

Timber – Primary energy non-renewable – Primary energy renewable Standard – Primary energy non-renewable – Primary energy renewable

0

10

20

30

of which proportion of heating value of which proportion of heating value

40

50

60

Comparison of primary energy consumption for construction, maintenance and disposal [in kWh for each m2 of net floor space and year]

Timber – non-renewable – renewable Standard – non-renewable – renewable

0

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1500 2

Comparison of material required for construction and maintenance [in kg per m of gross floor area] A 4.5

Notes: [1] COM (2007) 860 final: A lead market initiative for Europe. http://eur-lex.europa.eu/LexUriServ/ LexUriServ.do?uri=COM:2007:0860:FIN:en:PDF. 20.07.2015 [2] Basic data timber balance for timber construction products. http://www.holzundklima.de/projekte/ oekobilanzen-holz/docs/Rueter-Diederichs_2012_ OekoHolzBauDat.pdf. 23.11.2015 [3] Reporting under the United Nations Convention on Climate Change and Kyoto Protocol 2012 – National inventory report on the German greenhouse gas inventory (Nationaler Inventarbericht zum Deutschen Treibhausgasinventar) 1990 – 2010. Published by the Umweltbundesamt (German Environment Agency), 08/2012 [4] Rüter, Sebastian: Projection of Net Emissions from Harvested Wood Products in European Countries – For the period 2013 – 2020. Working report from the Institut für Holztechnologie und Holzbiologie No. 2015/1, Johann Heinrich von Thünen Institute (vTI), p. 63. http://literatur.thuenen.de/digbib_ extern /dn048901.pdf. 24.02.2017 [5] Kaufmann, Hermann; Nerdinger, Winfried et al.: Bauen mit Holz: Wege in die Zukunft. Munich, 2011 [6] Sathre, Roger, and O’Connor, Jennifer. Meta-analysis of greenhouse gas displacement factors of wood product substitution. In “Environmental science & policy” 13, 2010, p. 104 –114 [7] THG-Holzbau: Treibhausgasbilanzierung von Holzgebäuden – Umsetzung neuer Anforderungen an Ökobilanzen und Ermittlung empirischer Substitutionsfaktoren. Joint project of the RUB, Thünen Institute, TUM and Ascona GbR. Final report scheduled for publication in 2017 [8] Current calculations in the THG-Holzbau research project were carried out for this purpose. [9] Methodenentwicklung zur Beschreibung von Zielwerten zum Primärenergieaufwand und CO2-Äquivalent von Baukonstruktionen zur Verknüpfung mit Grundstücksvergaben und Qualitätssicherung bis zur Entwurfsplanung. German Federal Environmental Foundation (Deutsche Bundesstiftung Umwelt), File number 31943/01 [10] DIRECTIVE 2008/98/EC. http://eur-lex.europa.eu/ legal-content/EN/TXT/?uri=URISERV:ev0010. 10.08.2015 [11] In Germany this is done through the Altholzverordnung, AltholzV (Waste Wood Ordinance) , 2012 [12] König, Holger: Ökobilanz-Vergleich von Gebäuden in Holzbauweise im Vergleich zu Standard-Bauweisen bei Neubauten und bei Gebäudemodernisierung. In: Kaufmann, Hermann; Nerdinger, Winfried (eds.): Bauen mit Holz – Wege in die Zukunft. Supplement to the exhibition catalogue of the same name. Munich, 2015 [13] ibid. [14] as for Note 7 [15] ibid.

A 4.6

29

Interior air quality – the influence of timber construction Maren Kohaus, Holger König

A 5.1

A 5.1 A 5.2 A 5.3 A 5.4

30

Interior wood in a kindergarten, Bizau (AT) 2009, Bernardo Bader Architekten Recommended TVOC levels and resulting recommended action(s) Thermal effusivity coefficients of certain building materials Classification of chemical compounds by boiling point

Wood has been used as a construction material for human habitations for centuries and wood and wood-based materials are still used in a wide range of ways as a construction material, flooring, wall and ceiling cladding and to make fittings and furnishings in modern buildings. The material is highly prized for its naturalness and authenticity. Wood surfaces in particular, due to the material’s specific character, colour, grain, texture and porousness, are generally regarded as appealing to your senses, as various investigations by Maximilian Moser and the “Interaktion Mensch und Holz” study confirm [1]. Wood’s specific structural and physical characteristics such as low thermal conductivity (-value = 0.11– 0.17 W/mK) and low thermal effusivity coefficient or b-value (Fig. A 5.3) mean that wood surfaces are usually perceived as warm. Natural wood surfaces also help to regulate interior climates because wood absorbs moisture from the interior air and gradually releases it again [2]. The smell of wood, which is made up of emissions of volatile substances, has a pleasantly calming effect on some people. A 2003 study by the Joanneum Research Forschungsgesellschaft on the potential effects of stone pine wood in the immediate environment on people’s circulation and sleep found that it improved their performance and general wellbeing [3]. Maximilian Moser’s 2007 “Schule ohne Stress” (School without stress) study analysed the effect of solid wood fittings and equipment in classrooms. It came to the conclusion that the calming effect of wood, estimated by measuring the students’ heart rates and vagal tone, could have a positive effect on health [4]. Current research projects, such as the HOMERA study, are seeking to establish findings on the possible effects of wood and wood products on health by means of technical scientific observation and medical evaluation [5]. Given the complexity of the topic, the potential of research in this area is immense. Until further findings become available, discussions on the extent to which emissions from wood and wood-based materials in contemporary timber buildings can be regarded as harm-

ful to health, as inherent to wood and therefore natural and harmless, or even promote health, will remain current. To offer clients, users and planners some security and bring some clarity into the discussion, relevant aspects will be examined in detail below.

A healthy indoor climate Regardless of how a building is built, it must provide an indoor climate that users perceive as pleasant and accommodate activities for which rooms are designated. Comfort criteria (as specified in DIN EN 15 251) offer guidance on the factors that need to be taken into account: • Protection from cold, heat and moisture / damp caused by weather • Protection from high levels of moisture caused by usage and resulting condensation and mould formation • Protection from interior and exterior noise pollution • Optimum lighting and adequate daylight as well as protection from excessive sunlight (heat /overheating) • Sufficient ventilation for the particular usage and a resulting reduction in CO2 concentrations • Protection from ionising (e.g. radon) and non-ionising radiation (e.g. electric smog) • Low-level pollution of interior air from building materials, equipment and devices An adequate exchange of air provided by manual or mechanical ventilation ensures that emissions produced by building products, electronic devices and by people are dissipated, although toxin-free building materials should be used where possible.

Emissions in interior air Materials used inside buildings can pollute the air within by emitting particles in the form of dust, fibres or gases. Relevant for interiors are only those emissions that are released within the airtight layer (see “Airtight layers”, p. 97f.).

Interior air quality – the influence of timber construction

Recommended TVOC levels (interior air)

Hygiene assessment and recommended actions

Level 1: TVOC

< 0.3 mg/m3 (< 300 μg/m3)

Level 2: TVOC

> 0.3 mg/m3 (> 300 μg/m3

and and

< 1.0 mg/m3 < 1,000 μg/m3)

• Hygienically acceptable as long as levels for individual substances are not exceeded • Increased ventilation necessary

Level 3: TVOC

> 1.0 mg/m3 (> 1,000 μg/m3

and and

< 3.0 mg/m3 < 3,000 μg/m3)

• Hygienically dubious, use room for limited periods only • Impact of substances exceeding recommended levels on health must be tested; individual toxicological evaluation recommended

Level 4: TVOC

> 3.0 mg/m3 (> 3,000 μg/m3

and and

< 10.0 mg/m3 < 10,000 μg/m3)

• Hygienically unsound, use room for limited periods only • Individual toxicological evaluation recommended

Level 5: TVOC

> 10 mg/m3 and (> 10,000 μg/m3 and

< 25.0 mg/m3 < 25,000 μg/m3)

• Hygienically unacceptable, (avoid using room) • Individual toxicological evaluation recommended

• Hygienically acceptable as long as levels for individual substances are not exceeded • “Target level” (= hygienically safe range; recommended)

A TVOC concentration of more than 3,000 μg/m3 is regarded as hygienically unsound, so BNB certification may only be issued if TVOC levels are in the 500 μg/m3 to 3,000 μg/m3 range. A 5.2

In discussions on emissions in interior air and wood-based materials, two terms constantly recur: VOCs (volatile organic compounds) and formaldehyde.

people’s well-being and be allergenic (e.g. the smell of turpentine oil), but are not harmful to health in the concentrations usual in timber buildings.

VOCs

VOC emissions from building products There are no Europe-wide statutory limits or prohibitions imposed on VOC emissions from building products. For this reason, in Germany in 2004 the “Ausschuss zur gesundheitlichen Bewertung von Bauprodukten” (Committee for the Health-Related Evaluation of Building Products) introduced the AgBB evaluation scheme, which sets maximum levels for emissions from construction products and prescribes exclusion criteria governing situations in which a product may not be used.

In construction practice and the analysis of interiors, VOC gases are classified according to their boiling points (Fig. A 5.4): • VVOC: Very volatile organic compounds • VOC: Volatile organic compounds • SVOC: Semi-volatile organic compounds During construction measures, many different VOCs escape into the interior air temporarily. These higher concentrations can usually be greatly reduced by intensive ventilation during and after work. VOCs are a single group of substances but a very diverse one. They can be harmless, obtrusive due to their smell, or harmful to health. The most familiar VOCs are alkane / alkene, aromatic compounds, terpenes, halogenated hydrocarbons, esters, aldehydes and ketones. Wood gives off small amounts of terpenes and aldehydes in the form of its typical wood smell. The toxicity of VOCs varies hugely. Carcinogenic benzene is one of these indoor air pollutants as are many much more harmless VOCs such as terpenes from natural oils, natural paints and the natural resin of timber. In high concentrations, they may impair

Material

Insulating materials (Mineral fibre)

Thermal effusivity coefficient b value [KJ/Km2√s]

Recommended individual VOC levels in interior air The AIR (Ausschuss für Innenraumrichtwerte, formerly Ad hoc AG) recommendation on levels of VOCs in interior air (Fig. A 5.5, p. 32) issued by the Umweltbundesamt in its current valid form can be used to evaluate concentrations of individual VOCs in interior air [6]. Formaldehyde

Formaldehyde, with its low boiling point, belongs not in the group of VOCs, but in the group of VVOCs (very volatile organic compounds). Formaldehyde has frequently been the focus of discussions because for decades it was suspected of being harmful to health. In the EU, formaldehyde has been classified as a category 1B carcinogen in animal testing since early 2016. Small amounts of formaldehyde are present in natural wood, which may emit it, although

Abbreviation

Name

Boiling point [°C]

Examples

VVOC

very volatile organic compounds

0 to 50 (-100)

Formaldehyde, acetone, acetaldehyde

VOC

volatile organic compounds

50 to (-100) to 240 (-260)

Many solvents, such as styrene and xylene

SVOC

semi-volatile organic compounds

240 (-260) to 380 (-400)

Plasticisers, biocides, flame retardants, PCBs

POM

particulate organic matter

> 380

PAK in bituminous building materials

MVOC

microbial volatile organic compounds (produced by mould and bacteria)

in the VOC range

A wide range of different substances and substance classes

0.06

Cork

0.10

Wood

0.4 ... 0.5

Human skin

1.0 ...1.3

Glass

1.3 ...1.5

Water

1.6

Concrete

VOC emissions in interior air When concentrations of emissions in interior air are measured for analysis, they are referred to as TVOCs (total volatile organic compounds), i.e. the total amount of all VOCs measured in interior air. This figure does not distinguish between substances that are hazardous to health, allergenic, malodorous or those that are harmless to health, which makes it harder to conduct a toxicological evaluation on this basis. A directive from the Umweltbundesamt (German Environment Agency) classifies TVOC levels measured in interior air according to five

levels (Fig. A 5.2) and prescribes a hygienic evaluation and recommendations for action for each level. Different certification guidelines (BNB, DGNB, LEED, HQE, NaWoh etc.) recommend compliance with various levels of VOCs in interior air. Interior air hygiene quality targets based on a specific certification system and /or contractual stipulations should be set before planning and construction begins.

1.8 ... 2.2

Steel

14

Copper

36

Materials with high thermal effusivity coefficients such as metals are perceived as cold when their temperature is lower than that of our skin. In contrast, materials with low thermal effusivity coefficients such as wood or insulating materials are perceived as warmer at the same temperature. A 5.3

Gases /substances with a high boiling point are not very volatile so are released slowly for a longer period into ambient air. Gases /substances with a low boiling point are very volatile and released more quickly in a shorter time. Figures analogous with WHO classification. A 5.4

31

Interior air quality – the influence of timber construction

Substance / Substance class

Recommended level

Note

Bicyclic monoterpene 1)

RW I = 0.2 mg/m3 RW II = 2 mg/m3

Ad hoc AG (2003) 5)

Monocyclic monoterpene 2)

RW I = 1 mg/m3 RW II = 10 mg/m3

Ad hoc AG (2010) 5)

Saturated acyclic aliphatic C4 to C11 aldehyde

RW I = 0.1 mg/m3 RW II = 2 mg/m3

Ad hoc AG (2009) 5)

2-Furaldehyde (Furfural)

RW I = 0.01 mg/m3 RW II = 0.1 mg/m3

Ad hoc AG (2011) 5)

Benzaldehyde

RW I = 0.02 mg/m3 RW II = 0.2 mg/m3

Ad hoc AG (2010) 5)

Formaldehyde

0.1 ppm 3) / 0.124 mg/m3 0.08 ppm 4) / 0.1 mg/m3 0.08 ppm / 0.1 mg/m3

Bundesgesundheitsamt (German Federal Health Agency) 1977 WHO (2010) AIR has confirmed the level recommended by the WHO in 2010 for formaldehyde (2016)

this minor amount is not harmful to health (Fig. A 5.6). Formaldehyde is used in the manufacture of wood-based materials, insulating materials, paints and varnishes, cleaning agents etc. and in bonding agents such as glues (Figs. A 5.7 and A 5.8).

Lead compound  pinene Lead compound d-limonene 3) confirmed in 2006 by Ad hoc AG 4) defined for brief and long-term exposure 5) In March 2015 Ad hoc AG was renamed the “Ausschuss für Innenraumrichtwerte” (AIR) • RL II = recommended level II (dangerous level): is the concentration of a substance in the interior air requiring immediate action if the level is reached / exceeded. • RL I = recommended level I (safety level): refers to concentrations of a substance / group of substances in interior air identified in an assessment of individual substances from which no impairment to health is expected, based on current knowledge. RL I should be the goal in renovations and not be exceeded. If levels are in the I – II range there is a need for action. • Recommended levels do not offer any information on the possible effects of combining different substances. 1) 2)

A 5.5 Type of wood

Formaldehyde concentrations 1 ppb = 0.001 ppm = 1.25 μg/m3 at 20 °C and 1013 hPa

Beech

2 – 3 ppb

= 0.002 – 0.003 ppm

Oak

4 – 9 ppb

= 0.004 – 0.009 ppm

Douglas pine

4 – 5 ppb

= 0.004 – 0.005 ppm

Spruce

3 – 4 ppb

= 0.003 – 0.004 ppm

Pine

3 – 5 ppb

= 0.003 – 0.005 ppm

By comparison: threshold value for an E1 “Building product” = 0.1 ppm A 5.6

The following glues contain formaldehyde: • Urea-formaldehyde (UF) • Melamine-formaldehyde (MF) • Melamine-urea-formaldehyde (MUF) • Melamine-urea-phenol-formaldehyde (MUPF) • Phenol-formaldehyde (PF) Wood-based materials containing aminoplast adhesives (UF, MF, MUF) tend to release the most formaldehyde. Emissions often continue for decades and fluctuate depending on the interior climate. The warmer and damper it is, the more formaldehyde panels release. Alternative glues: • PMDI / PUR A 5.7

Wood-based material

Bonding agent

Proportion of resin

Chipboard, particle board

Urea-formaldehyde resin (UF) Modified melamine formaldehyde resin (MUF + MUPF) Phenol formaldehyde resin (PF) Polymeric diphenylmethane diisocyanate (PMDI)

5 to 20 %

MDF panels (Medium density fibreboard panels)

Urea-formaldehyde (UF) Modified melamine formaldehyde resin (MUF) Phenol-formaldehyde resin (PF) Polymeric diphenylmethane diisocyanate (PMDI)

8 to 13 %

Fibreboard (soft board)

Polyurethane (PUR)

0.5 to 3 %

OSB (oriented strand board)

Phenol formaldehyde resin (PF) Modified melamine formaldehyde resin (MUF) Polymeric diphenylmethane diisocyanate (PMDI)

5 to 10 %

Veneered plywood

Phenol formaldehyde resin (PF) Modified melamine formaldehyde resin (MUF)

10 to 20 % A 5.8

The following classes are applied to classify woodbased materials by the amount of formaldehyde they release: Emissions class E 1 Emissions class E 1 plus Emissions class E 0

[μg/m3]

[ppm]

= 124

= 0.1 1)

= 80

= 0.065

Does not release formaldehyde but often PU adhesive with isocyanates

RAL UZ 76 / RAL UZ 38

= 60

= 0.05

natureplus e. V.

= 36

= 0.029

1)

measured in a test chamber based on EN 717-1 A 5.9

32

A 5.5

Examples of interior air reference values for substances potentially relevant to wood and wood products A 5.6 Formaldehyde emissions from natural wood A 5.7 Information on adhesives A 5.8 Wood-based materials and their proportions of bonding agents containing formaldehyde A 5.9 Definitions of emissions classes A 5.10 Recommended levels of formaldehyde in interior air (as of Nov. 2016) A 5.11 TVOCs of various types of wood

Formaldehyde emissions from building products Formaldehyde emissions from building products have been regulated in Germany since the 1980s. The Chemicals Prohibition Order (Chemikalien-Verbotsverordnung) valid at that time prescribed that emissions from building products that come into contact with interior air may not exceed an equilibrium concentration of 0.1 ppm (= 0.124 mg/m3 = 124 μg/m3) under defined testing conditions. Products complying with these concentrations were declared as being in emissions class E1 (Fig. A 5.9) and could be labelled as “low formaldehyde”. DiBt guideline 100 (“Guideline on the classification and monitoring of formaldehyde release from wood-based panels”) replaced this order in 1994. The EU subsequently adopted the requirements specified in the guideline. In the AgBB scheme introduced in Germany to evaluate levels of individual VOCs, a level of 0.08 ppm (= 0.1 mg/m3 = 100 μg/m3) for concentrations of formaldehyde in building materials has also been evaluated since 2015. A new formaldehyde class, E1plus, with a concentration limit of 0.065 ppm (= 0.08 mg/m3 = 80 μg/m3), is currently being discussed in the DIN EN 13 986 standard committee. Some product quality certification systems, such as “Blauer Engel”, have set even lower levels for formaldehyde emissions in building products. A concentration of 0.05 ppm (= 0.06 mg/m3 = 60 μg/m3) is regarded as a particularly low level of formaldehyde (Fig. A 5.9). The timber industry is already seeking to reduce levels, offering a range of products that release much lower levels of formaldehyde than the current E1 emissions class level of 0.1 ppm (= 0.124 mg/m3 = 124 μg/m3). Formaldehyde in interior air The use of low-formaldehyde building products (E1 class) is a crucial prerequisite for ensuring that concentrations of pollutants in interior air remain low, although the following influential factors must also be considered when planning: • The amount of the material to be installed • The volume of interior air • Air exchange rate • Temperature of air in the room (e.g. the ambient temperature, air temperatures near heating system or due to sunlight etc.) • Humidity • Surface treatments • Cleaning agents used Individual EU member states prescribe different levels of formaldehyde concentrations in

The following guideline values for formaldehyde in indoor air can be assumed (as of: Nov. 2016) WHO

100 μg/m3 (30 min.)

= 0.08 ppm

Austria

100 μg/m3 short term (30 min.) 60 μg/m3 long term (24 hrs.)

= 0.08 ppm = 0.05 ppm

Switzerland

125 μg/m3

= 0.1 ppm

France

50 μg/m3 short term (2 hrs.) 10 μg/m3 long term

= 0.04 ppm = 0.008 ppm

Germany

100 μg/m3

= 0.08 ppm

Certification by the BNB, DGNB, NaWoh

< 60 μg/m3 = full marks (target value) > 120 μg/m3 = not certifiable (limit value)

SER [μg m-2h-1]

Interior air quality – the influence of timber construction

4000

3,700

3500 3000 2500 2000 1,400

1500 1000 500 0

30

30

Ash

Beech

20 Maple

110

210

Birch

Oak

pressing and heat treatments may however cause timber to form and release slightly more formaldehyde. People with particular sensitivities

People who are sensitive to chemicals or have allergies may experience reactions to natural emissions of VOCs and formaldehyde. Unfortunately, timber emissions can vary not only among types of wood, but within a single tree trunk, which makes it harder to reliably label this natural product. If a building is being built for people who may be particularly sensitive to emissions, precise targets and instructions involving the manufacturing process must be set for planning and the choice of products.

The impact of glued construction timber on interior air

Emissions in interior air from natural timber structural components do not usually reach concentrations that are hazardous to health.

The invention of glued laminated timbers [9] resulted in various wide-ranging material developments that have had a major influence on timber construction. Glued timber products such as glued laminated timber, cross laminated timber and dowel laminated timber elements have opened up new dimensions in timber construction.

VOCs

VOC emissions

The typical smell of fresh conifer woods (e.g. pine, spruce, larch and stone pine) comes from terpenes, natural solvents, and the smell of deciduous woods from aldehydes and carboxylic acids (e.g. acetic acid). Terpenes and aldehydes are both VOCs. TVOC levels depend on the type of wood (Fig. A 5.11) and processing conditions, such as the temperature at which the wood is dried [7]. Natural timbers do not usually emit TVOCs in concentrations that are hazardous to health.

The solvents that natural wood and construction timber products naturally contain may be released within interior air during construction in the airtight layer.

The influence of natural wood on interior air

Formaldehyde

Formaldehyde is present in natural wood and perceptible even in low concentrations, although the small amounts emitted by natural wood are toxicologically harmless [8]. Certain manufacturing processes such as drying, hot

Cherry

Pine

Spruce

(SER = specific emissions rate) A 5.10

interiors (Fig. A 5.10). The WHO recommends a level of 0.08 ppm (= 0.1 mg/m3 = 100 μg/m3). The Ausschuss für Innenraumrichtwerte (German Committee on Indoor Guide Values), AIR, decided to follow this guideline in 2016. Like the various guidelines on interior air levels of VOCs, there are various certification systems recommending different levels of formaldehyde concentrations in interior air that can be used as orientation. Certification under the BNB (Sustainable building evaluation system – “Bewertungssystem Nachhaltiges Bauen” – of the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety, BN_313-2), for example, prescribes maximum formaldehyde levels in interior air of 120 μg/m3. Complete compliance is achieved in this certification system with a level of 60 μg/m3. However, even concentrations in the 60 μg/m3 – 20 μg/m3 range may impair well-being, although we breathe in a mixture of air, so investigations into concentrations in this range tend to be speculative.

60

Formaldehyde emissions

The glue used in construction timber products often contains formaldehyde. Formaldehydefree glues such as PMDI and PUR may be used but it can generally be assumed that the following construction timbers contain certain glues and adhesive elements [10]: • Glued laminated timber (glulam): approx. 1– 2% adhesive (MUF or PUR) • Plywood (layer-bonded solid wood): approx. 0.5 – 2% adhesive (MUF or PUR) • Cross laminated timber: approx. 1 % adhesive (MUF or PUR)

A 5.11

A longer curing time in shaping cross laminated timber elements for example, may require the use of glues containing formaldehyde. Detailed information on this must be obtained from the manufacturer.

The influence of wood-based materials on interior air The development of a range of different woodbased materials has allowed some of wood’s natural properties such as anisotropy (changes in wood’s properties depending on the direction of its fibre structure) to be homogenised, opening up a wider range of applications for wood-based materials. The wood from which the various wood-based materials are made is first reduced to small pieces by means of technical processes (sawing, bark stripping, machining or separation of wood fibres) before being bonded together by the addition of bonding agents (glues). The finish of wood in composite wood boards makes it possible to estimate the amount of adhesive they contain. This can vary greatly depending on the product and its purpose (Fig. A 5.8). VOC emissions

Reducing wood to small pieces increases its emitting surface, allowing more of the wood’s natural VOCs to be released (Fig. A 5.11), depending on the type of wood. Specific manufacturing processes such as heating and pressing may further influence these emissions: • Terpene emissions fall with increasing temperatures and longer processing times because they evaporate during processing. • Aldehydes are subject to other effects because they form later. Aldehyde emissions increase with temperature. More details on this effect can be obtained from manufacturers. Formaldehyde emissions

Formaldehyde emissions from wood-based materials may result from two main factors; additives such as glues containing formaldehyde (Fig. A 5.7), and additional formal-

33

Interior air quality – the influence of timber construction

A 5.12 Safe range for groups of sensitive people 0

Target level DGNB-BNB 500

Threshold level DGNB-BNB

1,000

3,000

Ordinary new buildings normal measurement range 1,000 – 3,000 mcg/m3

Secondary school 116 – 447 mcg/m3

a Safe range for groups of sensitive people 0

Target level DGNB-BNB Threshold level DGNB-BNB 40

60

83

120

Ordinary new buildings normal measurement range 50 – 120 mcg/m3

Secondary school 3

b

7.4 – 37 mcg/m

Four weeks after the secondary school in Diedorf was completed the air in some rooms was measured and formaldehyde and TVOC levels determined. The following levels were found, compared with current recommended levels: • TVOCs in interior air: Levels well below permitted levels were measured, at 3,000 μg/m3 TVOCs. 500 μg/m3 was the target level, 116 – 447 μg/m3 was the level achieved • Formaldehyde in interior air: Levels of formaldehyde were well below the permitted level of 120 μg/m3. 60 μg/m3 was the target level, 7.4 – 37 μg/m3 was the level achieved A 5.13 Building material

Relevant emissions

Strategies for good quality interior air

Naturally grown softwood (pine, spruce)

Terpenes ( pinene), higher aldehydes (Hexanal), typical smell of coniferous woods

Naturally grown hardwood (oak, beech, maple, ash, etc.)

Woody smell typical of the species

None required

Glued laminated timber, plywood, solid wood panels, cross laminated timber panels

Wood content: Terpenes ( pinene), higher aldehydes (Hexanal), typical smell of coniferous woods Possible formaldehyde emissions from the adhesive system

Wood content: None necessary Adhesive system: • None required with formaldehyde-free glued products • Obtain information from the manufacturer on adhesives containing formaldehyde

OSB panels

Wood content (usually high proportion of pine): Terpenes ( pinene), higher aldehydes (Hexanal), strong coniferous wood smell Possible formaldehyde emissions from the adhesive system

Chipboard, particle board

Wood content: Terpenes ( pinene), higher aldehydes (Hexanal), typical smell of coniferous woods Possible formaldehyde emissions from the adhesive system

Medium density fibreboard (MDF)

Wood content: Terpenes ( pinene) and higher aldehydes (Hexanal), also furfural, slight coniferous wood smell Possible formaldehyde emissions from the adhesive system

Plywood (birch)

Wood content (birch): Acetic acid (acetate), acetaldehyde, acetic acid smell Possible formaldehyde emissions from the adhesive system

Wood content: None required. Large-scale use may cause strong smells that are problematic for sensitive people. Adhesive system: • None required for formaldehyde-free glued products • Obtain information from the manufacturer on adhesives containing formaldehyde

A 5.14

34

dehyde that may form and be released due to thermal, hydrolytic and/or oxidative processes. Although many composite wood board manufacturers have switched to PUR-based glues since 2001, around 40 % of all formaldehyde produced worldwide is currently used in various adhesives and additives in the timber industry [11]. This building material additive can be avoided by using formaldehyde-free (PUR glue) construction components where possible. Information and certificates for components, including any expected emissions, should be obtained from the manufacturer at an early stage of planning. Installation situation and working with composite wood board

High formaldehyde concentrations in interior air may be produced by wood-based materials, such as the surfaces of structural components within the airtight layer or furniture and fittings in rooms. Commercially available composite wood board must be in at least emissions class E1 of formaldehyde concentrations in testing. This is a legally prescribed minimum standard that cannot be equated with the term “formaldehyde-free”. The use of E1-classified products does not guarantee that the recommended formaldehyde concentration levels in interiors of 0.08 ppm (= 0.1 mg/m3 = 100 μg/m3) set in Germany by AIR will be complied with in every interior because levels also depend on the size of a room, the amount of woodbased panel material built into it, the air exchange rate and the overall interior climate (moisture, temperature etc.). Coatings on composite wood board can serve as vapour barriers and greatly reduce formaldehyde emissions so coated boards are permitted to exceed the E1 level prior to coating. Open drill holes such as those for acoustic panels and edges that are not coated may increase emissions because they increase the emitting surface and there is a risk of internal layers of glue containing formaldehyde being exposed when the drill passes through multilayered sheeting.

Interior air quality – the influence of timber construction

Building materials with treated surfaces (coated, oiled, waxed and painted) may contain general solvents (TVOCs) as well as less easily volatilised substances such as phthalates or fire retardants that can also negatively impact interior climates and inside air quality. Details on such additives must be obtained from the manufacturer in the form of an emissions certificate to ensure that the vapours expected in a particular installation situation and the working of boards meet interior emissions targets.

Strategies for managing emissions Since no consistent emissions standards have been set, desired levels of emissions concentrations in interior air (e.g. UBA, DGNB, BNB, LEED etc.) and emission levels of building products (e.g. E1, E1plus, the AgBB scheme, Blauer Engel, natureplus.org, Ecolabel, Nordic swan, the EU Flower eco label etc.) should be set at the outset of planning and before construction measures begin. To ensure relatively low emission concentrations of VOCs and formaldehyde when choosing low-emission products, the following steps should be taken: • Information provided by building product manufacturers should be checked for hazardous substances and planning coordinated with regard to construction methods and layer structures etc. • Precise details on the desired quality must be defined in the tender. • Before work begins, individual qualities of building products should be reviewed by companies carrying out the construction using comprehensive documentation including permits, conformity documents, test certificates, environmental product declarations, etc. and released for use by planners. • Use of approved building products must be monitored on the building site and building products not listed as approved are prohibited. • Concluding measurements of ambient air (for TVOCs and formaldehyde) should confirm compliance with the target levels previ-

ously set (see the example of the Schmuttertal secondary school building, Fig. A 5.13). • Compliance with quality targets set for interior air can be ensured by a ventilation system is that is shown to function in the actual usage situation.

Conclusion It is impossible to precisely forecast air pollutant concentrations in a planned building due to the complexity of the issues involved. The new Schmuttertal secondary school building in Diedorf, in the construction of which the strategies described above were applied, has extremely low VOC and formaldehyde concentrations, even though the entire primary structure was built using visible glued laminated timber elements, the inside of the building envelope lined with OSB panels, and the entire interior made with visible three-ply sheeting. What was decisive here was a careful choice of all the components, right down to paints and adhesives. Interior air hygiene measurements made after the school was completed showed that emissions were lower than the BNB target figures and the levels recommended for sensitive groups of people as a precaution (Fig. A 5.13) [12]. Timber construction does not result in dangerous levels of interior air pollution as long as construction and the choice of components is carried out carefully, although a distinction must be made between emissions from wood as a natural product and those from additives resulting from technical processes. Further scientific investigations into wood’s positive effect on interior climates and their users are ongoing.

A 5.12

A 5.13

A 5.14

Notes: [1] Teischinger, Alfred: Interaktion Mensch und Holz. Vienna, 2012. Teischinger, Alfred: Mensch und Holz – Eine Wechselbeziehung an ausgewählten Beispielen. In Holzbautage, Innsbruck 2012. Conference transcript. Innsbruck 2012 [2] ibid. [3] Evaluation der Auswirkungen eines Zirbenholzumfeldes auf Kreislauf, Schlaf, Befinden und vegetative Regulation. Published by the Joanneum Research Forschungsgesellschaft mbH, Institut für Nichtinvasive Diagnostik. Weiz 2003 [4] Schule ohne Stress. Published by the Joanneum Research Forschungsgesellschaft mbH, Institut für Nichtinvasive Diagnostik. Weiz 2007 [5] HOMERA research project – Gesundheitliche Interaktion Holz – Mensch – Raum, TU Munich, 2016 – 2017 [6] Table of current individual recommended levels, RWI and RWII, UBA: http://www.umweltbundesamt. de/themen/gesundheit/kommissionen-arbeitsgruppen/ausschuss-fuer-innenraumrichtwerte-vormalsad-hoc, as of 11 August 2016 [7] Paulitsch, Michael; Barbu, Marius Catalin: Holzwerkstoffe der Moderne. Leinfelden-Echterdingen 2015 [8] Marutzky, Rainer: Aspekte der Wohngesundheit beim Bauen mit Holz- und Holzwerkstoffen. In: Bauen mit Holz, 07– 08/2010, p. 38ff. Mersch-Sundermann, Volker: Gesundheitliche Bedeutung von VOC in Innenräumen. Forum Holz/ Bau/Energie, Cologne, 2008 Salthammer, Tunga; Marutzky, Rainer: Bauen und Leben mit Holz. Informationsdienst Holz. Berlin, 2013 [9] Glued laminated timber (glulam) was invented in 1906 by Otto Hetzer [10] Source: Thünen Institute, Lignatec (Lignum) and Wecobis [11] Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und pflanzliche Baustoffe. 2nd ed., Wiesbaden, 2012 [12] Report on VOC and formaldehyde measurements carried out in the Schmuttertal secondary school in Diedorf in 2015

Class room, secondary school, Diedorf (DE) 2015, Architekten Hermann Kaufmann / Florian Nagler Architekten Sample measurements of interior air emissions, Diedorf secondary school a Comparison of TVOC levels measured in Diedorf secondary school with levels usually found in new buildings b Comparison of formaldehyde levels measured in Diedorf secondary school with levels usually found in new buildings Strategies for achieving good quality interior air

35

Part B

The support structure

1

Abb. B

Structures and support structures From linear member to plane Combining building elements Combining materials Structural planning in timber construction Timber construction compared with other construction methods Conclusion

38 39 41 41

2 Structural components and elements Dowel laminated timber walls Panel construction Cross laminated timber walls Laminated veneer lumber walls Beams Dowel laminated timber ceilings Beam ceilings Box ceilings Cross laminated timber ceilings Laminated veneer lumber ceilings Composite timber-concrete slabs A comparison of timber construction elements

50 51 52 54 55 56 57 58 60 62 63 64

44 44 48

66

Beech laminated veneer lumber support structure, office building in Augsburg (DE) 2015, lattkearchitekten

37

Structures and support structures Hermann Kaufmann, Wolfgang Huß, Stefan Krötsch, Stefan Winter

B 1.1

B 1.1 B 1.2 B 1.3

38

Illwerke Zentrum Montafon, Vandans (AT) 2013, Architekten Hermann Kaufmann From linear member to plane From linear member to plane: solid timber and lightweight structural elements

“The basic element of modern timber construction is therefore the plane and no longer the linear member” [1], declared Swiss architect Andrea Deplazes in 2000, stating that timber construction is developing into a “plate tectonics” system. Technical and structural innovations emerging around the turn of the millennium have in fact fundamentally changed timber construction. Some ground-breaking material developments have been achieved over this period and the conditions have been favourable for reviving familiar structures, leading to further developments and new applications. One of the most impressive revolutionary changes in timber construction has been the development and growing use of cross laminated timber and laminated veneer lumber. This material minimises the inhomogeneity and anisotropy (directional dependency) inherent in wood’s fibrous structure and allows high-performance, precisely calculable planar building materials to be made with dimensions that are limited only by manufacturing conditions. The use of less homogeneous wood-based materials can also produce similar results if individual parts are combined to form structural elements that make optimum use of wood’s properties. In box elements, for example, linear ribs and planar planking are combined to produce a structural effect that reduces the height of components and the cross section of the ribs, making it possible to better distribute loads and create form stability. Fibre-based materials such as OSB and other sheeting and panel materials were developed in the USA from the 1950s (see “Solid wood and wood-based products”, p. 18ff.). From the late 1980s, they were increasingly used in Europe and are now available as standardised products, making it possible to further develop panel construction as a largely prefabricated and technically reliable construction method. Dowel laminated timber structures have been in use since the 1930s. One crucial further development of this construction method is the replacement of the nailing together of individual laminations with hardwood dowels or aluminium

pin connections. Dowel laminated timber elements can be worked like solid wood in ways that are easier on tools. Bonded dowel laminated timber elements made of industrially manufactured glued laminated timber are now often used. The first patents for combined timber-concrete structures were registered in the period of scarcity between the two world wars in an effort to keep steel and concrete in slabs to a minimum, because they were very expensive building materials at the time. This material combination has now also been rediscovered and new applications found for it. In keeping with these technical achievements, the architectural and structural appearance of timber structures have also changed. Geometrical and hierarchical structures such as pincer structures or stacked layers of beams were superseded by planar structural components with linear elements positioned on a single level. These structures’ spatial compactness made joints between building elements much simpler, expanded their range of applications, made it possible to build energy-efficient building envelopes, and increased these structures’ economic competitiveness. One driver and, at the same time, consequence of this revolutionary change in timber construction has been the extensive prefabrication of large basic individual elements, both linear and planar. Timber’s relatively low weight and easy workability are ideal prerequisites for producing these elements. Wood’s versatility also has many advantages. It can be used simultaneously for insulation, as a support structure, to enclose spaces, as the surface of structural elements inside and out, and can be linear or planar. This opens up a wide range of options for industrial manufacture (see “Timber production”, p. 138ff. and “Prefabrication”, p. 142ff.) and digitalised process chains (see “Planning”, p. 130ff.), which are resulting in pioneering alternatives in terms of building quality and manufacturing processes. The new construction processes could turn out to be even more formative in the development of timber con-

Structures and support structures

Dowel laminated timber / log cabin

Panel construction

Cross laminated timber / laminated veneer lumber

Vertical structural elements

Column

Dowel laminated timber / plank slab

Ribbed slab / box slab

Cross laminated timber / laminated veneer lumber

Horizontal structural elements

Beams / joists

B 1.2

From linear member to plane

Solid timber elements

Contemporary timber construction draws on a wide range of different structural components and products. Figure B 1.2 shows a selection of examples of structural elements in daily use. On the one hand, elements are made of solid wood-based materials (glued laminated timber, laminated veneer lumber), on the other hand they consist of linear (dowel laminated timber, logs) or linear and planar materials (panel construction, coffered ceilings). These elements function structurally as a framework with a linear function or a woodbased material acting as a plane. The transi-

tion can be fluid and there may be progression from a linear member to a plane. It is not only the composition of components that is decisive, but their composite effect. While solid wood elements such as dowel laminated timber or log-cabin walls have a structural effect like a sequence of individual rods and so correspond with the linear properties of their individual parts, the combined framework and planking of panel and box elements produces planar structural components that can bear loads simultaneously as slab (ceiling) and /or plane (wall). Solid wood structures and elements consisting of linear members and planes can be arranged

Lightweight structural elements

From linear member to plane

struction than new materials and will not be limited to specific construction methods such as standardised timber panel construction or those using large-format solid wood structural components, but could also become part of ecologically optimised, adhesive-free construction methods (see community centre in St. Gerold, p. 232ff.). It would seem advisable to use more or less prefabricated structural elements rather than individual wood-based materials as the fundamental elements of timber construction. Elements can be further classified as horizontal or vertical, depending on the primary requirements they are to meet.

B 1.3

39

Vertical structural elements

Structures and support structures

Horizontal structural elements

Frame structure

Solid timber structure (dowel laminated timber)

Panel construction

Solid timber structure (cross laminated timber) B 1.4

40

Structures and support structures

B 1.5

in specific sequences depending on their structural characteristics (Fig. B 1.3). What is decisive for the way they function as a planar structural component is the composite effect of individual parts and not the solidity or homogeneity of the wood-based material.

Combining building elements Joining different building elements to form hybrid structures has now become almost normal practice. Various elements in an overall system are combined so that their different properties best meet the demands on the structural element (Fig. B 1.4). The more specific and comprehensive these demands are, the more laborious, complex and costly is the use of a consistent construction system for an entire structure. Systematically dividing timber construction into more general methods such as panel, frame and solid timber construction seems no longer reasonable in this context. By intelligently combining various building elements, customised solutions can be created in construction practice and give planners the greatest possible design freedom. One frequent combination is timber panel exterior walls and ceilings and load-bearing interior walls made of dowel laminated timber or glued laminated timber, making use of elements’ individual thermal insulation, soundproofing and fire safety advantages (see “Protective functions”, p. 72ff.). Planar structural components have always been combined to brace structures and to enclose spaces in frame structures. It has also long been common practice to augment structures made of planes and slabs at points with beams and columns to create openings and passages between spaces (Fig. B 1.4).

Combining materials Combining various materials in structural components, structures and construction methods is a similar strategy. The different properties of various materials can be combined to optimise an overall system (Fig. B 1.5). In timber construction, this allows planners to specifically compensate for the inherent disadvantages of some materials without fundamentally challenging the concept of timber construction altogether. Hybrid construction methods expand the range of applications available to timber and they will be greatly further developed in future. Hybrid (from Latin “hybrida”, meaning mix-

ture, intersection) structures have been the rule rather than the exception in construction history. Brick or stone plinths or ground floors have always been common in timber structures. Before concrete slabs became widespread in the 1960s, a combination of timber beam ceilings and masonry walls was standard in European cities. In multi-storey timber construction, access cores (as emergency exits and those used to brace buildings), firewalls or entire reinforced concrete base storeys are now often combined with timber structures and steel reinforced concrete frames or compartmentalised structures with a building envelope made of highly insulated timber

B 1.4

Combinations of various structural elements in timber construction B 1.5 Expanding possible combinations with other materials – here using the example of a composite timber-concrete slab (dowel laminated timber with a layer of concrete) B 1.6 Hybrid structural elements, hybrid construction method and hybrid building B 1.6

41

Structures and support structures

a

b

panel elements are increasingly being used. Materials can be combined at the level of the structure, the construction method and the structural component (Fig. B 1.5, p. 41).

inforced top layer of concrete (Fig. B 1.10). Composite timber concrete slabs are probably the best-known hybrid structural components. They are made of a layer of concrete under compressive stress on the top side that has a shear-resistant bond to a layer of timber or wood-based material under tensile stress on its underside, creating a high-performance, structurally effective section. Compared with solid wood structures, this combination of materials offers the following advantages: • Allows for the longest possible spans • Better vibration, deflection and sagging behaviour due to the structural component’s greater stiffness

Timber and concrete

Concrete has some properties that complement timber, such as large mass and incombustibility, so combining the two materials in multi-storey buildings would seem advantageous. In the c 13 building in Berlin (p. 170ff.) the staircases were made of concrete and poured on site. In the rest of the building, solid timber ceilings and walls were combined with steel beams, timber columns and a re-

B 1.7

B 1.8

42

• Improved fire safety due to the layer of concrete poured on site, which produces a continuous non-combustible layer that is largely smoke-proof • Enhanced soundproofing resulting from the increased mass of the structural components • Vertical subsidence is minimised due to indirect support (vertical transfer of wall loads through the concrete layer; Fig. B 1.7 a) • The top layer of concrete protects timber beneath it during construction (see “Illwerke Zentrum Montafon in Vandans”, p. 214ff.) and in case of interior leaks

B 1.9

Structures and support structures

Composite timber-concrete structures can be heavier than those made solely of timber if the structural component’s mass doesn’t have to be increased by adding extra weight for soundproofing reasons (Figs. B 1.7 and B 1.10). Combining access cores and a reinforced concrete ground floor with a timber structure above it with timber-concrete composite slabs (Fig. B 1.8) offers various advantages. Complementary ground floor uses such as shops or offices often require different floor plans and spans at that level. The timber structure is then also outside the range of splashing water and earth moisture, and level transitions between inside and out can be created while providing structural protection for the timber without complex detailing. This type of structure also enables planners to create emergency staircases leading outside and access routes for emergency services without having to add special separate fire safety measures. Reinforced concrete staircases and lift shafts are advisable in timber buildings for bracing and fire safety reasons although not essential, as demonstrated by the Kampa administration building in Aalen (p. 211ff.) and Via Cenni residential complex in the in Milan (p. 174ff.). However, combining different materials in vertical structural components may also cause problems. Concrete staircases, lift shafts or similar structural components must usually be

built at an early stage of construction and drying times and formwork processes can greatly extend construction times. The dimensional accuracies that concrete and timber buildings require and their subsidence also differs substantially, with the result that supporting slabs on a steel reinforced concrete shaft involves additional cost and effort. In contrast, it is relatively unproblematic to make a solid ground floor, often together with an underground garage or basement. In this case, the timber structure is built up from the ground floor ceiling independently and largely without dimensional constraints. In the Aalen administration building (p. 211ff.), for example, two cross

laminated timber cores house the staircases, lift shaft and supply shafts. Only the stairs were made using prefabricated concrete elements and installed by the carpenters. This made it possible to install them storey by storey with the precision that timber construction requires, but without the additional cost and effort. Timber and steel

Timber and steel are often combined when heavy loads must be distributed along a series of points (Fig. B 1.7 b). Steel elements serve as connecting elements in frame construction, steel beams can be integrated into box elements or other slab elements and steel

B 1.7

Various ways of transferring loads in slab supports that resist subsidence: a Joining a composite timber-concrete slab via concrete edge beams to load-bearing columns. This prevents compression on the transom in vertical load transfer in tall hybrid timber buildings. LifeCycle Tower One, Dornbirn (AT) 2012, Architekten Hermann Kaufmann b Primary beam joined to supports with steel brackets, e 3 residential building, Berlin (DE) 2008, Kaden Klingbeil Architekten B 1.8 Hybrid timber building with composite timberconcrete slabs B 1.9 Hybrid timber building with concrete ground floor and emergency staircase B 1.10 Combination of solid timber ceiling and wall elements with steel beams, timber supports and a layer of concrete, here not yet poured, c 13 residential and office building, Berlin (DE) 2013, Kaden Klingbeil Architekten B 1.10

43

Structures and support structures

a

b

cables can be used to pretension beams or in frame structures. Hybrid timber and steel structures have long been customary in timber construction engineering, especially those with support structures covering long spans. Roof ridge ties for three-hinged trusses are made of steel elements, as are the solid steel bearings of columns that bear heavy loads. Joints that result in large beam sections and timber lengths in wholly timber structures can be geometrically minimised with steel components. In many contemporary timber buildings, steel columns or beams have been combined with timber elements to allow for longer spans, flush beams and joists, and more slender support cross sections (Fig. B 1.10, p. 43; see also “c13 residential and office building in Berlin”, p. 170ff.). A steel frame is also sometimes combined with a timber secondary structure (see “Terraced houses in Munich”, p. 190ff.). Steel structural elements are also often used to transfer heavy loads in multi-storey timber buildings (Fig. B 1.11 h). When steel structural elements are integrated into timber, the surrounding timber takes on a fire safety function for them, so the steel no longer requires a fire protection coating to ensure sufficient fire resistance duration.

Slab effect

c

Structural planning in timber construction The task of structural planning is to transfer vertical loads such as the structure’s own weight, snow and live loads, and horizontal loads such as wind loads, earthquakes or those resulting from imperfections (misalignments) into the ground in a way that uses resources as efficiently as possible and to develop structural systems that transfer these loads as directly as possible with appropriate cross sections and materials. The more the design takes structural planning requirements into account from the outset, e.g. the basic rules of bracing [2], the more efficient and effective the timber building will be, compared with buildings built using other construction methods. Planning timber support structures is often said to be very complicated compared with using other building materials. Considered more closely, however, we find that this (biased) opinion is due to planners’ lack of experience with timber construction and a lack of routine. A more exact comparison of the main building materials reveals many factors in common and various options for combining different systems with timber construction.

In-plane effect

d

B 1.11

Timber construction compared with other construction methods Masonry construction is generally seen as a monolithic construction method that is especially easy to calculate. This is in fact only the case if simplification rules are applied and sufficient cross-bracing walls are available, as is the case with detached residential buildings, because masonry absorbs mainly in-plane loads. In contrast, slender masonry columns require intensive calculation. Masonry frame structures can only be built in combination with steel or steel reinforced concrete. Fire safety verification for masonry structures can be usually relatively easily drawn up using tables. Steel construction partly resembles timber construction because of its very linear member-based construction method and its joints (screws, welding or adhesives). For slab loads (slabs), as in masonry construction, it uses mainly concrete or composite structural elements or trapezoidal plates and more rarely girder grid structures. The frequently thin individual structural components of support structure elements mean than bending and buckling must be accounted for, which

Combined loading as slab and plane B 1.12

44

Structures and support structures

e

f

requires a considerable calculation effort. Fire safety verification can also involve comprehensive calculations and supplementary verifications, such as the application of coatings or cladding, which are usually required because steel loses its strength from about 400°C. Steel reinforced concrete construction, like timber construction, is very versatile, and can be used to build linear structures and planar structural components such as slabs or planes (Fig. B 1.12) [3]. The whole system from linear member to plane described above (Figs. B 1.2 and B 1.3, p. 39) can also be applied to steel reinforced concrete construction. Another common feature of working with steel reinforced concrete and timber is that their anisotropic properties must be considered, i.e. the different, anisotropic load-bearing capacity resulting from tension resistance depending on the direction of the timber’s fibres and on the direction of the reinforcement in concrete, and properties emerging over time or due to moisture such as creep and shrinkage. With the exception of unreinforced solid concrete or solid timber structural components, both materials are usually used as composite materials. In steel reinforced construction, timber construction and in masonry and steel construction, the material’s properties can be adapted to a wide range of requirements (e.g. heavy and lightweight concrete, combined glued laminated timber). Crucial differences lie in the joining of structural components. Continuous reinforcement and the option of subsequently pouring a layer of concrete results in often relatively simple, homogeneous connections in steel reinforced concrete construction, between walls and ceilings, for example. In contrast, decoupling structural components requires a range of special solutions such as Tronsole sound impact protection in staircases or special parts to create connections to balcony slabs that keep thermal bridges to a minimum. The length of the relevant standards indicates the complexity of their design. The number of pages of standards dedicated to designs at normal temperatures and for fire safety in buildings (Parts 1-1 and 1-2 of the relevant

g

h

B 1.11

Eurocodes) are 347 pages for steel reinforced concrete, 195 pages for steel, 215 pages for timber and 201 pages for masonry, excluding the national appendices. In summary, if a material is to be used in a design in a way that makes use of resource, energy and cost efficiency, planners must intensively investigate the material. Some unique features of building with timber – information on construction

The following fundamental principles must be applied when building with timber: • Verification of vibration levels and of deflection is usually crucial to the design of slabs. The first natural frequency of slabs should be above 6 – 8 Hz to avoid unpleasant vibrations. To calculate the first natural frequency, the cross section’s stiffness is entered in the numerator, while the denominator contains the linear mass and the squared span. Mass with no flexural stiffness (e.g. infill to improve soundproofing) therefore reduces natural frequency. The chapter on “Structural components and elements” (p. 50ff.) describes and compares typical span ranges of various timber slab structures. • Wood is a very anisotropic material. It has high tensile and compressive strength and stiffness along its fibres relative to its weight. Its compressive strength and stiffness perpendicular to the grain is, however, comparatively low and it has almost no tensile strength perpendicular to the grain. • This low perp-to-grain compressive strength and stiffness means that vertical loads must not be transferred via joists and frames subject to compression perpendicular to the grain as far as possible, especially in multi-storey buildings, because this can cause major displacement. Loads imposed on timber perpendicular to grain must be bridged with steel parts or avoided entirely by directly transferring loads through end grain connections parallel to the timber’s fibres. This imposes a natural limit on timber panel construction with vertical load-bearing wall elements. Their use is usually unproblematic in buildings up to three storeys high, but for taller buildings a specific composition

B 1.11

Supports for various wall and ceiling elements that prevent compression on transoms and subsidence: a Timber supports with steel pins support a box element slab, housing complex in Dornbirn (AT) 1997, Architekten Hermann Kaufmann and Christian Lenz b Panel wall with stud uprights inserted through the plane and slab connected at the side c Panel wall with continuous stud uprights and slab set into a slot, housing complex in Zurich (CH) 2016, Rolf Mühlethaler d Holes through cross laminated timber slabs are filled with grouting to transfer loads without subsidence, H 8 residential and office building in Bad Aibling (DE) 2011, Schankula Architekten e Lateral slab connection in a continuous wall structure f Indirect support with composite timberconcrete slabs g Concrete edge beams for a composite timber-concrete joist ceiling; LifeCycle Tower One in Dornbirn (AT) 2012, Architekten Hermann Kaufmann h Steel element as support and connecting piece between supports and slabs, student residence in Vancouver (CA) 2017, Acton Ostry Architects B 1.12 Loading of vertical and horizontal structural elements as planes, as slabs, and combined loading

45

Structures and support structures

Cross-bracing against tension resistance

Timber panel

Supports rigid in tension and compression

Cross laminated timber

Stiffness

Low

Steel-reinforced concrete Very high B 1.13

of panel elements is required for load-bearing purposes (Figs. B 1.11 b and c, p. 45; see also “Zollfreilager housing complex in Zurich”, p. 206ff.). Alternatively, it may be advisable to combine solid timber structural elements (dowel laminated timber, cross laminated timber) with a frame structure. • Timber’s low tensile strength perpendicular to its grain has given rise to the construction rule of not transferring loads into timber structural components from below, but from above, using additional structures or reinforcement if necessary. To prevent cracking, it is also necessary to prevent transverse forces resulting from shrinkage (e.g. with large steel components).

Floor plan version 1

Bracing buildings

A range of bracing elements are available for timber construction that have different rigidities, so these must be calculated differently. The different rigidities of elements must be taken into account when transferring horizontal loads in timber structures. For low buildings (defined in building regulations as height of the floor of the uppermost storey less than 7 metres high, usually a three-storey building, see Fig. C 1.2, p. 73), timber framing elements have proven their worth as bracing elements. They are braced with mechanically connected wood-based or gypsum plasterboard panelling. The connections (staples, nails, screws) provide only a low shear stiffness, the number is determined

by the forces that must be transferred and stiffness required. Forces are distributed depending on the length of walls subject to loading. For framework constructions in contrast, bracing elements such as steel tie rods or bracing struts that concentrate forces only around themselves are used. Cross laminated timber or steel reinforced concrete walls are used mainly to brace higher buildings (height of the floor of the uppermost storey more than 7 metres), where loads are distributed depending on the in-plane bending stiffness of walls and stiffness is much higher (Fig. B 1.13). Steel reinforced concrete structural components, usually access cores, can

Floor plan version 2

B 1.13

Floor plan version 3

Stiffness and horizontal load-bearing capacity of bracing elements in hybrid timber construction. It should be noted that horizontal loads also always give rise to additional vertical loads. B 1.14 Various floor plans with bracing walls in different positions for a ten-storey building with external stairs; Kaden + Lager B 1.15 Various bracing elements: a Cross laminated timber plates brace and form the support structure of the Via Cenni housing complex, Milan (IT) 2013, Rossiprodi Associati b Steel tie members to brace a frame structure. e 3 residential and office building, Berlin (DE) 2008, Kaden Klingbeil Architekten c Steel reinforced concrete cores connected to a timber structure. Student residence in Vancouver (CA) 2017, Acton Ostry Architects

Floor plan version 4 B 1.14

46

Structures and support structures

also be used for bracing. Contrary to conventional wisdom, even where concrete cores are installed, additional bracing elements are often required to absorb horizontal forces in exterior walls or suitable interior walls, because not all wind and earthquake loads can be absorbed by cores, especially eccentrically positioned ones. Two cross laminated timber cores and some perpendicular to the grain cross laminated timber interior walls and gable walls brace the seven-storey Kampa administration building in Aalen (p. 211ff.). Figure B 1.8 (p. 42) shows another reasonable arrangement of load-bearing and space-forming elements. As well as the steel reinforced concrete core planned here, interior cross laminated timber walls partly brace the structure, the support structure opens up on the outside and devolves into a frame structure, with the columns and cross laminated timber walls bearing vertical loads. The exterior wall elements themselves are not load-bearing, i.e. they support only their own weight and wind loads on each storey. This makes it easier to subsequently replace them if an upgrade is required to improve energy use, or if there is an extension added or an architectural redesign, for example. Generally speaking, the further outside horizontal bracing elements are placed, the lower the forces will be that they must support. If a core and external wall planes are combined for bracing, calculations that take different stiffness into account using suitable framework or finite-element programs are required. In timber frame construction, it can be helpful to simply position a tie or brace to concentrate load-bearing at appropriate points because it can often save a large number of anchors and complicated load transfers. The fundamental rule is that in timber construction, more than with other construction methods, the strictest possible design discipline must be adhered to when designing load-bearing vertical structural components and positioning bracing elements, especially because of the lower flexural stiffness of timber structural components in distributing loads laterally. Where concrete construction with

its thick concrete slabs can conceal a great deal in a strong extra layer of reinforcement or reinforcement elements, timber construction will require solid wood beams or joists or hybrid solutions (Fig. B 1.10, p. 43). Direct transfer of vertical loads is always structurally clearer and less expensive and need not always necessarily negatively impact design variability, as demonstrated by Fig. B 1.14, which shows various floor plans for a ten-storey building. The number of storeys in timber structures all over the world is growing. As buildings rise higher and climatic conditions change, wind loads are also increasing. Greater earthquake loads, even in central Europe, generally greater vertical loads, and at the same time higher fire safety requirements require more intensive structural planning, which should ideally be coordinated in the first design phases with everyone involved. To absorb the increasing horizontal loads resulting from the growing height of timber buildings, systems very similar to those used in reinforced concrete and steel construction can be used, such as tube-in-tube systems (building support structures consisting of two concentric layers of load-bearing or bracing walls), exterior frames and all kinds of hybrid systems. Compared with reinforced concrete and steel construction, it must however be noted that rigid frame corners are very difficult if not impossible to construct in timber construction and have low stiffness. A completely open facade without surfaces for bracing elements is not feasible using this construction method.

a

b

Pretensioned structures

Timber structural components such as beams, supports, walls or slabs can be combined with inlaid steel cables to form pretensioned structures which could allow for longer spans and reduce deflection in beams. At the level of individual structural components, examples of this technique have emerged since the 1990s, among them the pretensioned primary beams of the Swiss Re Centre for Global Dialogue restaurant by Meili Peter Architekten and c

B 1.15

47

Structures and support structures

IPE 270

Beech laminated veneer lumber

Beech glued laminated timber

Spruce laminated veneer lumber

Spruce glued laminated timber

h = 270 mm b = 135 mm m = 36.1 kg/m

h = 270 mm b = 160 mm m = 29.4 kg/m

h = 440 mm b = 160 mm m = 48.8 kg/m

h = 360 mm b = 160 mm m = 29.4 kg/m

h = 460 mm b= 160 mm m= 31.3 kg/m

Assumptions: Steel S235: m=1.00 fy/x=235 N/mm2 Beech and spruce laminated veneer lumber: Performance class 1 k mod= 0.9 m=1.20 (EN 1995-1-1) Beech and spruce glued laminated timber: Performance class 1 k mod= 0.9 m=1.25 (EN 1995-1-1)

structural engineer Jürg Conzett (Fig. B 1.20). Pioneering applications involving entire pretensioned structural components have been used by Andy Buchanan in New Zealand [4] and in the House of Natural Resources at ETH Zurich [5] (Fig. B 1.17). Since 2016, various research projects all over the world have been further developing this technology. Pretensioning beams together or columns and beams could make timber structures possible that have hitherto not been reasonable or feasible, such as grids (Fig. B 1.19) or very slender frame structures. Joints between components could be much simpler in these structures because the timber structural components often only need to transfer compressive forces, while tension resistance is transferred into the tension cables and can pass through unhindered. Support structures built according to the construction principles of historic East Asian timber structures, with geometrically complex, inner friction activating connections, could, in combination with pretensioning per-

B 1.16

pendicular to the grain, offer new solutions for earthquake-resistant structures. As pretensioned structures, solid timber plane cores could be much more effectively used to brace buildings. Hardwoods

Hardwoods such as beech, oak and ash are much stronger than softwoods so the use of hardwoods to transfer vertical loads could open up completely new dimensions in timber construction. Further processing (hardwood glued laminated timber or laminated veneer lumber) can increase these materials’ strengths (Fig. B 1.16), but better connections will have to be developed. The increasing availability of hardwoods is also opening up new options in the production of beams, although the modulus of elasticity, the stiffness of these (bending) structural elements, does not increase to the same extent as their strength. Beech laminated veneer lumber can be used to create cross sections comparable with

those in steel construction, for multi-storey car park construction for example (Fig. B 1.18) [6]. These applications can also be used in general construction. Hardwood glued laminated timber and laminated veneer lumber can be used to build more slender cross sections that can bear the same or greater loads as thicker elements. If the use of hardwood products is planned, as with many innovative products, planners must first check that they are available and have the relevant official certificate of usability.

Conclusion In many areas, timber construction is now a high-quality alternative to conventional construction and has unique ecological advantages. Not only is timber construction catching up with construction methods used by mineral materials in some areas, but it is also opening up new opportunities, especially in areas B 1.16

Comparison of the cross sections of various glued laminated timber and laminated veneer lumber beams made of beech and spruce with an IPE 270 steel beam B 1.17 Grid building support structure made of glued laminated timber beams with steel cables glued into the beams, which tension the entire support structure to form an overall system, House of Natural Resources, ETH Zurich (CH) 2015, Meyer.Moser.Lanz.Architekten B 1.18 Prototype design of a multi-storey car park with beech laminated veneer lumber columns and beams. TUM.wood research project group from the Technical University of Munich (DE) 2015 a Axonometry of the support structure b Interior B 1.19 Grid platform projecting on all sides with timber framework and concrete node pieces, tensioned with steel cables. Cross section through the main beam and top view of the grid structure. Design for a training and education centre in Risch (CH), Peter Zumthor / Joseph Schwartz B 1.20 Pretensioned beam, restaurant, Swiss Re Centre for Global Dialogue, Rüschlikon (CH) 2000, Meili Peter Architekten, Jürg Conzett (structural engineer) a Visible overhang b Concept sketch by Jürg Conzett for a pretensioned overhanging beam to solve the problem of deformation under snow loads, with loads transferred into a column-free glass facade. B 1.17

48

Structures and support structures

a

b

that will dominate construction in the future, such as the efficient use of energy and resources and the improving of quality and construction processes by means of prefabrication. If good use can be made of wood’s unique features as a material in design and structural engineering, and hybrid solutions resorted to where necessary, building with timber can offer almost limitless possibilities. Combining different structures makes it possible to implement effective and competitive solutions for all timber construction applications.

[3] Slab: planar element bearing loads perpendicular to its plane; plane: planar element bearing loads in its plane; this loading is often combined in wall, ceiling and roof elements [4] Newcombe, M.; Pampanin, S.; Buchanan, A. H.: Governing criteria for the lateral force design of posttensioned timber buildings. WCTE 2012 Proceedings, Final Papers, Auckland 2012, p. 148ff. [5] Wanninger, Flavio; Franghi, Andrea: Experimental and analytical analysis of a post-tensioned timber frame under horizontal loads. Engineering Structures, Vol. 113, Kidlington 2016, p. 16 – 25 [6] Development of a construction system for multi-storey car parks using beech laminated veneer lumber. Concluding report of a research and development study (abstract), (Entwicklung eines Bausystems für Parkhäuser in Buchenfurnierschichtholz. Abschlussbericht Forschungs und Entwicklungsauftrag – Kurzfassung), April 2015. TUM.wood: Department of Architecture and Timber Construction (Fachgebiet Holzbau) at TU Munich with the Chair of Architectural Design and Construction (Lehrstuhl für Entwurfsmethodik und Gebäudelehre), Chair of Timber Structures and Building Construction (Lehrstuhl für Holzbau und Baukonstruktion) and the Chair of Wood Science and Department of Wood Technologies (Lehrstuhl für Holzwissenschaft und Fachgebiet Holztechnologie).

Notes: [1] Deplazes, Andrea: Holz indifferent, synthetisch. In: DETAIL 1/2000, p. 23 [2] Fundamental rules of bracing: at least one ceiling plane joined with three wall planes whose axes do not intersect at one point, or four wall planes whose axes intersect at at least two points.

B 1.18

B 1.19

Glued laminated timber beam with major deflection and deformation due to snow load

Timber's creep behaviour prevents the use of a preformed beam tensioned with tension cables in the facade plane.

a

Pre-tensioning with steel cables glued into the beam makes it possible to pre-tension the beam while retaining its shape, so the beam can be tensioned with cables in the facade plane and does not deform under snow loads. B 1.20 b

49

Structural components and elements Stefan Krötsch, Wolfgang Huß

Contemporary timber construction can no longer be accurately represented in terms applicable to more general construction methods (see “From linear member to plane” p. 39ff. and “Combining building elements” p. 41). The building process now customary in timber construction means that current notions of modern timber structures are based around prefabricated wall, ceiling and roof structural elements so the following description of indi-

vidual structural elements and components is limited to those most often used in multi-storey timber construction. Elements are discussed in the context of their different demands on the support structure as vertical (walls) and horizontal (ceilings and roofs) elements and not ordered by material properties depending on individual situations, which makes it easier to compare the various structural elements (see “A comparison of timber construction elements”, p. 66ff.).

B 2.1

50

Structural components and elements

Dowel laminated timber walls

B 2.3

B 2.2

Dowel laminated timber structures were initially developed as slab elements. They consist of low-cost, inferior quality boards that are joined to make high-quality, load-bearing solid wood structural components. Continuous connections between several boards compensate for their specific inhomogeneities. Materials Dowel laminated timber walls consist of solid wood planks, usually softwood, 20 to 60 mm thick, joined together. Storey-high wall elements are usually manufactured in widths that can be easily handled for assembly on site. Boards can run through the entire element, be fingerjointed or have staggered joints. The thickness of the elements is limited only by the maximum board widths and is usually up to 240 mm, or less commonly up to 280 mm. Originally, individual boards were nailed together, but nails (usually steel) can greatly disrupt subsequent working. If, however, boards are joined with hardwood dowels (usually beechwood), the resulting elements can be worked and recycled like solid wood. Subjecting hardwood dowels to extreme drying causes them to swell up subsequently, so they can be used to create stable, completely adhesivefree connections. Diagonal dowelling makes the form of elements more stable. More recently, boards have increasingly been glued in a manufacturing process like that used to make glued laminated timber. Dowel laminated timber walls swell and shrink mainly laterally and along the wall with the grain of the board fibres, while in the direction of the wall height they retain their form very well. Surfaces Boards can be planed, rough sawn, sharpedged or chamfered, depending on the relevant design requirements. They may also have various profiles to optimise their airtightness, sound proofing, acoustic properties and cable ducting (especially electronics and computer cables). Structural functions Dowel laminated timber walls, even slender ones, can absorb very heavy vertical loads

because loads are imposed only in the direction of the wood’s grain. Stacking the boards prevents them from buckling in the direction of their weaker cross-sectional axes. Bonding boards together ensures a homogeneous planar distribution of forces and minimises individual weak points. Dowel laminated timber walls are relatively pliant when subjected to horizontal loads along and transverse to the wall unless additional measures are taken to brace them. Wooden composite boards (e.g. OSB or three-ply panels) attached to one side can brace walls subject to horizontal loads applied in the direction of the wall. Boards can also be joined to a plate with a friction-locked bond to absorb loads applied transverse to the direction of the wall.

Nailing

Dowelling with wooden dowels

Gluing B 2.4

B 2.5

Openings Small openings (e.g. through walls for installations) can be made in dowel laminated timber walls without trimmer joists. It may be necessary to add horizontal elements like lintel beams or parapet transoms for larger openings such as those required for windows or doors.

B 2.6

B 2.1

Prefabricating timber wall panels shortly before installing the windows B 2.2 Prefabricated dowel laminated timber wall with OSB planking B 2.3 Dowel laminated timber wall element made of individual boards B 2.4 Various ways of joining planks: nailing, dowelling with wooden dowels, gluing B 2.5 Profiling of planks to interlock them and improve airtightness and soundproofing B 2.6 Increasing plate rigidity by adding bracing planking B 2.7 Improving slab efficiency by joining the board layers to the bottom and/or top plate B 2.7

51

Structural components and elements

Panel construction

B 2.8

Panel construction is a further development of frame construction, which in turn developed out of half-timbered frame construction and is still widespread in North America. Today’s panel construction elements are largely prefabricated, complex wall elements with various, coordinated building component layers and are made using a minimum of materials. A panel construction wall is now the structural element most frequently used in vertical timber construction in Europe. Their main advantage in exterior wall structures is that a single component layer can cost-effectively combine load-bearing functions with thermal insulation to save space. Materials Storey-high prefabricated timber elements usually consist of a support structure made up of linear elements, the stud frame, and bracing planking on one or both sides. Depending on requirements and the degree of prefabrication, further building component layers and infills may be added. A stud frame is usually made of solid construction timber, although using glued laminated timber can enable the structure to bear greater loads and have thicker walls (stud cross section > 240 mm). In contrast, Å-beams and ladder beams can help to reduce thermal transmittance. A slab’s structural (bracing) and physical properties and position (exterior or interior) are crucial aspects in choosing planking material. OSB boards are often used as interior bracing planking because they are inexpensive, relatively airtight and impede diffusion. Laminated materials such as three-ply board or laminated veneer lumber are more suitable for more stringent structural requirements. A gluefree alternative is to use formwork with planks, and diagonally positioned boards can be used to brace structures.

guided by computers can efficiently make joints entirely of wood. Workers using pneumatic tools can usually quickly attach planking to a stud frame with brackets, clamps or nails. Screws and sometimes screws combined with adhesives can be used to join frames subject to greater forces. Structural functions Vertical loads are distributed from lintels to studs, which transfer them to top plates. Crosspieces (top and bottom plates) are the weak points in vertical load bearing, which is why very few buildings more than five storeys high have been built with load-bearing, conventional panel construction walls, because they would require special measures such as continuous studs or hardwood top and bottom plates. The thickness of the stud cross sections transverse to the wall makes them stable enough to resist buckling, while the bond with the planking prevents buckling along the wall. Where load concentrations are higher, thicker studs are used or in some cases steel sections are integrated into the elements. Planking is also sometimes used to bear planar, vertical loads. Horizontal forces transverse to the wall direction subject the planking to bending forces and are transferred to the studs with cross

Construction grids Stud frames are usually based on a grid adapted to the dimensions of commercially available sheeting and panel materials (625 or 833 mm as divisors of 2,500 mm). These measurements do not necessarily determine the dimensions of the walls or sizes of openings, however, because stud frames and planking can be fairly easily adapted to fit in with edge areas and trimmers (lintels and window rails). Openings Narrow openings are most simply made with trimmers in the stud frame. The load-bearing capacity of planking (on one or both sides) will be sufficient for wide openings with lintels at the appropriate height, while a change of materials can accommodate longer spans (e.g. laminated veneer lumber to OSB). If the lintel height is too low, the lintel can be reinforced or made thicker or out of another material (glued laminated timber, a steel section).

Reinforced studs a

Joints The composite effect of a stud frame and planking lightens loads on joints in the stud frame, making them easy to build. They are often screwed together with simple butt joints. Carpenters’ joints such as dovetails are however also now often used and milling robots

Planking on both sides

a

Steel Load-bearing planking b

52

sections thick enough to absorb them adequately. Here the stud spacing and the thickness of planking are mutually interdependent. The planking transfers horizontal forces along the wall into the supports, while the stud frame prevents the planking from buckling.

B 2.9

b

B 2.10

Structural components and elements

Top plate Studs

Planking

Top / bottom plate

Horizontal load transfer along the wall

Horizontal load transfer transverse to the wall

Vertical load transfer B 2.11 B 2.8 B 2.9

B 2.10

B 2.11 B 2.12 B 2.13 B 2.14 B 2.15

B 2.12

Prefabrication of a wall panel Planking for meeting special structural requirements a diaphragm beam with planking made of suitable material on both sides joined appropriately b load-bearing planking made of a suitable material with studs to brace against buckling Reinforcement of panel construction walls subject to heavy load concentrations by integrating glued laminated timber (a) or steel (b) supports to bear loads at various points or form a frame structure Diagram of a panel construction wall Vertical and horizontal load transfer in a panel construction wall Various upright elements for a support structure Joints in a stud frame (between studs and top / bottom plate) Various ways of creating openings in a panel construction wall a panel construction wall with no opening and undisrupted vertical load transfer in the stud frame b panel construction wall with a small opening: gap in the stud frame to accommodate a lintel, window rail and extra studs c – f panel construction wall with wide opening, various means of making a load-bearing lintel: reinforced planking in the lintel (c), reinforced lintel (d), reinforcement with extra supports (made of steel, e), lintel outside the element, e.g. in the parapet area of the element above it (f)

Solid timber

Solid construction lumber

Glued laminated timber (glulam)

Å-beam

Ladder beam B 2.13

Screw joint

CNC-milled joint

Frictional connection between a stud frame and planking B 2.14

Panel construction wall with no opening a

Additional supports

Reinforced planking c

Reinforced studs

e

Lintel Reinforced lintel

Window rail

Lintel outside the element

Reinforced studs

b

d

f

B 2.15

53

Structural components and elements

Cross laminated timber walls

B 2.16

B 2.17

B 2.18

B 2.19 Opening cut out

Opening as a gap between elements

Materials Cross laminated timber elements usually consist of layers of boards arranged crosswise and glued together to form a large panel. This configuration greatly reduces the wood’s swelling and shrinking, which occurs mainly in the direction of the wood’s grain, so these elements have very good dimensional stability. The number of board layers (usually between three and eleven) and thickness of individual boards determines the thicknesses of elements (usually 60 – 400 mm). There is always an uneven number of boards to prevent the material from deforming due to asymmetrical strains. Cross laminated timber is usually made of spruce, pine or fir wood, although other woods such as oak or birch (e.g. for harder or decorative top layers) can also be used. Boards in the top layers can be glued together (flank adhesion) to make airtight, smoke-proof elements, which increases structural components’ fire resistance duration. In one special form of cross laminated timber, hardwood dowels join the boards, which is a glue-free, ecologically-friendly alternative. Cross laminated timber elements can also be made with curved surfaces with appropriately complex hollow moulds. Manufacture and assembly Cross laminated timber can theoretically be any size but in practice its size is limited by the manufacturing process and transport issues. Cross laminated timber walls are delivered to building sites in appropriate sizes, usually storey-high. Once there they can be quickly

Opening created by inserting a lintel and rail B 2.20

54

In 1998, the introduction of various cross laminated timber products approved for use by building inspection authorities in Germany and Austria marked a turning point in modern timber construction. Boards of various qualities are glued to planar, high-performance structural walls and ceiling elements to minimise the timber’s inherent anisotropic properties and inhomogeneities. This planar, solid material makes it easy to join building components and enables timber structures to meet modern demands, even in regions with no tradition of or experience in building them.

joined by simple means (e.g. diagonal screw connections) and assembled to form a complete shell. Their rigidity, surface qualities and good workability means that cross laminated timber elements are often used to prefabricate complex structural components or whole room cubicles. Openings Elements are usually cut to fit and openings are made in them during manufacture. Window and door openings are cut out of the homogeneous sheet, without requiring additional measures such as trimmers, as long as the opening is far enough from the sheet edge. Cutting into this high-grade material (for windows or gables for example) can result in considerable waste, which can be reduced through appropriate element sizes and cutting. Structural functions Vertical loads in cross laminated timber walls are optimally borne by vertical layers of boards, so a wall with vertical boards in the top layer will be stronger than a wall in which these boards are horizontal. Their planar homogeneous cross section and strength means that cross laminated timber walls can easily absorb horizontal loads in the direction of the wall, so they are suitable for bracing multi-storey buildings. Cross laminated timber walls can also be installed as beams (e.g. parapet or diaphragm beams) to accommodate long spans in the storey below.

B 2.16 B 2.17 B 2.18

B 2.19 B 2.20

Cross laminated timber wall installation on a building site Structure of a cross laminated timber wall made of crosswise layers of boards Vertical loads are transferred mainly in the vertical layers of the boards (left). If the top layers are horizontal (right) the wall cross section will have to be greater to bear the same loads. Cross laminated timber element as diaphragm beam Various means of making openings

Structural components and elements

Laminated veneer lumber walls

B 2.22

Laminated veneer lumber has long been used in construction, as planking in stud frame walls for example. Since the 1990s, thicker laminated veneer lumber panels made of softwood veneers have also been used as independent load-bearing structural elements. Materials Laminated veneer lumber is made of layers of rotary-cut veneers around 3 mm thick that are glued together. In contrast to veneer plywood, the fibre direction of the layers is parallel in laminated veneer lumber, with some layers laid at 90° angles (cross bands or strands) to reduce the wood’s anisotropic properties. The laminated veneer lumber typically used for beams does not usually have cross bands. The combination of many thin layers balances out any inhomogeneities in the wood, creating a reliable building material. Laminated veneer lumber is usually made of softwood, although since 2013 beech laminated veneer lumber, which is very strong, has been approved for use by building inspection authorities. Beech, which swells and shrinks significantly due to the way it grows, was once difficult to use in construction. Making it more homogeneous in the form of laminated veneer lumber makes it possible to cost-effectively use Europe’s most common type of deciduous wood as a load-bearing building material. Beech can be very efficiently used in this way. Crooked and bent logs unsuitable for squared timber or planks are sawn into straight pieces

about 2 metres long, radially peeled and processed into veneers. Laminated veneer lumber can also be used to produce curved surfaces with appropriately complex hollow moulds. Its many glued layers mean that laminated veneer lumber contains a much higher proportion of glue than does glued laminated or cross laminated timber. Manufacture, assembly and openings Like cross laminated timber, laminated veneer lumber panels are limited in their dimensions only by the manufacturing process and transport, although most manufacturers usually make panels 2.50 metres wide. Cutting, creating openings, assembling and joining elements made of this material is similar to working with cross laminated timber (see p. 54). Structural functions Vertical loads are optimally transferred in laminated veneer lumber walls that have fibres mainly in a vertical direction, which enables these walls to bear very heavy loads. Laminated veneer lumber walls are also very good at absorbing horizontal loads in the direction of the wall (to brace buildings) due to their planar, homogeneous structure and are also very effective beams, especially if the fibres in the layers are horizontal (parallel strand board). Laminated veneer lumber’s very good structural properties mean that it is now used to reinforce other timber structures in areas around bearings, joints etc. Laminated veneer lumber functions as a rigid plate and is well suited for bracing buildings B 2.22 Laminated veneer lumber wall, Kronenraumforschungsturm (research tower at Kaiserslautern Technical University) near Trippstadt (DE) 2011, Kirchspitz Architekten B 2.23 Making beechwood into laminated veneer lumber: Beech tree trunks are sawn into 2-metrelong straight sections, milled into a cylindrical form and peeled to form veneers B 2.24 Structure with layers of veneers with parallel fibres B 2.25 Laminated veneer lumber with no cross layers (left): All the fibres in the veneer layers are parallel. Laminated veneer lumber with cross layers (right): The fibres of some (e.g. every fifth) layers are rotated 90° to the other layers. B 2.26 Laminated veneer lumber beam with horizontal and vertical layers

B 2.23

B 2.24

B 2.21

B 2.21

B 2.25

B 2.26

55

Structural components and elements

Beams a

b

c

B 2.27

Beams are linear supports for slabs and roof elements and transfer loads to supports. They are installed as individual elements or as part of a system in a hierarchically structured frame structure, as downstand or upstand beams or joists, or flush with a slab. Because they are subject to structural bending loads, beams are almost always installed with upright, sometimes very slender cross sections that vary depending on construction type and size. Beams can also be integrated into other horizontal structural components such as beam or suspended ceilings. Materials Beams can be made of solid timber or solid construction lumber, but this does limit the dimensions of their cross sections. High-performance wood-based materials such as glued laminated timber or laminated veneer lumber can be used for greater loads and thicker cross sections or where less structural height is available. High-performance materials such as multilayer sheeting can be combined with beams to make box beams or girders or used in beams with a range of different geometries. Beam geometry The upper part of a single-span beam exposed to bending strain is subject to compressive forces and the lower part of the beam to tensile forces, as long as the two parts are rigidly connected. Many different beam geometries make

use of the fact that load-bearing capacity increases exponentially with the distance between the upper and lower areas of a structurally effective cross section. Glued laminated timber beams are built with upper and lower flanges made of high-strength boards or hardwood planks, while inferior quality softwood is used for the middle layers. Å-beams are made of thin wood-based material webs with solid timber upper and lower flanges that absorb tensile and compressive forces and brace the thinner web against buckling. Box beams follow the same principle, but their geometry helps them to better resist lateral buckling. Here the upper and lower surface layers take on the function of upper and lower flanges. Box beams and Å-beams can be glued or glued and screwed together. A trussed beam’s web is reduced to a minimum of material necessary to form a rigid, shear-resistant connection between its upper and lower flanges. Its members are subject mainly to normal forces, with only the upper flange also subject to bending loads. A trussed beam makes use of the fact that the lower flange is only subjected to tensile forces. The lower flange can be a steel cable kept at a distance from the upper flange with compression struts. The transfer of forces into connection points usually determines the dimensions and choice of profile in these types of beams made up of individual members.

d

a

B 2.28

b

c

d

e

f

B 2.29

B 2.27 B 2.28

B 2.29

B 2.30

B 2.30

56

Installing a beam on a building site Beams made of various materials: solid timber (a), solid construction lumber (b), glued laminated timber (c), laminated veneer lumber (d) Various beam geometries: beam with a solid cross section (a), box beam (b), Å-beam (c), truss beam (d), beam with inverted truss (e), prestressed beam (f) Various methods for joining beams and slab elements to supports in multi-storey buildings: Heavy loads are transferred from upper into lower supports without putting pressure on crosspieces.

Structural components and elements

Dowel laminated timber ceilings

B 2.31

Dowel laminated timber ceilings are a further development of historic structures made using layers of logs with individual elements systematically friction-bonded. Research carried out by Julius Natterer in the 1970s helped dowel laminated timber ceilings to become more widespread, as part of efforts to use inexpensive, inferior quality boards to make high-quality, load-bearing solid timber structural components. Materials, manufacture and assembly A dowel laminated timber ceiling is similar to a dowel laminated timber wall in terms of its materials, manufacture and assembly (see p. 51). Surfaces Boards can be planed, rough sawn, sharp edged or bevelled to meet different design requirements. Various profiles can also be added to optimise airtightness, soundproofing, acoustic properties, cable routing (especially electronics and computer cabling) and to form rigid, shear-resistant connections in composite timber-concrete elements and similar components. Structural functions and openings All the wood fibres in an optimum dowel laminated timber ceiling slab should be parallel with its span direction. Boards are upright and therefore very structurally efficient. These elements have the lowest structural height of all timber ceiling structures but always need a

Nailing

Gluing

Hardwood dowel – straight

Hardwood dowel – diagonal B 2.33

linear support. Ideally it should be assumed that every board is load-bearing, i.e. passes through from support to support. Continuously connecting several boards ensures that adjoining boards are coactivated when elements are subjected to loading at various points, balancing out inhomogeneities or weak points in individual boards. Dowel laminated timber ceiling slabs do not usually have the rigidity required to function as plates and brace a building, so they are nailed or screwed to suitable wood-based material panels (e.g. OSB boards), which provide the necessary rigidity and are also airtight. Smaller openings can be made in ceiling slabs (e.g. smaller pipe and cable ducts) by screwing the ends of boards to adjoining boards (e.g. stairs), while trimmer joists are used for larger openings.

B 2.31 Prefabricated dowel laminated timber element B 2.32 Structure of a dowel laminated timber element made of individual boards B 2.33 Various joining options B 2.34 Various types of dowel laminated timber: made of boards (a), made of squared timber (b), made of offset boards, e.g. for timber-concrete slabs (c), profiling to interlock boards to improve airtightness and fire safety (d, e), profiling to form cavities (f), acoustic profiling (g), special form of dowel laminated timber slab consisting of box beams (h) B 2.35 Structural functioning as slab and plate

a

b

c

d

e

f

g

h

B 2.32

Absorption of distributed load and its transfer to linear supports

Point loads distributed across several boards

Low level of rigidity of a slab exposed to loading

Planking with bracing effect B 2.34

B 2.35

57

Structural components and elements

Beam ceilings

Beam ceilings consist of beams covering the primary span and panels or boards extending from beam to beam to form a ceiling. This principle applies to ceiling structures with a wide range of beam spacings. Slender joists close together (approx. 25 – 50 cm apart) create a structured underside with a flat, twodimensional appearance. The classic beam ceiling (approx. 60 – 90 cm apart) has been widespread for centuries and due to its versatility, simplicity and cost-effectiveness still plays a major role in construction today. Beam spacing is the result of the spans of the slab formwork usually used (e.g. wooden formwork, OSB board, three-ply panels) and may be 20 to 30 mm. Spacing can be expanded indefinitely if the formwork is built with a load-bearing material (three-ply panelling, cross laminated timber, laminated veneer lumber) and thicker layers. Materials and structural functions A classic beam ceiling can be built using solid wood products and without adhesives. Beam ceilings with spans of 4 to 5 metres are particularly cost-effective. Glued cross sections are necessary for ceiling beams covering long spans and large loaded areas or where very stable forms are required. If loads are very heavy in some areas due to trimmers or other special conditions, trusses, laminated veneer lumber or steel beams can be used for these areas. Suitable wood-based material sheeting can also be screwed to ceiling beams to form a rigid ceiling plate. The thickness of the boards, span direction and type and spacing of fastening elements in timber formwork must be coordinated to meet these requirements. As with panel construction wall elements (see “Panel construction”, p. 52f.), transverse formwork can also be used.

the trimmer into the beams flanking the opening. The following measures can be taken to retain the structural height of the ceiling: • Making all ceiling beams the same size: Oversized ceiling beams that are not subject to the additional loads will be an outcome that will have to be accepted in visible ceiling structures. • Widening the affected ceiling beams: Where load concentrations are moderate, heavily loaded beams can be made wider and thereby strengthened. • Change of material: Ceiling beams subject to greater loads can be built using a stronger material, resulting in an even structural height. Manufacture and assembly Beam ceilings are either prefabricated as elements or assembled on site using individual linear members and planking. On-site assembly can be a useful alternative in situations in which lifting large elements into place would be costly and complex or impossible (e.g. on sites during renovations).

Openings While openings following the direction of the span have little impact on the load-bearing structure of beam ceilings, installing trimmers for openings against the direction of the span fundamentally changes load distribution in a ceiling slab. Loads from discontinuous ceiling panels are transferred at specific points along B 2.36

58

B 2.37

Structural components and elements

a

b

c Planking with no bracing effect

Planking with bracing effect B 2.38 d

e

f

Opening well positioned

Opening awkwardly positioned B 2.39

B 2.40

Oversized beam

B 2.36 B 2.37 Glulam Beam size for bearing calculated loading

Solid timber Solid construction lumber

B 2.38 B 2.39

B 2.40

Glulam Wider beam to absorb heavier loads

Beam size for bearing calculated loading

Steel B 2.41

Various types of structures with different axial spacings of primary joists Prefabricated beam ceiling shortly before installation on the building site Deflection of a beam ceiling under slab stress with and without bracing planking Openings in the direction of the beams can usually be made without special measures (left). Openings across the beams require trimmers and are usually complex (right). Various planking materials: Plank, diagonal and tongue-and-groove formwork, OSB board, three-ply panel, laminated veneer lumber panel a Plank formwork b Diagonal formwork c Tongue-and-groove formwork d OSB board e Three-ply sheeting f Laminated veneer lumber panel Various trimmers for openings across beams

B 2.41

59

Structural components and elements

Box ceilings

B 2.42

Top planking

Ribs Edge beams Bottom planking

Box ceilings, sometimes also called hollow box ceilings, are a further development of the beam ceiling towards more prefabricated, lighter ceiling slabs and ribs combined with planking to create a very high-performance planar support structure. They enable the ceiling slab’s thickness to be minimised. Wood’s anisotropic and inhomogeneous properties are not counteracted by the production of a homogeneous material, but by the composition of a composite element that takes advantage of the characteristics of its individual parts. Box ceilings are complex and costly to manufacture and are installed mainly to cover medium and long spans.

B 2.43 Three-ply panel Laminated veneer lumber panel

OSB board

Materials, manufacture and assembly Box ceilings elements consist of slender ribs in the direction of the ceiling slab’s main span, which together with edge beams form a frame and structurally are effectively joined to the top and bottom planking. This produces a composite element made up of individual constituents – a box. The ribs and edge beams are usually made of solid construction timber or glued laminated timber, more rarely of laminated veneer lumber. Depending on the support situation, additional cross beams can be built into a box element. Steel beams are often used in box ceilings to increase load-bearing capac-

ity or to connect ceiling slabs to supports. A box element’s planking is essential to its load-bearing capacity. This may be load-bearing sheeting such as three-ply, laminated veneer or OSB boards. The sheeting material must have the highest possible dimensional stability. Cavities between the ribs may be filled with insulation or infill, depending on requirements. Elements 2 to 3.50 metres wide and 5 to 20 metres long are usual due to the exigencies of transport, although in theory the element length, and with it the span, has no upper limits. Connections Once the load transfer is designed for the composite effect of a stud frame and planking, the connections within the stud frame play a subordinate role. They can be screwed together or joined with carpenters’ joints. Planking is usually glued or glued under pressure and screwed to the stud frame in a controlled process requiring specific approval. Structural functions and openings The composite effect of ribs and planking creates a H-shaped load-bearing cross section (grey area in Fig. B 2.47). The statically effective height (h) is increased by the thickness of both planks. Planking braces the ribs against buckling and

B 2.44

Screwed joint

CNC-milled tongue and groove joint B 2.45

60

Gluing under pressure with screws

Gluing B 2.46

Structural components and elements

B 2.42 B 2.43 B 2.44 B 2.45 B 2.46 B 2.47 B 2.48

tilting so they can be very slender (b/h < 1/4). The axial spacing of ribs is usually relatively narrow (40 – 70 cm). Box ceilings can transfer loads as planar structural elements and rest on a linear support or be supported at various points. The main load-bearing direction is in the direction of the ribs. The combined effect of the stud frame and planking allows bending moment to be transferred across gaps between the ribs (e.g. cross beams) while force components are transferred into the planking as tensile and compressive forces. This makes possible an even stud frame supported at various points, with cantilevers and a continuous beam effect in the main and ancillary loadbearing directions. As in beam ceilings, openings in box ceilings (see “Beam ceilings”, p. 58f.) are created by trimmers, with the combined effect of the stud frame and planking reducing additional loading on individual ribs.

Attaching top planking during production of a box slab element Structure of a box slab Planking materials for box slabs Joints in a framework Joints between a framework and planking made by gluing under pressure and screwing or gluing The combined effect of ribs and planking creates an H-shaped beam cross section. Various support situations of box slab elements and positioning of ribs, edge beams and trimmers, which together with the planking form a composite element a Linear support: the ribs lie squarely on supports.

b Support at various points: An edge beam transports loads from the ribs into the supports. c Linear support, cantilever at one end: The ribs lie squarely on supports and together with the planking secure the cantilever. d Support at various points, cantilever at one end: The ribs are joined to a trimmer, the cantilever makes use of tensile and compressive forces in the upper and lower planking. e Support at various points, cantilever at both ends: In the main span direction, the cantilever is supported like a cantilever at one end, in the ancillary span direction it is supported by the trimmers.

Linear support a

Support at various points b

c

d

Support at various points, cantilever at one end

e

Support at various points, cantilever at both ends

h

‡ Å-beam cross section h structurally effective section height B 2.47

Linear support, cantilever at one end

B 2.48

61

Structural components and elements

Cross laminated timber ceilings

B 2.49

Cross laminated timber elements are used without material-specific differences for slabs and walls (see “Cross laminated timber walls”, p. 54). Manufacture, assembly and openings The dimensions of cross laminated timber are theoretically unlimited but, in practice, sizes are limited by the manufacturing process and transport. Cross laminated timber ceiling slabs up to 4 metres wide and 22 metres long can be relatively quickly assembled on a building site with simple fasteners (e.g. diagonal screw connections). Depending on a ceiling slab’s rigidity, airtightness and fire safety requirements, cross laminated timber elements can be joined with a butt joint, overlapped, with a top joint or with a tongue-and-groove joint. Elements are usually cut to size and openings cut out during manufacture. Structural functions Cross laminated timber elements function structurally as relatively homogeneous slabs. Their spans depend on the slab’s thickness and support situation. Cross laminated timber elements have a main and ancillary load-bearing direction depending on the positioning and number of their layers of boards. An element’s main load-bearing direction is parallel to the top layers because layers of boards in the span direction determine its structural performance. A linear support that transfers loads evenly is optimal for cross laminated timber elements, although loads can also be supported at specific points (see “Student residence in Vancouver”, p. 166ff.). Elements can overhang on two sides in proportion to their load-bearing capacity in the main and ancillary load-bearing directions and be installed to have a continuous beam effect. Moving the supports from the corners towards the centre of a panel makes it easier to distribute loads in the element. Cross laminated timber elements can form rigid plates and if the ceiling slabs are appropriately joined can very effectively brace buildings.

h

B 2.50

Butt joint between elements

Linear support, span direction in the ancillary loadbearing direction

Linear support, cantilever at one end

Elements joined with an overlapping joint

Support at various points

Elements joined with a woodbased material board on the top

Support at various points, cantilever at both ends

Elements joined with a tongueand-groove joint

Effective plate function in the slab plane

B 2.51

62

h

Linear support, span direction in the main loadbearing direction

B 2.52

Structural components and elements

Laminated veneer lumber ceilings

B 2.53

Laminated veneer lumber (LVL) has been used since the 1990s without material-specific differences to make ceiling and wall elements. Initially made exclusively of softwoods, building inspection authorities have more recently approved the use of beech laminated veneer lumber.

Span direction in the main loadbearing direction, linear support

h

Span direction in the ancillary loadbearing direction, linear support

h

Materials, manufacture and assembly In terms of their materials, manufacturing and assembly, LVL ceiling slabs are no different from laminated veneer lumber walls (see p. 55). Structural functions Laminated veneer lumber ceilings function structurally as homogeneous slabs with a clear main span direction in the direction of the layers’ fibres, so linear supports are necessary. Laminated veneer lumber panels with crossed layers, however, also accommodate an ancillary load-bearing direction and can be supported at various points. The spans of these elements will vary depending on the panel’s thickness and the support situation. Laminated veneer lumber elements are rigid plates that can very effectively brace buildings as long as the slab elements are appropriately joined.

Linear support, cantilever at one end B 2.54

Support at various points B 2.49 B 2.50 B 2.51

B 2.52

B 2.53 B 2.54

B 2.55

B 2.56

Installation of a cross laminated timber element Structure of a cross laminated timber slab: crossed uneven number of boards Means of joining elements in cross laminated timber slabs: The two middle joints create rigid plates. Structural function, depending on the direction of top layers, support situation and imposition of horizontal loading Laminated veneer lumber ceiling, Grüne Universität pavilion, Stuttgart (DE) 1993, Peter Cheret Structure of a laminated veneer lumber slab element with parallel veneer fibres in the slab’s span direction Laminated veneer lumber – no crossed layers (above): The fibres in all the veneer layers lie parallel. Laminated veneer lumber with crossed layers (below): Some (e.g. every fifth) board layers are rotated at 90° to the other layers. Span direction and support situations

Support at various points, cantilever at both ends

Effective plate function in the slab plane B 2.55

B 2.56

63

Structural components and elements

Composite timber-concrete slabs

B 2.57

Concrete top layer

Timber slab

B 2.58

Beam ceiling with a concrete top layer

Dowel laminated timber slab with a concrete top layer

Dowel laminated timber slab with staggered boards and a concrete top layer

Composite timber-concrete slabs were developed in the 1920s to reduce the amounts of concrete and steel used in slabs. After World War II, this technique was used mainly to reinforce and repair old timber beam ceilings. Since the 1990s, it has once again become increasingly used in new buildings, with these slabs now the most frequently used hybrid components in timber construction. When compared with a solely timber structure, they can improve structural performance, sound proofing and fire safety characteristics while their extra mass reduces unwelcome vibrations. They are especially suitable for building medium to long spans. Structural functions A concrete compressive zone and timber tensile zone must have a rigid, shear-resistant connection in order to achieve a composite load-bearing effect. Composite timber-concrete ceiling slabs can be optimally used as single-span beams or girders, are only partly effective as continuous beams and are not suitable for larger cantilevers, because the course of the torque then reverses in the area of the supports. The concrete layer’s homogeneity and rigidity mean that horizontal forces are readily transferred into the ceiling plate. Materials, manufacture and assembly The tensile zone is generally a beam, dowel laminated timber, cross laminated timber or

laminated veneer lumber slab. A 6 –12 cm thick layer of concrete is usually poured onto the timber slab on site with secondary reinforcement added to prevent cracking. Prefabricated concrete elements or composite timber-concrete slab elements are also used. Only the element joints of these have to be poured on site, allowing for a largely prefabricated, dry construction process. Openings Openings in timber-concrete composite slabs depend mainly on the properties of the timber structure used in the tensile zone. Above the concrete layer, trimmers and reinforcements can be formed with additional reinforcement. Connections The following types of connections are usually used with timber-concrete composite slabs: • Where dovetail joints are used (cuts in a timber slab, usually transverse to the direction of shear forces), a positive bond forms between the concrete and the timber (Fig. B 2.61). Screws are also required to absorb lifting forces resulting from the eccentric connection. • Bonded metal inserts do not greatly reduce the timber layer’s load-bearing capacity. Continuous beams can be installed subject to approval from building inspection authorities.

Cross laminated timber slab with a concrete top layer

1 Compressive zone 2 Tensile zone 3 Rigid, shear-resistant connection

Laminated veneer lumber slab with a concrete top layer

3

2 B 2.59

64

1

B 2.60

Structural components and elements

• Flat steel ties are often used in dowel laminated timber structures, with steel flats driven into saw grooves that are around 4 % narrower at an angle of 5° to the vertical. Using this system, single-span bending beams with a maximum span of 10 metres have been approved for use by building inspection authorities. • Various pin or dowel-type fastener systems are approved for use by building inspection authorities. The upper sections of specially developed fully threaded screws are profiled to optimise the connection with the concrete. • Screwing prefabricated concrete elements to a timber support structure on site allows for a largely prefabricated, dry construction process. The materials can also be separated when the building is dismantled. • Initial promising investigations into soluble adhesive joints are currently ongoing.

B 2.57

B 2.58 B 2.59 B 2.60 B 2.61

Installation of prefabricated composite timberconcrete elements with a cross laminated timber tensile zone Structure of a composite timber-concrete slab Possible types of timber structures Structural function of a composite timberconcrete slab Common types of shear-resistant joints in composite timber-concrete slabs

Bird's mouth joints and screws

Flat steel elements set in sawn grooves

Upright special screws

Expanded metal plates glued in

Diagonally crossing pairs of screws

Prefabricated concrete component with pipe couplings inserted for screwing onto the beam layer on site B 2.61

65

Structural components and elements

A comparison of timber construction elements

The following figures, B 2.62– B.2.65, compare the structural components described above (p. 51– 65) based on the following parameters. Load-bearing capacity Ordinary panel construction walls are not usually suitable for buildings more than three storeys high unless they are specially built for this purpose (Figs. B 1.11 b and c, p. 44). In contrast, cross laminated timber, laminated veneer lumber and dowel laminated timber walls can bear very heavy vertical loads, so they are suitable for building very tall buildings. Plate function The plate function of panel construction and dowel-joined dowel laminated timber walls is minor compared to that of relatively homogeneous cross laminated timber and laminated

Panel construction element

Spans Beam ceilings are rare in multi-storey timber buildings and tend to cover fairly short spans. Cross laminated timber

Laminated veneer lumber

Panel construction element

Dowel laminated timber, glued

Cross laminated timber, dowelled Dowel laminated timber, dowelled Panel construction element with diagonal planking

Plate function

Dowel laminated timber, glued

Cross laminated timber

Panel construction element with OSB planking

Dowel laminated timber

high

Load-bearing capacity

low

0%

Additives Adhesives are the main additives in wood-based materials and structural components and elements. Dowel laminated timber and cross laminated timber walls and dowel laminated timber slabs may however be made without adhesives if their layers are joined with hardwood dowels. The same applies to panel construction walls and beam ceilings with planking in the form of diagonal – and thereby bracing – plank formwork instead of wood-based material panels (three-ply sheeting, OSB board, etc.).

Panel construction element with continuous studs

low

Dowel laminated timber, dowelled

veneer lumber walls, which are strong enough to brace taller buildings.

Cross laminated timber

Laminated veneer lumber

high

Laminated veneer lumber

Additives (adhesives)

3% B 2.62

66

Structural components and elements

Cross laminated timber slab, uniaxial

Beam ceiling

Cross laminated timber slab, biaxial Dowel laminated timber

Beam ceiling

0%

Softwood laminated veneer lumber

Dowel laminated timber

Beam ceiling

Softwood laminated veneer lumber

CO2 storage

Beam ceiling with OSB planking Dowel laminated timber, glued Cross laminated timber

Cross laminated timber

0.22 m3/m2

Material required

low

Dowel laminated timber, dowelled Beam ceiling with plank formwork

10 m

Beech laminated veneer lumber Dowel laminated timber

0.08 m3/m2

Box slab

Composite cross laminated timber-concrete slab, biaxial Composite timber-concrete Dowel laminated timber slab, biaxial

Spans

5m

Box slab

Box slab Composite timberconcrete beam ceiling

Cross laminated timber

Beech laminated veneer lumber

high

Laminated veneer lumber

Box slab

Additives (glue ratios)

3% B 2.63

67

Structural components and elements

Supports

a

a Composite timber-concrete slab with laminated veneer lumber (LVL) b Composite timber-concrete with cross laminated timber c Composite timber-concrete slab with beam ceiling d Composite timber-concrete and dowel laminated timber slab

e f g h i j

Laminated veneer lumber slab Cross laminated timber slab Box slab Dowel laminated timber slab Beam ceiling Composite timber-concrete slab with LVL and crossed layers k LVL with crossed layers

b

Material requirements Light slab structures such as box and beam ceilings are far more efficient than solid timber slabs made of dowel laminated timber elements, cross laminated timber or laminated veneer lumber in terms of the material required for the same span, so they can potentially be substituted for the heavier elements.

c

d

e

e

f

f

g

g

e

h

h

f

i

i

g

Linear support, single span

CO2 storage The greater volume of material comprising solid timber slabs means that they store more CO2 than light slab structures. Using hardwoods amplifies this effect, as shown by beech laminated veneer lumber.

Linear support Cantilever in two directions

Linear support Cantilever in the span direction of a linear support

j

b

k

k

k

f

f

f

g

g

g

Support at various points, single span

68

As, in most applications, it is not the load-bearing capacity but the vibration and sag and deflection behaviour which are the essential factors determining the dimensions of structural components, cross laminated timber and dowel laminated timber slabs are suitable for average spans, while composite timber-concrete and hollow box slabs are appropriate for long spans.

Support at various points Cantilever in span direction

Linear supports Linear supports are ideal for all slab elements. Composite timber-concrete slabs are often used only as single-span beams because the course of the torque in cantilever and continuous beams reverses in the area around supports, so in that area the layer of concrete would be subjected to tensile forces and the timber structure subject to compressive forces. In contrast, a cantilever or continuous beam effect transverse to a linear support is easily achieved with all timber slab elements. In multi-storey timber buildings, this is now being dispensed with to create acoustic separation and undisrupted load transfer from upper storeys. Cantilevers in two directions (primary and secondary loadbearing directions) only allow for planar crosslaminated timber slabs or laminated veneer lumber elements or box ceilings into which appropriate cross ribs are integrated. Support at various points Only elements that span in two directions such as those made of cross laminated timber, laminated veneer lumber with crossed layers, hollow box slabs and composite timber-concrete slabs combined with cross laminated timber or laminated veneer lumber can be effectively supported at various points. As with a linear support situation, a cantilever and continuous beam effect in the primary and secondary load-bearing directions can be achieved with cross laminated timber, laminated veneer lumber and appropriately designed box slabs, but only to a very limited extent with composite timber-concrete slabs.

Support at various points Cantilever in two directions B 2.64

A comparison of various slab structures Figure B 2.65 compares the structural heights of different slab elements for a residential building with spans of 4, 5 and 6 metres. Each slab structure meets similar fire safety and sound proofing requirements.

Structural components and elements

Ceiling structure

Composition

Span [m]

Support structure thickness [mm] (beam cross section)

Total slab thickness [mm]

Beam ceiling

Floor covering 20 mm Cement or anhydride screed, 80 mm, separating layer Mineral fibre footfall sound insulation, 30 mm Wood-based material sheeting 25 mm Solid construction timber beams C24 or glued laminated timber Gl24 h/c 120 / 240 –320 mm (axial spacing 625 mm) Mineral fibre insulation between beams, 100 mm Rubber-mounted universal bracket, 20 mm Battens, 30 mm Fire-resistant gypsum plasterboard / fibreboard 2≈ 18 mm

4

240 (120/240)

481

5

280 (140/280)

521

6

320 (120/320)

561

Floor covering 20 mm Cement or anhydride screed, 50 mm, separating layer Mineral fibre footfall sound insulation, 30 mm Three-ply sheeting 27 mm Glued laminated timber ribs, Gl28 h/c 80 /140 – 220 mm (axial spacing 625 mm) Mineral fibre insulation between ribs, 140 –160 mm Three-ply sheeting 27 mm Support structure for elastic mounting of fire-resistant cladding 20 mm Fire-resistant gypsum plasterboard / fibreboard 2≈ 18 mm

4

194 (80/140, 27, 27)

350

5

234 (80/180, 27, 27)

390

6

274 (80/220, 27, 27)

430

Floor covering 20 mm Cement or anhydride screed, 50 mm, separating layer Mineral fibre footfall sound insulation, 30 mm Crushed stone infill, 80 mm Dowel laminated timber, C24 120 – 200 mm

4

120

300

5

160

340

6

180

380

4

140

320

5

180

360

6

220

400

Floor covering 20 mm Cement or anhydride screed 50 mm, separating layer Mineral fibre footfall sound insulation, 30 mm Additional mineral fibre insulation, 40 mm Concrete top layer, 100 mm Dowel laminated timber, C24 120 –160 mm

4

220

360

5

240

380

6

260

400

Floor covering 20 mm Cement or anhydride screed 50 mm, separating layer Mineral fibre footfall sound insulation, 30 mm Additional mineral fibre insulation, 40 mm Steel-reinforced concrete, 200 – 260 mm

4

200

340

5

200

340

6

260

400

Box ceiling

Dowel laminated timber ceiling

Cross laminated timber ceiling

Composite timber-concrete ceiling

Steel-reinforced concrete ceiling

Floor covering 20 mm Cement or anhydride screed, 50 mm, separating layer Mineral fibre footfall sound insulation, 30 mm Crushed stone infill, 80 mm Cross laminated timber, C24 140 – 220 mm

B 2.65

Usage:

Ceiling slabs in residential buildings qk = 1.5 kN/m2 with lateral distribution or qk = 2.0 without lateral distribution Soundproofing: As defined in DIN 4109-1 and -2: R'W ≥ 54 dB, L'n, w ≤ 50 dB To take flanking transmission into account Rw ∫ R'W and Ln, w ∫ L'n, w are subject to a correction value of -3 dB or +5 dB Fire safety class: F 60, F 60 – K260 for beam and box ceilings

B 2.62 B 2.63 B 2.64 B 2.65

A comparison of wall elements A comparison of slab elements A comparison of support situations A comparison of structural heights of slab structures

69

Part C

1

Construction

Protective functions Fire protection Protecting timber from moisture Soundproofing and acoustic requirements Timber preservation Thermal insulation in winter and summer

72 72 79

2

Thermal insulation in summer The RIOPT study The influence of structural type Solar radiation and shade Air exchange and natural cooling

88 88 88 90 90

3

The layer structure of building envelopes Requirements for building envelopes Functions of layers of structural components Technical soundproofing aspects Technical aspects of fire safety Further criteria in choosing exterior wall structures Further criteria in positioning layers in horizontal and sloping structural components in building envelopes Polyfunctional layers Jointing principles

4 The layer structure of interior structural components The layer structure of timber slabs The layer structure of interior walls Principles of joining interior structural components 5

Fig. C

Building technology – some special features of timber construction Planning Prefabrication options The influence of apertures, openings and recesses on the support structure General building physics principles for the integration of building technology Measures for damp rooms Conclusion

82 83 85

92 92 92 100 101 102

103 106 106

114 115 118 120

122 122 122 122 123 126 127

14-storey residential building, Bergen (NO) 2015, ARTEC

71

Protective functions Stefan Winter

C 1.1

Like other buildings, a timber building’s structure must provide load-bearing capacity but must also perform other functions including fire, moisture and noise protection, wood preservation and ensuring thermal insulation in winter and summer without reducing specified performance levels. The relevant protection goals and their implementation in timber construction are described below.

Fire protection Preventative fire safety plays an essential role in the design, planning, technical drawing, construction, quality assurance and operation of multi-storey buildings of all kinds all over the world, whatever the predominant construction material chosen. Unlike steel-reinforced concrete, masonry and steel, wood is a combustible construction material, so it can add to a building’s fire load in case of fire. The material’s combustibility and memories of some devastating fires in cities in the Middle Ages and during wars have given rise to continuing bias against the fire safety of modern timber buildings. This bias is not based in fact, as an investigation of various typical issues below will show. The risk of fire starting in timber buildings

The risk of fire starting in a building is not inherently linked to its construction material. Studies carried out in the 1990s showed a direct correlation between the risk of fire starting in residential buildings and population distribution in buildings built using specific construction methods [1]. The same is probably true of office buildings. The risk of fire starting in a building results not from a building’s construction material, but from technical installations and, more significantly, from human error. Imploding old tube televisions, a saucepan of milk forgotten on a stove or improper electrical installation, as well as forgotten Christmas tree candles and people falling asleep while smoking are typically the main sources of fire risk. A timber structure does not pose an inherent fire risk.

72

Fire safety requirements

Fire safety requirements are roughly the same the world over and include • preventing fire from starting and fire and smoke from spreading, • enabling the rescue of people and animals, and • facilitating effective rescue and fire extinguishing. These requirements must be met by all buildings equally and, in doing so, a range of parameters must be considered, such as • the size of utilisation units that can be separated for fire safety purposes • fire load(s) • escape and emergency exits, depending on usage • the building’s structural situation such as accessibility, distance to adjoining buildings etc. • exterior facade design • equipment designed to prevent fire such as alarm or sprinkler systems These requirements can be further specified for some areas. Exterior facades, for example, should prevent fire and smoke from spreading through the facade and large elements should not fall off in flames during a fire. Most countries continuously develop prescriptive (detailed stipulations) structural and technical-equipment fire prevention rules based on the requirements outlined above and list them in building regulations. One example of these are the fire-resistance requirements imposed on load-bearing and bracing structural components, depending on a building’s height and dimensions, because these greatly influence firefighters’ ability to extinguish fire and rescue people. They also form the basis for the fireresistance requirements imposed on buildings in specific building classes, which in Germany are stipulated in the current valid German Model Building Code (Musterbauordnung – MBO) [2] (Fig. C 1.2). The MBO permits detached houses (class 1 buildings) to be built without a specific fireresistance duration because all building mater-

Protective functions

Building class

Number of storeys approx.

Height of the top storey floor above specific average ground level

>8

> 22 m

High-rise

Description

High-rise building

8 7

5

≤ 22 m Building of medium height

6 5

4

≤ 13 m

4 3

1 to 3

2

≤7m

Low-rise building

1 C 1.2 Building regulatory authority designation

ials must be of “normal combustibilty” as a minimum requirement. Class 2 buildings (terraced houses /semidetached houses) must fulfil a fire-resistance requirement of 30 minutes. A fire resistance of 30 minutes is sufficient for class 3 buildings (low multi-storey buildings regardless of use) because it is assumed that the building’s limited height will mean that users can be rescued promptly. The height limit of a storey floor to 7 metres above the average ground level is based on the ladders available to firefighters, which can be easily used on buildings up to a parapet height of around 8 metres. A ladder is no longer an adequate second emergency escape route in a taller building. Here firefighters must resort to turntable ladders or elevating rescue platforms if there is no fixed second emergency escape route, e.g. an access balcony with two staircases. Without alternative structural emergency escape routes, only a small number of people will be able to be rescued quickly and it will take firefighters much longer to do it, so class 4 (height of the uppermost floor ≤ 13 metres) and class 5 (height of the uppermost floor ≤ 22 metres) buildings require longer fireresistance durations of 60 and 90 minutes because fires are harder to extinguish in taller buildings. A further requirement is imposed on taller buildings (high-rise buildings with the top floor more than 22 metres above ground). Firefighters may simply be unable to effectively extinguish fires above these heights, so these buildings should be able to withstand being completely burnt out without their support structure collapsing. The German Model Building Code (Musterbauordnung) prescribes a fire resistance of at least 90 minutes and the use of non-combustible construction materials for high-rise buildings so that their structural elements will maintain their load-bearing

C 1.1 C 1.2 C 1.3 C 1.4

Ageing shingle facade Building classes as defined in the MBO (2012) Building materials classes Structural components classes

Non-combustible building materials

Additional requirements

European class as defined in EN 13 501 Construction products, apart from pipe thermal insulation and floor coverings

Pipe thermal insulation

‡

A1

A 1L

A 1fl

‡

A 2-s1,d0

A 2L-s1,d0

A 2fl-s1,d0

‡

B-s1,d0 C-s1,d0

BL-s1,d0 CL-s1,d0

A 2-s2,d0 A 2-s3,d0 B-s2,d0 B-s3,d0 C-s2,d0 C-s3,d0

A 2L-s2,d0 A 2L-s3,d0 BL-s2,d0 BL-s3,d0 CL-s2,d0 CL-s3,d0

A 2-s1,d1 A 2-s1,d2 B-s1,d1 B-s1,d2 C-s1,d1 C-s1,d2

A 2L-s1,d1 A 2L-s1,d2 BL-s1,d1 BL-s1,d2 CL-s1,d1 CL-s1,d2

A 2-s3,d2 B-s3,d2 C-s3,d2

A 2L-s3,d2 BL-s3,d2 CL-s3,d2

D-s1,d0 D-s2,d0 D-s3,d0 E

DL-s1,d0 DL-s2,d0 DL-s3,d0 EL

D-s1,d1 D-s2,d1 D-s3,d1 D-s1,d2 D-s2,d2 D-s3,d2 E

DL-s1,d1 DL-s2,d1 DL-s3,d1 DL-s1,d2 DL-s2,d2 DL-s3,d2 EL

A 2fl-s2 Bfl-s2 Cfl-s2 Dfl-s1 Dfl-s2 Efl

F

FL

Ffl

No smoke

No burning droplets falling

‡ ‡ ‡

‡

Building materials of low combustibility ‡

‡

Normally combustible building materials

Easily combustible building materials

Floor coverings

Bfl-s1 Cfl-s1

‡ = is applicable s (smoke); d (droplets) = burning droplets / falling; fl (floorings) L (Linear pipe thermal insulation products)

C 1.3

Building regulatory authority designation

Load-bearing structural elements no partition 1)

with partition 1)

Non-loadbearing interior walls

Non-loadbearing exterior walls

Double floor

Separate suspended ceiling

Fire-retardant

R 30

REI 30

EI 30

E 30 (i  o) and E 30-ef (i  o)

REI 30

EI 30 (a b)

Highly fireretardant

R 60

REI 60

EI 60

E 60 (i  o) and E 60-ef (i  o)

EI 60 (a b)

Fire-resistant

R 90

REI 90

EI 90

E 90 (i  o) and E 90-ef (i  o)

EI 90 (a b)

Fire-resistance period of 120 min.

R 120

REI 120

–

–

_

Firewall

–

REI 90-M

EI 90-M

–

–

1)

For steel structural elements coated with reactive fire prevention systems the specification “IncSlow” defined in DIN EN 13 501-2 is also required. i  o (in  out); a b (above  below) C 1.4

73

Protective functions

capacity, even after the cooling phase. The 90-minute period is calculated based on an average fireload in residential and office buildings of 600 to 750 MJ/m2, which a fully ventilated fire has usually used up in 90 minutes, i.e. the temperature in the burnt-out space falls relatively quickly to below 200 °C in the cooling phase (Fig. C 1.5). Combustibility and fire resistance

It is essential to clearly distinguish between the combustibility of building materials (defined in building material classes) and the fire resistance of individual structural components (defined by the fire-resistance classes of structural components).

The combustibility of building materials particularly influences the spread of fire immediately after it breaks out and as it spreads and intensifies. DIN 4102 divides building materials into non-combustible (A 1 and A 2) and combustible materials classes (B 1 to B 3). DIN EN 13 501 specifies seven “Euro-classes” (A1, A 2, B, C, D, E, F) and classes s1, s2 and s3 for smoke release (s = smoke), for burning droplets (d = droplets) classes d 0, d1 and d 2 and special classes for floorings (fl = floorings) (Fig. C 1.3, p. 73). A structural element’s fire resistance describes its ability to remain stable (criterion R) and the capacity of structural elements that enclose

spaces to prevent the passage of smoke and gases (criterion E) and heat (criterion I) for the required fire-resistance duration. Structural elements are classified in fire-resistance classes, which use the building regulatory authority terms “fire-retardant”, “highly fireretardant” and “fire-resistant” to describe fireresistance duration (specified in 30-minute increments) (Fig. C 1.4, p. 73). Load-bearing structural elements may also enclose spaces, e.g. partition walls between residential units, while individual supports must only be designed to retain their structural integrity (R). Figure C 1.5 shows the principles of fire development and classifications of the requirements outlined above.

Fire behaviour of non-combustible structural elements and structure

Building regulatory authority designation

Taking contiguous, adjoining building materials into account

Fire-retardant

Test standard

DIN EN 13 501-1 Fire classification of construction products and building elements – Classification using data from reaction to fire tests

DIN EN 13 501-2 Fire classification of construction products and building elements – Classification using data from reaction to fireresistance tests, excluding ventilation services

Temperature

Fire behaviour of combustible structural elements and structures

Fire-resistant

REI 30

Fire outbreak

Fire development

REI 90

Full-scale fire

Cooling

Diagram of the progress of fire Flashover

Ignition

30 min

90 min Time

Risks

Combustibility

Spread of flame on surfaces

Building materials: Heat build-up, smoke and toxicity Structural elements: Load-bearing capacity (R), Partition (E; Passage of flame, residual strength) and heat transition (I) C 1.5

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C 1.6

A building material’s combustibility and a structural element’s fire resistance are not directly related. Some examples illustrating this fact include: • A steel support (class A building material – non-combustible) that is not protected by fireprotection cladding or a fire protection coating usually loses its load-bearing capacity after 30 minutes at the latest. In contrast, a glued laminated timber support will burn on its outside but can retain its structural integrity for more than 90 minutes in a fire without any additional protective cladding or coating. • A pane of glass is not combustible, but heat passes through it almost immediately. A 30 mm-thick softwood fibre panel will burn, but largely prevents heat from passing through it, resulting in an increase in temperature only after around 15 minutes at the earliest on the side not exposed to the fire. Combustibility does play a major role in the outbreak phase and spread of fire, so to fulfil the general requirements described above, prescriptive building regulations require surfaces in emergency escape routes (e.g. in staircases and corridors) to be non-combustible and low-combustibility building materials to be used in facade cladding. Fire safety performance in timber structures

A timber building must ensure the same levels of safety as other structures, so the fire behaviour of timber and timber structures must be realistically assessed, regardless of combustibility, to make use of the material’s positive properties in the event of fire. The basic fire safety requirements (see p. 72f.) for all structures when subject to fire must be equally met by timber structures. Planners, clients and users involved in the construction of timber buildings often want to leave wood visible, at least in some areas, so here the material’s combustibility must particularly be taken into account. The behaviour of timber structural elements in fire is greatly influenced by the proportion of surface to cross section and the densities of various woods. The greater

Material

One-dimensional burn rate ß0 [mm/min]

Nominal burn rate ßn [mm/min]

0.65

0.7

0.65

0.8

0.65

0.7

0.50

0.55

Laminated veneer lumber with a characteristic density of ≥ 480 kg/m3

0.65

0.7

Panels Wood panelling Plywood Wood-based panels, apart from plywood

0.9 1) 1.0 1) 0.9 1)

Softwood and beech Glued laminated timber with a characteristic density of ≥ 290 kg/m3 Solid wood with a characteristic density of ≥ 290 kg/m3 Hardwood Solid wood or glued laminated timber with a characteristic density of ≥ 290 kg/m3 Solid wood or glued laminated timber with a characteristic density of ≥ 450 kg/m3

1)

These figures apply to a characteristic bulk density of 450 kg/m3 and a material 20 mm thick. C 1.7

a wood’s density, the lower its mass burning rate will be, i.e. charring in mm per minute (Fig. C 1.7). Burning wood contributes to the fire load in a room, although the charred layer on the fire-exposed sides protects the inner areas. The nominal combustion rate ßn takes an increased rate of corner charring into account (Fig. C 1.6). Wood’s thermal conductivity coefficient is also relatively low ( ≤ 0.13 – 0.17 W/mK), so the inner, unburnt area remains cool and load-bearing. Increasing the thickness of elements to more than the structurally required dimensions can effectively provide timber fire protection cladding. Another advantage of solid timber elements is that fire cannot penetrate into cavities in which it could spread unchecked and become almost inaccessible to fire fighters. Solid timber elements are easy to extinguish and no subsequent ignition occurs. This makes it possible, and has in many cases been achieved in buildings, to install solid and visible timber structural elements with a fire-resistance duration of 90 minutes (REI 90) in buildings up to highrise height, and in staircase walls to replace firewalls (REI 90-M; see “Kampa administration building in Aalen”, p. 211ff.).

In planning for fire prevention with timber the following criteria are among those to which particular consideration must be given: • The required corridors and staircases must be kept free of fire loads by means of panelling with non-combustible cladding. • Fire protection cladding with a defined protection period (encapsulation criterion, e.g. K 230 or K 260) limits the temperature on the side not directly exposed to the fire for the period specified to T ≤ 300°C and so prevents the timber from burning and contributing to fire load. Encapsulated cladding around structural panels with insulated or uninsulated cavities should also prevent fire from penetrating into the structure.

C 1.5

Diagram of fire development showing the influence of building materials and structural components C 1.6 Cross section of a solid timber beam that has been exposed to fire. In contrast to the onedimensional burn rate ß0, which measures the burn-off depth in the centre of a timber cross section, the nominal burn rate ßn takes into account the rounding of corners in the burning of cross sections and cracks in the timber. C 1.7 Combustion behaviour of various timber building materials as per DIN EN 1995-1-2

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Protective functions

• The proportion of open timber surfaces in rooms should be limited to minimise increases in fire load from timber structural elements. The rule of thumb here is that if the ceiling and floor are made of visible wood, the walls should be panelled with a non-combustible material, or if two walls are not lined, then either the ceiling or floor may be made of visible timber. • Individual visible and solid timber structural components (e.g. structurally supporting separate glued laminated timber supports) make only very minor contributions to the development of fire. • Shafts and the fire shutters of technical building equipment should be thoroughly planned. In timber construction, it has been shown to be worthwhile to position a fire shutter at each ceiling and to provide separate shafts for each fire compartment (see “Shaft type B”, p. 126). This allows for free installation of building services within storeys. The ceiling areas in the shafts can

also be concreted and fire shutter systems normally authorised for building services used there. Special fire shutter solutions for timber structures are unfortunately still rare at the time of this book’s publication, although various research projects have resulted in a series of transfer rules that have now been published and are recognised by building regulatory authorities as equivalent solutions [3]. • Facades on buildings in class 4 and higher building classes must be especially carefully planned and constructed if they are to be built as normally combustible timber facades. • For structures with heights at the borderline between low-rise (top of the finished floor ≤ 7 metres above the average ground height) and buildings in building class 4 it is worth ensuring that low-rise building height can be complied with. In this case, all load-bearing and space-enclosing standard building elements can be built to be fire-retardant,

i.e. fire-resistance class REI 30. Visible surfaces and timber facades are permitted by building regulations. As with restrictions on the size of utilisation units, the 7-metre limit must be adhered to because even slightly exceeding this height will result in classification in the next highest building class. • Visible box structures and other elements containing cavities should only be installed in low-rise buildings, because there is a risk that fire will spread around them and be hard to stop. Effective fire-resistant cladding must be installed in taller buildings. • If exposed timber planar structural components (ceilings, walls) are installed in buildings of medium height (top of the finished floor > 7 m), the possibility of using composite timber-concrete slabs should be examined because this is an easy way to make a “continuous non-combustible layer” in the storeys. This will limit the spread of fire and smoke and is required by some building regulations. Firewall F 90-A+M Fire-resistant F 90-A F 90-B+K260 F 90-B+K260 (from above) with exposed timber ceiling Fire-retardant F 30-B; for non-load-bearing exterior walls W 30-B Fire-retardant F 30-A Composite thermal insulation system (building materials class A) Composite thermal insulation system (building materials class B 1) Rear-ventilated timber exterior wall cladding (building materials class B 2) Door dT Door RS Door T30 Lift shaft

Necessary staircase Necessary corridor Access Primary emergency escape route Secondary emergency escape route provided by a position where a turntable ladder can be positioned Secondary emergency escape route provided by a position where a portable ladder can be positioned Smoke alarm C 1.8

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C 1.9

The following aspects apply to timber as well as to all other types of construction: • Clear and obvious emergency exit routes • A second fixed emergency exit route where possible, especially for spaces that may contain a large number of people (e.g. a large conference room). Firefighters using turntable ladders can usually only rescue around twelve people for each primary emergency exit route that is unavailable! • Clear configuration of fire and smoke control compartments: This is clearly prescribed in building regulations but usually complex to achieve because firewalls, firewall-equivalent walls or partition walls must be built. Making smoke protection compartments as small as possible, e.g. by partitioning corridors with smoke control doors, is even more important in this context because the smoke from fire poses a much greater risk than does direct exposure to fire. In office and school buildings for example, two separate smoke protection compartments should ideally always be accessible as emergency exit routes. This focus on ensuring an emergency exit route means that (smoke) protection periods of 30 minutes will usually suffice in such cases. • Stairways must be kept free of fire loads. They serve not only as emergency exit routes for residents, but also as a stronghold and retreat for firefighters. They must be built to ensure reliable structural protection from fire and there is no room for latitude here. • Enough fire alarms (which are now mandatory in homes anyway) and adequate fireextinguishing equipment so that people can help themselves. • Intensive reviews /quality assurance of all fire safety measures, especially correct

installation of fire shutters and technical fire safety equipment. These should be installed as far as possible in the prefabrication phase because fewer errors will be made in industrial manufacture and it is easier to monitor. All these points are consolidated in fire safety concepts, which contain a general description of the technical fire protection safety concept and give reasons for diverging from building regulations where this is necessary. Such divergences are usually necessary in timber buildings with more than three storeys because buildings over this height must comply with fire-resistance classes with requirements above “fire-retardant” and no visible timber structural elements are permitted (apart from in BadenWürttemberg). Taking the points mentioned above into account, appropriate solutions can however usually be found. Divergences can be compensated for by additional fire alarm equip-

ment, stairways built like emergency exit stairs (with access from outside or separate staircases; see fig. C 1.8 and “c13 residential and office building in Berlin”, p. 170ff.), second fixed emergency exit routes, smaller smoke control compartments and the like are usually sufficient, even with visible timber structural elements, to build multi-storey buildings up to high-rise height. Sprinkler systems

Sprinkler systems in residential and office buildings are unusual in German-speaking countries but common in North America, Australia and Nordic countries. This is because, to date, there are no sprinkler systems adapted to this usage (e.g. with water supplied from the drinking water network) involving less cost and effort than a comprehensive sprinkler system (separate system with its own water reservoir), as with the “home sprinklers” in residential buildings in the USA and Canada.

C 1.8

Example of fire prevention planning with an access balcony providing exterior access to stairs in an eight-storey timber building H 8, Bad Aibling (DE) 2011, Schankula Architekten C 1.9 Advantages of a sprinkler system, exposed cross laminated timber stairs, Library at the Dock, Melbourne (AUS) 2014, Clare Design and Hayball C 1.10 Open timber structure and floor plan with high fire loads made possible by a sprinkler system, Library at the Dock, Melbourne C 1.10

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C 1.11

In Central Europe, unlike in North America and the Nordic countries, a sprinkler system is not seen as a safety advantage and a positive feature, just as an expensive investment. The risk of inadvertent activation is another issue, although many years of experience in Scandinavia and countries outside Europe have shown that this is not a major problem. Sprinkler systems are not so established as technical equipment in Central Europe that their use would result in a direct reduction of required fire resistance or fire protection cladding and thus to lower investment costs for fire-resistant cladding and lining. Housing associations and companies also want to avoid the ongoing maintenance costs of such systems, which again are not a problem in other countries. Fire-resistant coatings

It is not advisable to use fire-resistant coatings or impregnate timber with these kinds of substances. Used on exteriors, the problem with them is that there are still no permanently weatherproof products that would result in a change of a building material’s fire safety class (from being of low combustibility to normally non-combustible) available to date. Coatings for timber in interiors to change the timber’s fire safety properties are not normally necessary – it is better to use solid, robust structures instead. The other disadvantage

C

of coatings is that they impact subsequent recycling. Their effects on interior air must also be carefully reviewed. As for structural protection for timber (p. 83ff.), the rule of thumb here is that “structural measures are better than chemical measures”.

This should be ensured by using building facade cladding materials of low combustibility. These requirements can also be met with normally combustible timber cladding on tested structures (see “Kampa administration building in Aalen”, p. 211ff.).

Structural measures

The main structural fire prevention measure for facades is cutting off the facade’s ventilation at each storey to prevent the chimney stack effect. This is also safe in terms of structural physics. A series of research projects, the results of which have been incorporated into the DIN 68 800 standards series, has shown that this kind of ventilation (just one opening at the bottom, closed at the top) adequately balances out a building’s moisture levels (see “Protecting timber from moisture”, p. 79ff. and DIN 68 800, para. 5.2.1.2). The fire behaviour of various facade cladding systems has been intensively researched in German-speaking countries in the past ten years and a summary of the relevant rules was published in 2014 [4]. These showed an equivalent solution in terms of the “low combustibility” requirement.

Structural fire prevention measures include non-combustible intermediate layers built into solid timber structural elements, such as those made of glued laminated timber, which prevent the layers below them from igniting. Some initial products have already been tested and used in some cases. The self-extinguishing behaviour of solid timber structures in particular will be further researched in future. Structural measures for facades A non-combustible facade on a timber building poses no problems as long as a continuous, non-combustible layer is added to the structure behind it, e.g. 15 mm-thick plasterboard. Figure C 1.11 shows the example of a ten-storey timber building in Melbourne with an aluminium sheeting facade. Clients often also want a timber building to have a timber facade. In those cases it must be ensured that fire cannot spread autonomously beyond the primary ignition area and no more than two storeys above the fire source are affected by spreading flames before firefighters arrive.

1 2 3 4

5 A B

A 1

2

3

4

B C

Optional existing structure Timber beam, e.g. double T-beam Composite wood or plasterboard Weather protection: cladding with ventilation or rear-ventilation or composite thermal insulation system Insulating material

C 1.11

Cross laminated timber building with an aluminium sheet facade, Forte high-rise residential building, Melbourne (AU) 2012, Andrew Nieland and Lendlease Australia C 1.12 Technical fire prevention requirements and isolation of non-load-bearing exterior walls from facade cladding, also for renovations of existing buildings

Facade: building materials class as defined in LBO (B 1 or B 2) Facade element: EI like a non-loadbearing exterior wall (EI 30 / W 30) Load-bearing structure in a new or existing building: REI compliant with building class (REI 30 – 90)

5 C 1.12

78

For facade elements, i.e. non-load-bearing exterior walls, particular attention must be paid to differences in fire prevention requirements (Fig. C 1.12). The element itself must be fireretardant up to high-rise level, a requirement

Protective functions

that can be achieved almost inherently within the system. Exterior wall cladding on low-level buildings must be normally combustible, so any kind of cladding can be used here. For buildings of medium height and higher, exterior wall cladding must be of low combustibility, so timber cladding can be used as described above only with a verification of equivalency with facades of low combustibility. A timber element’s exterior panelling must then be made non-combustible, by adding 15 mm-thick gypsum plasterboard, for example. The requirements for facade elements used in renovations of existing buildings (see “Renovation of a residential building in Augsburg”, p. 202ff.), are similar to the requirements for non-load-bearing exterior walls, as long as the walls do not serve to transfer roof loads, for example. Legal usability of building products and building assemblies

In the context of fire prevention, close attention must be paid to legal usability of building products and construction types. The combustibility of construction products can be verified based on building product standards. Construction timber is classified as normally combustible when it is more than 22 mm thick and has a density of 350 kg/m3 (DIN EN 14 081-1, paragraph 5.3), for example. Other building products are classified after testing according to DIN EN 13 501-1 and a building inspection authority verification of usability issued accordingly (in Germany with a national technical approval or a national test certificate – abP). The fire resistance of support structure elements and types of structures and building methods can be verified either by calculations specified in DIN EN 1995-1-2 or from classifications based on tests prescribed in DIN EN 13 501-1, according to which the building inspection authorities verify usability. Unfortunately, verification is not consistent in Europe and special national rules must often be observed. To make these rules easier to deal with in practice, Holzforschung Austria has developed an online database system –

dataholz.com [5], which shows the building inspection authority verifications of usability required in Austria for all the structures shown in the database. Planners and builders can use these structures without further verification, making planning and construction much easier. The database has been translated into English and Italian, among other languages. A German version, dataholz.de, containing updated structures, the usability of which has been verified by German building inspection authorities, is due to go online in 2018. Conclusions

As long as some basic fire prevention requirements are met, building with timber up to highrise height is unproblematic in Europe and the relevant construction law requirements are being continuously adapted in many European countries. There are also significant differences. While Switzerland and BadenWürttemberg do not impose any limits on the use of exposed timber, in other countries it is permitted only in buildings of medium height with effective fire prevention cladding (in most German states (Länder), Nordic countries and the United Kingdom) and /or sprinkler systems (Finland). Clients wanting to build timber buildings with (partly) exposed structures must still often apply for permission to diverge from applicable fire safety regulations and give reasons for this divergence with an appropriate fire prevention concept and a series of compensations. The more visible timber a client wants, the more cavity-free solid timber and composite structures should be used in planning and construction. Work is continuing to expand the range of standard structures and related proof of equivalency. Whether timber buildings will break through the high-rise limit in large numbers will depend on the acceptance and improvement of sprinkler systems, the further development of cost-effective fire prevention cladding and verifications that timber support structures can withstand burning out completely without being extinguished by firefighters. Some pilot projects in various parts of the world have shown that this is generally possible (see “Via Cenni residential complex in Milan”, p. 174ff.).

Protecting timber from moisture Wood is a natural material, so in the relevant conditions it is broken down by natural processes, which form the basis of the biological cycle in our forests. As well as these natural degradation mechanisms, a higher moisture content than that usually contained in timber in buildings is required (see “Timber preservation”, p. 83ff.). As long as timber stays dry, which DIN 68 800 defines as a constant moisture content u of ≤ 20 %, no biological degradation due to destructive fungi will occur. Thoroughly dried timber used as a construction material can last several hundred years, as many historic buildings impressively demonstrate. The main expedient in building with timber is to protect the timber from lasting increases in moisture by means of appropriate protective measures and to keep it dry in the long term. Brief increases in moisture levels, e.g. on timber surfaces in bathrooms, are not critical as long as the surfaces can dry quickly. Potential sources of moisture

Sources of moisture in timber structures and possible protective measures are described below. Condensation from diffusion Condensation can be caused by diffusion due to differences in partial water vapour pressure, usually in exterior structural elements, although amounts will be small. Moisture permeation from diffusion is not usually problematic in standard timber buildings with interior vapourproof layers and vapour-permeable outer layers because it causes no or only very small amounts of condensation to form. Structures’ compliance with regulations is verified by means of the Glaser method prescribed in DIN 4108-3 or through numerical simulation processes specified in DIN EN 15 026. DIN 68 800-2, para. 5.2.4 must also be applied as verification of the prevention of condensation. Condensation from convection Condensation can also be caused by convection, i.e. warm air flowing through exterior structural elements from the inside outwards. If the

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Material

Indoor climate

C 1.13 Outdoor climate

Air temperature

20 °C

0 °C

Relative humidity

50 %

80 %

Saturated water vapour pressure

2337 Pa

611 Pa

Partial water vapour pressure

1168 Pa

488 Pa

Diffusion Exterior wall area 15 m2

M = 6.6 g/d

Convection Slit: 3 mm wide, 1 m long Pressure differential: 3 Pa

M = 484 g/d Convection

Diffusion C 1.14

Heat leak

Outside

Outside

Inside

Inside Moisture leak C 1.15

Differential pressure measurement Δ p = 50 Pa ( 0.5 mbar )

Door

. V = m 3/ h Volume flow measurement

Ventilator

n 50 =

a

80

b

. Volume flow rate V Building volume V

air has time to cool, large quantities of condensation can form, hundreds of times more than the amounts caused by condensation from diffusion (Fig. C 1.14). Convection can be prevented by making structures sufficiently airtight, which also limits heat losses from leaks. A distinction is made here between simple “heat leaks” and “moisture leaks” (Fig. C 1.15). One example of a typical simple heat leak is a permeable joint between a window frame and the reveal. Air flowing quickly over short distances cools below the dew point only outside the structure, so heat is lost but the structure is not imbued with moisture. Flow paths through the structure are longer in the case of moisture leaks, so air flowing through cools below the dew point while still in the structure and large quantities of condensation form. Airtightness is also an essential precondition for effectively operating ventilation systems that use heat recovery. A building envelope’s airtightness is tested by means of a blowerdoor test, i.e. a test of negative and positive pressure at a given pressure differential of 50 Pa (Fig. C 1.16). Properly constructed timber buildings can easily achieve air exchange rates of 0.2 ≤ n50 ≤ 0.6, so they usually easily comply with passive house air exchange rate standards. Air flowing between two openings has only a low flow resistance, so structures should always have at least two flow-proof layers – an intact airtight layer inside and a windproof layer outside (Fig. C 3.3, p. 93). The robustness of structures can be further improved beyond this double flow resistance by installing blownin insulation, because it completely fills the spaces insulated, making them highly flow resistant. Cellulose blown-in insulation in particular has proven its value here because it is highly flow-resistant (installation density approx. 55 kg/m3) and can briefly buffer any moisture resulting from diffusion condensation. Moisture leaks Leaks in water supply and drain pipes, taps and valves and in washing machines and dishwashers, splash water zones in bathrooms and, in rare cases, malfunctioning sprinkler

[1/h]

C 1.16

Protective functions

C 1.17

systems can introduce so much water into buildings that drops form and run or drip down. Timber buildings are more vulnerable to this kind of moisture than structures made entirely of concrete, for example, so they should always be doubly protected with at least two separate sealing layers. Various publications contain tips on building bathrooms in timber buildings [6]. Solutions for protecting structures from leaks are dealt with in the section on “Measures for damp rooms” (p. 126f.). Moisture from driving rain The amount of moisture permeating a building due to driving rain will increase with a building’s height and related wind loads (see “Some unique features of building with timber”, p. 45f.). In tall buildings, rain can permeate horizontally or can be blown upwards from below due to turbulence, so all joints between structural elements in the facade require special protection against driving rain. Here too, at least two separate water dissipation layers must be installed. It should particularly be noted that on glass surfaces – unlike plaster or rough timber surfaces – large quantities of water drops can gather immediately. The principle of providing structures with double protection from driving rain must also be applied to the exterior facades of buildings. Facade systems of all kinds should also have at least two separate ways of preventing moisture from permeating them. A distinction is made between rear-ventilated curtain wall facade systems with upper and lower ventilation openings and ventilated systems with a ventilation opening only at the bottom (Fig. C 1.13). This ventilation is entirely sufficient to dry out the small amounts of interior moisture resulting from diffusion. Research has shown that in ordinary rear-ventilated systems no really measurable volume flows occur and ventilated systems have adequate air exchange rates due to wind-induced pressure fluctuations. No measurable differences in humidity behind the facades of both types of structures were identified. Ventilated facades are usually easier to build and much better in terms of fire safety because they prevent a chimney stack effect.

Building a second water protection layer behind the facade cladding and providing vertical drainage to reliably dissipate any water getting in behind the facade through small leaks is also crucial here (see “Timber preservation”, p. 83ff.). Moisture during construction Intensive wetting of timber structures during construction must be avoided at all costs for several reasons. Increased moisture levels followed by fast-drying will cause timber structural elements to crack. Moisture on surfaces can cause mould and leave water stains on surfaces that will remain visible. Timber structural components that swell up with moisture can also produce significant constraint forces. Brief moistening, such as from a rain shower during installation, is unproblematic for kiln-dried spruce because the moisture will not penetrate it deeply. However, some hardwoods (e.g. beech) and timber composite board (e.g. chip and particle board) are much more sensitive to temporary moistening, so continuous measures to protect such materials from moisture during construction must be planned and implemented. In Sweden, entire building sites are often completely enclosed for this reason, with even gantry cranes under cover (Fig. C 1.18). In

Germany, for reasons of space among others, moisture protection is usually integrated into slab elements (Fig. C 1.17) which protects the installed sections once an installation unit is completed (usually daily). If this protective layer remains in the finished structure, it can then protect the completed building from leaks and water from a sprinkler system or fire extinguishing, as long as there are appropriate ways of dissipating the water. Together with largely prefabricated and facade structural components that are watertight from the outset, this produces a building envelope that is watertight from top to bottom and ensures dry construction conditions (see “Prefabrication and Individuality”, p. 142ff.). If structures get wet briefly due to sudden changes in weather, the very low level of moisture absorbed during brief wetting and the possibility of quick drying will not be problematic for kiln-dried timber building products. Even if timber structures are protected from direct wetting during construction, the moisture content of timber structural components can still increase in this phase. Wood is a hygroscopic material, so its moisture content changes depending on the prevailing temperature and relative humidity. The pouring of screeds or other work involving water in a building can cause the timber moisture content

C 1.13

Ventilated (left) and rear-ventilated (right) facade /exterior wall cladding C 1.14 Water vapour transport due to diffusion and convection (amount of water released in a 24-hour period) C 1.15 Heat and moisture leaks C 1 16 Blower door test a Structure in practice b Principle C 1.17 Waterproof roof level in the construction of a four-storey building, H 4, Bad Aibling (DE) 2010, Schankula Architekten C 1.18 Enclosing a construction site for a seven-storey building (SE) 2009, Arkitektbolaget C 1.18

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Protective functions

to increase to 18 % and more. Timber can be prevented from absorbing moisture during construction by the application of diffusionresistant coatings. Structural elements, especially large glued laminated timber components such as long beams and solid supports, should not be allowed to dry too quickly during the transition from construction to building operation (e.g. at the beginning of the heating period, during the heat-drying of screeds etc.), otherwise cracks will form due to the very different drying rates in cross sections. Before the drying period begins, it is advisable to measure the moisture content of timber in solid cross sections and slow down drying by humidifying interior air if necessary. If planners are in doubt, they should obtain appropriate expertise.

a

Soundproofing and acoustic requirements

b

82

C 1.19

Soundproofing and acoustic requirements involve both protection from noise and spatial acoustics. The EU’s Construction Products Regulation states that the general goal of soundproofing is to keep noise to a level that will “not threaten (people’s) health and will allow them to sleep, rest and work in satisfactory conditions” [7]. These requirements, with which timber structures must also comply, are based on a basic noise level of 25 dB(A), which is designed to ensure discretion for normal speech and protection from unacceptable disturbance. What is regarded as “satisfactory” is defined in the regulations of individual EU member states as a minimum requirement and depends on various cultural and economic considerations. In Germany, DIN 4109 prescribes a weighted airborne sound reduction index of R'w ≥ 54 dB and a weighted impact sound level of L'n, w ≤ 50 dB for normal soundproofing between utilisation units. Stricter limit values for increased soundproofing can be agreed on in private construction projects. The airborne sound reduction index for exterior structural components is set based on expected prevailing outdoor noise levels and is R'w = 30 – 50 dB.

The prime symbol in the formula indicates the taking into account of so-called “byways” common in normal structures, distinguishing them from laboratory values, because sound is transmitted not only by the surfaces of structural components but also through joints between structural components. Weighted airborne sound reduction index means that calculations of these figures are based on people’s frequency-dependent hearing ability. In Europe, an expansion of the weighting of impact sound insulation to include deep frequencies (droning) in the 50 – 80 Hz frequency range (so-called Ctr value – an adapted range value) is currently being discussed. In Germany, this is not yet a requirement and has not been included in standards to date. Four different areas are crucial to any examination of soundproofing characteristics: Airborne sound insulation, structure-borne sound insulation, impact sound insulation and spatial acoustics: • Airborne sound insulation is specified by means of the airborne sound reduction index R'w. Because this is a sound reduction index, the greater the numerical value, the better the soundproofing characteristics. • Structure-borne sound insulation is only taken into account for impact sound insulation. Knocking on a wall or drilling a hole are not regarded as constant ordinary usage. This soundproofing requirement basically assumes that there is no absolute sound insulation and that a certain level of mutual consideration is required for coexistence. • Impact sound insulation is defined by the weighted impact sound level specified in the relevant standards. This is a sound level measurement, so the lower the figure, the better the sound insulating properties of a slab. In a laboratory or structural inspection test, slabs are struck with a standardised hammer system and the noise level in the space below measured. The lower the noise level in the space below the active hammer system (impact sound stimulation), the quieter it is – i.e. the better the soundproofing. • Spatial acoustics refers to the acoustic characteristics of specific spaces. This is

Protective functions

a comfort feature that building regulations do not require but is very important to users, e.g. in concert halls (Fig. C 1.20). Hard or concave surfaces in a space can cause unwelcome echoes that can give users an impression of interrupting themselves when they speak. Special features of soundproofing in timber structures

Various research projects have made major progress in soundproofing in timber structures in recent decades, so a wide range of walls and slabs with similar soundproofing properties to masonry and steel-reinforced concrete structures that have been tested in laboratories and in practice are now available. A timber structure does not have the heavy dead weight of a steel-reinforced concrete building. A heavy mass is much harder to stimulate with sound waves (airborne sound) or impact stress (impact sound) due to its inertia, so this mass has implicit soundproofing advantages, although it usually has a much weaker damping effect. Once a heavy mass is stimulated, however, it transfers sound very well. One example of the effect of structure-borne sound transfer is that you can wake up an entire apartment house by drilling into a steelreinforced concrete wall, while drilling in a cross laminated timber wall may not even be audible in the next room (Fig. C 1.19). To achieve the required soundproofing properties in timber buildings, two main strategies should be pursued: • For airborne sound insulation, acoustic decoupling by means of separate or elastically mounted facing shells. • For impact sound insulation, the addition of extra mass with solid screeds and heavy infills. The latter is especially effective

because it is not inherently rigid and rigidity can have a negative impact in certain frequency ranges. That is also the reason why solid timber ceilings, despite their greater mass, are treated like beam ceilings for soundproofing purposes. In choosing and planning slabs in timber structures, particular consideration must be given to two general conditions : • An impact sound reduction level, ΔLn, w is specified for floor coverings, screeds and suspended slabs. In consulting manufacturer’s specifications not specifically issued for timber buildings, it should be noted that improvements are normally measured in tests of concrete slabs. The different frequency responses of timber and concrete slabs mean that improvements measured for timber slabs will usually be much lower than those specified by the manufacturer. • To reliably achieve planned soundproofing values in construction, soundproofing structures must be airtight. Structural components weighted to accommodate specific acoustic properties can be found at www.dataholz.com and in future will also be

available at www.dataholz.eu. Figures C 3.16 and C 3.17 (p. 102f.) and the chapter on “The layer structure of interior structural components” (p. 114ff.) show examples of structural components and joints.

Timber preservation Timber preservation almost thwarted timber construction entirely in the 1970s and 1980s because timber preservation had become associated with chemical agents and the prevailing opinion was that the only way to make timber durable was by using toxins. In the past 25 years, a paradigm shift has occurred. With a return to old timber construction traditions and successful strategies, structural timber preservation has now again become a clear priority over all other measures. The main task of structural timber preservation is to keep a timber structure dry in the long term. If the moisture content of timber is below the fibre saturation point, which for construction timber is between 28 and 35 % average moisture content, biological degradation due to destructive fungi cannot occur. Only when a timber’s moisture content is above these levels

C 1.19

Assembling elements in timber buildings is easier and makes less noise than is the case with other construction methods a Screwing a screw into a timber structure with a battery-powered cordless screwdriver b Inserting dowels into a steel-reinforced concrete wall with an impact driver C 1.20 Timber elements make for good interior acoustics. Concert hall In Lahti (FI) 2000, Hannu Tikka and Kimmo Lintula C 1.20

83

Protective functions

C 1.21

in the long term does the cell water required by wood-destroying fungi for growth become available. Timber is defined as dry in this context when it has an average moisture content of ≤ 20 % (DIN 68 800-1, tab. 1). The gap between this figure and the fibre saturation point can be interpreted as a safety margin. If it is not complied with, neither will preventative chemical timber preservation help in the long term. If timber is constantly exposed to moisture, chemical timber preservation will at best delay infestation from destructive fungi, but not prevent it. Chemical timber preservation is also not necessary to repel wood-destroying insects. Here too, structural measures can effectively prevent infestations. Most insects need to be able to fly freely to lay eggs, which they cannot do in fully insulated structures covered on all sides. It has also been shown that kilndrying timber achieves two things: it kills any insect larvae in green wood and the changes to the timber’s constituents makes it uninteresting to the insects that can infest dried timber. DIN 68 800-1 defines kiln-dried wood as follows: “Wood that has been dried for at least 48 hours in an appropriate process-controlled technical plant at a temperature of T ≥ 55 °C to a moisture content below 20 %.” [8] Comprehensive investigations of support structures in the past ten years have also shown that, despite the timber at the edges of roofs being freely accessible, no kiln-dried wood showed signs of insect damage. The minimising of hazardous substances in workplaces and housing and better recycling options for untreated wood are further aspects in favour of a consistent renunciation of chemical timber preservation. If, however, individual situations occur in which increased hazards from moisture or insects are expected (e.g. thresholds too close to soil, terrace floors or garden and landscaping structural elements that are wholly exposed to weathering or touch the earth), resistant timbers such as larch and Douglas fir heartwood or more resistant types of wood such as oak or chestnut can be used as an alternative to chemical timber preservation agents. Thermally or chemically modified timber can also be used

84

in special cases. So-called “thermowood” is treated under pressure and at specific temperatures to transform its constituents so that it no longer provides nutrients for wood-destroying fungi or insects (Fig. C 1.25 d). The treatment does however cause the wood to change colour (from dark brown to black) and reduces its strength and stiffness. This is also the case with chemically modified timbers, e.g. those treated with acetylation (Fig. C 1.25 b). For multi-storey timber buildings, the following timber preservation rules can be summarised: • Exclusive use of kiln-dried timber: If woodbased materials such as glued laminated or cross laminated timber or the like are used, the basic materials (lamella, woodchips etc.) are kiln-dried and do not have to be separately specified. • Consistent application of structural timber preservation, e.g. with cladding on all sides, complete insulation of structural elements, distance from soil etc. – no possible water deposits and no open hollow moulds or joints etc. [9] • Avoiding the use of exterior structural elements wholly exposed to the weather: Exceptions may be made for supports made of resistant timbers or cases where protective planks are added. These were once frequently used and can be easily replaced (e.g. cross-grained timber covers for roof beams) [10] • Consistent application of all measures necessary to protect structures from moisture (see “Protecting timber from moisture”, p. 79ff. and “Facades”, below) • Use of resistant types of timber or chemically modified timber where necessary • Avoiding of preventative chemical timber preservation measures Relevant standards / rules

The DIN 68 800 series of standards contains the current rules on preventative structural and chemical timber preservation in Germany. The main parts regarding the fundamentals and preventative structural timber preservation were republished in 2011 and 2012. A practice-based commentary accompanying the standard (Praxiskommentar Holzschutz) offers

further information [11]. This series of standards classifies timber structural elements in use classes GK 0 to 5. GK 0 stands for conditions in which the application of timber preservation agents is not necessary. Part 2 of the standard prescribes the main structural measures defining the specific classifications. The wall, roof and ceiling and slab structures shown in this book meet these requirements and can be used without preventative chemical timber preservation. The installation of kilndried spruce or pine wood will usually suffice. Facades

The construction of facades plays a special role in protecting timber and the protection of structures from moisture is directly linked with their facades. If a structure also protects the timber, basically any timber facade a client desires can be built. The following structures provide sufficient protection from moisture for a facade and the timber structures behind it: • Ventilated, or rear-ventilated, curtain wall facades (with vertical battens) with permanent effective protection from the weather, e.g. closed plank cladding, fibre cement boards, suitable composite timber boards or metal sheeting • A cavity wall without ventilation (horizontal battens) with small-format cladding, e.g. slate, shingles, planking In these two cases, the battens will not require preventative chemical timber preservation but should be kiln-dried. Construction of a second water-bearing layer with permeable foils or suitable planking behind the battens is recommended. • Thermal insulation system with hard foam, mineral fibre or softwood fibre sheeting and plaster, for which a general technical approval (allgemeine bauaufsichtliche Zulassung) is required in Germany. • Masonry facing shell with a layer of air (d ≥ 40 mm) and insulation and water-draining layers added to the wall. Timber facades

The desire for a timber facade, especially in multi-storey buildings, raises the issue of maintenance and any necessary or desired col-

Protective functions

C 1.22

C 1.23

oured paints and coatings. Timber facades do not require preventative chemical measures to protect their timber. If structural conditions are complied with (drip edges, no accumulation of water etc.), completely untreated timber can be used here (Fig. C 1.21). The vertical positioning of facade planks has been shown to be better because water drains off in parallel with the timber’s fibres, but horizontal configurations have also proven their worth, as long as they are appropriately constructed. The top layers of sheeting materials such as solid timber boards must always be installed vertically, otherwise inevitable cracking in the top layer in parallel with the timber’s fibres will harbour draining water, which may result in the top layer being destroyed or peeling off.

ing rain. In areas exposed to weathering, the lignin washes out, leaving only the grey to silvery shiny cellulose (Fig. C 1.22). Different areas of a facade are exposed to water to varying extents, areas under window sills for example, so facades do not usually go grey evenly. To achieve a more even appearance, the facade can be treated in advance with a grey or grey-silver varnish. In areas more exposed to weathering, this will be “used up” and replaced by natural greying, while in areas not exposed to weathering it is retained, so the facade will have a more even appearance. Colour treatments should be applied to finely sawn surfaces and never to planed surfaces (Figs. C 1.23 and C 1.24). Industrially colourtreated finely sawn surfaces and permeable, ideally not film-forming coatings that allow the small amounts of water that permeate due to inevitable defects to dry out again can last for more than 20 years. The colour coating should, as far as possible, only be applied after facade elements are cut to size, otherwise great care must be taken in treating cut elements. An undercoat and at least one subsequent coating must be applied on all sides to prevent surfaces from absorbing moisture at varying rates. Rear-ventilated or ventilated areas of exterior wall structures are often exposed to very high

The facade’s appearance and colour treatments for facades

Untreated timber plank or panel facades are usually made of especially robust woods such as larch or Douglas fir. Facades made of untreated timber or thermowood will inevitably change colour over time because the lignin in timber photo-oxidises, making it look almost black and breaking its chemical bond with the rest of the timber structure. This darkens the timber in areas where it is shielded from driv-

C 1.24

levels of relative humidity, although in recent years the mineral-based colours now offered by some manufacturers have proven their effectiveness here.

Thermal insulation in winter and summer In most European countries, the requirements for the annual energy consumption of buildings are prescribed in legislation. The common goal of these laws is to minimise the energy consumed through building operations, with the long-term goal of creating climate-neutral building stocks, so they usually set limits for their annual primary energy consumption for heating, hot water, ventilation and cooling. Various requirements are made on the performance of building envelopes depending on climate conditions. Their insulation and airtightness greatly influence the energy consumed for heating, ventilation and cooling. The other major factor in this context is user behaviour, which is on the one hand purely individual and on the other hand determined by the overall interior climate. In Germany, the Energy Saving Ordinance (Energieeinsparverordnung – EnEV) [12] prescribes thermal insulation requirements.

a C 1.21 C 1.22 C 1.23

C 1.24

C 1.25

Ideal connection between a windowsill and reveal. NINA-huset, Trondheim (NO) 2013, Pir II Influence of slight variations in exposure to water on the colour of timber Dark glazed wooden boards, carpenter's workshop near Freising (DE) 2010, Deppisch Architekten Timber board facade with a coloured finish, Södra tennis centre, Växjö (SE) 2012, Kent Pedersen Modified pinewood with no coating, from left to right: at the outset, after 3, 6, 9, 12 and 18 months of exposure to weather, facing south at 45°, Vienna (AT) a untreated reference timber surface b acetylated timber c timber impregnated with chrome-free salts d thermowood e furfurylated timber

b

c

d

e C 1.25

85

Protective functions

C 1.26

The main protective goal of thermal insulation in winter is to largely reduce transmission heat losses through the building envelope. From a purely physical point of view, in the heating period, due to the difference between indoor (interior heated to 20 °C) outdoor temperatures (outdoor climate resulting from geographic conditions), a transient heat flow develops that must be minimised by a building envelope with the highest possible thermal resistance. The heat transmittance coefficient or U value [W/m2K] describes the thermal resistance of a building’s exterior structural elements. Differences between masonry, prefabricated concrete or timber structures lie mainly in their opaque structural elements because windows, doors and ventilation flaps etc. are the same in all these types of structures, depending on the requirements made. To minimise heat losses through a building envelope, structural elements must be insulated as highly as possible and the U value of structural components should be as low as possible. The challenge here is to wrap an insulating envelope around areas of the building requiring protection without any gaps, like a cocoon. It should be noted here, however, that at each corner and in insufficiently insulated parts of a structure, geometric and structural

thermal bridges will form and cause greater heat losses (Fig. C 1.28). Building envelopes should be as compact as possible and construction materials should have good insulating properties. Figure C 1.27 provides an initial overview of the required thicknesses of insulation for exterior timber walls. With exterior timber structural components if the structure is moderately over-insulated, with insulated installation levels and external layers of insulation and structural elements < 500 mm thick, U values of U < 0.1 W/m2K can be achieved, which is approximately the level of insulation required for passive or plus-energy houses. Current opinion regards this level of insulation as a reasonable limit. Further halving U values would entail doubling the thickness of insulation or using very high-performance insulation, such as a comprehensive use of vacuum insulation, neither of which would be structurally or economically advisable. A significant reduction in thermal insulation to U values of U ≥ 0.2 W/m2K would also not be expedient, even though using renewable energy could reduce the building’s primary energy consumption figures. The main goal should be to prevent heat loss and minimise the building’s energy consumption, regardless of the energy’s source. U values of U ≤ 0.2 W/m2K result in surface temperatures on the insides of exter-

nal structural elements that are in the room temperature range, which ensures a pleasantly warm indoor climate because radiation heat losses from the surfaces that can affect users are reduced. Keeping temperatures in this range also allows buildings to be operated with much lower inside temperatures with the same comfort and with timber’s low thermal conductivity as a construction material, thermal bridges in planar structures and corners can be easily avoided or minimised. Continuously effective insulating envelopes around timber structural elements and higher temperatures for all inner surfaces of external structural elements also prevent problems with mould forming on these surfaces. In an ordinary interior climate, high humidity levels of over 80 % near surfaces and resulting condensation do not occur, so there are no conditions suitable for the growth of mould. As well as having good thermal insulation, a building envelope must be airtight to prevent heat losses from unintentional ventilation. Such losses are caused by wind pressure and wind suction as well as by inner thermal conditions and the resulting differences in air pressure. In very leaky buildings this can lead to the famed “storm from the power socket”. Airtightness is also necessary to ensure good soundproofing of external structural components and

Low-energy house (EnEV)

3-liter house

Passive house / plus-energy house

Thermal insulation in winter

Wall 239 mm thick U = 0.2 W/m2K Wall 200 mm thick U  0.25 W/m2K

Wall 270 mm thick U = 0.2 W/m2K

Wall 234 mm thick U = 0.15 W/m2K

Wall 305 mm thick U = 0.15 W/m2K

Wall 300 mm thick U  0.15 – 0.18 W/m2K

Wall 434 mm thick U = 0.1 W/m2K

Wall 485 mm thick U = 0.1 W/m2K Wall 500 mm thick U ≤ 0.1 W/m2K C 1.27

86

Protective functions

a

b

the effectiveness of ventilation systems and preventing moisture resulting from convection from getting into structures (see “Protecting timber from moisture”, p. 79ff.). With the use of air conditioning systems currently usually used, a limit value of n50 ≤ 1.5/h must be maintained.

Notes: [1] Ondrus, Julia: Fire in low-rise residential buildings. In Building Research & Information, 22, 1994 (No. 1) p. 43ff. [2] Musterbauordnung – MBO of November 2002, last amended by resolution of the conference of construction ministers (Bauministerkonferenz) on 21.09.2012, Arbeitsgemeinschaft Bau der Länder (ARGEBAU) [3] Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Forschungsinitiative Zukunft Bau, F2923. Stuttgart 2014; Lippe, Manfred et al.: Kommentar mit Anwendungsempfehlungen und Praxisbeispielen zu der MusterLeitungsanlagen-Richtlinie MLAR, Muster-Systemböden-Richtlinie MSysBöR, Muster einer Verordnung über den Bau von Betriebsräumen für elektrische Anlagen MEltBauVO, Teil J. Winnenden 2011, p. 223ff. [4] Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Forschungsinitiative Zukunft Bau, F2923. Stuttgart 2014 [5] Holzforschung Austria, www.dataholz.com [6] Bäder und Feuchträume in Holz- und Trockenbau. Published by the Bundesverband der Gipsindustrie e. V., Industriegruppe Gipsplatten. Merkblatt 02/2014 http://www.gips.de/fileadmin/user_upload/ download/merkblaetter/gipsplatten_und_gipsfaserplatten/2014-01-20_MB5_Online_kor-2016_AU.pdf (accessed on 11.04.2017) Informationsdienst Holz (Pub.): Bäder und Feuchträume im Holzbau und Trockenbau. Merkblatt Reihe 2, Teil 2, Folge 5, 06/2007 Informationsdienst Holz: Holzrahmenbau. holzbau handbuch, Reihe 1, Teil 1, Folge 7. 06/2009 http:// informationsdienst-holz.de/publikationen/ (issued 11.04.2017) [7] Construction products regulation. Regulation no. 305/2011 of the European Parliament and of the Council of 09.03.2011 [8] DIN 68 800: Wood preservation – Part 1: General. Para. 3.20. 2011-10 [9] See Informationsdienst Holz (Pub.): Holz im Außenbereich. holzbau handbuch, Reihe 1, Teil 18, Folge 2, 12/2000 http://www.holzfragen.de/ bilder2/info_holz_aussenbereich.pdf (accessed on 11.04.2017) [10] ibd. [11] Willeitner, Hubert; Radovic, Borimir et al.: Wood preservation – Practice-based commentary on DIN 68 800 Parts 1– 4, 2. Completely revised edition. Berlin 2012 [12] German Energy Saving Ordinance (Energieeinsparverordnung – EnEV), edition of 24.10.2015 [13] ibid.

Thermal insulation in summer

It is often said that summer thermal insulation requirements are hard to comply with in timber structures. This is a legend from the barracks builders of the war years that still persists today. In fact, modern timber structures contain a range of storage mass, from solid cross laminated or glued laminated timber structural elements through to mineral screed systems, so they are no longer purely lightweight structures. A highly insulated exterior structural timber component deflects heat just as well as it insulates against cold, so in timber structures, as in all other structures, much depends on effective shading for non-opaque structural elements (Fig. C 1.26). Simplified verification processes therefore limit window areas and /or take shading factors into account. Local climatic conditions must be considered when calculating insulation requirements to protect structures against heat in summer. Either sun input parameters or hours of excessive temperature are used in this calculation, depending on the verification process. The former is a simplified process, while the latter involves dynamic simulation. Both processes take into account effective storage mass, shading, type of glazing and ventilation at night in their calculations. If there is any doubt, it is worth using more precise processes because simplified methods must always be on the safe side and improvements in planning can be more precisely drawn from more exact calculations. In Germany, summer insulation requirements are prescribed in the Energy Saving Ordinance (Energieeinsparverordnung) [13]. DIN 4018-2 specifies out the calculation processes used to identify them. Here it should also be noted that cooling often consumes more primary energy than heating.

C 1.28

C 1.26

C 1.27 C 1.28

Effective shading for thermal insulation in summer, bathhouse in Lochau (AT) 2010, Lang + Schwärzler Thickness of insulation required for exterior timber walls that must meet various requirements Thermal bridges a geometric (regardless of construction method) b structural (overlapping influences of geometry and materials on thermal bridges)

87

Thermal insulation in summer

[°C]

Outside Solid steel-reinforced concrete building Timber frame and panel building

Solid brick building

Solid cross laminated timber building

30

28 27 °C criterion

Daniel Rüdisser, Heinz Ferk 26

24

22

20 25.07.2003 26.07.

27.07.

28.07.

With our climate currently changing, there are two ways in which thermal insulation is particularly important in summer: firstly, as an indispensable comfort and health factor for building users and secondly, in the search for the causes of climate change, as potentially contributing to negative climatic effects, especially if the planning and construction or use of buildings is impeded by overheating and fossil energy must be used to cool them. Central Europe’s climate offers good preconditions for intelligently managing climates in structures in summer. Even given current prognoses, which assume that temperatures will rise and the situation will worsen, it is expected that the air will cool sufficiently on most summer nights to provide a useful, if limited, potential for preventing overheating. Making efficient use of this effect will be a particular challenge in urban heat islands where options for reducing heat by using air to cool buildings at night are already very limited. At the same time, urban density and the number of people affected in cities will probably continue to rise.

The RIOPT study

C 2.1

C 2.2

88

Temperatures during a week in July based on a simulation comparison of construction methods. The lightest types of structures achieved the highest and lowest temperatures. Average temperatures of various types of structures, thermal balance resulting from cooling due to a natural exchange of air

To evaluate the main factors influencing thermal insulation in buildings in summer in the context of future climate change, these factors were investigated in detail in the RIOPT research project in the Laboratory for Building Science (Labor für Bauphysik) at Graz University of Technology using comprehensive, dynamic building simulations with EnergyPlus software and evaluation tools specially programmed for this purpose [1]. The investigation concentrated mainly on housing because homes can easily be cooled by cooler night air. This type of cooling can usually only be used for buildings with other usages such as offices to a limited extent or with the help of automation, due to the greater inner loads and adverse effect of the long periods in which users are present. Buildings’ behaviour in summer can only be examined systemically, so the research team carried out more than 100 parameterised simulations of a standard storey of a residential building and analysed

29.07.

30.07.

31.07.

01.08. C 2.1

around 280 million resulting data sets. Sensitivities to overheating in terms of construction, shading and air exchange rates were analysed and compared based on four current basic structural types (steel-reinforced concrete, brick, cross laminated timber and timber panel structures). Structural elements and other relevant details were chosen to ensure that the insulating levels in different types of structures were comparable.

The influence of structural type As expected, a superficial comparative review of the RIOPT study’s results showed increasingly pronounced temperature fluctuations over the course of a day as storage mass is reduced. With more precise analysis, it became clear that differences in structural type are less important in overheating than two other factors: Protection from the sun and air exchange at night have a disproportionately large influence on overheating. The calculations showed that temperatures measured over longer periods in all four types of structure were remarkably similar, differing only by tenths of a degree (Fig. C 2.2). It should be noted here that if continuous mechanical air conditioning is used, mass that functions as storage is in fact irrelevant to temperatures and energy consumption. Mass that functions as storage absorbs heat in higher ambient temperatures and releases it when temperatures are lower, limiting temperature fluctuations in interiors. Cyclical cooling can only really be understood if it is measured over the course of a day so the temperatureregulating effect of mass functioning as storage must be used over a 24-hour cycle. Heat from solar radiation generated during the day should be as effectively absorbed as possible so that at night, when outdoor air temperatures are cooler, it can be released through flows into the environment. If periods of heat are longer and storage mass can no longer cool down at night, large storage masses will gradually warm up and individual rooms will overheat. Solid buildings warm up more slowly than lightweight

Thermal insulation in summer

ones, but they also cool down more slowly. This means that storage mass must always be regarded and planned for in the context of any exchange of air that could provide effective cooling, potential solar radiation and usage. As well as the factors mentioned above, various usage profiles must also be considered. While a slow rise in temperature up to a specific daily maximum may be desirable in workspaces and spaces used during the day, bedrooms, assuming that evening temperatures will be cooler, should allow room temperatures to fall rapidly for the night. If it can be assumed that there will be an overheating situation, which is likely to increasingly be the case in urban areas, it may be advisable, especially in bedrooms, to reduce storage mass to help cool the room overnight. Bedrooms in multistorey homes should not be on the top floor because the thermal lift at work there usually adds to heat loads. Only when mass functions as storage mass and heating is followed by cooling can it favourably influence temperature variations over the course of a day. The day-night cycle, which is crucial in combating overheating, reverses the direction of its heat flow every twelve hours, so only the top centimetres of surfaces actively participate in this process. This means that in planning and optimising a mass functioning as storage, planners must focus on the top layers of structures. Steelreinforced concrete buildings with light facing shells and suspended ceilings can have lower thermal transmission capacity than timber panel structures covered with plasterboard. Mass functioning as storage mass can also be greatly reduced by curtains, furnishings and other measures that limit the exchange of air in a room. Actual differences in mass that effectively functions as storage mass are therefore usually much slighter than is often assumed. Mass that functions as storage mass must always be evaluated in the context of the heat input – buffer – heat dissipation system. This makes it clear that overheating in summer usually results from too much heat entering a structure

Solid steel-reinforced concrete building

Solid brick building

Timber building Cross laminated timber building

Timber frame and panel building

20 20.5 21 21.5 22 22.5 Average operative temperature [°C] C 2.2

89

Thermal insulation in summer

during the day and inadequate heat release at night. If this daily thermal balance becomes unbalanced and is "overturned", a constantly increasing temperature cycle may be the result (Fig. C 2.3).

Heat input Day Mass functioning as storage

Solar radiation and shade Temperature rise Night

Heat dissipation C 2.3 [W/m2] 1,000

North

South

East

West

Roof

800

600

400

200

0 3

6

9

12

15

18

21 24 Time [h] C 2.4

Solar input Occupancy

Notes: [1] For the detailed basics, results and analyses of the study see Ferk, Heinz; Rüdisser, Daniel et al.: Sommerlicher Wärmeschutz im Klimawandel. Einfluss der Bauweisen und weitere Faktoren. att.zuschnitt, 06/2016

Transmission

Other inner loads

Exchange of air

Day

Air exchange and natural cooling

Mass functioning as storage

Natural cooling works on the principle of keeping all openings closed if outside air is warmer than the room temperature. Once outdoor temperatures fall below interior temperatures, the building must be effectively ventilated (Fig. C 2.5). When ensuring an effective exchange of air in a building at night, protection from break-ins and rain must be considered, as must the laws of physics. Air can only be moved by a difference in air pressure resulting from thermal lift or wind. Working on these

Occupancy Other inner loads Mass functioning as storage Transmission Exchange of air Night C 2.5

90

Solar radiation is the main factor in the heating of housing in summer. With improvements in the insulating properties of windows, the proportion of transparent areas in facades has now also increased. The often very large areas of window surfaces in modern buildings, which can have a positive effect on energy consumption in the heating period, can quickly cause overheating at hot times of year if shading is inadequate. The contribution of diffuse and reflected radiation is also often underestimated. Heat input can be considerable even through partly shaded windows or those on a building’s north-facing side not directly exposed to sunlight (Fig. C 2.4). The overriding goal in optimising structures is to ensure effective shading of all transparent areas. Protection from the sun must also be designed to ensure that users do not find it restrictive. Only automation can ensure efficient shading when users are absent. When users are present, sun protection should still allow sufficient light into rooms and enable people to see out. Experience has shown that sun-shading systems are not used enough and often seem ineffective to users.

basic principles, planners can greatly influence the efficiency of cooling at night by optimising floor plans, openings and building orientation, through urban planning and design of the surrounding landscape, and by making use of automated systems. Planners will face increasing challenges in minimising solar radiation and maximising the exchange of air at night. Using supplementary mechanical cooling, in office buildings for example, can greatly reduce the energy required for cooling. Given current climate forecasts, residential buildings of all structural types need to be effectively protected from summer heat without the use of air conditioning if we are to live comfortably in the future climate we are all facing.

C 2.3 C 2.4

Heat flow balance and mass acting as storage Solar yields over the course of one day in Graz, 15 July, clear skies C 2.5 Thermal balance resulting from cooling due to natural exchange of air C 2.6 Extracts from the RIOPT study a Average operative temperatures of individual simulation cases b Number of hours in which the temperature exceeded > 27 °C c Number of nights in which the temperature exceeded > 25 °C d Average operative temperatures from 10 pm to 6 am – comfortable temperatures for sleeping

Thermal insulation in summer

Reduced shading and exchange of air Reduced exchange of air

Solid steel-reinforced concrete building

Solid brick building

Solid cross laminated timber building

Timber frame and panel building

Reduced shading Base model Increased shading Increased exchange of air

a

Increased shading and exchange of air 19.5

20

20.5

21

21.5

22

22.5

23

23.5

Average operative temperatures in individual simulation cases The differences in temperature resulting from structural type are slight. Changes in shading and air exchange rates produce more significant effects.

24 [°C] Reduced shading and exchange of air Reduced exchange of air Reduced shading Base model b

Increased shading

Where there is a functioning thermal balance, i.e. adequate shading and exchange of air, all types of structures stay within the temperature limit. If the balance is disturbed, temperature limits are exceeded in all structural types and differences emerge in all structural types.

Increased exchange of air Increased shading and exchange of air 0

50

100

150

200

250

300

350

400

450

Number of hours in which the temperature exceeded 27 °C

500 [Hours] Reduced shading and exchange of air Reduced exchange of air Reduced shading Base model

c

Number of nights in which the temperature exceeded 25 °C

Increased shading At night too, temperature limits will not be exceeded if there is a functioning thermal balance. If the thermal balance is disturbed, temperature limits are exceeded in all types of structures. Light structural types actually have advantages in cases of extreme overheating, because they cool more quickly and effectively at night.

Increased exchange of air Increased shading and exchange of air 0

5

10

15

20

25

30

35 [Hours] Reduced shading and exchange of air Reduced exchange of air Reduced shading Base model Increased shading d

Increased exchange of air Increased shading and exchange of air 0

5

10

15

20

25

30

35 [Days]

Average operative temperatures from 10 pm to 6 am: temperatures comfortable for sleeping Differences in average temperatures comfortable for sleeping vary only very slightly for different types of structures. Light structural types have advantages in limiting overheating. C 2.6

91

The layer structure of building envelopes Maren Kohaus, Hermann Kaufmann

C 3.1

Modern timber construction, with the special opportunities offered by wood as a natural, renewable building material, is setting trends in environmentally-friendly construction. Many passive energy and plus-energy buildings feature highly insulated building envelopes based on a timber structure. Past concerns about interiors quickly overheating in summer are now unfounded. In fact, the opposite is the case. Timber construction offers very effective means of achieving low heat transmission coefficients with thin walls (Fig. C 3.2), as the many timber buildings that meet modern comfort standards prove. These advantages are being felt not only in new buildings but in renovated buildings. With the broader possibilities offered by prefabrication, envelope systems based on timber structures are now increasingly accepted.

• Airtightness • Protect structures from condensation (from convection and diffusion) • Protect structures from fire • Protect structures from noise (incl. acoustic measures)

The complex layered structures of timber structures do, however, place high demands on planners and the expert professional construction of structural elements. As the number of layers of structural elements increases, so does the complexity of joints between elements in prefabricated structures, so it is worth trying to reduce the number of layers. Work is continuing to limit the diversity of possible solutions through standardisation in order to achieve more clarity and increased planning reliability [1].

Functions of layers of structural components

Facades and roofs are subject to basically identical structural and physical requirements, although various functional requirements will call for different sequences of layers and materials in structural elements. To effectively manage the complexity of the functional allocation of individual layers to structural components, it is advisable to identify the functions involved at an early stage of planning and specify them in construction implementation plans (Figs. C 3.10 and C 3.11, p. 96).

Individual layers are described in accordance with their functions: • Exterior cladding • Windproof layer /second water-bearing layer • Structural layer • Insulating layer • Airtight layer • Vapour barrier layer • Installation layer (with / without insulation) • Interior cladding or lining

Requirements for building envelopes Building envelopes must fulfil the following protective functions (see also “Protective functions”, p. 72ff.): • Protect structures from weather (wind, rain, snow, sun / UV radiation) • Thermal insulation in winter /summer

C 3.1

C 3.2

C 3.3

92

Low-energy timber houses, Mühlweg residential complex, Vienna (AT) 2006, Architekten Hermann Kaufmann Developments in the layer structure of timber building envelopes (horizontal section), with a focus on thermal insulation Polyfunctionality of structural component layers

Each function in a structural component can be assigned to a specific layer, but some materials can also be polyfunctional and fulfil several functions at the same time (Fig. C 3.3). A vapour barrier layer and airtight layer are usually incorporated into the same layer of a structural component, e.g. a composite wood material panel or foil. Allocating functional requirements to structural component layers requires a continuous layer, which must be considered when creating joints with other structural components. Joints between elements in a cross laminated timber panel of an exterior wall that is left visible in the interior and has a load-bearing function as well as

The layer structure of building envelopes

1982

1972 2

Current models of exterior wall structures 2

U = 0.18 W/m2K

28.75 cm

Solid timber structure (here cross laminated timber) U = 0.16 W/m2K

42.25 cm

22.45 cm 2002

U = 0.25 W/m2K 26.15 cm

1992

Timber panel structure U = 0.16 W/m2K

38.4 cm

U = 0.28 W/m K 17,85 cm

U = 0.58 W/m K

C 3.2

being a vapour barrier and airtight layer must be tightly sealed. This can be done by covering joints or laying sealing tape or strips in joints and gaps (Fig. C 3.12, p. 97). Polyfunctional layers of structural components generally make it possible to reduce the number of layers and result in fewer work steps in building components. This reduction does, however, usually also require special connection details to other structural components (e.g. in incorporating interior structural components or pipes and cables into the building envelope). This means careful planning and monitoring in the construction phase, with particular attention being paid at an early stage.

Insulating layer and structure

There is a difference between the construction of two types of primary insulation levels, depending on their position in relation to the structural level. Insulation can be either outside on the structural layer, which is usually the case with cross laminated, dowel laminated or glued laminated timber element solid timber structures (Fig. C 3.13, p. 98), or it can be installed between linear support structure elements (Fig. C 3.14, p. 99). Structures insulated on the outside Hard insulating materials that do not require a special substructure are usually used for

structures insulated on the outside. Soft insulating materials, in contrast, are fitted between a one, two or even three-layer, substructure laid crosswise or between special profiles and optimised to minimise thermal bridges (e.g. Å-beams) (Fig. C 3.13 a, E, p. 98). Structures with insulation in interstices Wood’s low thermal conductivity (-value approx. 0.11 – 0.17 W/mK) makes it quite safe in structural physics terms in structures with insulation in interstices not to cover timber components, such as studs in an exterior wall or rafters, with insulation because no condensation forms there. Thermal bridges can

Protective functions exterior wall Protection from weather

AirAcoustics Protection Protection Protection Sound tightness from heat from con- from fire insulation densation

°C Structural component layers exterior walls

Outside

Inside

Polyfunctionality: 4 functions assigned to 1 structural component layer

Exterior cladding

Facade membrane (windproofing, second water-bearing layer)

Thermal insulation (hard / soft)

Structural layer

Airtight layer

Vapour barrier

Sanded stainless-steel sheeting, 2 mm Steel substructure Rear ventilation Vapour permeable facade membrane Three-ply mineral wool, 380 mm with its own support structure Cross laminated timber element e.g. 72 mm, glued on the narrow sides, airtight joints, exposed timber quality on the inside

Inner lining (with / without an installation layer)

Functional layers exterior walls C 3.3

93

The layer structure of building envelopes

Cladding

Structural component

x

C 3.4

be minimised by increasing the insulation’s thickness or using load-bearing elements with special geometry (e.g. Å-beams) (Fig. C 3.14 a, E, p. 99). Additional exterior insulation Where additional insulation is added to a structure with insulation in interstices, pressure-resistant, vapour-permeable insulation such as wood fibreboard with a waterresistant surface is often used, if possible from a fire safety aspect, to protect structural components from the weather and mechanical damage during installation and construction (Figs. C 3.14 a, D – F, p. 99, C 3.25 b, p. 106). This type of extra layer may also be advisable in structures insulated on the outside (Figs. C 3.13 a, D – F, p. 98 and 3.25 d, p. 106)

Cladding type

Building material / Structural component

C 3.5

to eliminate any thermal bridges in the substructure and protect structural components during the construction phase. The soft, inexpensive insulating materials in composite thermal insulation systems can be laid between battens and covered with a suitable, pressure-resistant, load-bearing insulating material, which can at the same time serve as a base for exterior plaster (Fig. C 3.13 b D – F, p. 98). The inherent system specifications of the composite thermal insulation system that are provided by the manufacturer must be also be considered. Additional interior insulation If an extra installation layer for routing pipes and cables is added to the inside of a building envelope to avoid penetrating the airtight layer or vapour barrier, filling that layer with insula-

Schematic diagram

horizontal alignment Planar composite wood material

Form-locking cladding

Force-locked cladding

Open cladding

• • • • • •

Timber or wood-based material Bulk density ≥ 330 kg/m3 Closed surface Panel thickness ≥ 18 mm Edge length ≥ 200 mm Panel area ≥ 0.20 m2

Examples

tion will improve the structural component’s effective insulation (Figs. C 3.13 C, F, p. 98 and C 3.14 C, F, p. 99). The rule of thumb is that the proportion of insulation on the inside of a vapour barrier layer should not exceed an equivalent thickness of approx. 20 % of the insulation’s total thickness. If the inner insulation is thicker, carrying out a general calculation of the structure’s physical properties may be advisable (Glaser method or hygrothermal calculation). Exterior cladding layer/weather protection

Exterior cladding material for a timber building is chosen based on the same principles as those applied to conventional construction with mineral building materials. Almost all cladding materials can be used for an exterior wall or roof. Some prefabricated

Alignment Depth Minimum overhang of fire aprons of rear installed on each storey (measureventilation ment x in Fig. C 3.5) layer

vertical alignment

≥ 200 mm ≥ 100 mm ≥ 50 mm ≥ 20 mm • • • • • •

Solid timber panels Cross laminated timber Laminated veneer lumber Parallel strand lumber OSB Particle board

• Relief grooves: - Remaining thickness ≥ 10 mm - Groove spacing ≥ 30 mm • Plank thickness ≥ 18 mm • Board width: - pith-free ≤ 160 mm - half rift or rift sawn ≤ 250 mm

• Tongue-and-groove cladding • Board-and-batten cladding with profile • Tongue-and-groove

• Relief grooves: - Remaining thickness ≥ 10 mm - Groove spacing ≥ 30 mm • Plank thickness ≥ 18 mm • Board width – none fixed

• Shiplapped cladding • T-profile cladding

• Board thickness ≥ 18 mm • Board cross section area ≥ 1,000 mm2 • Cover strip thickness ≥ 10 mm • Board width – none fixed

• Open cladding • Weatherboard • Board-and-batten cladding • Clapboard • Board-and-batten cladding

≥ 50 mm horizontal / vertical ≥ 100 mm

≥ 50 mm horizontal / vertical ≥ 100 mm ≥ 50 mm horizontal ≥ 100 mm ≥ 50 mm vertical ≥ 100 mm ≥ 50 mm horizontal ≥ 100 mm ≥ 50 mm vertical ≥ 100 mm C 3.6

94

The layer structure of building envelopes

exterior wall elements cannot be assembled in a factory because they must be fairly robust and repairable for transport. The need to add a layer of air behind cladding depends greatly on the cladding’s diffusion behaviour inrelation to other layers of structural components. Ventilated and rear-ventilated exterior wall cladding (Fig. C 1.13, p. 80) differs from cladding with a permanent layer of air. Lacking a drainage level, the latter types are far less able to drain off any condensation or surface water penetrating a building due to driving rain, so they should be avoided (see “Protecting timber from moisture”, p. 79ff.). Fire safety for facade cladding The fire safety requirements to which an exterior wall component is subject will vary depending on the building’ class and height (see “Fire safety requirements”, p. 72ff.). Exterior facade cladding only needs to limit the spread of fire beyond the fire’s primary site.

C 3.7

Facade cladding on buildings up to three storeys high (building class 1– 3) is not subject to any special requirements so normally flam-

C 3.4

C 3.5 C 3.6 C 3.7

C 3.8

C 3.9

Fire-resistant plate in a facade; angled metal sheeting surrounds each storey in an eight-storey timber residential and office building, Bad Aibling (DE) 2012, Schankula Architekten Schematic diagram of a steel sheeting fireresistant storey partition (clear overhang x) Types of timber facade structures with B1 equivalence Rear-ventilated facade structure for a solid timber building clad on the outside with ground steel sheeting. The prefabricated room modules were clad with the exterior cladding at the building site. Hotel Ammerwald near Reutte in Tirol (AT) 2009, Oskar Leo Kaufmann and Albert Rüf Rear-ventilated facade structure for a solid timber building with exterior cladding made of glass fibre reinforced concrete elements. The rigidity of these elements allows for more space between this structure and the aluminium substructure. Residential and office building, Zurich (CH) 2010, pool Architekten Facade structure with a composite thermal insulation system for a timber panel building. c 13 residential and office building, Berlin (DE) 2013, Kaden Klingbeil Architekten

C 3.8

C 3.9

95

The layer structure of building envelopes

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C 3.10

t

C 3.11

The layer structure of building envelopes

mable building materials (B 2 as defined in DIN 4102-1) such as timber cladding and biogenic insulating materials (made of renewable raw materials) can usually be used as exterior insulation and as a composite thermal insulation system. Only building materials of low flammability (B1 as defined in DIN 4102-1) can usually be used as cladding on taller buildings with four to seven storeys (building class 4 and 5), so timber cannot be used as ventilated /rearventilated cladding material here, because it is regarded as normally flammable. However, many standardised and natural fire tests [2] have shown that, if details are appropriately built, timber can be used to create an equivalent to “low flammability” (see “Combustibility and fire resistance”, p. 74f.). A fire barrier at each storey can prevent fire from spreading into other storeys (Figs. C 3.4 and C 3.5, p. 94). These can be made with a steel plate, for example, which depending on the cross section of the boards and proportion of joints in the cladding, can project 20 to 200 mm out of the facade and continue back to the bare wall or the fire prevention cladding of the exterior wall component (Fig. C 3.6, p. 94). This will prevent fire from spreading through the layer of air or within layers of the support structure. Only insulating materials of low flammability (B1 as defined in DIN 4102-1) can be used in composite thermal insulation systems in taller buildings (building classes 4 and 5). It should be noted that only approved composite thermal insulation systems are permitted here. Only non-flammable materials in building materials class A1 may be used as facade cladding for buildings of high-rise height and higher. Windproof layer / second water-bearing layer

A second water-bearing layer is provided as additional security for ventilated or rear-ventilated facades and sloping roof structures. This is, at the same time, a windproof layer and prevents outside air from getting through the insulation or joints in the insulation panels, which would greatly impair their insulating function. A windproof layer also supports the airtightness of the entire structural component, which greatly reduces the amount of warm,

moist air that can permeate a structure through leaks in the airtight layer and considerably minimises condensation (see “Condensation from diffusion”, “Condensation from convection”, p. 79f.).

Flat roofs can also be rear-ventilated (Fig. C 3.24, p. 105), but these types of roof are rarely built in practice for reasons of cost and because such structures must be high in order to facilitate a functioning flow of air.

Windproof layers in facades Materials used in windproof layers must be as vapour-permeable as possible, with an sd value of < 0.3 m (DIN 68 800) (see “Correlation with other structural component layers”, p. 99), have surfaces that can dissipate water and be laid to create airtight joints (e.g. tongueand-groove joint or adhesion). Vapour-permeable foils and composite wood boards (e.g. construction MDF) or insulating wood fibreboard are all suitable. If fire safety requirements are more stringent, either mineral-bonded composite wood board (e.g. cement-bonded chipboard), which must provide adequate vapour diffusion resistance on the structural component’s inside, or gypsum-bonded panelling (fireresistant gypsum plasterboard, gypsum fibreboard) is used to protect the structural element’s exterior and meet the fire safety requirements (Figs. C 3.16, p. 102 and C 3.17, p. 103). The latter can form the windproof layer but must also be protected from moisture by a vapour-permeable foil. If facade cladding has open joints or perforations, the windproof layer will be the only water-bearing layer, so absolutely tight sealing and unobstructed water dissipation is essential here. Depending on the way it is built, cladding will diminish only the impact of precipitation here. In facades without a layer of air incorporated into them, e.g. standard certified composite thermal insulation systems, the exterior layer of plaster must fully adopt the functions of the windproofing and water-bearing layer because there is no second water-bearing layer.

Polyfunctional windproof layers Building the windproof layer in a facade or sloping roof with a panel material, e.g. wood fibreboard, can help to protect a prefabricated structural component from moisture and mechanical damage during transport and installation. During the construction phase, it can be used to seal the building or as a temporary roof and is, at the same time, a second water-bearing layer. Wood fibreboard with thermal conductivities of 0.09 to 0.045 W/mK thick enough to function as additional insulation can also minimise any thermal bridges around studs or rafters (Figs. C 3.13, p. 98 and C 3.14, p. 99).

Windproof layers in rear-ventilated roof structures A second water-bearing layer in the form of a suspended ceiling is built into rear-ventilated sloping roofs to dissipate any moisture forming due to condensation or leaks in the roof membrane (Fig. C 3.25 a– d, p. 106).

Airtight layer consisting of an additional foil on the inside or outside of the planking Single-sided adhesive tape

Double-sided adhesive tape

Airtight layers

Airtight layers are vitally important because leaks detract from the protection the layers offer against heat, noise, fire and condensation or can even destroy it entirely, which can result in energy losses, condensation from convection and thermal bridges and may allow smoke and fire to spread in the event of fire. Significance of the airtight layer Laboratory tests carried out by the Fraunhofer Institute for Building Physics in Stuttgart have demonstrated the importance of airtight layers in buildings. Leaks let moist, warm air into

C 3.10

Axonometric diagram of the correlations between structural component layers /functional layers in a solid timber wall insulated on the outside C 3.11 Axonometric diagram of the correlations between structural component layers / functional layers in an exterior wall with insulation in interstices C 3.12 Various ways of building airtight layers, horizontal sections a By adding foils b By gluing to composite wood board c With a solid timber element and appropriate element joints

Airtight layer created by inner planking

Single / double-sided adhesive tape

Airtight layer created by solid structural components

Single-sided adhesive tape

Single-sided adhesive tape

outside

outside

outside

a

b

c

Precompressed sealing tape

C 3.12

97

The layer structure of building envelopes

structures and can cause far more condensation than vapour diffusion produces (Fig. C 1.14, p. 80). Air usually leaks through inadequate seals where materials are penetrated, at the edges of structural components, at joints such as window and door joints, and in ceiling, floor and roof connections or due to incorrect construction or damage to the airtight layer itself. To prevent the most frequent source of errors, pipes and cables should always be routed on the interior side of an airtight layer so that the layer cannot be penetrated. Exposed solid timber elements that form an airtight layer require special detailed solutions. Within these elements, pipes and cables can only be routed in structural components to a certain depth that

will allow the remaining layers of timber to be sufficiently airtight and vapour-proof, otherwise additional sealing measures will be required (see “Protective functions”, p. 72ff. and “Building technology – special features of timber construction”, p. 122ff.). Construction of the airtight layer Airtight layers are usually made of plastic foil materials, specially coated paper web, composite wood, gypsum fibre or gypsum plaster boards. In timber panel elements, this layer also normally has a bracing function and may even be load-bearing. If this is the case, planking must have adequate flow resistance and joints between elements must be airtight.

Cross laminated timber elements can also form an airtight layer, if the timber laminate layers are glued along their narrow sides and joints between elements are made airtight, e.g. with joint sealing tape (EPDM sealing tubing, precompressed sealing tape) laid in the joints or by gluing joints together with adhesive tape. Foils used in an airtight layer must be glued to joints (Figs. C 3.12 a, p. 97 and C 3.26, p. 107). Overlapping is not sufficient. It is strongly recommended that airtightness be tested with a blower door test (see “Condensation from convection”, p. 79f.), which should be carried out before inner planking is installed. Element joints and structural component connections in pre-

Structure insulated on the outside

B

A

Cross laminated timber, here exposed, as a vapour barrier and airtight layer, laminate layers glued along their narrow sides Extra airtight foil / vapour barrier if boards are not glued along their narrow side or for installations in the cross laminated timber layer

Additional non-flammable planking may be required for fire safety reasons; the airtight layer/vapour barrier can then be attached on the inside C Installation layer insulated on the outside improves the U value

Extra airtight foil /vapour barrier optional

additional panel material/additional insulation

D

a

98

Vapour-permeable wind proofing planking and second water-bearing layer and providing mechanical protection during transport Extra exterior insulation, e.g. softwood fibre panels coated with paraffin wax, improve the U value and offer mechanical protection during transport

E

F

composite thermal insulation system on an extra layer of insulation

single second water-bearing layer

Foil windproofing

Å- or H-beams reduce thermal bridges

Installation layer insulated on the outside improves the U value

Extra airtight layer / foil vapour barrier if the narrow edges of the cross laminated timber are not glued together b

B

C

Cladding

Installation layer

Solid timber structure

Composite thermal insulation system

Cladding

Installation layer

Solid timber structure

Exterior insulation

without a layer of air as composite thermal insulation system

single layer composite thermal insulation system

A

Layer of air

Cladding

rear-ventilated / ventilated

Cross laminated timber, here left visible, as vapour barrier and airtight layer, narrow edges of the laminate layers glued

With additional airtight foil / vapour barrier (if boards are not glued along their narrow side or for installations in the cross laminated timber layer) an extra support panel for a composite thermal insulation system may be necessary (see manufacturer's specifications) Additional non-flammable planking may be required for fire safety reasons; the airtight layer / vapour barrier can then also be installed on the inside Installation layer insulated on the outside improves the U value

Additional airtight foil /optional vapour barrier D

Composite thermal insulation system as extra external insulation on exterior insulation between battens/counter battens

E

Additional non-flammable planking may be required for fire safety reasons

Additional airtight foil/vapour barrier can then also be installed on the inside. F

Installation layer insulated on the outside improves the U value Additional airtight layer/ vapour barrier as foil if the laminate boards in the cross laminated timber layer are not glued along their narrow sides C 3.13

The layer structure of building envelopes

fabricated elements must remain accessible so that any leaks can be located and repaired. Vapour barrier layer

A vapour barrier is installed on the inside of an insulating layer to stop condensation from forming in a structure. Structural components in building envelopes must be as vapour-permeable as possible and as vapour-proof as necessary, with the layers of structural components always more vapour-permeable from the inside towards the outside so that more water vapour cannot penetrate the structural component than diffuses out again. Vapour-permeable structures have proven their value because of their ability to dry out and are regarded as very robust.

Correlation with other structural component layers Here the rule of thumb is that the thickness of the water vapour-equivalent layer of air of the vapour diffusion-regulating layer, as represented by the sd value, must be at least five to six times as high as the sd value of the exterior layers(s). Foils on the inside of ventilated/rear-ventilated exterior wall structural components with sd values of 500 to 1,000 m were once used, but sd values now range from 5 – 20 m or moistureadaptive vapour barriers are used [3]. If you want to build an exterior wall structure without using foil materials, a structure with

C 3.13

C 3.14

Schematic diagram of the layer structure of a structure insulated on the outside, using the example of a cross laminated timber element a Rear-ventilated / ventilated b Without a layer of air as composite thermal insulation system Schematic diagram of the layer structure of a structure with insulation in interstices, using the example of a timber panel building a Rear-ventilated / ventilated b Without a layer of air as composite thermal insulation system

structure with insulation in the interstices

single second water-bearing layer

B Additional non-flammable planking may be required for fire safety reasons

Additional airtight foil / vapour barrier can also be installed on the inside

Installation layer insulated on the outside improves U values

additional panel material / extra insulation

D

a

Foil windproofing

E

single layer composite thermal insulation system

Additional airtight layer / foil vapour barrier if interior planking is not glued to make it airtight

C

A

Exposed bracing planking as vapour barrier and airtight layer ∫ airtight e.g. glued joints necessary

Å- or H-beams reduce thermal bridges

F

Additional airtight foil / vapour barrier if interior planking is not glued to make it airtight

b

Installation layer

Cladding

Exposed bracing planking as vapour barrier and airtight layer ∫ airtight e.g. glued joints necessary

Additional airtight foil / vapour barrier if interior planking is not glued to make it airtight Additional non-flammable planking may be required for fire safety reasons

Additional airtight foil / vapour barrier can also be installed on the inside C Self-supporting insulating panels, e.g. softwood fibre panels Insulated installation layer improves U values D

Extra vapour-permeable planking as windproofing / second water-bearing layer offers mechanical protection during construction; can also be installed for manufacturing technology reasons (level of prefabrication, insulating material such as cellulose wadding that is not self-supporting etc.) Additional exterior insulation (protected from moisture) serves as windproofing / second waterbearing layer, offers mechanical protection and improves the U value

B

Frame structure filled with insulation

Composite thermal insulation system

Cladding

Installation layer

Frame structure filled with insulation

without a layer of air as composite thermal insulation system

composite thermal insulation system on an additional insulating layer

A

Layer of air

Cladding

rear-ventilated / ventilated

Additional airtight layer / foil vapour barrier if interior planking is not glued to make it airtight Additional exterior planking can be used for production reasons (level of prefabrication, insulating material that is not self-supporting, such as cellulose wadding etc.)

E Additional non-flammable planking may be required for safety reasons Additional airtight foil / vapour barrier can also be installed on the inside

F

Additional airtight layer / foil vapour barrier if interior planking is not glued to make it airtight C 3.14

99

The layer structure of building envelopes

Moisture-adaptive vapour barrier around an integrated storey slab, residential complex, Jenbach (AT) 2010, Architekten Hermann Kaufmann a Vertical section Scale 1:20 b Building site photo

Structural component

C 3.15

Structural component

Various applications of a moistureadaptive vapour barrier

100

Inner linings

The rule of thumb is: Ideal value inside: sdinside = 6 ≈ 0.3 m = 1.8 m; Actual value inside: sdOSB = 2.0 m; Comparison: 2.0 m > 1.8 m

• Direct planking on a bearing layer Direct planking is sometimes used for economic reasons. If its construction is carefully monitored it can also fulfil airtight and vapour barrier functions. This layer should not be perforated by pipes or cables.

Sealing layers with sd values of approx. sd ≥ 100 m are now used for flat roofs insulated on the outside without an extra layer of air. The sd value of the vapour barrier on the inside should be sd ≥ 500 m. This can only be achieved with foil materials or suitable bitumen sheeting, which can also serve as a temporary roof during construction. DIN standards (DIN 68 800) and databases such as www.dataholz.com contain superstructures already certified by their manufacturers. If there is any doubt, calculation methods prescribed by building inspection authorities should be used to verify exterior wall and roof components in structures. Moisture-adaptive vapour barriers Moisture-adaptive vapour barriers can modify their sd value. In low relative humidity, they largely impede diffusion and in high relative humidity they are very vapour-permeable, so any moisture accruing in the structure from condensation or leaks can dry out, which is essential in flat roofs with insulation in interstices that are not rear-ventilated (see “Flat roof structures”, p. 104f.). Moisture-adaptive vapour barriers should be used for some connections between structural components, e.g. if the vapour barrier layer cannot be in its optimum position in the layer structure for structural reasons. This can be the case, for example, when a slab is integrated into an exterior wall, because then the vapour barrier functions from the inside outwards around the slab support (Fig. C 3.15).

a

b

insulation in interstices and ventilated or rearventilated exterior cladding and a vapourpermeable windproof layer of sd < 0.3 m, for example, OSB board with an sd value of 2 m attached to the inside can provide both airtightness and a vapour barrier. Butt joints between elements and connections to other structural components must be airtight.

C 3.15

A building envelope’s inner lining involves design aspects and must also meet functional requirements such as fire prevention, acoustic qualities, soundproofing and protection from moisture. Mass that also stores energy can be increased here if the appropriate materials are used. The following types of lining are commonly used:

• Planking on the bearing layer with a cavity – installation layer An extra facing shell can be built as an installation layer on the interior side of a structural component so that pipes and cables can be routed on the inside of the airtight layer without penetrating it. The additional space required to do this is usually balanced against the benefits of easier installation and safer construction. Adding extra insulation to this installation layer can further improve its U value, reduce any thermal bridges, and has a positive effect on the sound reduction index of the whole structural component.

Technical soundproofing aspects Despite their lack of mass, timber structures with suitable layer structures can provide good soundproofing and guarantee compliance with applicable standards (see “Soundproofing and acoustic requirements”, p. 82f. and “The layer structure of interior structural components”, p. 114ff.). Various exterior wall structures have now been tested and certified and can be found in various structural component catalogues. The fundamental prerequisite for good airborne sound and impact sound insulation is the airtight construction of structural compo-

The layer structure of building envelopes

nents. Special structures can be calculated, although any potential secondary sound transmission paths must always be very carefully assessed. The airborne sound reduction index of solid timber structural components also depends on how joints are constructed. Attaching insulation to exterior cladding and interior lining layers will reduce the sound insulation index [4]. Improving the soundproofing of exterior walls The sound reduction index of exterior walls can be reduced by taking the following measures on the room side of a structural component (see [5] for approximate standard values for a cross laminated timber exterior wall with exposed timber on the inside and a composite thermal insulation system): • Direct planking on a cross laminated timber wall with a composite thermal insulation system: 12.5 mm plasterboard ∫ improvement of approx. 0 –1 dB • Double direct planking on a cross laminated timber wall: 2≈ 1.5 mm plasterboard ∫ improvement of approx. 1–2 dB • Facing shell insulated with mineral wool on a cross laminated timber wall ∫ improvement of up to approx. 6 dB • Facing shell insulated with mineral wool on a cross laminated timber wall attached with sound insulation clips and clad with 2≈ 12.5 mm plasterboard ∫ improvement of up to approx. 15 dB • Facing shell on a cross laminated timber wall, completely decoupled, cavity (85 mm) insulated with mineral fibre cavity insulation (50 mm), CW profile clad with 12.5 mm plasterboard ∫ improvement of up to approx. 22 dB • Facing shell on a cross laminated timber wall, completely decoupled, cavity (85 mm) insulated with mineral fibre cavity insulation (50 mm), CW profile clad with 2≈ 12.5 mm plasterboard ∫ improvement of up to approx. 23 dB Structural components with insulation in interstices generally have good soundproofing in the high frequency range, with an increase of 12 dB per octave compared with just 6 dB

per octave for solid timber structural components [6]. The soundproofing influence of facing shells on timber panel walls is therefore less than with solid timber walls, because it is assumed that structural components with insulation in interstices will have a higher sound insulation level. The type of construction of exterior cladding also influences a structural component’s sound reduction index. In composite thermal insulation systems, for example, the dynamic rigidity and bulk density of insulation panels and bulk density and thickness of the plaster are relevant to soundproofing values. The linear flow resistance r of insulating materials is an important aspect of insulation on the outside of a rear-ventilated facade [7]. Details on specific structures and installation situations should be requested from insulation materials manufacturers. The sound reduction index of rear-ventilated facades can be improved by optimum planning of the points at which the substructure is attached to the studs of cavity insulation, e.g. if the facade substructure and battens on the inside of an installation layer are not on a plane with the studs in a timber panel structure or the studs of exterior cavity insulation in a solid timber structure insulated on the outside. This can improve the sound reduction index in timber panel structures by up to 7 dB [8]. Sound insulation for adjoining utilisation units

Where structural components such as building envelopes or slabs extend over several utilisation units, the transmission of airborne and structure-borne sound must be prevented. Measures frequently used to do this include integrating slabs into the facade structure [9] or decoupling structural components by installing elastomeric bearings at structural support points (see “Decoupling layers in structural components”, p. 120f.). Additional flexible layers such as facing shells for walls and ceilings (see “Cladding”, p. 118) are also sometimes used. Here too, all the structural components must be airtight.

Technical aspects of fire safety Cladding on tall timber buildings (four storeys and higher) is usually subject to more stringent fire prevention requirements. Such structures may, however, still be built with exposed timber based on certification drawn up for the specific structure (fire safety concept) (see “Fire safety performance in timber structures”, p. 75ff.). Fire prevention cladding is usually made of gypsum fibreboard or fire-resistant gypsum plasterboard. A composite thermal insulation system with mineral wool insulation and silicate plaster attached to gypsum fibreboard or fire-resistant gypsum plasterboard can also be used as fire prevention cladding on the outside of a wall (Fig. C 3.17 a, p. 103). Fire prevention cladding (e.g. K260) requires a proof of usability certificate issued by a building inspection authority (in Germany with a general building authority test certificate (abP), national technical approval (abZ) or ETA). Gypsum fibreboard or fire-resistant plasterboard can take on several functions and reduce the number of layers in a structural component, serving for example as inner lining for design purposes and as an airtight layer in the form of direct planking without an installation layer (Figs. C 3.16, p. 102 and C 3.17, p. 103). This board, with its low sd values (μ value of approx. 13: 13 ≈ 0.018 m = 0.23 m = sd) can, however, only be used with an additional vapour barrier foil with an sd value of ≥ 2 m if another structural component layer (e.g. inner planking with an OSB board, as in Fig. C 3.17 c (p. 103) does not take on this function. However, walls panelled with gypsum fibreboard or fire-resistant gypsum plasterboard have comparatively low horizontal load-bearing capacity, so supplementary composite wood board is usually used under plasterboard in multi-storey buildings. Their other advantage is that they make it easier to subsequently attach pictures and cupboards etc. to walls. If an inside installation layer is provided, the inner planking should not be built as an airtight layer or necessary fire prevention layer. Airtight and fire prevention sealing of areas where pipes

101

The layer structure of building envelopes

Solid timber structure with composite thermal insulation system

Solid timber structure, rear-ventilated

Solid timber structure (visible inside) rear-ventilated, minimal use of foil

Structural component layer Structural component layer

Structural component layer

Exterior plaster render 10 mm Mineral wool 180 mm Fire-resistant gypsum plasterboard 12.5 mm (additional airtight layer, optional) Cross laminated timber (with μ = 50; sd = approx. 7 m) 140 mm Fire-resistant gypsum plasterboard 2≈ 18 mm Installation layer, optional

Rear-ventilated facade Planking membrane (liner) (sd ≤ 0.3 m) Mineral wool 180 mm Fire-resistant gypsum plasterboard 18 mm Cross laminated timber (with μ = 50; sd = approx. 7 m) 140 mm Fire-resistant gypsum plasterboard 2≈ 18 mm Installation layer, optional

Possible values without installation layer: REI 90/K260 U = 0.152 W/m2K R w, R = 39 dB

Rear-ventilated facade Windproofing, optional Wooden composite board (e.g. cement-bonded particle board) Rock wool lamella insulation 180 mm T ≥ 1,000 °C; t ≥ 40 mm Gypsum fibreboard 15 mm Exposed cross laminated timber (with μ = 50; sd = approx. 7 m) 140 mm

Possible values without installation layer: REI 90/K260 U = 0.15 W/m2K R w, R = 40 dB

Possible values: REI 60 U = approx. 0.15 W/m2K R w, R = n. a.

Function

Function

Function

Plaster render system: Protection from the weather, windproofing, exterior fire safety cladding

Protection from weather

Protection from the weather

Windproofing, second water-bearing layer

Windproofing, second water-bearing layer, extra insulation

Load-bearing layer, vapour barrier Airtightness, interior fire-resistant lining

Exterior fire safety cladding Load-bearing layer, vapour barrier

Exterior fire safety cladding Load-bearing layer, vapour barrier, airtight layer, dimensioned to withstand complete burnout (fire safety certificate for the specific building required)

Airtightness, interior fire-resistant lining a

b

c

and cables penetrate is possible but requires precise planning and for prefabricated elements should be carried out in the factory or in strictly controlled conditions as far as possible.

ous top and bottom plates up to a maximum height of three to four storeys, otherwise the subsidence ratio from the lateral loading of top and bottom plates becomes too great (Figs. B 1.11 b and c, p. 44). Higher buildings can be built with timber panel walls using hardwood bottom plates and /or supplementary structural measures. Loads should be transferred in solid timber walls directly through the end grain so slabs should only partly rest on the walls or be laid on walls with a cantilever. Vertical loads can be transferred through steel structures integrated into slabs or cut-outs filled with grouting (Fig. B 1.11 d, p. 44).

Non-load-bearing walls up to high-rise height must only be fire-retardant (REI 30). Beyond this height, the fire resistance required depends on the specific fire safety concept.

Further criteria in choosing exterior wall structures As well as the requirements made on a building envelope described above, other factors must be considered when choosing an exterior wall structure. Structural factors

If the building envelope is part of the primary structure relevant to the building’s overall structural integrity, timber panel or solid timber walls consisting of cross laminated timber elements (see “c 13 residential and office building in Berlin”: timber panel rear building, solid timber front building, p. 170ff.) or dowel laminated timber elements (see “Residential and commercial building in Zurich”, p. 178ff.) can be used. Load-bearing timber panel walls can be installed in a standard structure with continu-

102

A frame structure with appropriately dimensioned supports that transfer loads directly into the supports below them is the most suitable construction method for tall buildings, including those at high-rise height (see “Student residence in Vancouver”, p. 166ff.). Elements that partition spaces in this type of facade will therefore not be load-bearing parts of the building envelope, so fire safety requirements on them will be less stringent (see “Fire protection”, p. 72ff.).

C 3.16

Indoor climate factors

Exposed solid timber structures influence a building’s indoor climate. Wood’s low thermal conductivity, relatively high bulk density and high specific thermal capacity (c = 2,100 J/kgK) increase thermal inertia, making wooden buildings very comfortable in summer (see “Thermal insulation in summer”, p. 87). Cross laminated timber can provide almost three times the storage capacity of timber panel walls with comparable U values [10]. Wood’s ability to absorb moisture from interior air and release it again after a certain period balances the humidity of air in rooms and improves the comfort of exposed structural components. Economic factors

A building envelope’s cost depends not only on the material price of its individual layers but also on the efficiency of manufacturing and assembly processes connected with pre-

The layer structure of building envelopes

Timber panel structure with composite thermal insulation system

Timber panel structure, rear-ventilated

Timber panel structure, rear-ventilated, minimal use of foil

Structural component layer Structural component layer

Structural component layer Exterior plaster render 10 mm Rock wool lamella insulation 40 mm T ≥ 1000 °C; t > = 40 mm Fire-resistant gypsum plasterboard 12.5 mm Mineral wool 240 mm Vapour barrier (sd ≥ 2 m) Fire-resistant gypsum plasterboard 2≈ 18 mm Installation layer, optional

Rear-ventilated facade Vapour-permeable planking membrane sd ≤ 0,3 m Fire-resistant gypsum plasterboard 2≈ 18 mm Mineral wool 240 mm Vapour barrier (sd ≥ 2 m) Fire-resistant gypsum plasterboard 2≈ 18 mm Installation layer, optional

Possible values without installation layer: REI 60/K260 U = 0.14 W/m2K R w, R = 47 dB

Rear-ventilated facade Windproofing, optional Concealed insulation, wooden composite board (e.g. cement-bonded particle board) Fire-resistant gypsum plasterboard 2≈ 18 mm Mineral thermal insulation 240 mm OSB board (sd = approx. 4 m), airtight 24 mm Fire-resistant gypsum plasterboard 2≈ 18 mm Installation layer, optional

Possible values without installation layer: REI 60/K260 U = approx. 0.16 W/m2K R w, R = n. a.

Possible values without installation layer: REI 60/K260 U = 0.165 W/m2K R w, R = 49 dB

Function

Function

Function

Plaster render system: Protection from the weather, windproofing, exterior fire safety cladding

Protection from the weather

Protection from the weather

Windproofing, second water-bearing layer

Windproofing, second water-bearing layer, extra insulation

Vapour barrier Exterior fire-safety cladding Bracing, airtightness, interior fire-resistant lining

Exterior fire safety cladding Vapour barrier Bracing, airtightness, interior fire-resistant lining

Bracing, airtight and vapour-resistant layer Interior fire-resistant lining

a

b

fabrication, so very careful and timely planning is essential. There is considerable potential for rationalisation in the detailing of element joints and joints with other structural components, for example. An expedient construction and installation process, the degree of elements’ prefabrication and transport options must be coordinated with the construction company in good time. This is usually difficult, especially when working on public buildings, because companies have often not yet been commissioned when the work is planned, due to procurement rules. Alternative procurement processes should be developed here to accommodate prefabrication (see “The planning process”, p. 130ff.), because the ways in which individual timber construction companies work can make it necessary to adapt plans, which can be complex and expensive when planning is already advanced (see “Features of planning a timber building”, p. 130).

the building’s environmental performance that increases with the amount of timber used in it. Planners need to strike a balance between an efficient use of energy and materials and carbon storage in achieving sustainability and to use all resources, including renewable resources, carefully and sparingly. Choosing insulation with a view to ecological considerations is becoming increasingly important and may affect the type of construction and layer structure. Drafting accompanying environmental performance assessments at an early stage can help planners make the right choices.

Environmental factors

The more timber is used in a building, the more carbon it binds in the long term. The resulting CO2 sink has a positive effect on

Further criteria in positioning layers in horizontal and sloping structural components in building envelopes Even when the functional layers described above are incorporated into vertical, horizontal and sloping structural components in building envelopes, there are other aspects of the arrangement of layers that must be taken into account, depending on their position.

c

C 3.17

C 3.16

Typical facade structures of multi-storey timber buildings with insulation on the outside, including fire prevention cladding (structure of a and b as for [11]) a Solid timber structure with composite thermal insulation system b Solid timber structure, rear-ventilated c Solid timber structure (with exposed timber interior) rear-ventilated, minimal use of foil C 3.17 Typical facades multi-storey timber buildings with insulation in interstices, including fire prevention cladding (structure of a and b as for [12]) a Timber panel structure with composite thermal insulation system b Timber panel structure, rear-ventilated c Timber panel structure, rear-ventilated, minimal use of foil

103

The layer structure of building envelopes

Inside

Ceiling: analogous to exterior wall structure Floor: analogous to flat roof structure with a layer of air

C 3.18 Slabs bordering on outside space

The underside of a projecting structure and topside of a loggia are subject to the same structural and physical rules as an exterior wall component in terms of the arrangement of their structural component layers (Figs. C 3.18 – C 3.20). They can be built with insulation in interstices or exterior insulation (or, in rare cases, with insulation on the inside), as ventilated or rear-ventilated structures or without a layer of air. The structural interdependencies of structural component layers in terms of moisture protection follow the principles explained above. To ensure a continuously airtight building envelope, the airtight layers of an exterior wall component and floor element

Composite thermal insulation system

Outside a

with a layer of air

b

must be glued together at transitions between structural components. This is often complex and must be precisely considered in planning, especially for prefabricated elements. If the top of a storey slab abuts outside space, as is the case with a recessed attic storey or loggia, the structural component must be built like a flat roof that can be walked on (Fig. C 3.21). Flat roof structures

Flat roof structures are usually built without a rear ventilation layer because this simple structure is both functional and cost-effective (Figs. C 3.21 and C 3.24). Rear-ventilated flat roofs are rare, although their suspended ceilings offer the advantageous additional

c

C 3.19

Flat roof with exterior insulation The structure of a flat roof with exterior insulation is the same as that of an ordinary warm roof. A vapour barrier with an sd value five to six times that of the exterior sealing layer serves as an airtight layer and a temporary roof during construction. In timber construction this is indispensable in preventing the structure from getting wet during assembly. In this type of structure, the structural components are in

C 3.20 C 3.21

C 3.22

C 3.23

C 3.24

104

Exposed cross laminated timber

security of a second water-bearing layer. As with exterior walls, the thermal insulation layer can be outside on the support structure (Fig. C 3.21) or between support structure elements (Fig. C 3.22).

C 3.18 C 3.19

C 3.20

Composite thermal insulation system

Schematic diagram of the layers of a loggia Diagrams of examples of structural component layers in slab structures in a cantilever / loggia, vertical sections a In a structure with insulation in interstices b In a structure insulated on the outside (cross laminated timber) c In a structure insulated on the inside (cross laminated timber) Loggia of the c 13 residential and office building, Berlin (DE) 2013, Kaden Klingbeil Architekten Flat roof with no rear ventilation and insulation on the outside: Protective layer Sealing layer Compression-resistant thermal /gradient insulation Vapour barrier / airtight layer (Temporary sealing during construction) Load-bearing structure (shown in red) Flat roof without rear ventilation with a structure with insulation in interstices: Sealing layer (possibly with extra exterior insulation) Outer planking Thermal insulation in the construction layer Moisture-variable vapour barrier /airtight layer Inner lining (possibly boards), with / without installation layer 7 golden rules for a flat roof with insulation in interstices that will not require additional certification Matrix of various versions of flat roof structures

The layer structure of building envelopes

Sealing

Beam ceiling

Gravel

Dowel laminated timber ceiling

Extensive greening

Hollow box ceiling

With no additional exterior insulation (structural physics certification required for green roofs, gravel layers etc., see also C 3.23)

Terrace floor

Hollow box ceiling, partly with Cross laminated insulation between members timber ceiling

With additional exterior insulation

Beam ceiling

C 3.21

These dynamic interdependencies mean that flat roofs with insulation in interstices must be calculated by means of hygrothermal simulation if they are not a standard structure as defined in DIN 68 800. This structure offers little security and must be extremely carefully built (Fig. C 3.23). Economic reasons can justify such a solution in some cases. To prevent more condensation forming in the load-bearing structure, extra insulation is often laid on the outside of flat roofs with insulation in interstices (Fig. C 3.22). Sloping roofs

Sloping roofs are usually a simple ventilated roof with a suspended ceiling (Fig. C 3.25 a – d, p. 106). The structure can be built with insulation between the rafters or on the outside of the roof. If a suspended ceiling’s sd value is low, rear ventilation of the roof membrane allows the entire structure to remain vapour-permeable. Compared with roofs with no rear ventilation, these are very robust and secure structures.

1. 2. 3. 4. 5. 6. 7.

Gradient of ≥ 3 % before or ≥ 2 % after deformation Dark roof surface (solar radiation absorption a ≥ 80 %) and not shaded No covering layer (gravel, green roof, terrace floor) Moisture-adaptive vapour barrier No cavities that cannot be inspected on the cold side of the insulating layer Proven airtightness Documentation of the moisture content of timber in the support structure, cladding (should be u ≤ 15 ± 3 %) and composite wood planking (should be u ≥ 12 ± 3 %) before the structure is closed

Consensus of speakers at the Holzschutz und Bauphysik conference in Leipzig, 10/11 February 2011, on the rules that must be observed in planning a flat roof with insulation between elements. Also applicable to buildings with a normal interior climate as defined in DIN EN 15 026 and WTA data sheet 6-2.

C 3.23

Structure insulated on the outside

Flat roof with insulation in interstices and no rear ventilation Flat roofs with no rear ventilation and with insulation between beams can be built, but difficulties are often encountered here in practice because moisture can enter through even minor construction defects or due to damage to the airtight layer or vapour barrier layer. Any moisture in an interior must be able to dry out, otherwise it can cause structures to rot or fail entirely. Using a moisture-adaptive vapour barrier is one solution here, although their effectiveness depends not just on the sd values of other structural component layers but on external factors such as: • Type of roof structure: green, not green, covered with gravel, bare • Exterior surface layer or sealing sheeting’s solar absorption: light, dark • Exterior and interior climate • Periods during which the roof surface is shaded etc.

C 3.22

7 golden rules for a flat roof with insulation in interstices that will not require additional certification

Structure with insulation between members

the vapour diffusion-regulating, airtight layer in the warm indoor climate, so no condensation can accumulate in it.

Flat roof, not rear-ventilated

Flat roof with rear ventilation

Exterior protective layer Sealing layer Thermal / gradient layer Vapour barrier/airtight layer

Exterior protective layer / sealing layer Rear ventilation layer Vapour-permeable underlay Thermal insulation Vapour barrier / airtight layer

Exterior protective layer Sealing layer (possibly extra insulation) Thermal insulation in the structural layer Moisture-variable vapour barrier / airtight layer Inner lining (possibly planking) No additional insulation: See Fig. C 3.23

Exterior protective layer / sealing layer Rear ventilation layer Vapour-permeable underlay Thermal insulation in the structural layer Vapour barrier / airtight layer Inner lining (possibly planking)

C 3.24

105

The layer structure of building envelopes

• Rear ventilation layer • Insulation between rafters Roof covering (here schematic diagram of a tin roof) with roof boards Rear ventilation layer Exterior planking / underlay Vapour-permeable Rafters / thermal insulation Inner planking as vapour barrier / OSB, airtight

A roof that is not rear-ventilated can however still be built as a sloping roof in a manner analogous to a flat roof (Fig. C 3.25 e) although here there is no secondary security such as that offered by the suspended ceiling of a rear-ventilated structure, so the water-bearing layer must be very carefully planned and built, especially at the detail points of the eaves, roof ridge and barge board.

Polyfunctional layers a

• Rear ventilation layer • Insulation between rafters Roof covering (here schematic diagram of a tin roof) with roof boards Rear ventilation layer Housewrap as vapour-permeable underlay Extra compression-resistant insulation, vapour-permeable Rafters with thermal insulation between them Vapour barrier / airtight layer Inner planking / lining Plasterboard

b • Rear ventilation layer • Above-rafter insulation (exposed rafters) Roof covering (here schematic diagram of a tin roof) with roof boards Rear ventilation layer Housewrap as vapour-permeable underlay Compression-resistant thermal insulation Vapour barrier / airtight layer / emergency sealing Inner planking / cladding Exposed rafters

• Rear ventilation layer • Topside insulation (here cross laminated timber) c

Roof covering (here schematic diagram of a tin roof) with roof boards Rear ventilation layer Housewrap as vapour-resistant underlay Vapour-resistant compression-resistant, additional insulation Insulation Vapour barrier / airtight layer Cross laminated timber element, exposed

The number of layers in a building envelope depends on the type of structure and element layers may differ greatly here. An appropriately dimensioned solid timber wall can, in principle, take on all functions in one layer, providing load-bearing capacity and insulation, offering protection from wind and weather and being structurally robust. Each functional requirement made on a structural layer can also be met with a separate structural component layer. It is advisable to build with as few layers as possible and as many layers as necessary, using polyfunctional materials to meet several requirements at the same time. It is also advisable to prefer types of structures that use as little foil as possible because they are more robust and reduce material diversity.

Jointing principles In joining structural components, it must be ensured that individual functional layers continue throughout the building envelope beyond joints between structural components. The allocation of functions to structural component layers in the building envelope is clearer in multilayered structures than it is in structures with few layers so joints between structural elements should be very carefully planned. Joints between layers on a single level and in the plane are relatively easy to manage compared with joints between layers that are on different levels or offset. Three-dimensional thinking and construction is crucial here. Joints between an exterior wall and storey slab

The example of integrating a storey slab into an exterior wall reveals how the fundamental requirements of continuous layers with a changed geometry of the support point produces various details.

d • No rear ventilation layer • Topside insulation (here cross laminated timber) Roof covering (here schematic diagram of a tin roof) above the sealing level Thermal insulation Vapour barrier / airtight layer Cross laminated timber element, exposed

Resting a slab on the entire thickness of an exterior wall in a timber frame building weakens

C 3.25 C 3.26

e

106

C 3.25

Different ways of building a sloping roof Integration of storey slabs into exterior walls in structures with insulation in interstices or on the outside and the resulting changed support situations

The layer structure of building envelopes

the insulating layer’s continuity (Fig. C 3.26 a) and extra insulation will be needed on the outside to reduce thermal bridges. The airtight layer must pass around the slab’s front edges and be adhered to the airtight structural component layer above. Vapour barriers in the area of the slab’s front edges must also be continuous, taking the changed layer structure into account. Moisture-adaptive vapour barriers are often used here. If a solid timber wall is insulated on the outside, the insulating layer in the area of the slab’s front edges is not weakened, so element joints must only be glued together to make them airtight (Fig. C 3.26 d).

If the storey slab does not lie on the entire thickness of an exterior wall, filling the recessed area in front of the slab’s edge with insulation will compensate for the weakening of the insulating layer (Fig. C 3.26 b). Compression on crosspieces in and around the storey slab in a wall insulated on the outside can be avoided with such a load-bearing situation (Fig. C 3.26 e and axonometry, p. 209). Element joints between exterior wall components can easily be made airtight by gluing. To meet soundproofing and fire safety requirements, airtightness also between individual storeys must be ensured. If a slab is not integrated into an exterior wall because the slab’s span direction means that

Prefabrication and assembly

Building envelopes are often prefabricated so that buildings can be sealed as quickly as possible in short assembly times on site. Elements are made as large as possible for financial reasons and to provide the maximum mass for transport. This reduces the numbers of element joints and with them sources of errors in construction to the necessary minimum. A higher degree of prefabrication greatly Timber panel structure

Slab

Solid timber structure

no support is required here, in facade elements with insulation in their interstices or on their outsides for example, the airtight layer’s continuity only needs to be ensured at joints between airtight elements (Figs. C 3.26 c and f).

Slab lies across the entire thickness of the exterior wall

Slab lies partly on the exterior wall

Slab hangs on the exterior wall

Timber panel structure

Wall

Slab

Solid timber structure

a

Slab

b

Slab

d

Slab

c

Slab

e

Slab

f

C 3.26

107

The layer structure of building envelopes

Prefabricated structural layer If only the structural layer is assembled on the building site, all joints between elements and structural components must be made on site. This type of structure does not make use of the advantages of prefabricated elements, such as the benefits of making individual structural component layers in stable weather conditions and at consistent temperatures in a factory and their faster assembly times.

Joint complexity

Prefabricated structural layer, insulating layer and cladding If an exterior wall element, including its exterior cladding layer, is prefabricated, the subsequent work necessary after assembly must be taken into account in planning joints. The exterior cladding and its underlying substructure is often prefabricated as a separate element and delivered to the building site separately (Fig. C 3.28).

High

Vertical structural component joint

Horizontal element joint

Structure with insulation in interstices

Structure insulated on the outside

Low

Prefabricated structural layer and insulating layer If a structural layer and insulating layer are prefabricated and delivered to the building site together, the formation of element joints and joints between it and other structural components must be carefully planned in advance. To protect structural components and especially insulation from moisture and mechanical damage during construction, exterior weather protection is added to components.

Low

Degree of prefabrication

High C 3.27

108

The layer structure of building envelopes

C 3.27

Joint formation depending on the degree of elements’ prefabrication C 3.28 Prefabrication of exterior wall elements, secondary school, Diedorf (DE) 2015, Architekten Hermann Kaufmann / Florian Nagler Architekten a Exterior wall element support structure with insulation b Installation of window elements c Joints are sealed by gluing to make them airtight d Loading of exterior wall elements C 3.29 Comparison of individual structural components (roof /exterior wall /storey slab) from examples of projects in part E of this book, p. 159ff., scale 1:20 a

improves construction quality compared with assembly on site. The degree of prefabrication of exterior walls also depends on design requirements. It is not possible to assemble all exterior and inner cladding and linings in the factory, because of the greater risk of damage to them during transport. For soundproofing and fire safety reasons, in completing installations, it is sometimes advisable to only partly prefabricate interior linings and complete them on site. In many cases, an additional assembly with further elements can be advisable. A higher degree of prefabrication depends on complete planning, including planning of the building’s technical equipment. Window elements, including sun protection, are generally assembled in the factory, which is advisable because airtight connections to wall structures can be precisely built, protected from the weather and at constant temperatures, and be inspected there (Figs. C 3.28 b and c). Construction companies usually plan the formation of element joints, although architects should think through a possible sequence of work steps for assembling elements while planning construction, ideally supported by the construction company, and include it in overall planning. To avoid major changes during a later planning phase, various planning, tendering and award scenarios can be run through (see “Planning process”, p. 130ff.). Prefabricated elements can also be built so that joints do not have to be reworked or finished. Sufficient space to work in must be left around joints so that structural component layers can be properly built once elements are installed (Fig. C 3.27). Large-format, prefabricated exterior wall components can also be advantageous in renovating buildings to improve their energy use because quick assembly and short construction times can mean that residents will not have to move out (see “Solutions for modernising buildings”, p. 150ff.). Solid timber elements are sometimes prefabricated by cross laminated timber manufacturers then delivered to the building site to be immediately assembled there. They are subsequently finished on site or with appropriate prefabricated subcomponents.

Exposed timber structures

Joints in exposed timber structures must be especially careful planned because structural joint details, the adhesion of airtight layers and joints necessary for fire prevention must be concealed. This is easy to do with a joint between an airtight layer and a floor element because the floor structure is usually installed later so any joints are covered. Exposed ceilings and exterior walls may have to be provided with airtight glued joints from the outside of elements or in the storey above, before the next wall element is then installed. Notes: [1] Holzforschung Austria’s Internet-based structural component catalogue at www.dataholz.com [2] Winter, Stefan; Merk, Michael: Teilprojekt TP 02 Brandsicherheit im mehrgeschossigen Holzbau. High-Tech-Offensive Bayern – Holzbau der Zukunft. Published by the Bavarian State Ministry of Sciences, Research and the Arts. 15.07.2008 www.hb.bgu. tum.de/fileadmin/w00bpc/www/Forschung/ Abgeschlossene/2008/080702-mm-HTO-Zusammenfassung_final.pdf [3] www.dataholz.com [4] Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz: Bauen mit Brettsperrholz im Geschossbau. Published by Holzforschung Austria. Vienna, 2014 [5] ibid. [6] Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz: Holzrahmenbauweise im Geschossbau – Fokus Bauphysik. Published by Holzforschung Austria. Vienna, 2014 [7] as for Note 4 [8] as for Note 6 [9] Stein, René et al.: Konstruktionskatalog Fassadenelemente für Hybridbauweisen. TU Munich 2016 (unpublished) [10] Informationsdienst Holz (pub.): Bauen mit Brettsperrholz. Tragende Massivholzelemente für Wand, Decke und Dach. Holzbau Handbuch, Reihe 4, Teil 6, Folge 1, 04/2010 informationsdienst-holz.de/publikationen/ [11] Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 [12] ibid.

b

c

d

C 3.28

109

The layer structure of building envelopes

02 c 13 residential and office building in Berlin, see p. 170ff.

04 Residential and commercial building in Zurich, see p. 178ff.

06 Residential complex in Ansbach, see p. 186ff.

Round gravel 80 mm Filter layer 50 mm Double sealing Gradient insulation 200 mm Vapour barrier OSB board 15 mm Dowel laminated timber ceiling 160 mm

Round gravel 80 mm Protective sheeting 10 mm Sealing 7 mm Gradient insulation 150 – 250 mm Vapour barrier 3-5 mm OSB board 10 mm Dowel laminated timber slab 200 mm Airtight foil Spring clamps 27 mm Gypsum fibreboard 18 mm

Sealing Gradient insulation Vapour barrier Cross laminated timber

0.15 W/m2K

0.14 W/m2K

0.12 W/m2K

High-pressure laminate board 8 mm Substructure 25 mm Thermal insulation 50 mm Facade membrane 2 mm Exterior planking 13 mm Metal studs, thermal insulation 152 mm Vapour barrier 2 mm Plasterboard 16 mm

Plaster render Thermal insulation Gypsum fibreboard Vapour barrier Cross laminated timber Two-ply gypsum fibreboard

Glass-fibre reinforced concrete elements 70 mm Substructure, rear ventilation 30 mm Facade membrane Thermal insulation 160 mm Dowel laminated timber wall 100 mm Thermal insulation 80 mm Substructure 30 mm Felt strips Gypsum fibreboard 2≈ 12.5 mm

Silver fir cladding Battens Facade membrane OSB board Timber studs, mineral wool OSB board, joints glued Plasterboard

0.35 W/m2K

0.22 W/m2K

0.13 W/m2K

0.15 W/m2K

Floor covering Screed Cross laminated timber Plasterboard Drywall profile Spring clamps Plasterboard

Floor covering 16 mm Screed 74 mm Separating layer Footfall sound insulation 30 mm Emergency sealing Top layer of bonded concrete 120 mm Cross laminated timber ceiling 140 mm

Floor covering 10 mm Screed 70 mm Separating layer Footfall sound insulation 30 mm Hollow box element with 50 mm chipping infill 240 mm Spring clamps 27 mm Gypsum fibreboard 18 mm

Floor covering Screed Separating layer Footfall sound insulation Bonded chipping infill Emergency sealing Cross laminated timber

Roof Complete structure U value

01 Student residence in Vancouver, see p. 166ff.

Sealing Bituminised panel Gradient insulation Variable vapour barrier Plasterboard Corrugated sheeting Sloping steel beams Suspended ceiling

6 mm 12 mm 114 mm 2 mm 12 mm

Storey slab Complete structure REI; footfall sound insulation; airborne sound insulation

Exterior wall Complete structure U value

0.23 W/m2K

C 3.29

110

40 mm 169 mm 16 mm 38 mm 19 mm 2≈ 16 mm

120 Min.; L'n,w = 55 – 60 dB (estimate); R'w = 58 dB (estimate)

15 mm 140 mm 18 mm 85 mm 36 mm

REI 90; L'n,w ≤ 46 dB; R'w ≥ 54 dB

REI 60; L'n,w = 50 dB; R'w = 62 dB

210 – 390 mm 160 mm

20 mm 40 mm 15 mm 280 mm 15 mm 12.5 mm

10 mm 65 mm 40 mm 80 mm 180 mm

F60-B / fire-retardant; L'n,w = 50 dB; R'w = 65 dB

The layer structure of building envelopes

08 Residential development above car park in Munich, see p. 194ff.

Exterior wall Complete structure U value

Roof Complete structure U value

07 Terraced houses in Munich, see p. 190ff.

Extensively planted green roof 100 mm Sealing Thermal insulation 300 mm Vapour barrier Three-ply sheeting 75 mm

Round gravel Drainage 40 mm Building protection mat 6 mm Sealing Gradient insulation 20 – 200 mm Thermal insulation 60 mm Latex-bonded chipping infill 60 mm Vapour barrier, emergency sealing Cross laminated timber 140 mm

Extensively planted green roof 120 mm Fleece protective layer 10 mm Two-ply roof membrane 10 mm Gradient insulation 60 –140 mm Thermal insulation 140 mm Vapour barrier Construction phase sealing 3.5 mm Hollow box element 274 mm Spring clamps Cavity insulation 60 mm Plasterboard 2≈ 12,5 mm

Extensively planted green roof 128 – 328 mm Sealing Gradient insulation 10 –190 mm Thermal insulation 140 mm Vapour barrier Ribbed ceiling with 22 mm OSB board, glued 242 mm Cavity, installation, ventilation 68 mm Cavity insulation 50 mm Plasterboard 15 mm

0.12 W/m2K

0.13 W/m2K

0.14 W/m2K

0.08 W/m2K

Slates Timber battens Counter-battens Facade membrane Thermal insulation Vapour barrier Gypsum fibreboard

Larch facade cladding 19 mm Horizontal battens 35 mm Vertical battens 15 mm Facade membrane Gypsum fibreboard 2≈ 12.5 mm Timber studs, thermal insulation 200 mm Gypsum fibreboard 12,5 mm PE foil vapour barrier Gypsum fibreboard 12.5 mm

Plaster on substratum 12 mm Rear ventilation 40 mm Facade membrane Thermal insulation 100 mm Gypsum fibreboard 15 mm Timber studs, thermal insulation 180 mm OSB board 22 mm Timber studs, thermal insulation 50 mm Plasterboard 2≈ 12.5 mm

Silver fir facade cassettes Rear ventilation Facade membrane Gypsum fibreboard Timber studs, thermal insulation OSB board, joints glued Gypsum fibreboard

0.24 W/m2K

0.15 W/m2K

0.12 W/m2K

Floor covering 10 mm Screed 55 mm Footfall sound insulation 20 mm Concrete panels 40 mm Separating fleece Hollow box element 274 mm Spring clamps, cavity insulation 60 mm Plasterboard 2≈ 12.5 mm

Floor covering 15 mm Screed, separating layer 53 mm Footfall sound insulation 27 mm Infill, bonded Installation 30 mm OSB board 15 mm Dowel laminated timber ceiling 180 mm Gypsum fibreboard 18 mm Cavity, installation, ventilation 50 mm Cavity insulation 50 mm Plasterboard 15 mm

REI 60; L'n,w = N.a.; R'w = 58 dB

REI 60; L'n,w = 50 dB; R'w = 55 dB

30 mm 20 mm 220 mm 15 mm

0.17 W/m2K

Storey slab Complete structure REI; footfall sound insulation; airborne sound insulation

09 Addition of storeys and conversion 11 Zollfreilager housing complex in Zurich, see p. 206ff. to residential and commercial building in Zurich, see p. 198ff.

Floor covering Screed Separating layer Footfall sound insulation Three-ply sheeting N.a.

10 mm 60 mm 80 mm 50 mm

Floor covering Screed Separating layer Footfall sound insulation Latex-bonded chipping infill Trickle protection Cross laminated timber

5 mm 55 mm 40 mm 100 mm 140 mm

REI 60; L'n,w = 53 dB; R'w = 54 dB

22 mm 33 mm 15 mm 360 mm 15 mm 18 mm

111

The layer structure of building envelopes

14 Office building in St. Johann in Tirol, see p. 220ff.

16 Office building in ClermontFerrand, see p. 228ff.

17 Community centre in St. Gerold, see p. 232ff.

Exterior wall Complete structure U value

Roof Complete structure U value

13 Illwerke Zentrum Montafon in Vandans, see p. 214ff.

Extensively planted green roof 100 mm Roof seal Thermal insulation 300 mm Gradient insulation 140 mm Vapour barrier Composite timber-concrete ribbed ceiling: steel reinforced concrete 80 mm Glued laminated timber ribs 240/280 mm Acoustic panel

Sealing 10 mm Thermal insulation 280 mm Vapour barrier 4 mm OSB board on wedge battens Cavity 22 mm Hollow box structure: OSB board on glued laminated timber ribs 740 mm

Extensive planting 70 mm Sealing Thermal insulation 210 mm Vapour barrier Laminated veneer lumber with plasterboard 40 mm Glued laminated timber beam 250 mm

Two-ply sealing 5 mm Timber cladding 27 mm Substructure, ventilation 500 mm PE foil 2 mm Timber cladding 27 mm Sloping floor sleepers Wood fibre insulation 40 – 230 mm Squared timber, wood fibre insulation 180 mm Timber beam, wood fibre insulation 110 mm Timber cladding, vapour barrier 27 mm Installation layer 110 mm Acoustic insulation 30 mm Trickle protection fleece Silver fir battens 40 mm

0.10 W/m2K

0.16 W/m2K

0.20 W/m2K

0.10 W/m2K

Corrugated metal sheeting Battens, facade membrane OSB board Timber structure, thermal insulation Vapour barrier Thermal insulation Plasterboard

Rough sawn silver fir battens 30 mm Battens 30 mm Counter-battens /rear ventilation 30 mm Facade membrane Diagonal planking 25 mm Studs, wood fibre insulation 125 mm Diagonal cladding 25 mm Studs, wood fibre insulation 200 mm Cladding, vapour barrier 25 mm Battens, installation layer Acoustic insulation 40 mm Silver fir cladding 20 mm

Oak groove and rebate cladding 27 mm Counter-battens 40 mm Rear ventilation battens 40 mm Cement-bonded particle board 16 mm Structure, thermal insulation 340 mm Vapour barrier 18 mm OSB board 18 mm Thermal insulation / installation layer 10 mm Oak panelling 20 mm

Storey slab Complete structure REI; footfall sound insulation; airborne sound insulation

0.12 W/m2K

112

Vertical larch battens Battens Facade membrane Wood fibre insulation board Timber structure, thermal insulation OSB board 0.12 W/m2K

85 mm 85 mm 32 mm 280 mm 22 mm

Floor covering 10 mm Mineral materials panel 38 mm Insulated installation level 122 mm Cavity insulation 30 mm Composite timber-concrete ribbed ceiling: Steel-reinforced concrete 80 mm Glued laminated timber ribs 240/280 mm Suspended ceiling

Floor covering with footfall sound insulation OSB board Footfall sound insulation Box element, with chipping infill Plasterboard Suspension, cable routing OSB board

REI 90; L'n,w = 30 dB; R'w = 60 dB

REI 90; L'n,w = N.a.; R'w = N.a.

10 mm 18 mm 32 mm 520 mm 60 mm 2≈ 20 mm 500 mm 18 mm

30 mm 30 mm 10 mm 145 mm 60 mm 2≈ 10 mm

0.40 W/m2K

0.12 W/m2K

Floor covering Dry screed Footfall sound insulation Honeycomb infill Cross laminated timber Suspended cooling ceiling Installation

Floor covering 27 mm Floor sleepers with mud brick panels 62 mm Fibreboard footfall sound insulation 30 mm Doweled dowel laminated timber 220 mm Installation layer Cavity insulation 40 mm Gypsum fibreboard 15 mm Installation layer Acoustic insulation 30 mm Trickle protection fleece Silver fir battens 40 mm

10 mm 25 mm 15 mm 30 mm 147 mm 495 mm

REI 60; L'n,w = 82 dB; R'w = 38 dB

REI 30; L'n,w = 48 dB; R' = 65 dB

The layer structure of building envelopes

Exterior wall Complete structure U value

Roof Complete structure U value

18 Secondary school in Diedorf, see p. 236ff.

19 European School in Frankfurt am Main, see p. 242ff.

21 Renovation and new addition to boarding school, see p. 250ff.

22 Hotel Ammerwald near Reutte in Tirol, see p. 254ff.

Extensively planted green roof 150 mm Sealing Thermal insulation 20 mm Timber battens, thermal insulation 60 mm Thermal insulation 160 mm Timber battens, thermal insulation 160 mm Vapour barrier Separating layer Laminated veneer lumber board / Heraklith 51 mm Glued laminated timber rafters 100/360 mm

Sealing Gradient insulation at least 120 mm Vapour barrier Cross laminated timber 80 mm Thermal insulation 50 mm Wood wool acoustic panel 25 mm Beech laminated veneer lumber beam 360 mm

Extensively planted green roof 110 mm Sealing 13 mm Gradient insulation 300 – 500 mm Vapour barrier 4 mm Three-ply sheeting 40 mm Joists, layer of air 360 mm Installation layer 290 mm Sheep’s wool 30 mm Acoustic fleece 1 mm Silver fir wood slatted ceiling 30 mm

Round gravel Sealing Thermal insulation Vapour barrier Cross laminated timber

0.10 W/m2K

0.18 W/m2K

0.11 W/m2K

0.12 W/m2K

Aluminium sheeting 1 mm Wind paper Thermal insulation 120 mm Beech laminated veneer lumber columns 120 mm

Pine cladding Battens / counter-battens Facade membrane Lining Timber structure / thermal insulation Cladding, vapour barrier Plasterboard Installation layer / thermal insulation Silver fir wood cladding

0.25 W/m2K

0.09 W/m2K

Floor covering 2,5 mm Dry screed 38 mm Footfall sound insulation 25 mm Cross laminated timber 80 mm Levelling insulation (module joint) 60 mm Cross laminated timber 60 mm Acoustic insulation 60 mm Acoustic panelling 25 mm Beech laminated veneer lumber beam 560 mm

Floor covering Floor sleepers with insulation between them Footfall sound insulation Expanded clay infill Bonded steel-reinforced concrete Dowel laminated timber element Installation layer Acoustic insulation Acoustic fleece Silver fir wood slatted ceiling

N.a.; L'n,w = N.a.; R'w = N.a.

N.a.; L'n,w = 48 dB; R'w = 57 dB

Upright battens Horizontal battens Upright battens Composite wood panel Structure, thermal insulation Structure, thermal insulation OSB board (= vapour barrier)

30 mm 40 mm 50 mm 16 mm 140 mm 220 mm 18 mm

Storey slab Complete structure REI; footfall sound insulation; airborne sound insulation

0.13 W/m2K

Floor covering Screed Footfall sound insulation Levelling insulation Separating layer Bonded steel-reinforced concrete OSB board Joist Acoustic insulation Acoustic panelling

5 mm 85 mm 30 mm 50 mm

98 –120 mm 22 mm 320 mm 40 mm 35 mm

N.a.; L'n,w = 53 dB; R'w = 55 dB

60 mm 10 mm 200 mm 140 mm

30 mm 60 mm 20 mm 370 mm 20 mm 12.5 mm 40 mm 20 mm

Stainless steel sheeting Rear ventilation Wind paper Thermal insulation Vapour barrier Cross laminated timber

2 mm

380 mm 72 mm

0.14 W/m2K

27 mm 30 mm 40 mm 53 mm 120 mm 200 mm 290 mm 30 mm 1 mm 30 mm

Cross laminated timber Layer of air (module joint) Cavity insulation Cross laminated timber

140 mm 30 mm 50 mm 60 mm

REI 60; L'n,w = 48 dB (estimate); R'w = 55 dB (estimate)

113

The layer structure of interior structural components Christian Schühle

C 4.1

Interior structural components in multi-storey timber buildings such as storey slabs and partition walls are vitally important in partitioning buildings into utilisation units and fire safety compartments. At the same time, planners must take sound insulation and broader fire safety requirements into account. In contrast, the thermal insulation required between utilisation units results solely from the structure, so it does not require any further measures and protection from moisture is only necessary in damp rooms. The airtightness of structures is an important criterion in ensuring fire safety and sound insulation because air or smoke and fumes flowing through leaks in structural components or leaky joints between structural components can allow fire to spread. Leaks will also greatly impair the sound reduction index of structural components. However, the layer structures of slabs and walls are influenced by more than structural and physical requirements. Pipe and cable routing and design aspects are also crucial in planning and building functional layers (Fig. C 4.2). There is a detailed description of the various requirements involved in the chapter on “Protective functions” (p. 72ff.). Sound insulation

Timber structures are usually built with multiple layers to achieve the required sound insulation, because of their low mass. The sound reduction level that can be achieved in such structures depends on the properties of individual layers, their connections to each other and insulation laid in cavities. Flexible shells with extensive surface dimensions can be used as cladding to achieve good sound insulation values, with decoupled mounting to improve sound insulation where possible. During construction it must be ensured that joints between layers are smooth, tight and closed. Slab structures provide the required footfall sound insulation by the adding of mass in the form of heavy infill, a layer of concrete blocks or, in the case of composite timber-concrete structures, a load-bearing layer of concrete,

114

or by decoupling floor structures. Slabs that meet footfall sound insulation requirements usually also meet airborne sound insulation requirements. Fire safety

Introduction of the Musterholzbaurichtlinie (M-HFHHolzR) (Model Timber Construction Directive) in 2004 meant that, for the first time, it became possible in parts of Germany to use timber, a flammable building material, in buildings up to building class 4, i.e. those with up to five normal storeys as defined in the Model Building Ordinance (Musterbauordnung – MBO), for load-bearing and bracing structural components without having to apply for exceptional exemption from construction regulations. The precondition for the use of timber in such cases is the continuous cladding of timber structural components with two layers of non-flammable panel materials, so-called K260 “encapsulation”. Certified fire safety cladding usually consists of 36 mmthick plasterboard. Non-flammable insulation with a melting point above 1,000 °C must still be installed in cavities and building technology installations can only be routed through loadbearing and bracing structural components to a very limited extent. “The directive applies to structures that are to a certain extent prefabricated, such as timber panel, timber frame and half-timbered structures; it does not apply to solid timber structures such as dowel laminated timber and log structures, except for dowel laminated timber slabs” [1]. This means that many common types of structures are not regulated by the Model Timber Construction Directive and, as is the case for very tall buildings, they still require an application for exceptional exemption from construction regulations, specific fire safety concepts and possibly compensation meas-

C 4.1

Wood Innovation Design Centre, Prince George (CA) 2014, Michael Green Architecture C 4.2 Functional layers and structural component layers of storey slabs, here showing housing in Zurich as an example (CH) 2016, Rolf Mühlethaler

The layer structure of interior structural components

ures. Structural components may, however, also be built using cladding thicknesses that do not comply with standards but are based on the results of manufacturer-specific tests, and such timber structures can be left exposed if they are appropriately designed and dimensioned. At the time of publication, the fire behaviour of timber buildings is being intensively researched as part of a planned review of the Model Timber Construction Directive. The huge range of different manufacturerspecific fire safety tests and approvals for products for use in timber construction can quickly overwhelm planners and builders and is probably one of the main obstacles to more widespread multi-storey construction with timber in Germany and Austria. The Austrian interactive structural component catalogue dataholz.com has standardised structural components and details as a basis for verification. A version adapted for German standards and certifications is scheduled to go online in 2018.

The layer structure of timber slabs The layer structure of timber slabs differs greatly in its complexity from that of timber partition walls due to footfall sound insulation requirements. Standard slabs can include the following layers:

Floor structures: • Floor covering • Substructure: wet or dry screed, flooring sleepers, cavity or double floor • Footfall sound insulation • Additional mass /levelling fill • Possibly trickle protection Load-bearing layers: • Beam ceiling • Hollow box element • Dowel laminated timber ceiling • Cross laminated timber ceiling • Composite timber-concrete ceiling • Special forms Suspended ceilings: • Direct or suspended cladding, possibly as acoustic cladding • Cavity insulation • Possibly trickle protection Sound insulation and fire safety strategies for slab structures will vary depending on whether a bare slab is to be left exposed or be clad. An unclad structure’s fire resistance must be designed to withstand burning out due to a fire load from below. For soundproofing this means that it is essential to add mass to the top side of a slab structure because only a few layers are available to reduce sound transmission.

Floor structures

Although the choice of floor covering can positively affect a floor’s sound insulation properties, floor coverings are not included in sound insulation certification, because they are easily changed during usage. The choice of floor coverings is not a criterion specific to timber construction, so will not be further dealt with here. Screed systems Normal wet and dry screed systems are used in timber buildings. Wet screeds have sound insulation advantages due to their greater mass. Cement screed is preferable to anhydride screed because of its lower water content. Footfall sound insulation must have the lowest possible dynamic rigidity of s' ≤ 10 MN/m3 to minimise the floor structure’s resonant frequency, which is critical in timber structures. The insulation’s rigidity must always be appropriate for the overall screed system. Measures for improving the sound insulation of screeds bonded to bare timber slabs, infills and suspended ceilings are contained in their manufacturers’ information or certification reports on complete structures. Figure C 4.3 (p. 116) shows some examples of commonly built examples. Screed usually forms a top fire-preventive layer in a floor structure. Wet screed layers 50 mm

Structural component layers in a storey slab Floor covering

Protective functions of a storey slab

Protection from weather

REI 60 Ln, w' < 53 dB R'w > 52 dB

Airtightness

Thermal insulation Protection from condensation

Fire safety

Sound insulation

Screed / substructure

Decoupling for sound insulation Separating layer

(Additional mass)

(Trickle protection)

°C

Airtight layer

Load-bearing structure

Functional layers in a storey slab

Floor covering oak on-edge lamella parquetry, glued 15 mm Heated anhydride screed 53 mm PE foil separating layer Mineral wool footfall sound insulation 2≈ 20 mm OSB 15 mm Dowel laminated timber slab 180 mm Gypsum fibreboard 18 mm Installation cavity 30 mm Suspended battens with spring clamps 25 mm Cavity insulation between battens 50 mm Plasterboard 15 mm

Installation layer

Cavity insulation

Acoustics Ceiling lining C 4.2

115

The layer structure of interior structural components

Hollow box slab Cement screed 50 mm Footfall sound insulation 40 mm Hollow box element 200 mm L n, w = 62 dB R w = 60 dB

Cement screed 50 mm Footfall sound insulation 40 mm Honeycomb infill 60 mm Hollow box element 200 mm L n, w 45 dB R w = 67 dB

Cement screed 50 mm Footfall sound insulation 40 mm Honeycomb infill 60 mm Hollow box element 200 mm with infill 100 kg/m2 L n, w = 39 dB R w = 74 dB

Cross laminated timber slab Cement screed 50 mm Footfall sound insulation 20 mm Cross laminated timber 80 mm Mineral wool insulation Flexibly mounted rails Plasterboard 2≈ 18 mm L n, w = 47 dB R w = 58 dB REI 60

Cement screed 50 mm Footfall sound insulation 20 mm Elastically bonded infill 25 mm Cross laminated timber 80 mm L n, w = 48 dB R w = 58 dB REI 60

Beamed slab Cement screed 50 mm Footfall sound insulation 30 mm Loose infill 40 mm OSB 18 mm Construction timber 220 mm Glass wool 100 mm Spruce wood open joint cladding 24 mm Flexibly mounted rails 27 mm Gypsum fibreboard 25 mm

Screed element 25 mm Footfall sound insulation 20 mm Honeycomb infill 60 mm Kraft paper trickle protection Cross laminated timber 140 mm Plasterboard 12.5 mm L n, w ≤ 51 dB R w ≥ 51 dB REI 90 Composite timber-concrete slab

Cement screed 50 mm Footfall sound insulation 20 mm Composite wood board 19 mm Construction timber 90 mm Mineral wool insulation 40 mm Substructure decoupled for sound insulation Gypsum fibreboard 2≈ 18 mm L n, w = 48 dB R w = 60 dB REI 60

Heated screed 74 mm PE foil separating layer Mineral wool insulation 30 mm Concrete 120 mm Glued laminated timber 1400 mm Ln, w = max. 46 dB R w min. = 54 dB REI 90

L n, w = 41 dB R w = 70 dB REI 60 C 4.3

thick and more, with appropriate mineral wool edge insulation strips, meet the “highly fireretardant” requirement. Most dry screed plasterboard elements have footfall sound insulation bonded onto them in the factory and have the advantage of dry installation as well as being slimmer. The necessary classification “highly fire-retardant from above” can be achieved by installing 18-mm gypsum fibre dry screed boards [2]. These do, however, have much lower mass than wet screeds so they need additional soundproofing measures, which can detract from the advantage of their slimness. Cavity or double floors Cavity or double floors are often built into office buildings to allow for flexible pipe and cable routing. Fire safety in timber buildings must be ensured by cladding the raw structure on the top side because otherwise installing pipes and cables in floor cavities and every rising conduit will be problematic. Floorboards on flooring sleepers One special type of structure is a floating floor structure on flooring sleepers. Here mounting battens lie on the footfall sound insulation and hard insulation panels or ballast completely fill the interstices. The timber flooring planks are screwed or nailed onto battens and lie completely on the substructure. This is a particularly ecologically friendly and adhesive-free

116

structure and was used in the St. Gerold community centre building (Fig. C 4.4 and p. 232ff.) and the agricultural college in Altmünster (see p. 250ff.). Additional mass / levelling infill A heavy layer must usually be installed under footfall sound insulation to ensure the necessary sound insulation. The dry chipping infill (possibly in honeycomb cardboard) usually used for this purpose is flexible, so it damps resonance effects. Infill can be bonded with latex milk to keep it flexible. It must not be bonded with cement, because this adversely increases the infill’s rigidity. Small-format concrete or mud brick panels can be used for weighting, although they are not as good as infill with the same mass, because of their greater rigidity. Pipes and cables can also be routed through infill in a floor structure. Such installations must be completely covered with infill to prevent them from transmitting sound and they cannot be allowed to cut into the footfall sound insulation layer. Pipes and cables for ceiling lights etc. in exposed storey slabs between utilisation units should not be routed through the floor of the utilisation unit above, because penetrating the airtight layer makes it impossible to meet the necessary soundproofing and fire safety requirements. This type of installation can also cause organisational difficulties because power cables must be routed through the

“extraneous” adjoining unit (see “Building technology – special features of timber construction”, p. 122ff.). Exposed beam, dowel laminated timber or cross laminated timber ceilings must have weight added to them to achieve the footfall sound insulation required by slabs separating utilisation units (see “Protective functions”, p. 72ff.). Trickle protection Foils, building paper, cladding and lining with sealed joints and panel materials with glued joints laid on a bare ceiling slab prevent infill from trickling through and uncontrolled settling, as well as providing the airtightness necessary for soundproofing and fire safety reasons. Cross laminated timber slabs with layers glued at the sides and glued joints do not need trickle protection and are airtight. Dowel laminated timber slabs that are not glued together are usually covered with a panel that has a bracing function and offers adequate trickle protection and, if the joints are glued, they also ensure the necessary airtightness. Trickle protection in the form of a fleece layer is necessary in perforated acoustic ceilings to prevent trickle-through of fibres from insulation installed to dampen sound in cavities or enhance a room’s acoustics. The load-bearing layer

Construction of the load-bearing layer has a major influence on a ceiling component’s layer structure. Clad timber beam ceilings or box

The layer structure of interior structural components

Function Floor covering Substructure Footfall sound insulation Load-bearing layer

Cavity insulation Fire safety / sound insulation cladding Acoustic insulation

Sound-permeable cladding

Structural component layer Rough-sawn silver fir floorboards, nailed 27 mm Floor sleepers with mud brick panels between them, 62 mm Wood composite board 30 mm Doweled dowel laminated timber slab 220 mm Suspended ceiling 110 mm Sheep’s wool insulating felt 40 mm Grouted gypsum fibreboard 15 mm Installation layer 36 mm Sheep’s wool insulating felt 30 mm Black trickle protection fleece Silver fir battens 40/35 mm

L'n, w = 48 dB R'w = 65 dB REI 30 C 4.4 Function Floor covering C 4.3 C 4.4

C 4.5

C 4.6

C 4.7

Common slab structures with various loadbearing layers Floor structure: Functions and structural component layers, community centre, St. Gerold (AT) 2010, Cukrowicz Nachbaur Architekten Floor structure: Functions and structural component layers, residential complex, Ansbach (DE) 2014, Deppisch Architekten Floor structure: Functions and structural component layers, c 13 residential and office building, Berlin (DE) 2013, Kaden Klingbeil Architekten Floor structure: Functions and structural component layers, Illwerke Zentrum Montafon, Vandans (AT) 2013, Architekten Hermann Kaufmann

Screed Separating layer Footfall sound insulation Additional mass

Load-bearing layer

Structural component layer Oiled oak mosaic parquetry 10 mm Heated screed 65 mm PE foil separating layer Mineral wool 40 mm Bonded chipping infill 80 mm Elastomer-bitumen emergency sealing Cross laminated timber 180 mm

L'n, w = 49 dB R'w = 65dB REI 60 C 4.5

elements, with their inherently multilayered structures, have advantages for sound insulation because of the considerable distance between the upper and lower planking. With appropriate cavity sound insulation, this results in better sound insulation than can be achieved with monolithic solid timber ceilings. Suspending a ceiling from battens on spring clamps or spring bars so that it is decoupled for sound transmission purposes can improve sound insulation by 10 –12 dB compared with a rigid joint with a timber beam ceiling [3]. Some box element ceilings are manufactured already containing infill or cavity insulation (Fig. C 4.7). When combined with an appropriate floor structure they can make additional soundproofing measures unnecessary. In contrast, solid timber slabs, despite their higher weight due to their rigidity, even if mitigated by a suspended ceiling decoupled for sound transmission purposes, still need additional mass to ensure a footfall sound insulation level of L'n, w ≤ 53 dB. They may, however, be useful in exposed timber structures because they are inherently free of cavities. As part of a fire safety concept, timber linings can be attached to the underside of a solid timber slab (dowel laminated timber made of glued laminated or cross laminated timber), which will improve their acoustic and fire-safety characteristics, serve as a protective layer in case of fire, and can easily be replaced after a small fire.

Function Floor covering

Structural component layer Parquetry 16 mm Screed 74 mm Separating layer PE foil separating layer Footfall sound insulation Mineral wool 30 mm Load-bearing layer / mass Concrete 120 mm Load-bearing layer Glued laminated timber 140 mm L'n, w = max. 46 dB R'w = min. 54 dB REI 90

C 4.6

Function Floor covering Substructure Foot fall sound insulation Cavity insulation Load-bearing layer / mass Load-bearing layer

Structural component layer Carpet 10 mm Cavity floor 38 mm Installation cavity 122 mm Mineral wool 30 mm Concrete 80 mm Glued laminated timber beam 240/280 mm

L'n, w = max. 30 dB R'w = min. 60 dB REI 90

C 4.7

117

The layer structure of interior structural components

Type of bare ceiling

Ln, w [dB]

Open exposed timber ceiling

85 – 87

Enclosed timber beamed ceiling

74 –75

With flexibly hung suspended ceiling

64 – 65

Solid timber ceiling

76 – 80

Improvement achieved by various substructures

Ln, w, H [dB]

Cement screed on polystyrene/softwood fibreboard panels

14 –16

Cement screed on mineral fibre footfall sound insulation matting

19 –20

Dry screed

6 –10

Improvement achieved by different types of weighting 2

Ln, w, H [dB]

Concrete panels/stone blocks 80 kg/m

ca. 10

Elastically bonded infill 80 kg/m2

ca. 16 C 4.8

Composite timber-concrete structures use concrete’s properties for load-bearing, fire prevention and soundproofing purposes. Only a conventional decoupled floor structure meets the soundproofing requirements made on separating ceilings here. The c 13 residential and office building in Berlin (Fig. C 4.5, p. 117 and p. 170ff.) and Illwerke Zentrum Montafon in Vandans (Fig. C 4.6, p. 117 and p. 214ff.) represent examples of simplified ceiling structures in overall layer structures. Suspended ceilings

If the load-bearing layer or underside of a ceiling structure will not be visible, building technology pipes and cables can be routed along it and covered, or if special room acoustic requirements need to be met, a suspended ceiling will usually be necessary. Cavity insulation Insulating materials in structural component cavities absorb sound within the component and prevent cavity resonance. Highly porous building materials with a linear flow resistance of r ≥ 5 kPa s/m2 are advantageous for this purpose. Mineral wool is usually used as cavity insulation although cellulose, sheep’s wool, flax, cotton and open-pored insulation foams can also be used, provided that their use complies with fire safety requirements. The latter, which are not sealed off from air in the room, are often used as acoustic insulation to avoid problems with loose fibres. The effect of complete filling with insulation is not significantly better than that of partial filling with insulation, so usually only a third or half of a cavity space is insulated. For safety reasons, complete filling with insulation may be required at slab edges in order to join it to rising structural components without any cavities. Cladding As well as design aspects, structural and physical issues such as fire safety, sound insulation and room acoustics must be considered when choosing cladding. If non-flammable surfaces are required for fire safety reasons, mineral cladding, such as plas-

118

terboard, calcium silicate or mud brick panels, is usually used. Given different national requirements, and depending on its fire-resistance period and slab structure, cladding may range in thickness from 12.5 mm for REI 30 structures up to 36 mm for “encapsulated” REI 90 structures. Cladding may be single or multilayered and built as direct cladding, a facing shell or suspended ceiling. Grouting around joints can make planar cladding an airtight layer, as long as the edges are also made airtight by means of gluing, filling and sealing or appropriate joint tape. An effectively flexible shell decoupled on the underside with no gaps can improve sound insulation by up to 12 dB. Multilayered planking consisting of thin boards provides better results than single-layered planking of the same total thickness due to its lower bending stiffness, so cladding made of two 12.5 mmthick gypsum plasterboard panels is preferable to a single 25-mm layer. A flexibly hung suspended ceiling must be at least 50 mm from the bare ceiling slab to prevent resonance in solid timber structural components. Structural and physical necessities may impose conflicting demands on the choice of cladding. Room acoustics usually require surfaces that let sound through, while fire prevention and sound insulation demand the exact opposite, namely airtight cladding. This can mean that a desire for exposed wooden surfaces may not be compatible with fire safety requirements or it may not be possible to route building technology installations through a fire prevention layer. In such situations, the requirements are often assigned to several, separate structural component layers, e.g. direct cladding of a timber structure from below with plasterboard or a decoupled suspended structure with appropriate fireresistant panelling (Fig. C 4.4, p. 117). The space between a suspended acoustic ceiling and a sound-insulating and fire safety layer may be used as space for technical installations and to integrate ceiling lights. The wide range of bare slab structures in timber construction and combinations of layers in floor structures and suspended ceilings mean

that exact verification based on test certificates, standards specifications or the use of calculations are needed for a precise forecast of the required sound insulation. Figure C 4.8. provides reference points.

The layer structure of interior walls Interior walls can be built as solid timber walls or as more or less prefabricated timber panel walls. Both types of structure can meet all sound insulation and fire safety requirements. Their layer structure consists of a load-bearing layer and direct cladding, flexibly-mounted, or freestanding facing cladding. Solid exposed timber partition walls must be double walls to meet sound insulation requirements. Panel walls installed as non-load-bearing interior walls not subject to specific fire safety requirements have the advantage that building technology installations can be routed inside the wall cavity almost without restriction. They also offer more flexibility because they are easy to remove and from the outset have a better sound reduction index than simple unlined walls in solid timber structures. However, the advantage of routing pipes and cables through the cavity of a panel wall is soon lost if it is a load-bearing wall in a multistorey building, due to the limitations resulting from fire safety requirements, and, as with solid timber walls, an extra installation layer must be added here. Load concentrations, the need for more rigid structural components, and the inferior subsidence behaviour of panel walls in buildings from three to four storeys high mean that solid timber walls are preferable as load-bearing structural components. Their greater surface dimensions mean that they do offer soundproofing advantages in deeper frequency

C 4.8

Approximate values for footfall sound insulation and levels of improved footfall sound insulation for various combinations of layers C 4.9 Common single and double wall structures

The layer structure of interior structural components

Single walls in solid timber structures Cross laminated timber 100 mm REI 60 Rw = 33 dB

GF 15 mm Cross laminated timber 100 mm GF 15 mm REI 90 Rw = 38 dB

GF 2≈ 12.5 mm Battens on sound insulating clips 70 mm Mineral wool 50 mm Cross laminated timber 100 mm

GF 2≈ 12.5 mm Free-standing facing shell 85 mm Mineral wool 50 mm Cross laminated timber 100 mm

REI 60/90 Rw = 51 dB

REI 60/90 Rw = dB 62

GF 2≈ 12.5 mm Battens on sound insulating clips 70 mm Mineral wool 50 mm Cross laminated timber 100 mm Battens on 70 mm GF 2≈ 12.5 mm REI 90 Rw 53 dB

GF 2≈ 12.5 mm Free-standing facing shell 85 mm Mineral wool 50 mm Cross laminated timber 100 mm Free-standing facing shell 85 mm GF 2≈ 12.5 mm REI 90 Rw = 68 dB

Single panel construction walls GFRP 15 mm Studs 60/80 mm Mineral wool 60 mm GFRP 15 mm

GFRP 2≈ 12.5 mm Studs 60/80 mm Mineral wool 60 mm GFRP 2≈ 12.5 mm

EI 30 Rw = 38 dB

EI 60 Rw = 43 dB

GFRP 2≈ 12.5 mm OSB 15 mm Studs 60/100 mm Mineral wool 120 mm OSB 15 mm GFRP 2≈ 12.5 mm

GFRP 2≈ 12.5 mm OSB 15 mm Studs 60/100 mm Mineral wool 100 mm OSB 15 mm GFRP 2≈ 12.5 mm

REI 90 Rw = 46 dB

REI 90 Rw = 49 dB

GF 2≈ 12.5 mm Battens on sound insulating clips Mineral wool 50 mm BSP 90 mm Mineral wool 40 mm Cavity 10 mm Cross laminated timber 100 mm

GF 2≈ 12.5 mm Free-standing facing shell 85 mm Mineral wool 50 mm BSP 90 mm Mineral wool 40 mm Cavity 10 mm Cross laminated timber 100 mm

REI 30/60 Rw = 60 dB

REI 30/60 Rw = 68 dB

Double walls in solid timber structures Cross laminated timber 90 mm Mineral wool 40 mm Cavity 10 mm Cross laminated timber 90 mm REI 30 Rw = 52 dB

GF 2≈ 12.5 mm Cross laminated timber 90 mm Mineral wool 40 mm Cavity 10 mm Cross laminated timber 100 mm GF 2≈ 12.5 mm REI 60 Rw = 58 dB

GF 12.5 mm Cross laminated timber 90 mm GF 2≈ 15 mm Mineral wool 50 mm Cavity 50 mm GF 2≈ 15 mm Cross laminated timber 100 mm GF 1.5 mm REI 60 Rw = 70 dB

GF 2≈ 12.5 mm Cross laminated timber 90 mm GF 2≈ 15 mm Mineral wool 50 mm Cavity 50 mm GF 2≈ 15 mm Cross laminated timber 100 mm GF 2≈ 12.5 mm REI 90 Rw = 75 dB

Double walls in timber panel structures GFRP 2≈ 12.5 mm Studs 60/100 mm Mineral wool 100 mm GFRP 2≈ 12.5 mm Mineral wool 20 mm REI 60 Rw = 59 dB

GFRP 2≈ 12.5 mm OSB 15 mm Studs 60/100 mm Mineral wool 100 mm OSB 15 mm GFRP 12.5 mm Mineral wool 20 mm REI 90 Rw = 60 dB

GFRP 2≈ 12.5 mm OSB 15 mm Studs 60/100 mm Mineral wool 100 mm GFRP 2≈ 18 mm Mineral wool 50 mm REI 90 Rw = 64 dB

C 4.9

119

The layer structure of interior structural components

ranges, although these are not in the relevant normative range, so do not have a full arithmetical effect. Solid timber walls without additional cladding are only suitable for areas with lowlevel sound insulation requirements, e.g. within residential units. In combination with facing shells, either freestanding or mounted on sound insulation clips, such walls can become effective structural components. Installing facing shells with staggered joints and appropriate grouting makes them sufficiently airtight, so no extra airtight foils in the plane are necessary. As mentioned above, connections with other structural components must be made airtight by gluing them, and joints must be permanently sealed. The Model Timber Construction Directive (M-HFHHolzR) stipulates that areas through which more than three electrical cables supplying the adjoining room are routed require fire prevention and cable routing functions to be separate. In detail, this means that the timber structure must first be clad to comply with fire safety requirements before the installation layer is added. As well as ordinary plasterboard, a facing shell’s cladding can also be built with exposed wood composite board, exposed cladding with sealed joints or acoustic cladding. To achieve the required sound insulation, for partition walls between utilisation units or walls adjoining access zones and lifts, for example, it is advisable to make double walls with two completely decoupled load-bearing layers. Depending on the structure’s physical requirements, they can also have more layers of cladding, either decoupled or directly mounted.

Fully-clad structure

Wall unclad

Wall with cladding

Wall with cladding

Airtightness between utilisation units is indispensable as a flanking measure for sound insulation and fire safety. Within utilisation units, only an airtight joint on at least the interior side ensures effective insulation from sound and smells. Continuity of functional layers

One fundamental prerequisite for meeting structural and physical requirements is that individual functional layers be continuous. Layers designed to be fire-resistant must be continuously joined to prevent fire and hot gases from getting into flammable structural elements or into cavities in structural components. To ensure sufficient airtightness and to check the transmission of smoke and gases, sound and smells between spaces or utilisation units, planar airtight structural components must also be connected with airtight joints. This may sound trivial, but often turns out to be complex in practice. Exposed structures and the need for airtight connections between individual penetrating structural components such as beams or columns can make construction more difficult. Prefabricated interior structural components can maximise construction quality and optimise construction times. In practice, only partly prefabricated structural components are mainly used because building technology and final fittings are usually installed after the building envelope is closed. Modular structures consisting of stacks of completely equipped room cells are an exception. Decoupling layers in structural components

Partition walls in buildings are generally double walls due to building approvals, structural and sound insulation and for fire safety reasons. They are regarded as equivalent to fire safety walls for fire safety purposes. Their fire resistance from the inside towards the outside, i.e. from the interior towards the building’s outer surface, is equivalent to the fire resistance of their respective building class. From the outside, i.e. from the building’s outer surface towards the interior, they have a fire resistance of 90 minutes, which is provided in the form of appropriate cladding. Figure C 4.9, p. 119 shows an overview of common single and double wall structures.

Slab with cladding

Slab with cladding a

Principles of joining interior structural components NE 1 Unclad slab

NE 2

NE 1 Unclad slab

NE 2

b

120

The construction of joints between structural components is crucial in meeting sound insulation and fire safety requirements. Whether requirements on a partition element can be met or whether secondary sound channels detract from a structural component’s soundproofing levels as measured in a laboratory will depend on careful planning and precise construction of joints on the building site. C 4.10

Timber structures’ low mass means that sound insulation requirements can usually only be met by decoupling multilayered structures. This applies to both structural components and their joints, through which sound can be transmitted through flanking structural components. In structures built to be fully decoupled for sound insulation purposes, facing cladding and lining on ceilings and walls stops the transmission of sound energy into the underlying structure and prevents sound from being transmitted into adjoining rooms or utilisation units. Joints in the cladding of such structures are not as critical in construction. This type of decoupling is much more difficult in partly or completely exposed support structures of the type planners and clients often want. Here structural elements are exposed to sound energy in the room and without additional measures would transfer it directly into structural components. To prevent this socalled “flanking transmission”, supports must be decoupled by means of elastomer bearings and /or an expansion joint. Figure C 4.10 shows examples of joints between an exterior or partition wall and a slab in various feasible configurations ranging from visible exposed assemblies through to completely decoupled facing shells.

The layer structure of interior structural components

Elastomer bearings (shown in red) must be installed on the topsides and undersides of visible supporting walls and slabs. The slab must rest on the partition wall and be separated by a gap, and here the partition wall must be a double wall. If the walls in both storeys have decoupled facing shells, a transfer and radiation of sound energy through the walls is prevented, so elastomer bearings are not necessary. There must, however, also be a gap above the partition wall. In a structure consisting of an unclad wall and clad slab, attaching an elastomer bearing to the top or underside of the slab will prevent sound from being transmitted through the slab from wall to wall. In this case, an expansion joint is not necessary, because the ceiling suspension reduces sound energy. Exposed slab structures need acoustic decoupling to prevent longitudinal flanking sound transfer through partition walls between utilisation units, so exposed ceilings that function as a continuous beam extending across several utilisation units are not possible in timber structures. Exposed structures demand strict discipline in floor plan design. Longitudinal flanking sound transfer in slab structures means that partition walls cannot be positioned offset on top of one another, because the structural components cannot be decoupled if that is the case (Fig. C 4.10 b). Joint formation

At first glance, the prerequisites of “continuity” and “decoupling” outlined above for achieving the structural and physical requirements of joints seem to contradict each other. On the one hand, joints often have to be airtight and fireproof, yet on the other hand flanking sound transmission should be checked. With the right design, however, it is possible to meet both requirements (Fig. C 4.12 a, c). Manufacturers recommend various kinds of structures completely clad with plasterboard. Rigid connections can be made by grouting joints with gypsum filler. However, joints in the building’s shell structure must also be glued to ensure airtightness because a plastered joint will not be permanently airtight. Another option that helps absorb any deformation due to shrinkage and offers a certain degree of decoupling for sound insulation purposes is the use of elastic sealing materials for joints. Both types of joint formation can basically be used to join timber structural components, although the problem of flanking sound transmission means that a joint between a plaster shell and timber structural component cannot be rigid (Fig. C 4.12 b), so this type of joint is not suitable for meeting sound insulation requirements. A research project at the Technical University of Munich tested the fire safety behaviour of a joint decoupled for sound insulation purposes and optimised to provide the best possible

soundproofing and provided appropriate certification for this assembly [4]. Here a gap of up to 10 mm is left between layers of cladding or cladding and an exposed surface and is stuffed with mineral wool and filled with fire protection acrylic sealing compound or foam. Alternatively, joint tape made of intumescent material can be used as a partition. These joint tapes foam up when exposed to heat and form an insulating layer with low thermal conductivity (Fig. C 4.12). If an elastomer bearing for decoupling structural components is installed in the joints of a visible timber structure for sound insulation purposes, the joints between the timber structural elements must be flexibly filled with mineral wool when partitioning the space (E). A joint tape made of intumescent material can be used to close joints in exposed surfaces on the interior side.

C 4.11

Notes: [1] Musterrichtlinie über brandschutztechnische Anforderungen an hochfeuerhemmende Bauteile in Holzbauweise (M-HFHHolzR), 07/2004 www.bauordnungen.de/Hochfeuerhemmende_ Bauteile_in_Holzbauweise.pdf [2] Standard building authority approval for Knauf Brio dry screed elements [3] Köhnke, Ernst Ulrich: Schallschutztechnische Ausführungsfehler an Holzdecken. 4. HolzBauSpezial Akustik und Brandschutz Bad Wörishofen 2013, p. 5f. www.forum-holzbau.com/pdf/HBS_bauphysik_13_ Koehnke.pdf [4] Merk, Michael; Werther, Norman: Erarbeitung weiterführender Konstruktionsregeln/-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014, p. 71, 119f. www.irbnet.de/daten/rswb/14109008377.pdf

Floor structure

Joint up to 10 mm wide, packed with non-flammable insulating material with a melting point of > 1,000 °C or fire protection foam

a

Floor structure

Butt joint not grouted or grouted joint

b

C 4.10

C 4.11 C 4.12

Joints between slabs and exterior and interior walls a correct type of structure for preventing flanking transmission b an unclad slab structure with no joint will be problematic from a sound insulation perspective Installation wall shell, residential and commercial building in Zurich (CH) 2010, pool Architekten Types of joint structures a rigid connection, flanks decoupled b rigid connection, flanks not decoupled c connection decoupled to improve sound insulation

Floor structure

Joint up to 10 mm wide, packed with non-flammable insulating material with a melting point of > 1,000 °C or fire protection foam Elastomer bearing c

C 4.12

121

Building technology – special features of timber construction Martin Teibinger

C 5.1

Growing demands on buildings’ energy efficiency and comfort have led to the increasing importance of building technology and technical building equipment in recent years. Ventilation systems in ultra-low-energy and passive energy buildings now make an essential contribution to reducing heat losses from ventilation. Technical building equipment planners have taken up a central position in the ranks of specialist engineers working in prefabricated timber construction because the demand for precise planning of details from technical timber construction, structural and physical and manufacturing viewpoints is very high [1].

use of prefabricated, pre-installed building technology has become common practice in the prefabricated housing industry and modular construction (Fig. C 5.2) [2]. Element prefabrication involves assembling individual components in a factory, but most installations are still assembled on the building site (Fig. C 5.3). Here there is also significant potential for further development. To further improve quality and shorten construction times, more prefabricated building technology components should be offered in the future.

The influence of apertures, openings and recesses on the support structure Planning Service pipes and cables and their routing in timber structures should be planned at an early stage, ideally during design planning. It is essential to organise the position and size of any vertical shafts required or any that will intersect multiple storeys, the main pipe and cable routes and any necessary openings and breaches to fit in with the structural concept at an early stage to ensure smooth planning and construction. Subsequent replanning invariably increases planning and construction costs and usually detracts from overall construction quality. It is also essential to network specialist timber construction, structural physics and building technology experts to produce a high-quality timber building. The higher the overall level of prefabrication, the earlier decisions on building technology must be made and the more precisely and better networked detailed planning with other trades must be organised.

The following issues must be considered when planning apertures, openings and recesses (for building technology). Openings in bracing wall panels

Wall panels must be designed to absorb vertical and horizontal loads. Eurocode 5 sets out calculations for wall panels. DIN EN 1995-1-1 states that wall panels with openings (door and window openings as well as large installation openings) may only be used for load transmission in areas free of openings. For a wall panel with openings, this means that the areas next to the openings must usually be treated as separate wall panels. Individual openings in planking smaller than 20 ≈ 20 cm can be ignored when calculating loads. If there are several openings, the sum of their lengths must be less than 10 % of the panel length and the sum of their heights less than 10 % of their panel height. The effects of larger openings must be separately verified. Beam breakthroughs

Prefabrication options One main technical production and economic advantage of timber structures lies in the potential for a high degree of prefabrication. Such buildings can be built in closely controlled conditions, allowing for high quality despite short on-site assembly times. The

122

Beam breakthroughs are clear openings in plate girders of more than 80 mm or with a diameter greater than h/10 (h = girder height). Smaller apertures are not structurally relevant. These apertures should be considered at an early stage of planning so that the necessary size of the girder can be determined. A distinction is made between re-

Building technology – special features of timber construction

C 5.2

inforced and non-reinforced beam breakthroughs. Beam breakthroughs can be unreinforced If the following conditions are met: • No planned transverse stress • No major climatic loads (e.g. inadequately insulated heating pipes) • Only for buildings in usage classes 1 and 2 as defined in DIN EN 1995-1-1 • Compliance with geometric requirements as shown in figure C 5.4 At the corners of non-reinforced beam breakthroughs the stress components (transverse and shear stress) must be certified. Larger openings and apertures for which the requirements of stress and tension analyses for nonreinforced beam breakthroughs cannot be met require reinforcement to absorb transverse loads at the corners of apertures. This reinforcement can be provided in the form of wooden composite board glued onto both sides, steel rods glued into the inside (threaded rods or reinforcing rebar) or screwed in steel rods (fully threaded screws). Apertures must meet the geometric requirements shown in figure C 5.5.

General building physics principles for the integration of building technology

C 5.3

Cables may not be routed transverse to the covering layer without consultation with a structural engineer. Apertures in exterior structural components must be built to be airtight and windproof (Fig. C 5.7, p. 124).

Various kinds of installation situations are described below. Installations in exterior walls

Normally, installation layers (at least 40 mm thick) inside exterior timber panel walls make it possible to install electrical equipment without damaging the airtight layer. However, an installation layer is not necessary in industrially prefabricated walls, with their specially monitored production conditions, and cables can be routed outside their airtight layers, although airtight cavity wall power sockets must be installed (Fig. C 5.6, p. 124). Subsequent installations are only then permissible when they are carried out by authorised companies. Electricity cables, switches and power sockets of the usual size and quantity can be directly installed in recesses cut in cross laminated timber walls, except for walls that form part of fire safety compartments. The fire safety of the remainder of the timber cross section must be evaluated in keeping with the requirements.

Installations in partition walls and walls that are part of fire safety compartments in timber panel structures

In timber panel structures, it is advisable to route electricity installations through facing shells in partition walls, which are usually subject to fire safety requirements. Pipes and C 5.1 C 5.2 C 5.3

C 5.4

C 5.5

Building technology installation in a timber building Building technology module used in the prefabricated housing industry Prefabricated building technology shaft with planking on one side in the “Kölner Holzhaus”, Architekturbüro Laur Overview of geometric requirements for unreinforced slab break-throughs (spacings also apply to beams of changing thickness) Overview of geometric requirements for reinforced slab break-throughs (Spacings also apply to beams of changing thickness. Here h must be applied at the least favourable position at the edges of the break-through)

a lV ≥ h h

Permissible areas for apertures

hro ≥ 0.35 · h

Rounded corners r ≥ 15 mm

hd hd ≤ 0.15 · h

hd ≤ 0.15 · h

lA ≥ 0.5 · h hru ≥ 0.35 · h

lV ≥ h

d hd

lA ≥ 0.5 · h lA ≥ 0.5 · h

lz ≥ 1.5 · h ≥ 30 cm a ≤ 2.5 · hd

hd = 0.7 · d

a

a ≤ 2.5 · hd

C 5.4

a

lV ≥ h

Permissible areas for apertures

hro ≥ 0.25 · h

h

Rounded corners r ≥ 15 mm

hd hd ≤ 0.30 · h lv ≥ h

hd ≤ 0.30 · h

lA ≥ 0.5 · h hru ≥ 0.25 · h

d hd hd = 0.7· d

lA ≥ 0.5 · h lA ≥ 0.5 · h a

lz ≥ 1.0 · h ≥ 30 cm a ≤ h ≤ 2.5 · hd

a ≤ h ≤ 2.5 · hd C 5.5

123

Building technology – special features of timber construction

C 5.6

C 5.7

are not subject to any structural physical and fire safety requirements. This type of structure is not at all advisable for (residential) partition slabs.

cables can be laid in support structures as long as the insulation there is mineral wool with a melting point ≥ 1,000 °C, a minimum bulk density of 30 kg/m3 and at least 5 cm thick. In this case, the distances between installations and timber studs in load-bearing structural components should be more than 15 cm (Fig. C 5.8). Should this not be the case, cavity wall power sockets must be enclosed with suitable non-flammable materials (Fig. C 5.9) or tested fire-resistant power sockets (Fig. C 5.10) must be used.

Installations in partition slabs

For reasons of subsequent conversion, fire safety and soundproofing installations should generally be built within individual utilisation units. Pipes and cables should not be laid in the construction layer (spaces between joists) of partitioning slabs for fire safety and soundproofing reasons. Electricity cables, water and heating pipes and cables are routed through the top of the floor structure, usually in the infill (Fig. C 5.12). Here, as E.U. Köhnke [3] has noted, direct contact closure between the screed and ceiling slab resulting from pipes or their intersections will impair footfall sound insulation by up to 4 dB. For this reason, especially where pipes and cables cross, infill must have the necessary thickness.

Installations in partition walls and walls that are part of fire safety compartments in solid timber structures

Electrical installations can be directly cut into the panels of double partition walls in solid timber structures as for exterior walls. With walls that are part of fire safety compartments, it is recommended that they are laid in insulated facing shells, which also improves sound insulation.

A suspended ceiling is often installed on the underside and electricity cables, ventilation pipes and wiring can be routed through it. Here the height of cables and pipes and any necessary intersections must be considered when planning. Unfortunately, major difficulties are often encountered here in practice due to inadequately harmonised and uncoordinated planning.

Installations in residential ceilings

To minimise pipe and cable lengths in ceilings in a residential unit (maisonettes), ventilation ducts can be laid in the floor of the storey above (Fig. C 5.11). Outlets are then in the ceiling of the lower floor or in the floor of the storey above. This optimised pipe and cable routing can only be built in storey slabs that

> 150 mm

When laying electricity ducts for ceiling lights etc. in exposed cross laminated timber ceilings, it must be ensured that walls, including those within residential units, are airtight for soundproofing reasons. These ducts are usually routed on the underside of the bare slab. Any milled recesses cut for ducts, pipes and cables must be cut longitudinally to the cover layer. Milled recesses can only be cut at an angle to the cover layer after consultation with a structural engineer. Pipes, ducts and cables must be installed so that the subsequent retrieval of individual cables is possible if necessary. C 5.6 C 5.7 C 5.8

C 5.9 C 5.10 C 5.11 C 5.12 C 5.13 C 5.14 C 5.15 C 5.16

Airtight cavity wall power socket Airtight opening for a pipe using a prefabricated collar Compensation with mineral wool (melting point ≥ 1,000 °C, bulk density ≥ 30 kg/m3, secured against shifting / falling out) a in load-bearing walls b in non-load-bearing walls Compensation with a plasterboard housing Cavity wall power socket with a coating that forms an insulating layer Ventilation ducts laid on the top side of a floor slab in a residential building Electrical cables laid on the top side of an exposed timber floor slab in a solid timber building Laying of ventilation pipes in a suspended ceiling structure Enclosed aperture in a flat roof: Vertical and horizontal cross sections Schematic diagram of shaft type A Schematic diagram of shaft type B

th th

Cavity wall power socket

th

> 150 mm

> 150 mm

th

≥ 50 mm a

124

Cavity wall power socket

Cavity wall power socket

b

≥ 50 mm C 5.8

th

th C 5.9

C 5.10

Building technology – special features of timber construction

Ventilation duct Hall or foyer

C 5.11

C 5.12

Screws 4 ≈ 40 mm

Screws 4 ≈ 40 mm

Inset drainpipe

FPY panel

FPY panel with milled groove Drain pipe

a

a

Round groove filled with insulation

Screws 4 ≈ 40 mm

C 5.13

Ventilation pipes and cables in partitioning slabs may not be horizontally distributed through the construction layer, because this is not compatible with fire safety requirements. Ventilation pipes and cables must be routed in appropriate installation layers such as suspended ceilings, facing wall structures or floor structures (Fig. C 5.13). Apertures in structural components that form part of fire safety compartments must be sealed off (see also “Protective functions”, p. 72ff.). Installations in roofs

Screws 4 ≈ 40 mm

Pre-drilled holes C 5.14

aa

1

1

EI tt (ve, iC o) No requirements

EI tt 2

2 3 3

Residential space

EI tt (ho, i Co )

EI tt (ve, iC o)

Pitched roofs are subject to the same general principles of building technology installation planning as those governing exterior walls. An installation layer on the room side of the vapour barrier is recommended for the laying of different pipes and cables. Cables and pipes routed through flat roofs with exposed timber ceilings must be flow-proof and building site sealing must be very carefully constructed (water penetrating exposed surfaces). Apertures must be joined in a way that they are flowproof, for which structures require insulation between openings connected with the frame, such as the example shown in figure C 5.14. The cavity between the penetrating pipe and housing must be insulated and the pipe joined to the airtight layer on the inside with an airtight joint. If a joint cannot be enclosed, pipe collars can be used to make joints airtight around apertures. Vertical distribution in shafts

No requirements

EI tt

EI tt (ho, iCo) 4

EI tt (ve, iCo) 1 2 3 4

EI tt (ve, iC o) 1

Storey slab Shaft wall with fire safety requirements Installation cable Firestop between cellar and ground floor

2 3 C 5.15

Slab with horizontal firestop Shaft wall with fire safety requirements Installation cable

The dimensions of an installation shaft depend on the configuration of the building technology concept. The installation of controlled residential ventilation systems in particular requires a large amount of space. Installations extending beyond individual utilisation units or fire safety compartments are normally vertically distributed through installation shafts. Shafts are divided into two types based on the position of sealing measures of apertures – shaft type A (Fig. C 5.15) and shaft type B (Fig. C 5.16). Shaft type A Type A shafts are subject to requirements in terms of the fire resistance of the shaft walls

C 5.16

125

Building technology – special features of timber construction

Metal pipe

Plastic pipe

Cable bundle

20 × 50 mm GM-F type plasterboard as defined in EN 15 283-1

Type A

Joint formation compliant with guidelines

Classified shaft wall system 2× GKF

C 5.17 Metal pipe

Plastic pipe

Cable bundle

20 × 50 mm GM-F type plasterboard as defined in EN 15 283-1

Type A

Joint formation compliant with guidelines

Classified shaft wall system 2× GKF

C 5.18 Metal pipe

Plastic pipe

Cable bundle

Type B Mineral wool Fire-resistant joint sealing mass

Cable sheathing Soft firestop

Joint formation compliant with guidelines

20 × 50 mm GM-F type plasterboard as defined in EN 15 283-1

Fire-resistant collar

1× GFRP

C 5.19 Metal pipe

Plastic pipe

Cable bundle

Type B Mineral wool

20 × 50 mm GM-F type plasterboard as defined in EN 15 283-1 1× GFRP

Cable sheathing Soft firestop

Joint formation compliant with guidelines Fire-resistant collar C 5.20

126

and apertures in them. The requirements apply from the outside inwards and from inside outwards. The shaft must be horizontally sealed between the first floor above ground and a basement storey and the top storey and an uninhabited attic storey. Shaft walls are usually timber stud structures. They must be classified and built to meet the requirements, as must the sealing systems used and inspection openings for shaft wall apertures. The ceiling opening reveal must be clad with at least 2≈ 12.5 mm non-flammable fire-resistant plasterboard and it must be ensured that the plaster reveal cladding completely covers the timber. If it does not, the timber surface and the joint between the plasterboard and timber must be sealed using a similar product. If the corners of a ceiling opening are not sharpedged or the plasterboard is not properly fitted, any joints must be coated with an intumescent product. Intumescent material prevents the passage of smoke and toxic gases by foaming up when it is exposed to heat, closing any remaining openings. DIN EN 15 283-1 stipulates that a strip of fireresistant plasterboard measuring at least 20 ≈ 50 mm must be attached to the inside of the shaft in the area around a joint between a shaft wall and a timber slab element (Figs. C 5.17 and C 5.18) [4]. Shaft type B Walls in type B shafts are not subject to any specific fire safety requirements. These shafts are horizontally sealed at each storey in accordance with the slab’s fire-resistance requirements. Soft or hard firestops combined with fire-resistant pipe collars, duct insulation and the like can be used for sealing (Figs. C 5.19 and C 5.20). Concrete can also be poured around the slab, after which fireproof sealing must be installed in compliance with the usual rules for steel-reinforced concrete structures. The chapter on “The layer structure of interior structural components” shows a series of installation options (p. 114ff.). DIN EN 15 283-1 stipulates that a strip of fire-resistant plasterboard measuring at least 20 ≈ 50 mm must be attached on the inside of a type A shaft around the joint between a shaft wall and a timber slab element [5]. Here the reveal does not have to be faced around the firestop. Exposed timber surfaces in the shaft must be covered with non-flammable cladding. No separate fire safety requirements are made regarding the walls of type B shafts, so they can also be single-layered, although to meet soundproofing requirements it is recommended that shaft walls be multilayered and shafts insulated. The reveals of openings around apertures must be completely clad. If they are not, any joints must be covered with an intumescent coating [6]. If a soft firestop is installed, the reveal does not have to be clad and this may even be counter-productive if the installation does not cover the complete surface.

Coated mineral fibreboard with a minimum bulk density of 150 kg/m3 and melting point of ≥ 1,000 °C is used as a soft firestop. A hard firestop is usually made of gypsum or cement mortar. Reinforcing rods or threaded bolts are often used to permanently join a structural component and hard firestop. Soft firestops can be installed with or without cladding the reveals of timber elements. In building plaster reveal cladding it must be ensured that it completely covers the timber, otherwise the timber surface and joint between the plaster and timber must be sealed. The reveal (plaster or timber surface) and side edges of the mineral fibreboard must be given an intumescent or ablative coating [7]. The chapter on “The layer structure of building envelopes” provides installation details and construction recommendations (p. 92ff.).

Measures for damp rooms The above recommendations also apply to bathrooms in residences or similarly used bathrooms (e.g. in hotels or other forms of accommodation) but do not apply to wet rooms or public bathrooms subject to comprehensive requirements. Moisture must be generally prevented from penetrating timber structures for a long time due to the risk of damage from rot. Burst pipes are usually quickly discovered thanks to the large amount of water that pours out in a short period of time, so they can be quickly repaired and the structure dried rapidly. Careful sealing measures are required in areas where small amounts of water can leak out over a long period, such as around apertures for taps or grouting of tiles and joints around shower trays. Elastic joints must be regularly maintained. For damp rooms in timber structures, the relevant standards prescribe sealing on the bare slab with sealing extending up the walls. Installing sealing on a gradient with a controlled drain, as proposed in the standards, is a theoretical optimum for the structural protection of timber. For practical and structural reasons (laying of pipes and cables, installation of a gradient) and in assessing risk by comparing the potential for water damage from other rooms such as kitchens (drains, dishwashers), a waterproof tank with a gradient for a private bathroom is however a disproportionate measure [7]. Far more important than building a waterproof tank under a bathroom’s entire floor structure is the sealing of taps and sanitary equipment in showers and the careful construction of the joints of showers and bathtubs to prevent gradual leaks. Various other considerations are necessary in installing building technology in timber buildings, compared to building with mineral materials. Water-bearing pipes should be laid with a view to optimising their length. Pipes should

Building technology – special features of timber construction

C 5.21

C 5.22

also be laid in facing structures that are easy to maintain and control. Prefabricated room modules that contain the damp areas of residential units and all building technology service pipes and cables, and which can be integrated by means of plug & play must be further developed. In this area, there is a need for developments that can help to reduce the costs of building technology and improve the quality of timber buildings. Interesting solutions to leaks are already in use in Nordic countries: here, in pre-wall installations, before additional sealing is installed, layers are added that are routed through the first water-bearing layer, making any accumulating water immediately visible (Fig. C 5.21). Funnels also enclose heating pipes and, if there are any leaks in the pipes, the water is released through pipes into a drain at the bottom of the shaft (Fig. C 5.22).

Notes: [1] Teibinger, Martin et al.: Haustechnik im mehrgeschossigen Holzbau. In: Zuschnitt Attachment – Sonderthemen im Bereich Holz, Holzwerkstoff und Holzbau. proHolz Austria. Vienna, 2014 [2] Hausladen, Gerhard; Huber, Christian; Hilger, Michael: Holzbau der Zukunft. Teilprojekt 12: Modulare, vorgefertigte Installationen in mehrgeschossigen Holzbauwerken. Reihe Holzbauforschung, Vol. 7/12, Stuttgart 2009 [3] Köhnke, Ernst Ulrich: Fehler werden nicht verziehen. Typische Einbaufehler und deren Auswirkungen auf den Schallschutz. From the conference documentation for the 3rd Internationalen Holz[Bau]PhysikKongress 2012. Leipzig 2012, p. 97–101 [4] Teibinger, Martin; Matzinger, Irmgard: Brandabschottung im Holzbau. Planungsbroschüre der Holzforschung Austria. Vienna 2012 [5] ibid. [6] Coatings that form insulating layers (intumescent coatings) react to increases in ambient temperature in the event of fire. If a specific limit temperature is exceeded, a voluminous layer containing carbon forms, insulating the building materials or surfaces beneath it and protecting them from heat. The insulating layer forms due to various temperaturedependent chemical reactions. Coatings that form insulating layers usually consist of a binding agent, a gas producer, phosphoric acid, which reacts with alcohol to form phosphate esters, which in turn decompose and release non-flammable carbon dioxide, catalysators and other additives. The coatings need space to expand, which must be considered when planning. Source: http://www.baunetzwissen.de/standardartikel/Brandschutz-Brandschutzbeschichtungen_ 3502507.html. Retrieved on: 28.11.2016 [7] Ablative coatings contain materials that undergo an endothermic (= energy must be added) chemical reaction when exposed to heat. These materials can evaporate, sublimate (direct transition of a material from solid into a gaseous aggregate state) or melt. This cools the coated materials. The coatings can also release substances with a flame-retardant effect. After the chemical and physical processes are complete, a porous, inorganic, non-flammable and sometimes fused structure (ceramic) that also has a thermal insulation effect is left. Ablative products are used wherever structural components are exposed to the weather or outside conditions that could impair the coating, because once they are thoroughly dried they have no water-soluble components or any that can be modified by water or oil. In contrast to fire prevention coatings that form insulating layers, ablative coatings can withstand mechanical loads. Source: http://www.baunetzwissen.de/standardartikel/Brandschutz-Brandschutzbeschichtungen_ 3502507.html. Retrieved on 28.11.2016 [8] Köhnke, Ernst Ulrich: Schlagregen im Bad. Abdichtung von Bädern und Feuchträumen im Holzbau. In: Holzbau, die neue quadriga 04/2007, p. 22 – 27

Conclusion Prefabricated timber construction requires an interdisciplinary and precisely coordinated planning process with a sufficient time budget. Some of the construction time these structures save must be invested in careful planning from the outset. Decisions must be made as early as possible because building technology planning imposes special requirements on the level of detail in and timeliness of work. Wood’s greatest enemy is water, so particular attention must be paid to the quality and careful construction of water-bearing pipes and it is advisable to plan details so the leaks can be quickly discovered.

C 5.17 C 5.18 C 5.19 C 5.20 C 5.21 C 5.22

Example format of an aperture in a Type A shaft with a solid timber slab Example format of an aperture in a Type A shaft with a timber panel construction slab Example format of an aperture in a Type B shaft with a solid timber slab Example format of an aperture in a Type B shaft with a timber panel construction slab Leak protection in a pre-wall installation Leak protection in a construction project in Helsinki

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Part D

1

2

3

4

Fig. D

Process

Planning Features of planning a timber building The planning process The digital process chain in timber construction

130 130 130

Timber production The raw material industry Industrial panel prefabrication Subtractive manufacturing in timber construction companies Additive manufacturing in timber construction companies Prospects

138 138 139

Prefabrication Prefabrication and individuality From linear member to room module Prefabrication methods The influence of prefabrication on design and construction

142 142 144 147

Solutions for modernising buildings Adding storeys Facades

150 151 154

135

140 140 141

148

Installation of a prefabricated facade element, student residence, Vancouver (CA) 2017, Acton Ostry Architects

129

Planning Wolfgang Huß, Sonja Geier, Frank Lattke, Manfred Stieglmeier

D 1.1

Planning a contemporary timber building is different from planning a conventional building due in particular to prefabrication and the special characteristics of timber as a construction material.

Features of planning a timber building Classic architectural issues and some very specific factors concerning timber construction need to be considered in the initial design and integrated into the planning. Timber’s linearity as a material gives rise to interdependencies between the creation of space and a support structure that will be appropriate for a timber building (see “Structures and support structures”, p. 38ff.). The framework conditions of fire safety, prefabrication, the energy concept and building physics will shape the structure and influence its design and planning. Including safe emergency exit route concepts in planning means that timber can be used in areas outside those that building regulations generally designate as safe for timber. An appropriate arrangement of spaces that emit sound and other areas where noise should be avoided can reduce the soundproofing levels required for structural components. Prefabrication is essential in the timber construction process. The sizes and assembly sequences of elements must be integrated into design considerations because transport and manufacturing options will influence their preliminary design. This is most evident in the planning of room modules, prefabrication of which demands definitive decisions at an early stage. It is almost impossible to make subsequent corrections on site because any changes made as the planning process progresses will have an increasing impact on deadlines, quality and costs (see “Prefabrication”, p. 142ff.). The main difference between timber construction and more robust solid construction is that timber construction is multifaceted in a literal sense and more complex. An overwhelming variety of materials offering a wide range of construction options are now avail-

130

able on the market. Building authority approvals are often issued only for specific individual products and are not valid for apparently identical competing products, and there is currently no overarching standard regulating this issue for timber construction. Each timber construction company prefers its own structures and details, which will in turn depend on their particular production options, supplier network and experience, making it harder to make plans without relying on a specific firm. Fire safety and sound insulation in interior construction and thermal insulation and protection from moisture in the building envelope are functions usually provided by a building’s layer structure as a whole, i.e. the shell and finishing jointly, so planners must consider and plan all of a structure’s layers together. Planners must design the facades and interiors of exposed timber structures at the same time and in the same design phase with the rest of a timber structure, making planning far more complex (Fig. D 1.2).

The planning process

Every construction project has its own special features and dynamic. One frequent cause of problems in the planning process is a failure to comply with its fundamental preconditions, an issue that does not just affect timber construction. Planners should define general requirements and goals in the project development phase with the client as far as possible. The budget and time frames, functional requirements and personal ideas are important fundamentals in planning. The projectspecific need for expert planning to ensure an integral planning approach should be identified at a very early stage and the planning team should be put together and their tasks assigned at an early point, because only the involvement of the specialist knowledge of expert planners in initial design considerations will produce a coherent overall result. The leanWOOD research project provides some approaches to solutions and recommendations in this area [1].

Planning

Scheduling and communication

Resources planning for all participants should be based on a realistic and binding schedule. A good communication structure with regular coordination meetings is one prerequisite for success here. Clear agreements with everyone involved on the planning progress and change management are also required. A conclusive end of individual task phases that is coordinated with everyone involved in planning can help to ensure successful processes. Results should be regularly monitored with clients so that corrections can be made during individual performance phases but not across different phases, and the defined planning tasks of all participants can be harmonised. An understanding of the demands and perspectives of other disciplines will make cooperation easier. The planning period

In timber construction in particular, it is important to specify a planning period that is ad-

Evaluation of the basics

equate for the complexity of the task at hand. A longer planning process is usually offset by time savings in the construction phase. Skills and experience with timber construction should ideally not only be present in the disciplines of architecture, structural engineering, fire safety and structural physics, but also in the planning of technical building equipment installation. A clear definition of interfaces is also very important here. Critical points at interfaces between construction, fire safety und technical building equipment installation must be identified at an early stage and planning deliverables in each phase clearly defined and agreed.

• Preliminary design phase: Definition of the main requirements of all disciplines (fire safety, soundproofing, energy, support structure and prefabrication) and integration of them into the development of the spatial layout • Design phase: Development and clarification of all fundamental concepts involving the support structure, timber construction system, layer structure, jointing, surfaces, definition of interfaces, degree of prefabrication and element sizes • Construction planning by architects and expert planners: Detailed development of

Prefabrication means that major decisions must be made earlier in timber construction than is the case with conventional construction, so it is advisable to assign considerations that are essential to the project to individual work phases:

D 1.1

Preliminary planning

Control + reworking: Result – costs – deadline

Design planning

Control + reworking: Result – costs – deadline

Regular coordination meetings in the planning phase are indispensable for a successful planning process D 1.2 Planning phases from the initial enquiry through to element production with their central issues. The conclusion of one phase forms the basis for the following phase.

Implementation planning

Production planning

Control + reworking: Result – costs – deadline

Initial enquiry Schedule Site Requirements Budget / time frame Planning team

Defined tasks Spatial concept

Synthesis, Preliminary design

Support structure Prefabrication Fire safety Building physics Energy / technology

Spatial concept

Synthesis, Design

Support structure Prefabrication Fire safety Building physics Energy / technology

Support structure Prefabrication

Synthesis, Implementation planning

Production

Prefabrication

Preparation of CNC

Building physics

Review of capacities

Energy / technology

Course of construction Material ordering

Framework conditions

Concepts

Detailing

Organisation D 1.2

131

Planning

Tendering + award

Other construction participants

Other planners

Input Coordination / Synthesis

Building physics planner

Timber construction company

Fire safety planner

Architect

Building technology planner

Structural engineer

Status quo:

Planning

Implementation

a

Strategy 1:

Tendering + award

Specific timber construction expertise

Planning

Implementation

b

c

132

Overlapping = cooperative planning

Tendering + award

Strategy 2:

Implementation

D 1.3

For the integration of specific timber construction skills in early phases of the project, two main strategies are appropriate: • Strategy 1: Integration of specific timber construction expertise (Fig. D 1.3 b) • Strategy 2: Award at an early stage of the project phase (Fig. D 1.3 c) Both strategies are also fundamentally represented in the full service general contractor model. The full service general contractor model

At the conclusion of this process, when the substantive and technical issues have been resolved in construction and assembly planning, planners can concentrate on the organisational aspects of production and assembly (e.g. preparing for work with capacity and operations planning, ordering materials). Integrative cooperation models

Implementable planning

Planning

concepts defined in the design; coordination of assembly sequences and jointing methods (element joints and other joints and connections). • Construction and assembly planning by participating companies: Merging of the construction plans of the architect and structural engineer to provide a coherent overall plan and implementation of planning tasks using specific construction products that have been approved for use by building inspection authorities for just those tasks.

The term “award and cooperation model” describes a type of contract award and organisational structure for cooperation in planning and construction. The model defines responsibilities, roles and information and communication channels. The choice of award and cooperation model will depend on the client’s profile, the specific construction task and its framework conditions. The traditional award and cooperation model is based on detailed performance specifications and contracts awarded to individual trades. It is one of the most frequently used models in German-speaking countries and is based on a separation of specialisations and hierarchical structures in planning and construction (Fig. D 1.3 a). Architects and contractors often refer to its advantages: the ease of comparing bids for clients, the moderate effort involved in calculation for contracting companies and the architect’s fiduciary function in respect of the client. This classic model has proven its worth over the years, although it reaches its limits if there are no skills specific to that company in the planning team, if designs and structures have to be optimised or if creative solutions need to be developed under time and cost pressure.

A full service general contractor takes on both construction and planning, which is especially interesting for large construction companies. Large timber construction companies with their own planning departments and processes are increasingly offering private and commercial clients this complete service. For clients, planning and construction from a single source has the advantage of one sole contact and reliable cost and scheduling planning at an early stage. Disadvantages of this model include: • The dual control principle, i.e. planners and builders monitoring each other’s work, no longer applies. • Without directly commissioned architects, engineers and expert planners, the client loses their expert general administrator function, which can involve major risks for the client. The client also loses the consultancy and fiduciary function in respect of the architects and expert planners who are independent of implementation. Depending on the configuration of roles, there is a risk that architectural aspects will become subordinate to economic concerns. Functional tendering

Functional tendering enables contracts to be awarded at an early stage of planning. The construction company obtains tenders based on plans approved by building inspection authorities and the main architectural details, leaving the company some leeway to propose suitable construction. Detailed technical development is then carried out in the team with the architects. Particular attention must be paid

Planning

when defining qualities and performance limits, so as to avoid conflicts in settlement. The disadvantage of this model is that follow-up management cannot be carried out based on customary procedures. “Bouwteam” models

Integrative planning approaches that combine planning and construction skills, ideally in early phases, are not new. In Germany, many state-funded model projects have been implemented using the Dutch “Bouwteam” model. The different approach and project development of the early German Bouwteam projects show that there is no single

Conventional award (Theory)

consistent standard for handling processes, which is why reference is made to “Bouwteam models”. The only contractual relationship provided for in the early Bouwteam models was a contract between the construction and planning team and the client. In the Netherlands, newer Bouwteam models have improved the legal liability situation and are now based on separate contracts between individual planners and participants and the client, to better manage any liability issues. Here an extra Bouwteam framework agreement stipulates the performance criteria of cooperative development in the Bouwteam and defines “exit clauses” in case of failure by the team.

D 1.3

Status quo and possible planning and implementation strategies a Status quo: The award can be an obstacle to communication, separation of planning and implementation b Strategy 1: Integration of specific timber construction expertise into planning c Strategy 2: Award at an earlier phase of the project D 1.4 Comparison of a conventional planning process and planning with a cooperative planning team

Contract Timber construction company

Planning Architect + engineers

Deadline Handover

Workshop planning Timber construction company Prefabrication Assembly

Conventional award (Practice)

Planning Architect + engineers

Deadline Handover

Redesign = delay

Input

Workshop planning Timber construction company

Delay Delay

Prefabrication

Assembly

Contract Timber construction company

Cooperative planning

Planning Architect + engineers

Deadline Handover

Cooperation

Workshop planning Timber construction company Prefabrication Contract Timber construction company

Assembly

Time saving

D 1.4

133

Planning

D 1.5

Evaluation of the basics

Preliminary planning

Design planning

Approvals planning

Implementation planning

Building technology

• Clarification of the task • General planning conditions • Consultancy on services required

• Analysis of the basics • Development of versions of the planning concept with preliminary dimensioning • Draft of a functional layout • Clarification of processes, general conditions, interfaces • Preliminary negotiations with authorities • Costs estimate

• Planning concept • Selection of systems and equipment • Technical equipment design • Submission of calculations • Cost calculations • Negotiations with authorities • Cost calculations

• Completion of building documentation • Completion of plans and calculations

• Implementation planning • Continued updating and specification of calculations • Slot and breakthrough planning • Continued updating and specification of schedule planning • Planning accompanying construction • Review of company planning

Support structure

• Clarification of the task • Compilation of planning intentions

• Analysis of the basics • Consultancy on support structure • Work on planning concept • Work on preliminary negotiations of eligibility for approval • Work on cost estimates • Work on scheduling

• Support structure solution • Approximate dimensioning • Construction details concept • Approximate determination of materials quantities • Work on building description, negotiations with authorities, cost calculations

• Verifiable calculations • Structural element position plan • Coordination with inspection authorities • Completion of plans and calculations

• • • • •

Architecture

• Clarification of the task • Site inspection • Clarification of services required • Definition of the need for specialist planners

• Analysis of fundamentals • Reconciliation of goals • Versions of preliminary planning • Clarification of interdependencies • Coordination of specialist planners • Preliminary clarification of eligibility for approval • Costs estimate • Approximate deadline planning

• Design planning • Coordination of specialist planners • Building description • Negotiations on eligibility for approval • Coordination of specialist planners • Costs calculations • Scheduling update

• Completion of building documentation • Documentation submission

• Implementation planning • Coordination of specialist planners • Planning accompanying construction • Review of company planning • Scheduling update

Timber construction input

• Client consulting

• Consultancy costs • Element system concept

• Main details • Degree of prefabrication • Element sizes

Review of planning Formwork plan Construction drawings Steel and parts lists Continued coordination with inspection authorities

• Structural component structures • Joint details • Coordination of completion • Element sizes • Assembly sequence D 1.6

D 1.5

Three-dimensional CAM model as the basis for the CNC timber frame D 1.6 Scope of services as defined in the HOAI 2013 with the input "timber structure" D 1.7 Comparison of the advantages and disadvantages of conventional and cooperative planning models from the point of view of the client D 1.8 Brought forward and traditional planning process for timber construction – reorganisation of work and its influence on costs development (based on work by MacLeamy, 2004)

134

Planning

Conclusion

Finding an award and cooperation model appropriate for the project and client is essential to the success of a timber construction project. Manufacturing companies and entrepreneurs profit when they are awarded contracts that largely match their own skills profile. Various studies of practice in this area have shown that cooperative models have many advantages in very difficult projects. Integrative planning and concept development in the team mean that a building’s form, material and structure can be harmonised with its profitability and quality. Even when there is significant cost and time pressure, involving specialist qualified companies at an early stage enables creative solutions to be implemented. Various planning models can be used in timber construction. Which one is chosen will depend on the building’s complexity and the detailed requirements of the client and architect. Functional tenders achieve cogent results for simple buildings as long as they are based on good central planning details. For more complex buildings, effective construction execution planning is advisable as the basis for tendering, which in turn requires involving the timber construction skills of those working on the building and specialist timber structural engineers at an early stage (Fig. D 1.7).

Digital process chains in timber construction Digital process flows in timber construction are based on a comprehensive organisation of data. This begins with the architect’s design, is developed in more depth in construction planning and calculations carried out by expert planners, followed by optimisation processes, and concludes with final production in a timber construction company.

When the 2D or 3D CAD (Computer Aided Design) data of architects’ plans is used in the timber construction company’s CAM (Computer Aided Manufacturing) planning, the particular features of the manufacturing processes that the specific firm can offer can be taken into account (Fig. D 1.5). CAM data is usually based on a 3D model and forms a basis for machine control and the choice of tools used by CNC milling machines (see “Subtractive manufacturing in timber construction companies”, p. 140). Aspects of manufacturing such as cutting, materials consumption, structural dimensioning, the element system etc. can be evaluated and optimised at this stage. Subsequent changes to planning will result in higher implementation costs and complexity (Fig. D 1.8). This necessity to make planning decisions earlier in preliminary and design planning is one factor that modern timber construction has in common with the BIM (Building Information Modelling) method. BIM is an optimised process of planning, construction and operation of buildings that uses 3D software to digitally record all the relevant building data, network it and ideally store it on a shared data platform. The software can also clearly geometrically present the building as a virtual 3D model, unlike conventional 2D floor plan and sectional presentations, which only partly depict a building and so are more abstract. 3D presentation

enables planners to concretely represent and manage more information at an early stage. As with modern timber construction prefabrication, the BIM method requires an earlier planning process than usual (Fig. D 1.8) to form a basis for planning decisions in the initial stages. Any collisions in planning among different technical experts must be promptly identified and avoided. Costly and time-consuming planning during construction, which is otherwise usually necessary, can be avoided with the BIM method. The data files also provide more information, enabling planners to continuously and more precisely estimate costs, profitability and energy efficiency.

Conventional models separating planning and implementation

Cooperative models integrating construction participants into planning

+ Quality offered in the bid can be easily compared due to precise services specifications and forms a clear basis for decisions

– Comparison of various bids requires a qualitative and sophisticated evaluation

+ Single solution approach

+ Creative solutions possible

– Compliance with budgets and deadlines must be continuously monitored

+ Integrative development improves cost and adherence to schedules

– Client bears the risk in the event of unforeseen events during the construction phase

+ Implementation team bears the risk in the event of any unforeseen events

The closed or lonely BIM model

The most common form of BIM currently used in prefabricating components for timber construction is the so-called “closed” or “lonely” BIM model in the timber component manufacturer’s company. The design plans are transferred into the manufacturing software using software compatible with that system and the structure is represented as a 3D model in keeping with internal processes. This 3D model contains as much information as possible. As well as containing drawings and plans, it can be used to calculate costs and dimensions, draw up parts lists, quotes, tenders and invoices, and to organise building site logistics.

D 1.7 Effect

Tendering for services is carried out on a functional basis. In another type of Bouwteam model, the construction company is included in technical planning and optimisation with a Bouwteam contract based on an architectural design. If the company can ensure completion of the project on schedule and within the predefined budget after planning is concluded, it is awarded a construction contract. If no agreement is reached, it is compensated for its efforts and the client can obtain alternative tenders based on the planning foundations that have been laid. These integrative planning approaches that are based on the principle of involving all necessary technical and construction disciplines at an early stage are still in an early phase of their development. Adjustments will first have to be made to the legal framework conditions of public procurement and tendering laws if such integrative approaches are to be used in projects.

Influence on function and costs Cost of changes in design Planning process brought forward

Concept Preliminary phase planning

Design planning

Traditional planning process

Execution planning

Tendering

Implementation

Operations Time D 1.8

135

Planning

a

b

c

The open BIM model

Standardising information models

Conclusion

The open BIM model involves a comprehensive integrative planning process in which data from everyone involved in planning and construction is consolidated and coordinated with the production process at an early stage of planning. Architects, expert planners and supply companies process their data in a 3D model in accordance with a previous agreement on the degree of detail (also called an LOD – Level of Detail or Development). A data exchange format (e.g. IFC) then merges the models into a shared 3D model on a data platform that is ideally linked with data from the 3D manufacturing model, so that the requirements of prefabrication and BIM can efficiently complement each other. This largely shared data platform forms the basis for the open BIM model, although no suitable software is currently yet available for integrating the timber construction company’s CAM files into a shared data model. Libraries of structural components with consistent standards are also not yet sufficiently developed and the exchange of data is still quite awkward, due to a lack of available interfaces. At the moment, the recipient does not receive the information transported by the data exchange format in the same way as it was submitted, so much of the information attached to these files cannot be read by different kinds of software.

Austrian structural component platform dataholz.com has contributed to the further development of standard libraries of structural components with tested structural component layers. However, countless test procedures are required in advance in order to meet the necessary standards and fire safety requirements. The final result could eventually be a 3D library that provides a selection of certified applications.

A design that does justice to the special features of timber construction requires expert planning. Various cooperative models and degrees of complexity in projects offer all architectural firms opportunities to participate in the planning of multi-storey timber buildings or undergo training in this area. If the planning process is to be successful, the specific timber construction skills and experience required must either be available in the planning team or implementing companies must be involved in planning at an early stage. For private and public-sector projects there are processes suitable for both strategies. Interfaces and communication within the planning team and among those working on buildings require precise specifications and standardisation. The profession of structural engineers specialising in timber structures, which is currently becoming established and will produce engineers able to provide structural planning, fire safety and building physics solutions, will close the current skills gap between planning and construction in future. The ongoing standardisation of available timber construction solutions will greatly strengthen and simplify this development.

Overlaps in timber construction planning – BIM

A timber construction company’s 3D model, with its set drawing standards and its own catalogue of structural components coordinated to fit in with their internal manufacturing processes, largely corresponds with the structures of the 3D model used in the BIM method. The high degree of prefabrication and automation in production also corresponds with the BIM idea. To make optimum use of the BIM method’s potential and reconcile the 3D planning model with the 3D production model of modern timber construction without interfaces, the timber construction companies’ requirements of the software must first be defined.

136

BIM and its prevalence

In Central Europe, in contrast to Anglo-American and Nordic countries, mandatory use of BIM has not yet been introduced. Its dissemination among architects here is limited so far to larger firms with a greater volume of contracts generated mainly abroad. For small firms, which make up 90 % of architectural firms in Germany, introducing BIM involves a major investment, additional cost and effort in managing projects, and acquisition of the necessary BIM management expertise. The data exchange problems described above mean that 60 % of BIM users use the data only internally for 3D models, so a continuous digital process chain from planning through to prefabrication is not yet possible in practice. Current developments aim to establish an integrative way of working within a structure established at the beginning of the process and which, accompanied by a BIM coordinator, would result in an integrative planning and manufacturing process from design up to machine control. The process could be coordinated by appropriately trained architects and structural engineers specialising in timber structures, because they have an overview of the entire planning and production process. The willingness of participating experts to take part in interdisciplinary communication and development of a suitable software or appropriate file formats for everyone involved are two of the more important prerequisites for a continuous planning and production process.

D 1.9

Notes: [1] LeanWOOD: An international research project coordinated by the Technical University of Munich that aimed to develop a planning culture appropriate for prefabricated timber construction, with a focus on innovative planning processes and cooperative models. It ran from June 2014 until May 2017. www.leanwood.eu

D 1.9

Planning phases shown using the example of the school building in Diedorf (DE) 2015, Architekten Hermann Kaufmann / Florian Nagler Architekten a Structural engineering concept b Final plans detail, architecture c Construction detail, timber construction company D 1.10 Decisions in the planning process (exemplary): The table is based on an example and shows the decisions made by planning participants in each planning phase. This section focuses increasingly on one detailed point in the building level.

Planning

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Building technology / energy Pipe and cable routing Position of building technology rooms Ventilation concept Heating and cooling concept Daylight concept / sun screening Insulation standard Building envelope

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Spatial geometry Building’s orientation Spatial layers / spatial plan Storey heights Access concept Openings concept Main body of the building

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Implementation planning

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Building regulations Building regulation / statutory requirements Master plan requirements Building class

Design planning Architecture

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Standards and guidelines requirements State-of-the-art technology / accepted code of practice technical requirements

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Type of construction, material Preliminary dimensioning Jointing concept

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Preliminary dimensioning of pipes and cables in shaft Prelim. dimensioning of pipes and cables in corridor ceilings Positioning / crossing of media cables Delivery points Lighting concept Coordination of breakthroughs Fire walls in the technical building equipment concept Pipe and cable inspection

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construction methods

Insulation of pipes and cables Spacing of pipes and cables Attachment of pipes and cables Products, switches, power sockets, lights Underfloor heating system Underfloor heating loop

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Fire safety certification ‡ Structural component structure ‡

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Fire wall spacing

Building physics Soundproofing concept Acoustics concept

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Soundproofing certification Acoustics measures

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Structural component – storey slab ‡ ‡ Sequence of functional layers ‡ ‡ Floor structure height ‡ ‡ Suspended ceiling design ‡ ‡ Floor covering ‡ ‡ Element system

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Floor covering Screed Separating layer Footfall sound insulation Infill Suspended ceiling system Slab surface

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Structural component – partition wall Sequence of functional layers ‡ ‡ Wall thickness ‡ ‡ Wall surface ‡ ‡ Element system ‡ ‡

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Facing shell system Shell surface Insulation Cross laminated timber quality

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Structural component – glass corridor wall Partitioning ‡ ‡ ‡ ‡ Wall thickness ‡ ‡ ‡ ‡

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D 1.10

137

Timber production Wolfgang Huß

D 2.1

The timber production chain begins with timber harvesting. In Scandinavian countries, wood harvesting is largely industrialised, often involving the clear cutting of small areas and use of harvesters (Fig. D 2.2). In Central Europe in contrast, apart from the processing of logs due to windthrow or forest calamities (widespread disease due to pests etc.), single trees are selectively harvested. The tree’s local situation and aspects such as incident light and the future growth of surrounding trees are checked in detail when it is harvested. Trees are still sometimes cut down and delimbed by hand. Logs due to be taken away within days or weeks are usually stacked in piles along logging roads with the bark still on them so that they retain the moisture content they had when they were felled. This is important for conserving the logs because only wood cells full of water resist the penetration of exterior air, which pests such as beetles need to survive. If logs are to be stored for longer, they can be stacked to dry after being debarked to prevent fungal infestation. The precondition for storage of debarked logs is healthy logs that are not infested by pests or fungal rot. After a forest calamity, “live conservation”, where a fallen tree is left lying and connected with some of its roots, is also common. Airtight foil wrap is also sometimes used here. It may be necessary to store logs for several years if there is an oversupply of fallen trees due to

D 2.2

138

storm damage. If this is the case, logs can be conserved by means of more complex and costly wet storage, which can involve sprinkling with or immersion in water (Fig. D 2.3).

The raw material industry Wood as a raw material is increasingly processed by companies operating on an industrial scale using largely automated methods. Smaller sawmills specialise in more select product ranges and qualities. The first step in the process is the delivery and sorting of logs. They are then cut to length and debarked, inspected for any metal inclusions and x-rayed for defects, measured in three dimensions and sorted based on the criteria of wood type, quality, length, diameter and taper (a log’s changing circumference from root to crown), then stacked for storage. Logs are then cut into core and side boards in a saw line and the side boards are further processed using combinations of various technologies such as milling machines, gangsaws, bandsaws and circular saws. The wood is again sorted into different wood types, dimensions and qualities and the sawn lumber is then packed. Kilns can dry wood to the desired construction moisture within a few days. If wood with very precise dimensions or a smooth surface is needed or glued products are to be made out of rough sawn wood, it will have to

D 2.3

Timber production

D 2.4

be planed. In glued timber production, this is usually done at most 24 hours before gluing, when the dimensional stability of planks is highest. Remnants such as bark, chips and sawdust can be further processed to make bark mulch, composite wood boards or pellets, or be used to supply energy for production (drying etc.).

D 2.5 Additive manufacturing Element production

Subtractive manufacturing Timber framing /assembly

Industrial panel prefabrication Solid timber products and composite wood materials are made in downstream industries. Composite wood fibreboard and chipboard are made as standard industrial products. Many solid timber products such as glued laminated timber and cross laminated timber are customised for a specific project at an early stage. Using the CAM files of the timber construction company, large-format glued laminated timber beams and columns containing drill holes, cuts and built-in parts can be precisely cut to size in preparation for assembly (see “Digital process chains in timber construction”, p. 135f.). Cross laminated timber panels are industrially produced in standard sizes then cut to size with notches, cut-outs and gaps cut in the factory. The gantry machining centres required to do this are only practical on an industrial scale and are not cost-effective for a medium-sized timber construction company. Depending on their degree of prefabrication,

Logs: Cut to length and notched, milled and drilled on all sides, marked and labelled

Panels: Cut to size, openings cut, milled on five sides and drilled, marked and labelled

Stud frame: Joined and fixed (semi-automatic / fully automatic)

Planking: Laid out, nailed and stapled, protrusions sawn off, openings and slots cut

Panel construction element Ceiling element Roof element

Panel construction element Ceiling element Roof element

Solid timber Solid construction timber Cross laminated timber

Composite woodbased material Material max. 120 mm thick

Cross laminated timber / glued laminated timber Material max. 480 mm thick

CNC milling machine

Panel machining system

Panel processing Framing station Multifunction bridge centre Combination wall system

All the functions mentioned above + additional functions: Laying down and aligning parts, adhesion D 2.1 D 2.2 D 2.3 D 2.4 D 2.5 D 2.6

Factory workshop of a timber construction company manufacturing elements Logging with a wood harvester Stacks of logs and wet storage Router cutter of an individual milling unit Multiaxial arm of a CNC milling machine Overview of the automatic machining tools used in subtractive and additive timber construction manufacturing

Gantry system with robotic arm and tool magazine D 2.6

139

Timber production

elements made in this way can then be delivered direct to a building site or further processed in the timber construction company workshop.

Subtractive manufacturing in timber construction companies While small timber workshops carry out joinery by hand or have planks processed in specialist centres, medium-sized companies usually have their own joinery machines that use CNC. These can translate the plank geometry defined in a threedimensional CAM drawing into an automated machining operation and autonomously select the processing method and appropriate tool head. Multiaxial robots and the ability to move a piece and tools during machining makes it possible to manufacture almost any conceivable geometry. Two types of CNC milling machines are used to process planks:

• Systems with arrays of individual modules that each deploy one type of tool such as a multiaxial drill, end mill, side milling cutter, dovetail cutter, slot cutter, or marking and labelling machines etc. (Fig. D 2.4, p. 139). These machines are useful for companies that frequently repeat the same production steps and build largely standardised structures such as those common in timber panel construction, so they are now very widespread. • More recently developed milling robots, which are equipped with a multifunctional six-axis swivelling arm and alternating magazines containing a wide range of tool heads, can perform various tasks and allow for highly flexible production, although processing times can be longer. These machines are ideal for complex, customised tasks (Fig. D 2.5, p. 139). Larger timber construction companies also use automated processing machines to produce composite wood panels. These

D 2.7

140

machines can cut and mill material to a thickness of about 120 mm, use software to optimise their cutting, and can be equipped with automatic feed-in. Fully automated processing, the use of kilndried wood, and the very slight changes in the cross sections and length of timber structures due to changes in temperature compared with other materials mean that structural components with the highest dimensional precision in the millimetre range are now available. This must be considered when combining various types of construction methods, especially when planning the joining of elements.

Additive manufacturing in timber construction companies The additive joining of prefabricated boards and panels to form wall, ceiling and roof elements is now largely automated, although some of this work is still done by hand, especially in small and medium-sized enterprises. Large timber construction companies and prefabricated housing makers largely use the potential of automation in this production step. The production of panel construction walls usually begins with horizontal elements (Fig. D 2.7). Semi-automatic framing stations with automatic feed-in, positioning aids and automatic screwing and nailing units mean that stud frames can be assembled by a single person working in ergonomic conditions. Multifunction bridges then largely automatically attach planking to elements. Vacuum lifting devices lay panels down and a robotic stapler fixes them to the stud frame (Figs. D 2.8 b and c). Projecting parts of panels are cut off in a computer-controlled process and cuts are made for window openings or other installations. A butterfly table can be used together with a gantry to make elements easier to process on both sides and to manufacture closed elements (Fig. D 2.8 a). Cranes can also be used to turn elements. This is often followed by the installation of pipes, electrical cables, ventilation ducts and fire damper flaps in wall and ceiling elements, which is generally done by hand due to the

Timber production

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very specific requirements of different projects. The attaching of battens and cladding is now also largely automated. Structural components such as windows and roller shutters are installed by hand in vertical assembly. Elements are lowered into a narrow trench in the factory hall floor to provide ergonomic working conditions.

assemble complex structural components from individual boards and glue them together. These robots highlight the potential for further industrialisation. More options for designing and manufacturing highly individualised products, a significant increase in productivity, and lower costs for more standardised multistorey construction are the main motivating factors for establishing comprehensive automation. Future developments will show how far timber construction companies are willing to go in relinquishing their partly manual ways of working and approaching a level of automation that is already common in industries such as aircraft construction, shipbuilding and car manufacturing.

Prospects A few timber construction companies are already using gantry robots that can perform the subtractive and additive manufacturing described above and also automatically

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Disposal

D 2.7

Production of a stud frame of a timber panel construction element at a framing station D 2.8 Prefabrication of a timber panel construction element: a Butterfly table for working on elements on both sides b Vacuum lifting arm for laying down panels c Nailing planking with a multifunction bridge D 2.9 Production processes, example of an ideal factory workshop layout, Gumpp & Maier timber construction company, Binswangen (DE)

Heating and compressed air

Mill

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D 2.8

Metalworker’s shop

CNC automatic milling machine Framing

Storeroom

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Material

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Montage of ceiling and roof elements

Office

Material deliveries

Loading yard Assembly of exterior wall elements

Multifunction bridge

Assembly table Assembly of interior wall elements

Material

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Warehouse Material

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Storage area Window assembly

Insulation blower (for blowing in insulation) D 2.9

141

Prefabrication Wolfgang Huß

D 3.1

Wood and wood-based composite materials are especially suitable for prefabricating large structural elements and components because of the ease with which they can be worked, the techniques used to join them, and the light weight of elements and room modules, which makes them easy to transport.

Prefabrication and individuality

D 3.1

Prefabrication of room modules, European School, Frankfurt am Main (DE) 2015, NKBAK D 3.2 Prefabrication of panel construction elements in an assembly hall D 3.3 Prefabrication of linear elements (linear members) a Schematic diagram b Office building in Augsburg (DE) 2015, lattkearchitekten D 3.4 Prefabrication of planar elements a Schematic diagram b LifeCycle Office Tower (LCT One), Dornbirn (AT) 2012, Architekten Hermann Kaufmann D 3.5 Prefabrication of modular room elements (room modules / modular construction) a Schematic diagram b Hotel extension, Bezau (AT) 1998, Kaufmann 96

142

The widespread image of prefabricated buildings is still largely shaped by the architecture of the 1960s and 1970s, which was characterised by the use of serial prefabricated steelreinforced concrete parts and can seem to embody unimaginative design, monotony, rigidity and a focus on joints. However, prefabricated high-rise buildings (Plattenbau), built on a large scale in Europe’s former socialist countries, were based on a technology completely contrary to the type of prefabrication used in timber construction. These high-rise buildings were efficient because they used many of the same structural components. The formwork for their prefabricated elements could be repeatedly reused and structural analyses, which are costly and complex to draw up, did not have to be modified. Modern timber construction manufacturing does not rely on this type of rigid formula. Modern software can automatically generate frame data for even complex buildings (see “Planning”, p. 130ff. and “Timber production”, p. 138ff.). Using CNC to plot a timber frame, the cost and effort involved in manufacture does not depend on different parts and it is only the cost and effort of planning and organisation that increases with the number of different types of elements. Automated manufacturing is also becoming more customised. In practice, this great freedom in construction is more problematic than any restrictions imposed by prefabrication. Large timber buildings now usually have a prototype character and their structures and joints are individually developed and optimised for each specific building. Developments in this area are producing innovations and high-quality detailed solutions, but they are generally only suitable for specific buildings.

More standardisation would greatly improve efficiency on several levels. A comparison with conventional construction

Compared with industrial production, conventional construction does not seem entirely optimised. Its dependence on weather conditions, the complex coordination of many separately commissioned tradespeople, and inherently unergonomic working conditions on the building site make processes inefficient. Problems are often only identified and solved on the building site and late changes to plans often further delay progress. Work done by other trades sometimes damages work previously done by different groups. Schedules often cannot be met and additional costs only become clear during construction. The many work steps required on site and necessary drying times can greatly prolong construction periods and impact users and the neighbourhood equally, especially in urban settings. Prefabricated timber construction could be an effective alternative. The tradition of prefabrication

Carpentry has always been closely connected with prefabrication. Historical log cabin structures and half-timbered buildings required at least the preparation of individual timbers in a workshop. Traditional carpenters’ joints are geometrically complex and demand a high degree of precision, which is much easier to achieve in workshop conditions protected from the weather. Here organisation can also be optimised and heavy tools are always on hand. The production of a frame in a workshop, with the outlining of a structure on a scale of 1:1 and production, marking and the trial assembly of members, minimises the need for corrections on the building site. It is also easier to develop solutions for difficult points and to test the assembly of complex structures in advance in a workshop. Some advantages in the construction process

Moving production into a workshop (Fig. D 3.2) makes assembly times on site shorter, which has two positive aspects for the construction of timber buildings. Firstly, the assembly phase

Prefabrication

D 3.2

through to completion of a sealed building envelope, which is critical for wood, a building material sensitive to moisture, can be extremely short, which minimises dependency on weather conditions. A sealed building envelope implies at least temporary sealing of roofs and exterior walls and installation of sealed facade elements. Prefabrication reduces both the risk of damage from moisture during the construction phase and the cost and effort involved in measures to protect structures from the weather. The second aspect affects the overall construction period. The degree to which a building’s technology, interior fittings and building envelope are prefabricated is decisive in saving more time in the construction phase. Shorter

construction times have economic advantages that will have a varying impact for each project. In the case of a new building built to replace an older one, expensive loss of use is reduced. Prefabrication can also make it possible to work on existing buildings while they are in use, which would be impossible using conventional construction methods. For example, school buildings can be extended and renovated during holiday periods. However, timber construction does not usually involve a shorter overall planning and implementation process, because the planning phase is more complex so it takes more time. These types of projects stay “virtual” for a long time, so the investment costs of implementation must only be paid at a relatively

late stage and financing is only required for a shorter time. A workshop’s protected conditions, which are ideal for manufacture, improve the quality of both implementation and process control. The ability to work independently of the weather, very short paths and the permanent availability of a complete assembly team, materials, and tools increase efficiency. An assembly bench is a much more ergonomic workplace than a scaffold. It is also easier to coordinate and control external tradespersons in a workshop, and the risk of damage to already completed structures is much lower. Prefabrication can also help to save materials: Elements are optimally cut to size in a process that is partly computer-controlled, and leftover

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D 3.5

143

Prefabrication

material can be collected and used in more controlled ways than is usually possible on a building site.

out on existing buildings, a comprehensive analysis of the existing building and detailed survey of the building’s measurements will be necessary.

Some disadvantages of prefabrication

Prefabrication in construction requires very detailed planning (see “Planning”, p. 130ff.) and planners and clients must be prepared to make all the necessary decisions in due time, considering all the possible consequences. Corrections on site usually have a significant negative effect on schedules, costs and quality. Prefabrication can make construction more complex and costly in smaller projects, which must be weighed up against its potential advantages. If prefabricated solutions are used in work carried

Structural elements such as linear members, planar elements and room modules are prefabricated in very different ways (Fig. D 3.6). Linear elements (linear members)

Linear elements, i.e. prefabricated linear members, represent the simplest level of prefabrication (Fig. D 3.3, p. 143) so there are few dependencies between their design

Planar elements

Room modules (modular construction / room elements)

Dimension of prefabrication horizontal elements

Dimension of prefabrication vertical elements

Linear elements (linear members)

From linear member to room module

and prefabrication. Prefabricated linear members of the type used in traditional timber construction are still used today. It may be advisable to assemble individual linear members of frame structures with long spans to form load-bearing structures only on site or to combine them with planar elements. Advantages of these structures include their compactness for transport and the fact that simpler lifting equipment can be used to lift them. If they are assembled at the building site, much smaller simplified structures can result. For traditional timber beam ceilings assembled on site, this means that the double beams necessary at the ends of butt joints in prefabricated planar elements can be omitted, for example. This can

D 3.6

144

Prefabrication

D 3.7

be important for ceilings with visible undersides, although assembly on site can involve a longer construction phase and a certain loss of precision. Planar elements

Room modules (modular construction / elements enclosing spaces)

Room modules can be used to overcome the limitations of planar elements. All the surfaces and joints in each room can be completely prefabricated to a high quality, reducing assembly times on site to a minimum (Fig. D 3.5, p. 143). Modules can also be delivered with various interior fittings, ranging through to fixed furniture. Technical building installations can also be largely preassembled so

D 3.6

From linear members to room modules – steps in prefabrication D 3.7 A truck delivers a room module, European School, Frankfurt am Main (DE) 2015, NKBAK D 3.8 Transport sizes and resulting measures

≥ 4.00 m

≥ 4.80 m

Planar elements such as walls, ceilings and roofs are the most frequently prefabricated parts of buildings (Fig. D 3.4, p. 143). The building’s element grid influences design and configuration because, depending on the degree of prefabrication and designer’s intentions, joints between elements may remain visible. Using planar elements offers a greater degree of design freedom than building with room modules and all conceivable configurations of rooms can be built with them.

Complete prefabrication, including all layers and integrated windows and doors, is both possible and expedient for vertical elements such as exterior walls. A certain restriction is imposed by element joints, however, which, like fire safety compartments, must often be completed on site. Slab elements are usually prefabricated without a floor structure, for various reasons. These types of structures often include loose infill that can only be added subsequently, for example. Floating screeds can only be joined to form a larger contiguous area if they are added later, and joints in a floor covering that are unsatisfactory from a design and technical point of view can be avoided by installing the floor on site at a later point in time.

> 2.55 m

≥ 3.00 m

≥ 3.50 m

≥ 4.00 m

≥ 4.20 m

≥ 4.50 m

≥ 5.50 m

Approvals process Special permit required 1) 2) Involvement of all road safety authorities along the route, road construction authorities, police and, if necessary, railway company 3) Transport connection to rail transport must be verified 4) Transport connection to water transport must be verified 4) Escort vehicle

a)

On urban and country roads 5) On motorways b) with a maximum of two lanes c) 5) With at least two lanes

d) 5)

Police escort On urban and country roads 5) On motorways b) with a maximum of two lanes c) 5) With at least two lanes d) 5) 1)

pursuant to the German Road Traffic Act (STVO) s. 18 para. 3 and STVZO s. 32 para. 1 2) pursuant to the German Road Traffic Act (STVO) s. 29 para. 3, s. 46 para. 1 no. 5 and STVZO s. 70 3) pursuant to the General Administrative Regulations of the German Road Traffic Act (VwV-STVO) V. 2 and 4 4) pursuant to the General Administrative Regulations of the German Road Traffic Act (VwV-STVO) V. 5 5) pursuant to the General Administrative Regulations of the German Road Traffic Act (VwV-STVO) V. 7 a) with traffic lights b) Length of a standard semi-trailer and roads constructed like motorways c) Longer transport vehicles can be used no hard shoulder d) (but may require a special permit) with hard shoulder

approx. 13.50 m

D 3.8

145

Prefabrication

E.g. office space made up of two open modules

Module for a complete apartment

D 3.11

Module including wet room

E.g. classroom made up of several modules

Module = room D 3.9

a

D 3.9

b

Types of room modules: Proportion of room – module D 3.10 Methods of joining prefabricated elements and resulting element joints a Joint largely in the element joint b Coupling elements c Resolution into several layers D 3.11 Interior (classroom) with visible joints between room modules, European School, Frankfurt am Main (DE) 2015, NKBAK D 3.12 Types of room modules, vertical cross sections of module joints, scale 1:20 a Hybrid construction with room modules open at the top; student residence, Heidelberg (DE) 2013, LiWooD AG b Slender structure thanks to the short spans

146

c

D 3.10

bridged by the cross laminated timber slab. European School, Frankfurt am Main (DE) 2015, NKBAK c A solid cross laminated timber slab also forms the floor, with structure-borne sound insulation only between elements, Hotel Ammerwald near Reutte (AT) 2009, Oskar Leo Kaufmann and Albert Rüf D 3.13 Levels of prefabrication showing the example of an exterior wall element a, b Low level of prefabrication: Open elements c, d Medium level of prefabrication: Closed elements with windows e, f High level of prefabrication: Elements with complete layer structure

that pipes and cables must only be connected once modules are in position. The decision to use room modules must be made at the beginning of the design phase because they will greatly shape a building’s overall design, especially its floor plan and the size of rooms. The maximum dimensions of rooms will depend on transport conditions between the factory and building site. One limiting factor is the width of room modules. A standard truck can deliver elements approximately 13.50 metres long and 3.50 metres high (Fig. D 3.8, p. 145). Module construction is currently mainly used for structures with large numbers of similar room units, such as hotels and residential and nursing homes. Yet construction with room modules is not necessarily limited to the arranging of a series of modules, but can, with certain restrictions, allow for freer floor plan structures (see “European School in Frankfurt am Main”, p. 242ff.). The basic idea of room modules is that each individual room is a prefabricated structural unit. In this regard too, the range of possibilities has been greatly expanded (Fig. D 3.9). Very large room modules up to the size of 2-room apartments are now being prefabricated for use as complete utilisation units. Individual groups of rooms in apartments can be created using large room modules (see “Residential complex in Jyväskylä”, p. 182ff.). Larger rooms such as combi offices or classrooms can also be made up of several room modules (Fig. D 3.11) although here the floor structures cannot be completely prefabricated. Modular structures are theoretically more expensive and complex to build and take up more space because of their double walls, floors and ceilings. More recent examples have shown, however, that very slender structures can also be built in this way. Room modules with no ceilings but with steel-reinforced concrete floors were used in a fivestorey student residence in Heidelberg, for example. The room modules were assembled in a so-called “field factory” near the building site, removing the need for transportation of the heavy structures (Fig. D 3.12 a). The European School in Frankfurt am Main has

28 cm

32.5 cm

28 cm

Prefabrication

23 cm

30.6 cm

26.8 cm

a

b

c

a very thin, dry floor screed that is decoupled to ensure soundproofing. Here joints between the modules provide a second decoupling layer. Short spans between the main beams made very thin cross laminated timber structures possible here (Fig. D 3.12 b). The architects of the Ammerwald hotel near Reutte (see p. 254ff.) chose an unconventional module solution. Here the load-bearing cross laminated timber floor has no added floor structure and sound insulation is provided solely by decoupled joints between modules (Fig. D 3.12 c). Cross laminated timber was mainly used to make the modules because it is more robust, but all types of timber construction methods could in principle be used. The modules are flexibly mounted to prevent sound transmission. This type of structure is efficient when its division into utilisation units reflects the division into room modules. The larger the modules, the more cost-effective this structure will be.

Prefabrication methods

used in construction, if rarely so far, in the automated assembly of elements, for example. Gantry robots and robots with articulated arms can join and connect elements by means of nailing, screwing, riveting or adhesion (see “Additive manufacturing in timber construction companies”, p. 140f.).

a

c

e

b

d

f

As well as having organisational advantages, prefabrication makes it possible to apply new manufacturing technologies linked to factory production. The automated production of linear members using computer-controlled trimming machines with integrated circular saws, drills and milling machines has become standard in contemporary timber construction companies. Machines can now inexpensively mill traditional carpenters’ joints such as dovetail joints, which have undergone a renaissance in recent years and are now more frequently used to join linear members in panel construction elements, for example. Trimming machines can also be used to process panels, sawing or milling breakthroughs and slots and drilling holes for structural connections. This type of prefabrication is often carried out by industrial panel manufacturers. As well as this subtractive manufacture, additive manufacturing processes are also

D 3.12

The carpenter’s changing occupational profile

The changing conditions outlined above are increasingly influencing the occupational profile of the carpenter, demanding different skills from employees in modern timber construction companies. Requirements are shifting partly away from manual skills towards working with automated production methods. As in other industrialised processes, there is a need for both highly-qualified and less qualified workers, in contrast to this occupation’s traditional profile, with its extensively trained workers and master craftsmen. A reduction in the physical effort involved is making this kind of work

D 3.13

147

Prefabrication

a

b

easier for older workers and those with physical limitations, opening up this promising occupation to more women.

formation of the corner of a panel construction wall. Not only must this detail meet the structural and physical requirements, it must also be considered that two prefabricated, closed wall elements are being joined. The influence of prefabrication is even clearer in construction using room modules. The resulting structures, consisting of floor, ceiling and wall shells for two modules, were almost entirely developed out of the requirements of assembly. The degree of interaction between a structure’s prefabrication and its design and appearance may vary greatly. Based on the division of a structure into prefabricated elements, a planner can design its room structure, the facade’s interior and exterior, and the undersides of ceilings or roofs, which usually favours a very high degree of prefabrication. It is just as possible to design spaces and structure rooms largely independent of element joints and limit them to those that are technically necessary, which can involve slightly less prefabrication. In both cases

Manual trades versus industrialisation

Smaller and medium-sized companies currently predominate in modern timber building production in Central Europe, so this innovative industry will retain its artisanal character in the foreseeable future. Only prefabricated detached and semi-detached houses are now produced on an industrial scale. The slowly but steadily increasing proportion of multi-storey timber buildings will probably lead to more industrialised production in this market sector in the medium to long term.

The influence of prefabrication on design and construction Prefabrication influences construction as much as the structural physical solutions chosen, as made clear by the simple example of the

D 3.14

D 3.15

148

comprehensive knowledge of manufacturing processes is required at an early stage in the design process. There is a formative conflict in detail development in horizontally and vertically joining planar elements. On the one hand, elements should be joined with prefabricated exposed surfaces on both sides as far as possible. On the other hand, structural component layers must be joined continuously for statical-structural, structural physics and fire safety reasons. This conflict can be solved by means of joint formation, by adding subsequently installed coupling elements or by dividing a structure into several prefabricated elements (e.g. exterior cladding, wall element and interior lining). A combination of the first two strategies was used to assemble frame elements with complete wall panels and join them to previously erected frame supports in the Ölzbündt housing development project in Dornbirn (Fig. D 3.14 and D 3.15). The elements were suspended from the outside and screwed down from the inside. They are windproof on the outside because each element is pressed into a timber profile in the joint. The resulting cavity in the joint was subsequently filled with thermal insulation from above. In a last step, panels with sealing strips laid in them were attached to the inside, completing the airtight layer and vapour barrier. The example of two alternating element joints in the timber panel facade of a renovated building in figure D 3.16 shows how greatly the assembly process and prefabrication can influence the formation of structural details. In a residential building renovation in Augsburg (see p. 202ff.), storey-high elements could be screwed together so that the timber panel structure was geometrically interlocked, minimising thermal bridges (Fig. D 3.16 a). In the renovation of a residential and office building in Munich, extensive metal cladding projecting over elements did not allow for this type of solution, so the elements were mounted from above, stacked on top of each other, and fixed in place with hardwood dowels (Fig. D 3.16 b). The structure was completed once the element was lifted into place and no further attachment on the face of the building was necessary.

Prefabrication

a

b

Combinations of various levels of prefabrication

for this lack of cooperation lies less in inherent construction obstacles and more in the currently prevailing separation of trades into one construction company carrying out concrete construction and another performing timber construction and the resulting organisational issues on the building site (e.g. crane use). In Central Europe, a tendency is currently emerging for large construction companies operating as general contractors to merge with timber construction companies with the aim of securing a share in the promising timber construction market. In future, such companies may increasingly offer hybrid construction methods as well as an appropriate organisational company structure, which could greatly accelerate hybrid building construction processes.

Just as there is potential in the simultaneous use of different timber construction methods, there is also potential for combining various levels of prefabrication that has so far been scarcely exploited. Modular construction is a method suitable for smaller, comprehensively equipped units or rooms containing complex equipment such as kitchens, washrooms and central access cores. In contrast, planar or linear elements are ideal for flexible, open spatial structures with long spans. An intelligent combination of systems could be used to assemble buildings with high design quality, functional flexibility and a maximum degree of prefabrication extremely quickly. Another application of this method could elegantly solve the central problem of renovating bathrooms in residential buildings, by adding replaceable modules to the building’s periphery. There may also be great potential for combining spaceenclosing and planar elements when further storeys and horizontal extensions are added to buildings while they remain in use (Fig. D 3.17).

D 3.16

a

Hybrid construction methods

It is both possible and probable that the combination of timber with other building materials, primarily concrete and steel-reinforced concrete, will be further developed. Such solutions are already available in the form of hybrid structural components such as composite timber-concrete slabs that provide a joint prefabrication process for both materials. Some structures also allow for an intelligent joining of prefabricated elements, separated based on their material, on the building site (see “Composite timber-concrete slabs”, p. 64f.) in reaction to the different structures of construction trades companies and individual trades. There has been little effort to get different trades to work together on building assembly so far. Building components made of mineral materials such as firewalls or bracing access cores are usually made independently of timber structures, even where prefabricated steelreinforced concrete elements are used in such structures. This greatly slows down the construction process and increases the cost and complexity required for scaffolding. The reason

D 3.14

Ölzbündt housing development, Dornbirn (AT) 1997, Architekten Hermann Kaufmann / Christian Lenz a Prefabricated facade element on site b High level of prefabrication, horizontal section of an element joint, exterior wall, scale 1:20 D 3.15 Prefabrication visible in the facade, housing development in Dornbirn (AT) 1997, Architekten Hermann Kaufmann / Christian Lenz D 3.16 Prefabricated modernisation facade, vertical cross section of an element joint a Cladding allows for screws through the face. Renovation of a residential building, Augsburg (DE) 2012, lattkearchitekten b Cladding does not allow for screws through the face, residential and office building, Munich (DE) 2016, Braun Krötsch Architekten D 3.17 New applications for room modules a As services core (washrooms, access) b As replaceable bathroom c Modernisation of and extension to an existing building

b

c

D 3.17

149

Solutions for modernising buildings Frank Lattke

D 4.1

Much of our existing building stock is showing its age. It’s expensive and complex to operate, inadequate in terms of energy consumption and it often no longer meets users’ current demands, so it is becoming increasingly essential to modernise and refurbish existing buildings. Comprehensive modernisation of building envelopes and building technology and functional room remodelling through to conversions making buildings more accessible are important current construction tasks. Large buildings, e.g. school, office and residential buildings, are often converted and modernised while remaining in operation because there are no alternative facilities of an adequate size available or that would be economically viable. Concepts and methods that can be quickly and precisely implemented and disrupt operations as little as possible are needed. These would need to be long-term, cost-effective and environmentally sustainable solutions that could equip an existing building for the future, making it energy-efficient and CO2-neutral and giving it a usage structure designed to meet today’s demands. Maintaining existing buildings and the primary energy stored in them instead of demolishing them and disposing of their building materials has major environmental potential. The use of building products made of renewable raw materials also reduces the building’s environmental footprint, so wood and wood-based building materials become particularly environmentally and technically significant in construction work done on existing buildings [1]. Comprehensive modernisation can involve the meeting of financial, building regulation and structural requirements such as thermal insulation, fire safety and soundproofing and structural stability and earthquake safety, and always changes a building’s appearance. It offers an opportunity to upgrade the building’s interior and exterior situation in architectural and design terms and to improve and change its structure. A new shell, possibly combined with added storeys, can completely modify an existing building, giving it an entirely new architectural face. There are almost no limits to the range of design possibilities here. Timber

150

construction can also have major design potential for building modernisation. Proven wall structures can be plastered or clad with a wide range of facade materials, the timber character of which need not necessarily be immediately apparent. The low weight of timber structures compared with steel-reinforced concrete or masonry structures gives them many advantages. Prefabricated timber panel elements or room modules are suitable for work such as renovating facades and replacing or adding to individual structural components right through to extensions and added storeys. By adding to buildings in this way, tried and tested structural solutions specifically adapted for timber construction that have been developed in the new building sector can be used. With widely used CNC (Computerised Numerical Control) production technology, even complex, three-dimensional, prefabricated and highly heat-insulated components adapted to the existing building can be mass-produced for panel or modular construction methods (Fig. D 4.2). The high degree of prefabrication and resulting fast construction process with precise planning and logistics decreases any unnecessary inconvenience that building sites may represent, especially in urban environments. Standard transport and lifting technology allow for precise assembly of large-format, prefabricated wall elements or room modules, even in confined spaces in existing buildings. Short assembly times mean that the building can be better protected from precipitation during construction, which reduces the potential for damage due to the weather. A thorough analysis of the building by architects and expert planners is indispensable in recording the building’s regulatory, fire safety, load-bearing, hazardous waste management, usage and technical building equipment requirements. The more information about the building and its load-bearing structure and the building materials used in it can be gathered, the better solutions can be coordinated in the planning phase. This analysis should not be limited to surfaces, but should

Solutions for modernising buildings

Tachymetry

Photogrammetry

3D laser scanning

Geometric congruence

++

+

++

Level of accurate detail

+

++

+

Completeness of the model

™

+

++

Interference by external influences

™1)

+

™1)

Inclusion of interiors

++

+

++

Options for analysis

+

+

++

™ incomplete or error-prone ++ very good + acceptable Rated lower because this method is vulnerable to vibrations and shaded areas of facades

1)

D 4.2

also go into detail, opening and drilling into structural components. As well as architectural considerations, a comprehensive analysis of the building, relevant building regulation conditions, the size and geometry of structural elements and their transport logistics and assembly conditions must be considered in the effective planning of a timber structure. The existing building’s statical and structural properties are essential to the proper joining of new construction components and in ensuring that structural fire safety, airtightness and soundproofing requirements are met. Joint and connection details that have been tried and tested in new buildings ensure effective structural and building physics functions in timber structures. Cavityfree construction of structural components and joints is important in preventing uncontrollable convection and the spread of fire in the structure. An exact survey of the geometry of the existing building forms the basis for the planning of a new, prefabricated building envelope. Joints to the existing building must have appropriate tolerances so that they can compensate for any irregularities and discrepancies in the structure. The new should fit onto the old like a mould. The more prefabricated the structural components are, the more minor installation tolerances will be. Details of the floor plan and cross sections based on existing plans or approximate measurements are usually enough for the architect’s design and implementation planning. Exact, digital measurements should ideally be provided by the construction company or carpenters as part of their production planning so that the contractor will bear the responsibility for the subsequent dimensional tolerances and accuracy of structural components. Non-contact measurement (e.g. photogrammetry, tachometry or a 3D laser scan) provides a three-dimensional digital building model that forms the basis for workshop planning in CAD. Defining all points of a building to be measured and documented and a shared interpretation of results in the planning team are the most important part of preparations. Precise meas-

D 4.3

urements include the building’s edges, window openings, position of inner and outer reveals and the building’s projections and recesses. The choice of methods depends on the desired result and technical options offered by the different measuring methods (Fig. D 4.3).

Adding storeys Most buildings have sufficient structural load reserves to enable one or several storeys to be added. Financing a construction measure by adding attractive floor space can be an interesting option from a financial point of view. Timber construction offers the advantages of light, prefabricated, rapid construction for the conversion or replacement of an existing attic or the addition of one or more storeys, and largely minimises adverse effects on lower storeys during the construction phase. Protecting the structure has a high priority and a temporary roof, extra scaffolding or sealing on the top storey slab will protect it from dam-

age caused by weather. Rapid construction greatly reduces the risk of the existing building getting wet. The range of timber construction elements that can be adapted to an existing building extends from individual frame components (e.g. roof beams and purlins, supports and beams) through prefabricated timber panel elements for walls and roofs up to complete room modules. Combining the adding of one or more storeys with a new timber panel facade has the advantage that the transition from the facade to the roof structure will not have any thermal bridges and a single trade will be responsible for interfaces with the building.

D 4.1

Installation of a facade element, renovation of the Grüntenstraße residential complex, Augsburg (DE) 2012, lattkearchitekten D 4.2 Parametrical building model based on digital measurements D 4.3 Comparison of measurement methods D 4.4 Storeys added to a building in Flachgasse, Vienna (AT) 2007, Dietrich Untertrifaller

D 4.4

151

Solutions for modernising buildings

D 4.5 Load transfer

As well as meeting building regulations requirements, the feasibility of adding one or more storeys is mainly a question of the existing building’s load-bearing capacity. Adding one or more storeys will depend on the structural load reserves of existing foundations, columns, walls and ceilings. The low weight of timber structures compared with masonry or concrete means that they impose lighter loads on an existing building’s structure. This means that the horizontal inertia forces resulting from the new structures in the event of an earthquake will be relatively minor. If the existing structure no longer meets the more stringent structural stability requirements for the event of an earthquake, it must be reinforced by additional longitudinal and transverse bracing. Loads from added storeys are transferred either directly into existing structural compo-

nents or into additional walls or columns, which can also be integrated into the plane of a new added facade. A timber structure’s lower weight means that it is sometimes possible to concentrate load bearing at points in the existing building and position load-bearing structural components in the building’s interior, keeping the facade largely free of load-bearing elements, and thereby giving planners more freedom to design openings. The four storeys added to a residential and commercial building in Zurich (see p. 198ff.), which were built without additional reinforcement [2], are an example of this approach. Its timber frame walls and hollow box slabs reduce the structure’s dead weight by more than 50 % compared with solid structures built with mineral materials. It may be necessary to upgrade existing structural components as part of the modernisation. Top-storey slabs, especially in buildings built in the 1950s and 1960s, are often thin and have

D 4.6

152

Solutions for modernising buildings

Composite wood panel screwed on

Composite timber-concrete slab

a Reinforcement

Addition of a cross laminated timber panel

Addition of a beamed section

b Retrofitting

no additional load reserves [3]. Here reinforcement will be necessary if the existing structure’s load-bearing capacity, soundproofing or bracing has to be upgraded. The following structural options can be effective in this context (Fig. D 4.7): • Reinforcing the original slab’s shear strength (e.g. by screwing a composite wood panel to it or installing a composite timber-concrete slab) • Upgrading the load-bearing section (e.g. by fitting a layer of joists or cross laminated timber panel) • Replacing the existing structure with a new timber slab.

New beamed section

New cross laminated timber panel

c Replacement D 4.7

Reaction to existing building

The simplest form of extension is the renovation, upgrading or replacement of the whole roof truss. If one or more storeys are added, the new room structure will be determined by the existing access, the arrangement of loadbearing walls and columns to form spaces, and the supply and service shafts for technical building equipment. Integration of these structural elements often conflicts with the need for different rooms due to new usage or a desire for greater design freedom. Light, large-format timber panel wall elements and ceiling and roof structures with long spans such as beam, dowel laminated timber, cross laminated timber or hollow box ceilings can be used to follow the arrangement of existing walls or columns (Fig. D 4.8), or the new support structure can be positioned transverse to the main direction of

D 4.5

Construction under a temporary roof, Treehouse Bebelallee, Hamburg (DE) 2010, blauraum Architekten D 4.6 Treehouse Bebelallee, Hamburg (DE) 2010, blauraum Architekten D 4.7 Various ways to strengthen slab structures: a Reinforcing the shear stiffness of the original slab b Reinforcing a load-bearing section c Replacing an existing structure with a new timber slab D 4.8 Timber structural elements follow an existing load-bearing structure of walls and slabs D 4.9 Timber structural elements positioned obliquely on an existing load-bearing structure D 4.10 Geometries of added storeys

D 4.8

D 4.9

D 4.10

153

Solutions for modernising buildings

existing walls or columns (Fig. D 4.9, p. 153). Based on the existing building, the geometry of added storeys can have various forms. Structurally effective timber panel elements can distribute loads over several storeys where structural components project. The following solutions are possible (Fig. D 4.10, p. 153) [4]: • added storeys are flush with the exterior wall • added storeys project over the existing wall • added stepped storeys with a roof terrace.

storey residential building made of timber panel compartments and timber slabs follows its own grid and shaft logic and is accessed through access balconies. It was only the timber structure’s low weight and utilisation of the lower floors and foundations that made it possible to add three residential storeys to the top of this old industrial building without additional retrofitting. Building regulations and fire safety

One example of a superimposition of various types of support structures and rooms for different uses is the Wylerpark project in Berne by Rolf Mühlethaler (Fig. D 4.11) [5], where a three-storey timber residential annex was added to a two-storey steel-reinforced concrete office building with two underground storage floors. The support structure’s grid, type of access and building technology installations were varied for the office and residential uses. A prefabricated ribbed concrete panel lies on a grid of concrete columns, projecting over the two-storey ground floor. On this load-distributing platform is an elevated cavity floor for the distribution of ventilation and sanitary system installations from the few shafts for office use to the several shafts for residential use. The three-

An attic conversion or added storeys can result in more stringent relevant building regulatory requirements being made on the structure if the building is assigned to a higher building class after modifications. Normally no more stringent requirements are made on a top storey’s loadbearing structural components, as long as they are not special components such as a firewall. Planners must determine at an early stage which fire resistance duration requirements may be made on structural components and the flammability of building materials, given that the building class for the building as a whole may also change. The existing building may have to be upgraded and the timber structure may have to be built to be highly fire-resistant or fireproof (see “Fire protection”, p. 72ff.).

Facades Highly insulated, prefabricated timber panel elements can be an interesting alternative to common methods of renovating building envelopes such as composite thermal insulation systems or aluminium or steel element facades to improve their energy performance. Elements are added in front of an existing wall or used to replace the facade. Closed timber panel elements with ribs made of solid construction lumber, glued laminated timber or Å-beams and structurally effective planking and thermal insulation in interstices (e.g. cellulose or mineral fibre insulation) and built-in windows are usually used. The facade cladding forms a separate layer. Depending on the building regulations requirements, the layer facing the timber panel element may have to be built with non-flammable building materials and the rear ventilation layer cut off at each storey for fire safety reasons. A range of different cladding materials (e.g. weatherboard siding, wood or wood fibre panels, glass or metal) can be attached to the timber panel element loadbearing structure, opening up more possibilities for facade designers. Renovating a building envelope offers an opportunity to reconfigure an existing facade’s design, structural and technical properties, depending on the original structure. The effort involved in changing openings in the building envelope will depend largely on the existing exterior wall structure. The options for modifying a load-bearing, monolithic brick structure are limited. A masonry window parapet can easily be broken open, but enlarging openings

D 4.11 D 4.12 D 4.13

D 4.14 D 4.15 D 4.16 D 4.11

154

Added storeys at Wylerpark, Bern (CH) 2008, Rolf Mühlethaler Horizontal and vertical positioning of facade elements Facade element installations a set-in b projecting c suspended d suspended Vertical loads transferred through a single foundation Vertical loads transferred through a cantilever Vertical loads transferred through a bracket

Solutions for modernising buildings

a

b

c

D 4.13

D 4.12

along their sides is a costly and complex undertaking, especially in a building in which people are still living. A steel/glass or steelreinforced concrete curtain wall facade is in contrast easier to dismantle and replace with a new facade and offers an opportunity to completely redefine the facade’s architectural and technical characteristics. A prefabricated wooden outer shell can also be installed in front of an existing multilayered facade made of prefabricated steel-reinforced concrete elements, the outermost shell of which protects the structure from the weather, so that the existing facade layers are retained, which improves the system’s cost-effectiveness. Projecting structural components such as balconies or loggias are usually major thermal bridges and need to be eliminated because it is generally either impossible or too expensive to insulate them. Enclosing these structural components can also upgrade the spatial situation by extending the living area and adding heated space to the building volume. During the modernising of the Grüntenstraße residential complex in Augsburg, for example (Fig. D 4.1, p. 150), the steel-reinforced concrete balconies were retained and covered with prefabricated facade elements, thus being incorporated into the building’s heated space (Fig. D 4.20, p. 157).

D 4.14

d

Facade load transferral

A new facade’s additional horizontal and vertical loads can be transferred through the existing building’s load-bearing structure or into a separate foundation. The existing building’s load reserves must be precisely defined in planning so that the additional dead load and wind, snow and seismic loads can be absorbed into the existing building by means of positive force. Before new structural components are installed, the existing structure may have to be reinforced. The structural effectiveness of load-transferring connections must be verified and they must be designed to fit in with the existing structure. Depending on the building’s geometry, horizontal storey-high or vertical building-high timber panel elements can be installed in front of an existing exterior wall (Fig. 4.12). Depending on the type of load transfer, they can be installed in front of an existing load-bearing structure in four ways (Fig. 4.13): • set on an existing slab edge (a) • set on an additional foundation (b) • suspended (c) • lowered (d) Horizontal and vertical loads can be transferred through a single support. If they are transferred separately, vertical dead loads

D 4.15

are distributed through additional foundations or bearing brackets and horizontal loads transferred through anchors into the existing slab structure. Vertical loads should ideally be directly transferred into the base area into a single foundation (Fig. D 4.14), cantilever beam (Fig. D 4.15) or bracket (Fig. D 4.16). Structural protection of the new timber wall elements must be maintained and the base area must be durably protected from moisture. Horizontal wind suction and wind pressure loads can be transferred storey-by-storey through anchors in the area of the front edges of slabs by means of angled steel brackets. A better solution is to anchor a circumferential guide beam or girt at the height of slab front edges that can serve as a stop for facade elements during assembly and as a fastening point for horizontal load transferral. If a facade is installed in front of a pre-existing exterior wall, a 6 to 8-cm space has been shown to be effective in compensating for unevenness in the wall surface. This compensating layer between the existing wall and new facade must be free of cavities and filled with insulating material, either with floc that is blown in or in the form of a mat previously attached to the rear of the facade element to prevent uncontrolled convection.

D 4.16

155

Solutions for modernising buildings

D 4.17

As with hybrid structures, the open connection joint between a set-in facade element and storey slab must be filled, preferably with insulating material that can withstand temperatures in excess of 1,000 °C [6]. The inside of the facade element is constructed as an airtight layer and vapour barrier to protect the wall from damp due to convection and diffusion. In buildings with various utilisation units, such as multi-storey residential buildings, it must be ensured that sound is not transferred through cavities in the element’s compensating layer. Various jointing and connection details that have been tried and tested for joining timber panel elements in new buildings can be used to securely seal exterior facades. Where elements are highly prefabricated and facade cladding is already attached, it must be ensured that anchor points and joints can be easily accessed. Experience has shown that an interlocking butt joint such as a mortise joint or tongue-and-groove joint makes it much easier to install individual structural components as a guide and allows elements to be horizontally anchored in the existing building without eccentricity.

build the window connections with a prefabricated reveal frame (made of composite woodbased panels for example), which can be pushed into the structural frame from the inside (Figs. D 4.18 and D 4.19). Particular attention must be paid to the planning of joints and sealing of a second waterbearing layer under the windowsill flashing that drains moisture away from the building. Window reveals must be covered with insulation from the outside to reduce thermal bridges in compliance with standard requirements. The window reveal and, in particular, the lintel area must be carefully covered and encapsulated for fire safety reasons. Transitions between the wall and window opening, which result in a compensating gap, must be filled with at least 50 cm-thick, circumferential strips of mineral wool (with a melting point > 1,000 °C) and can be closed with any configuration that complies with fire safety requirements. Non-flammable panels or cementbonded particle board in building materials classes A2-s1, d0 can be used for this purpose (Fig. D 4.17). Building regulations and fire safety

Window installation

Exact measuring and careful planning with the necessary tolerances can make it possible to install prefabricated window units in facade elements, with the reveal, windowsill flashing and sunshading all fitted by the manufacturer, which reduces the adjustment work required on the construction site. Joining an inner window reveal with a timber panel facade installed in front of it is a particular challenge. If the building is occupied, it is advisable to remove the old windows from the outside. After facade elements are installed, the inner reveal is levelled and plastered or clad with a double layer of plasterboard. The reveal, which sits in the plane of the timber panel element on its inner edge, can be glued to the first layer to form an airtight connection. This is a visibly homogeneous and smooth solution but will require several operations inside apartments. A quicker alternative that is especially suitable for buildings that are occupied is to D 4.18

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Exterior wall elements that are connected with the building in the modernising of a building envelope and designed to transfer only dead weight and wind loads are regarded as non-load-bearing structural components for the purposes of fire safety regulation [7]. This means they only have to be built to be fireresistant, even in taller buildings. It should be noted however, that a new wall element will have a space-enclosing function (EI) from a building regulatory viewpoint if it replaces the facade. Here cavities must be avoided and mountings and attachments must have the appropriate fire resistance duration so that there is no possibility of danger from large elements falling out in the event of fire.

Solutions for modernising buildings

D 4.19

Architekturfotografie Gempeler Alexander Gempeler Fotograf SBF|SWB Seidenweg 8a Postfach 524 CH-3000 Bern 9 E-Mail T +41 31 301 84 10 D 4.17

Fire stop and sealing of a window reveal, elevation, Grüntenstraße residential complex, Augsburg (DE) 2012, lattkearchitekten D 4.18 Vertical cross section, Grüntenstraße, scale 1:20 D 4.19 Horizontal cross section, Grüntenstraße, scale 1:20 D 4.20 Facade at Grüntenstraße

Notes: [1] König, Holger: Bauen mit Holz als aktiver Klimaschutz. In: Kaufmann, Hermann; Nerdinger, Winfried: Bauen mit Holz – Wege in die Zukunft. Munich 2011 [2] Schihin, Yves: Brown land densification – Urbane Aufstockung in Zürich. In: Tagungsdokumentation 18. Internationales Holzbau-Forum. Garmisch-Partenkirchen 2012 [3] Isopp, Anne: Belastungstest. Was ist dem Bestand zuzumuten? In: zuschnitt 42, 06/2011 – Obendrauf, p. 9 [4] Tulamo, Tomi-Samuel et al.: Book 2. TES Extension. Munich 2014 [5] Mooser, Marcus et al.: Aufstocken mit Holz – Verdichten, Sanieren, Dämmen. Basel 2014 [6] As for Note [3] [7] ibid. D 4.20

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Part E

Examples of buildings in detail

E 1 Joints in detail

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01

Acton Ostry Architects, Student residence in Vancouver

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02

Kaden Klingbeil Architekten, c13 residential and office building in Berlin

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Rossiprodi Associati, Via Cenni residential complex in Milan

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pool Architekten, Residential and commercial building in Zurich

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OOPEAA, Residential complex in Jyväskylä

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Deppisch Architekten, Residential complex in Ansbach

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Bucher-Beholz Architekten, Terraced houses in Munich

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Florian Nagler Architekten, Residential development above car park in Munich

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burkhalter sumi architekten, Addition of further storeys and conversion to a residential and commercial building in Zurich

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lattkearchitekten, Renovation of a residential building in Augsburg

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Rolf Mühlethaler, Zollfreilager housing complex in Zurich

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12 Florian Nagler Architekten (system development and design), Kampa GmbH (construction), Kampa administration building in Aalen 211

Fig. E

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Architekten Hermann Kaufmann, Illwerke Zentrum Montafon in Vandans

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architekturWERKSTATT, Office building in St. Johann in Tirol

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Michael Green Architecture, Wood Innovation and Design Centre in Prince George

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Bruno Mader, Office building in Clermont-Ferrand

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Cukrowicz Nachbaur Architekten, Community centre in St. Gerold

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18 Architekten Hermann Kaufmann and Florian Nagler Architekten, Secondary school in Diedorf

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NKBAK, European School in Frankfurt am Main

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Agence R2K, School complex in Limeil-Brévannes

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Fink Thurnher, Renovation and new addition to a boarding school in Altmünster

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Oskar Leo Kaufmann and Albert Rüf, Hotel Ammerwald near Reutte in Tirol

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Residential complex in Jyväskylä (FI) 2015, OOPEAA

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Joints in detail Stefan Krötsch

The option to combine various support structure systems, the complexity of structural components, different types and degrees of prefabrication and the continually growing requirements placed on structural design can result in very complex and specific detailed structures. Self-explanatory, generally applicable, standardised structures are still the exception rather than the rule in timber construction. When a support structure is left visible, the technical aspects of joints between structural components are directly linked with its design features. A storey slab’s connection to a load-bearing exterior wall documents the interdependencies in joining structural components in multi-storey timber structures especially well. An exterior wall layer’s continuity, involving as it does the building’s insulating envelope and slabs separating the storeys, must be harmonised with the slab supports and transfer of loads from higher storeys. Added to these parameters are specific principles resulting from prefabrication and the construction process. The taller a building, the more formative this standard detail, repeated on each storey, becomes to its structure. This chapter compares joints between slab supports and exterior walls in five very different timber buildings as an introduction to the documentation of individual projects. The Illwerke Zentrum Motafon in Vandans and the St. Gerold

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community centre building are frame structures that could hardly be more different in terms of their user requirements, slab structures and assembly process. The support structures of both the Hotel Ammerwald in Reutte and the Via Cenni residential complex in Milan consist of cross laminated timber wall plates and slabs, yet they are fundamentally different buildings. While the hotel’s rooms are prefabricated room modules, the residential buildings have a conventional structure made up of wall and slab elements. These examples are compared to the multi-storey Zollfreilager housing complex, with its load-bearing frame structure walls. While the projects are described in detail and shown as a whole in the next section, here just one specific detail is compared – the joint between the storey slab and exterior wall. Like the key topics dealt with in parts B, C and D, each joint is analysed in terms of its support structure, structural design and construction process and presented in the context of the building’s overall system.

Joints in detail

Detail 1 Panel construction wall – Dowel laminated timber slab

Zollfreilager housing complex in Zurich Project documentation p. 206ff. Isometry not to scale Vertical cross section, scale 1:50

Support structure

The load-bearing exterior walls are made of panel elements. An L-shaped wall purlin set in a recess in the stud uprights at the upper end of the elements forms a linear support for the dowel laminated timber element slabs. The panel elements have no top or bottom plates and the studs run through the wall’s entire height, so vertical loads are transferred through the element joint without crossbars and from the end grain to the end grain of the studs, making them less susceptible to subsidence.

Layers

The exterior wall’s panel elements have a double layer of insulation. Joints in the inner planking are glued so it also forms an airtight layer that continues in the form of foil sheets laid around the intersecting storey slabs and glued to planking in the floor area. Short roof projections protect the timber facade and windows from weathering. The sound insulation and fire safety requirements of the storey slabs are met by a floating screed and suspended ceiling on the underside.

Prefabrication and assembly

The panel elements, including windows, sunshading fixtures, inner lining, the exterior cladding substructure and exterior lintel cladding were prefabricated as structural components, each with four window axes. Only the prefabricated, storey-height exterior wall cladding and projecting roof panels were fitted on site. Once the wall elements had been erected, the slab elements were laid on them with a straight edge on top, which was then fitted into a recess on the underside of the next wall element above it.

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Joints in detail

Detail 2 Panel wall / frame structure – Dowel laminated timber slab

Community centre in St. Gerold Project documentation p. 232ff. Isometry not to scale Vertical cross section, scale 1:50

Support structure

Solid construction timber columns and beams integrated into the exterior and interior walls form a frame structure made clear by the columns in the strip windows. Doweled dowel laminated timber element slabs lie in a linear position on the beams. The load-bearing frame and additional studs are integrated into the exterior wall panel elements, which are braced by diagonal siding planks. Its four exterior walls and cross laminated timber panel lift shaft brace the building as a whole, so its dowel laminated timber slabs do not have to be rigid plates.

Layers

The exterior wall panel elements are insulated and have a second insulating layer on the outside. The windows were set into this second layer, which continues in front of the slab supports and support structure. Oiled paper between the inner timber lining and insulation forms an airtight layer. Foil sheets around the front edges of the intersecting slabs join the airtight layer to the wall above and below it. Floating screed and a suspended ceiling on the underside meet the sound insulation and fire safety requirements of the storey slabs.

Prefabrication and assembly

The building’s exterior walls, made of buildinghigh panel elements, and the lift core, made of cross laminated timber elements, were built first. Slits in the wall elements were used to mount the dowel laminated timber elements of the storey slabs, with foil sheets previously laid in them forming a connection with the walls’ airtight layers. Its interior walls, supports and beams were successively erected as the storey slabs were installed. Once the support structure was completed, the second insulation layer,the windows, facade cladding, installation layer, floor structure and suspended ceiling were added on site.

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Joints in detail

Detail 3 Cross laminated timber walls – cross laminated timber slabs

Via Cenni residential complex in Milan Project documentation, p. 174ff. Isometry not to scale Vertical cross section, scale 1:50

Support structure

The span direction of the slabs is rotated 90° in various storeys to distribute loads longitudinally and transversely across all the walls and linear supports transfer loads across long spans. Despite the building's height of nine storeys, these two measures made it possible to simply join the cross laminated timber elements without compressing horizontal members and causing any resulting subsidence. Its slabs lie squarely on the walls and they are diagonally screwed together.

Layers

The load-bearing plane of the cross laminated timber walls is also the airtight layer. The intersecting storey slabs have foil sheets glued over them on the outside. An insulating layer is attached to the outside of the walls using a simple geometry and the composite thermal insulation system plastered over. Windows were installed from the inside in the cross laminated timber wall. Together with the sun shading, they create a break in the layers. The floors have a conventional structure that is decoupled for sound insulation purposes. To meet fire safety requirements, slabs and walls were clad with gypsum fibreboard and the exterior wall covered by the installation layer. Prefabrication and assembly

Walls and slabs are made of hardened cross laminated timber panels and joined with diagonal screws and steel connecting parts to form a box-like support structure. Window and door openings were cut in the factory. Once the building's shell was completed, the windows and sunshading were installed from the outside, the balcony slabs sealed, the airtight layer was created by gluing the panel joints and the composite thermal insulation system attached. The floor structure was built and the encapsulation of walls and slabs created conventionally on site.

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Joints in detail

Detail 4 Cross laminated timber walls / Cross laminated timber slabs in room modules

Hotel Ammerwald near Reutte Project documentation p. 254ff. Isometry not to scale Vertical cross section, scale 1:50

Support structure

This three-storey support structure made up of room modules forms a regular grid structure spanning the building’s longitudinal direction, so the exterior wall on the building’s long side is not load-bearing and window openings could be left without lintels and required no further measures. Five-ply cross laminated timber panels run parallel to the facade, lie on double three-ply cross laminated timber wall plates and also brace the building. The panel on the underside of the double slab structure is a result of the manufacture of the room modules and is not load-bearing.

Layers

The facade consists of short wall sections and floor-to-ceiling windows. Its wall sections are made of exposed cross laminated timber with an exterior vapour barrier as the airtight layer, three layers of mineral fibre insulation between a substructure arranged crosswise and rearventilated stainless-steel sheeting facade cladding. The double ceilings and interior walls created by the stacked room modules were acoustically isolated by means of neoprene bearings and insulation in cavities, providing sufficient sound insulation.

Prefabrication and assembly

The joints’ logic follows the building’s prefabricated room module composition. Its support structure is formed by the stacked modules, and the resulting double walls and ceilings provide good sound insulation. Joints in the exterior wall were insulated and sealed during assembly on site. The facade cladding was also attached on site, so the room modules are not evident from the outside. The interior fittings and services technology in the modules were completely prefabricated, so only the connection points had to be joined during assembly.

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Joints in detail

Detail 5 Frame structure – Composite timber-concrete joist slabs

Illwerke Zentrum Montafon in Vandans Project documentation p. 214ff. Isometry not to scale Vertical cross section, scale 1:50

Support structure

The primary load-bearing structure consists of support axes in the facade on the building’s long side, double-spaced support columns inside the building and longitudinal main beams. Between the main beams are composite timber-concrete joist slabs. The edge beams and top layer of the prefabricated slab elements are made of concrete and are the main beams in sections. The next storey’s columns rest on the edge beams so loads from the storey above it are transferred without cross-beams from the grain ends of the columns through the concrete. Layers

The exterior walls comprise strip windows alternating with solid wall areas made of panel elements with a double layer of insulation. Its support structure (columns and concrete edge beams) is in the inner insulating layer. At the window level, the outer insulating layer extends without thermal bridges. Planking in the exterior wall panels forms an airtight layer that continues around the storey slabs and exposed columns and is joined to the window frames. Porches at each storey protect the timberframe windows and facade from weathering and house the sunshading. Prefabrication and assembly

The composite timber-concrete slabs were prefabricated as elements consisting of four timber beams, edge beams and a concrete top layer. They also contained gudgeons, which were set onto pintles on the column tops, immediately fixing the elements in position. Once the element joints were grouted, the concrete layer protected the structure from moisture during construction. Each prefabricated element was made up of a solid wall panel area and three columns, so all the joints between the columns and panel elements were made in the factory. The windows, facade cladding and porches were installed on site.

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Example 01

Student residence Vancouver, CA 2017 Architects: Acton Ostry Architects, Vancouver Russell Acton, Mark Ostry, Matthew Wood (project leader) Team members: Rafael Santa Ana, Andrew Weyrauch, Gjergj Hondro, Nebojsa Slijepcevic, Nathaniel Straathof, Warren Schmidt Timber construction consultants: Hermann Kaufmann, Christoph Duenser Structural engineers: Fast + Epp, Vancouver Concept The University of British Columbia is behind one of the world’s most ambitious timber construction projects. When completed, this hall of residence for 400 students will be 55 m tall – the tallest solid timber building on the planet. Its 18 storeys will be accessible via two stairwells and reinforced concrete elevator cores. The project was conceived as part of the Canadian Wood Council’s Tall Wood Initiative. The timber industry believes that there is enormous potential in British Columbia for using solid wood as an alternative to the conventional balloon-frame style of construction. The local construction industry has little experience in solid wood construction and modular prefabrication, but the Tall Wood Initiative hopes to change that. The 18-storey timber building on the Brock Commons campus, with around 15,000 square metres of floor space, demonstrates how efficient the material can be. To allow for taller wood buildings, local authorities raised the maximum permissible number of storeys from four to six back in 2009. In addition, the Canadian Building Code allows exceptions to be made under a “site-specific regulation”. In addition to that, the campus has a separate building authority. These factors ultimately allowed the university to erect a timber building of this size once it had met stringent requirements. Construction The vertical construction elements consist of glued laminated supports that measure 26 ≈ 26 cm and two concrete stairwells that were continuously poured on site and which provide reinforcement. The supports are arranged in a grid measuring 2.85 ≈ 4.00 metres. On top of them are five-layer cross laminated timber (CLT) ceiling slabs with a total thickness of 16.6 cm. The staggered two and three-field panels have biaxial tension and allow for a ceiling without joists. In addition to being quick to install, this solution has the advantage of enabling easy installation of the building’s technical equipment. The shear bond between the individual CLT panels is provided by a recessed three-layer

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Student residence in Vancouver

panel, and together the individual panels form a statically usable disc. Steel bands transfer all horizontal forces (wind and earthquakes) from this disc to the concrete stairwells. Load transfer from support to support poses a particularly difficult challenge in tall buildings. This challenge was addressed using specially developed steel components, which also

for 120 minutes. The wood is only visible in the top storey, which serves as a common room for students and provides a close look at the building’s wooden architecture. The fire safety concept assumes that, due to the gypsum enclosure and the density of the timber beams, any fire caused will extinguish itself after 90 minutes. Prior to this time, the

allowed for quick assembly. The building was constructed in a very short time, with two new storeys being added each week. Fire safety To make the timber construction more fireretardant, wood components are enclosed in plasterboard to keep them from catching fire b

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Work room Technical and electrical systems Rubbish Laundry Studio apartment Shared apartment

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Example 01

Concrete support structure

Timber support structure

timber construction should not add to the building’s fire load. In addition, there is a built-in sprinkler system and a redundant system that provides the main system with water and electricity in the event that the connection to the public grid is interrupted. Facade The building’s facades feature the steel-frame construction typically found in Canada, with high-pressure laminate (HPL) cladding made of wood and paper, although the large HPL panels alternate with floor-to-ceiling windows, and the corners of the building feature rounded glass. The building has a serious look that fits in well with the rest of the buildings on the campus. Facade elements, including built-in windows, were prefabricated and mounted storey-bystorey in the steel angle sections that had been preinstalled in the ceilings. This enabled the structure to be quickly protected from precipitation – essential in Vancouver’s rainy climate. The university has other sustainability goals besides demonstrating what is technically feasible in today’s wood-hybrid construction: It wants to receive LEED Gold certification and comply with the ASHRAE 90.1-2010 standard (Energy Standard for Buildings Except Low-Rise Residential Buildings). To achieve this, the new hall of residence must use 25 % less grey energy and material than conventionally constructed buildings. With its choice of construction materials, it is off to a good start towards attaining that: The solid wood structure saved some 2,650 cubic metres of concrete, which is equivalent to about 500 tonnes of CO2.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

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18 15,115 m2 About EUR 35 million About 2 months 17 months

Installations

Student residence in Vancouver

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Aluminium window with double-insulated glazing Connector for facade elements Sealing Prefabricated facade: High-pressure laminate (HPL) 8 mm Battens 25 mm, steel substructure thermally separated by thermal insulation 50 mm Sealing, vapour-permeable (applied in liquid state) Plasterboard 13 mm Substructure steel, between it thermal insulation, glass fibre 152 mm Added on site: Vapour barrier Plasterboard 16 mm Interior paint

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Windowsill, ornamental wood Steel angle bracket, continually installed after the facade, anchored in sealing layer to prevent water and screed penetration during construction Floor slab: Flooring Screed 40 mm Separating layer Cross laminated timber ceiling 169 mm Plasterboard, moisture-resistant 16 mm Suspended ceiling, steel retaining profile 38 mm Steel substructure 19 mm Plasterboard 2≈ 16 mm Interior paint Upright support, glued laminated timber (standard size 265 ≈ 265 mm in basic grid of 2.85 ≈ 4.00 m) Cladding, plasterboard, three layers Threaded rod Ø 16 mm Steel connection as plug connector

Partially clad elements during the construction process

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Example 02

c13 residential and office building Berlin, DE 2013 Architects: Kaden Klingbeil Architekten, Berlin Designer: Tom Kaden Team members: Tom Kaden, Tom Klingbeil, Kora Johanns, Malte Reimer, Fabio Verber Structural engineers (timber): Pirmin Jung, Rain

Concept The c 13 residential and office building has been constructed on an empty plot on the edge of a late-19th century block in Berlin’s Prenzlauer Berg district. It consists of a sevenstorey front building and a five-storey rear building, enabling it to exploit the entire depth of the plot along a 46-metre-long, six-storey fire wall of its western neighbour. The entire length of the building is set back from its eastern neighbour, opening up a view into the interior of the city block. This joint provides vertical access in the form of two free-standing stairwells. The rear building has been separated from the fire wall via three inner courtyards that transport light from the south and east into the depths of the building and allow carefully staged views into, out of and through the building. Despite the engineering discipline that was necessary for economic implementation as a timber construction, an extraordinary spatial diversity has emerged across all storeys, reflecting the building’s different uses (bistro, meeting place, childcare centre, family centre, doctors’ surgeries, offices and apartments) in the most various of forms. The large spans of the skeleton construction and the independent access system over the entire length of the building allow a high degree of flexibility that proved to be valuable during the planning phase, given that the usage concept was changed multiple times.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

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7 4,673 m2 About EUR 4.7 million (net) 5 months 15 months

c 13 residential and office building in Berlin

Plan Scale 1:3,000 Sectional view • Floor plans Scale 1:500 1 2 3 4 5 6 7 8 9 10 11

Fire safety Berlin’s building code prohibits essential structural parts from being flammable in buildings with a top floor higher than 13 metres above the finished ground floor level. Although the top floor height is 19.50 metres, the wood structure was approved thanks to an individual fire protection concept, the essential elements of which are analogous to its predecessor building E3 (Fig. A 1.8, p. 12), which in 2008 was the first seven-storey timber construction in Germany. In addition, the decision to open up the stairwells and move them away from the building, making the utilisation units accessible from the outside on all levels, is the result of a concept from urban planning and architecture of a complex, vertically interlinked, multifunctional urban building. In terms of fire safety, it also offers the particular advantage that each utilisation unit has a direct escape route into the open, and the open design means there is no danger of smoke filling the emergency stairwell. The wooden structure of the walls and columns was encapsulated with gypsum fibreboard to provide fire resistance for at least 90 minutes. The soffits of the dowel laminated timber ceilings have a transparent, flame-retardant protective coating and the bases of the steel girders are clad with gypsum fibreboard strips that reproduce the construction.

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Play street Courtyard Childcare centre Kitchen Office Hall Bistro Underground garage entrance Airspace Terrace Apartment

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Example 02

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Thermal insulation, composite system with plaster mineral 110 mm Plasterboard 18 mm, vapour barrier Solid wall, cross laminated timber 140 mm Gypsum fibreboard 2≈ 18 mm Floor slab, living space: Flooring, parquet 16 mm Heating screed 74 mm, separating layer Impact sound insulation 30 mm, sealing Concrete topping, reinforced 120 mm Dowel laminated timber ceiling with fire-retardant coating (B1) 140 mm Ceiling structure, bay window (bare roof): Sealing, plastic, single layer Gradient insulation, EPS on average 135 mm Concrete topping, reinforced 120 mm Dowel laminated timber ceiling with fire-retardant coating (B1) 140 mm Steel beams, HEB 220 Plasterboard (fire prevention cladding) 25 mm Gypsum fibreboard 15 mm Timber windows, spruce with insulating glazing Composite thermal insulation system, plaster, mineral 150 mm Plasterboard 18 mm, vapour retarder Solid wall, cross laminated timber 100 mm Gypsum fibreboard 2 x 18 mm Support, reinforced concrete 300/300 mm Composite thermal insulation system, plaster, mineral 70 mm Gypsum fibreboard 18 mm Wooden stud construction 60/180 mm, in between thermal insulation, mineral fibre 180 mm Gypsum fibreboard 18 mm, vapour barrier Gypsum fibreboard 18 mm Edge beam, laminated veneer lumber (LVL)

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c 13 residential and office building in Berlin

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Vertical section, front building (north facade) Scale 1:20 Vertical section, rear building (south facade) Scale 1:20 Static system Shear bond Inversion of the torque curve in the bearing area thanks to the projecting ceiling Vertical section, exterior ceiling, 4th storey, rear building Scale 1:10

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The cross laminated timber wall with horizontal ceiling layer functions as a wall-like support. The position and size of windows is matched to the supporting effect of the wall. The concrete footbridge of the stairwell rests on the wall. The wall spans from support to support. Cross laminated timber wall with push cams at the bottom. The cross laminated timber wall rests on steel girder supports, not on the floor slab. The concrete topping of the timber-concrete composite slabs is poured shear-resistant thanks to kerfs in the wall.

Support structure and prefabrication A hybrid skeleton construction of ceiling-level steel girders resting on concrete slabs in the first storey and laminated veneer lumber and glued laminated supports in the storeys above divides the building into roughly equal-sized ceiling areas with a span of approximately 5 metres each, traversed by a dowel laminated timber ceiling with a top concrete layer as a composite construction. The 14-cm thick dowel laminated timber ceilings are visible on the underside and rest on the lower flange of the HEB profiles of the primary beams, while the 12-cm thick layer of concrete that is applied on site is flush with the top edge of the beams. The reinforcing walls of the five-storey rear 10

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building consist of panel-construction elements in which the supports of the skeleton structure are partially integrated. The reinforcing walls of the seven-storey front building are made of cross laminated timber (CLT); here the supports stand in front of the walls. During assembly of the structure, the CLT elements with kerfs on the bottom were placed on the steel girders. Pouring the kerfs when applying the concrete layer established a shear-resistant connection to the timber-concrete composite (TCC) ceilings in a very simple way. Besides serving as stiffeners, the CLT elements in the western outer wall function as wall-like supports that rest on both sides of the steel girders, and therefore on the supports to

which the stairwell is attached via the access bridge. The bay windows in the facade facing the street and the fourth storey of the back building are supported by ceiling overhangs. TCC construction is normally not suited for continuous beams or for projections due to the reversal of the compression and tension zone. However, by reinforcing the reinforcing layer, which is guided by recesses in the steel beams, the concrete layer was converted to the tension zone of a cantilever beam. The pressureresistant connection of the dowel laminated timber ceiling to the steel girder via swelling mortar enables its effect as a pressure zone (see Fig. E).

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Exterior ceiling: Flooring parquet, 16 mm, cement screed 80 mm Impact sound insulation 30 mm, sealing, Concrete topping, reinforced 120 mm, dowel laminated timber ceiling 140 mm Vapour barrier, metal profile, between them thermal insulation 100 mm, plaster 10 mm Steel reinforcement Grouting, swelling mortar Steel profile, HEB 220 Composite thermal insulation system 70 mm Gypsum fibreboard 18 mm, wood frame construction, between them thermal insulation 180 mm Gypsum fibreboard 18 mm, vapour barrier Gypsum fibreboard 18 mm

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Example 03

Via Cenni residential complex Milan, IT 2013 Architects: Rossiprodi Associati, Florence Team members: Davide Canepa, Maria De Santis, Vincenzo Inforzato, Benedetto Selleri, Gaetano Selleri Structural engineers (solid construction): Tekne, Milan Structural engineers (timber): Borlini & Zanini, Pambio Noranco

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Bedroom Footbridge, covered Rooms Studio apartment

Via Cenni residential complex in Milan

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

9 30,325 m2 EUR 15.8 million 6 months 18 months

Concept The residential complex at Via Cenni is located in a very architecturally heterogeneous suburb of Milan between a small garden estate, a railway depot, an old farm, barracks and residential buildings. The two opposing bent lines of the complex create an introverted, open space in the middle. From the two-storey pedestals rise four nine-storey residential towers with a base of 13.60 ≈ 19.10 metres and a height of about 27 metres. In total, the complex comprises 124 apartments and various accompanying uses. The building complex is Italy’s first pure-timber structure with more than three storeys.

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Example 03

Support structure All load-bearing walls and ceilings above the concrete basement level are made of cross laminated timber (CLT) – even the elevator and installation shafts and the stairwell. Whereas the two-storey connecting buildings feature regular aligned crosswall construction, the walls of the residential towers are loadbearing on all sides. Four transverse wall axes and three longitudinal wall axes combine with the ceilings to form a three-dimensional, honeycomb-like supporting structure that achieves optimum efficiency through linear connections between the CLT elements, which appear to be two-dimensional. In a few places, the structure dissolves to allow for openings in the upright supports and beams. The tension direction of the ceiling changes slightly from storey to storey so that vertical loads are distributed to all load-bearing walls. This distribution of loads to all CLT walls and the length of the free supports allows the ceilings to simply be placed on the walls without any transverse compression from the wall of the storey above, even with nine storeys. Depending on the direction of stress, the cantilevered balconies are either on different sides or are supported by cantilevered wall

Wood connection system Scale 1:10

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panels. The load-bearing walls are made of five-layer CLT, the thickness of which gradually reduces from 20 cm on the ground floor to 12 cm on the eighth floor. The ceilings, with spans of up to 5.80 or 6.70 metres, are made of five-layer CLT (20 cm thick) and seven-layer CLT (23 cm thick). In places where high tensile forces may occur, the linear connections of the wall panels and ceiling panels comprise slotted sheets with dowels which have head plates that are screwed together using the ceiling elements. In areas that experience less stress, the CLT elements were “sewn” together with full-thread screws, meaning they were connected by diagonally inserting the screws in opposite directions. Earthquake safety and robustness Like all of Italy, Milan is located in an area of high seismic activity. The support structure of CLT panels gives the overall structure high rigidity, enabling it to meet stringent seismic safety requirements. Connections are designed to absorb a large part of an earthquake’s kinetic energy by deforming elastically. The engineers had to demonstrate the robustness of the residential towers separately. The support structure was designed in such a way

that in the event of an earthquake or gas explosion, for example, the building’s walls or columns can fail at several points without the entire building collapsing. The ceilings are bolted to the walls above, which act like a carrier, so that they can hang on if the loadbearing wall below were to fall away. Fire safety Italian law does not have flammability requirements for structural components that meet the required fire classifications, in this case REI 60 or 90. The load-bearing walls have a double layer of plasterboard while the stairwells and primary escape routes have a double layer of plasterboard fire-protection panels. Ceilings are faced with a single layer of suspended plasterboard.

Via Cenni residential complex in Milan

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Vertical section Scale 1:20 1 Roof construction: Levelling layer with waterproof coating 40 mm Sealing 3 mm, gradient insulation 120 –150 mm Cross laminated timber 220 mm Substructure, aluminium Plasterboard 40 mm 2 Facade (non-load-bearing): Facade slab, lightweight concrete 12.5 mm Metal stud construction, in between thermal insulation, mineral wool 80 mm Air space 10 mm, thermal insulation 40 mm Metal stud construction, in between thermal insulation, mineral wool 80 mm, Vapour barrier, plasterboard 2≈ 12.5 mm 3 Facade (load-bearing): Plaster 10 mm, thermal insulation 120 mm Cross laminated timber 160 – 220 mm (varies from storey to storey) 4 Loggia sunblind: sliding element, aluminium 5 Floor slab: Flooring, tiles 15 mm, heating screed 55 mm Thermal insulation 30 mm Screed as levelling layer 80/110 mm Sealing, PE foil 0.3 mm Cross laminated timber 220 mm Substructure, aluminium Plasterboard 12.5 mm 6 Loggia, floor construction: Flooring, tiles 15 mm, screed 50 mm Sealing 1.5 mm Screed as levelling layer 40 mm Thermal insulation 60 mm, PE foil 0.3 mm Cross laminated timber 220 mm 7 Floor construction, ground floor: Flooring, tiles 15 mm Heating screed 55 mm Thermal insulation 30 mm, sealing, PE foil 0.3 mm Thermal insulation 100 mm Base slab, reinforced concrete 280 mm

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Example 04

Residential and commercial building Zurich, CH 2010 Architects: pool Architekten, Zurich Mathias Heinz, David Leuthold Team members: Andreas Wipf, Jves Lauper Structural engineering: Henauer Gugler, Zurich Structural engineering (timber): SJB Kempter Fitze, Herisau

Concept The residential and office building on busy Badenerstraße is the first building in Zurich to be strictly developed according to the criteria of the 2000-Watt Society. Its goal is to have every resident reduce their energy use to 2,000 watts and their carbon emissions to one tonne of CO2 per year by 2050. Timber construction is particularly well suited to meeting these high standards. Six building volumes offset from each other, each with four to six residential storeys, rise above a supermarket. Recesses allow optimal daylight exposure for the apartment floor plans, which are up to 24 metres deep. The windows face east and west due to the busy road to the north. This ensures better noise protection for the apartments. Inside the 54 apartments, the linear sequence of rooms allows for continuous views that create a generous sense of space despite the limited area of the two and three-room dwellings. The folded facade elements support the urban character and refer to the ashlar masonry on upper-middle-class residential buildings of the late 19th century, without concealing the suspended structure.

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Supermarket Living room Kitchen Bedroom Balcony Roof terrace

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Residential and commercial building in Zurich

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Vertical section Scale 1:20 7 Roof structure: Round gravel 80 mm, protective sheet 10 mm Waterproofing, bitumen two-layer (root-proof top layer), gradient installation, mineral wool 150 – 250 mm (on the edge near the attic: thermal insulation PUR, aluminium, laminated, pressure-resistant 130 mm) Waterproofing EVA 3.5 mm, OSB panel 10 mm Dowel laminated timber ceiling 200 mm Air-sealing foil, substructure with spring clips 27 mm, gypsum fibreboard (fire protection) 18 mm, white plaster 5 mm 8 Sun protection, external venetian blinds with beaded slats 9 Floor slab: Flooring, parquet 10 mm Cement screed with underfloor heating 70 mm Separating layer, PE foil Thermal and impact sound insulation, mineral wool 30 mm Hollow box element (total 240 mm) made of: Three-layer panel 40 mm, timber ribs 160 mm filled with chipping infill of approx. 50 mm Three-layer panel 40 mm Substructure with spring clips 27 mm Gypsum fibreboard (fire protection) 18 mm, White plaster 5 mm 10 Floor duct with steel plate 80 ≈ 150 mm, screwed into gypsum fibreboard 11 Floor structure, roof terrace: Timber grate, larch, solid, glazed battens 35 mm, separating layer / roof foil 8 mm Waterproofing, bitumen, two-layer Gradient insulation, PUR with aluminium laminate, pressure-resistant 60 −100 mm, vapour barrier Gypsum fibreboard 15 mm Dowel laminated timber ceiling 200 mm, air-sealing foil Substructure with spring clips 27 mm Gypsum fibreboard (fire protection) 18 mm White plaster 5 mm 12 Wall structure: Facade cladding, glass-fibre-reinforced concrete element 70 mm Timber substructure / rear ventilation 30 mm Wind paper, thermal insulation, mineral wool 160 mm Dowel laminated timber wall 100 mm Thermal insulation, mineral wool 80 mm Substructure 30 mm, felt sheet Gypsum fibreboard 2≈ 12.5 mm White plaster or putty 5 mm, glass fabric 13 Apartment partition: Glass fabric White plaster or putty 5 mm Gypsum fibreboard 2≈ 12.5 mm, felt sheet Substructure 30 mm Timber plank 100 mm Thermal insulation, mineral wool 40 mm Timber plank 100 mm Substructure 30 mm, felt sheet Gypsum fibreboard 2≈ 12.5 mm White plaster or putty 5 mm, glass fabric

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Example 04

Axonometry, plug connection Wall – floor slab – wall Assembly steps for timber building above ground floor (supermarket) ceiling: A newly developed solid wood system using storeyhigh square spruce was used for the first time in this residential and office building.

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Residential and commercial building in Zurich

Support structure The basement level and the access cores are made of reinforced concrete for better fire safety and structural reinforcement. The offset residential floors above are made of timber. The simple crosswall style, which remains the same on all storeys, allows for economical construction and is dissolved by rows of columns on the retail storey. For the exterior walls and apartment partitions, a newly developed solid wood system was used for the first time: A series of floor-to-ceiling planks measuring 100 ≈ 195 mm were attached to a bottom plate using hardwood dowels, without the help of machines, and aligned halfway down using a transverse dowel. Shorter planks are used above and below the windows. A two-person team was able to complete one such storey per day. The top plate and bottom plate are made of birch plywood; there are no problems from transverse compression because standing timber covers a large portion of the area. Prefabricated ceiling elements made of box girders were placed on top of the wall, and a horizontal binder was used to bring them into alignment. The plane of these elements forms a disc to stabilise the building and transmits

their horizontal forces to the massive stairwells. A packed bed of slag provides excellent sound insulation in the cavity between the ribs. The wood surfaces are planked with plasterboard for fire safety reasons and are therefore not visible. Sustainability and building technology The wall planks are connected to each other and to other components using only wooden dowels and can therefore be taken out of the structure and reused. The curtain wall made of glass-fibre-reinforced concrete elements can be easily replaced. The extruded profile is particularly stable due to its angular shape – more space was added between the bottom battens, which saved material. Residential ventilation is decentrally controlled, with a single room fan integrated in the windows (including heat recovery). This made it possible to completely dispense with ventilation ducts, which are tricky to assemble and must be clad with fire-safe material. A control unit measures the CO2 content of the exhaust air and regulates the air flow. Heat is generated by using the waste heat from the refrigeration units in the supermarket

on the ground floor and via a groundwater heat pump. Electricity for heat recovery, ventilation fans and building technology is generated on the roof.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

7 13,876 m2 EUR 33.5 million About 2.5 months 18 months

Horizontal section, window Scale 1:10 1 Glass-fibre-reinforced concrete element 70 mm Timber substructure /rear ventilation 30 mm Wind paper, thermal insulation 160 mm Dowel laminated timber wall 100 mm Thermal insulation, mineral wool 80 mm Substructure 30 mm, felt sheet Gypsum fibreboard 2≈ 12.5 mm Glass fabric 2 Timber-metal window with double-insulated glazing 3 Ventilation element

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Example 05

Residential complex Jyväskylä, FI 2015 (building 1), 2017 (building 2) 2018 (buillding 3) Architects: OOPEAA, Helsinki /Seinäjoki Anssi Lassila (project leader) Team members: Jussi-Pekka Vesala, Iida Hedberg, Juha Pakkala Structural engineers (timber): SWECO, Helsinki Heikki Löytty, Lauri Lepikonmäki Concept Finland’s first eight-storey wood residential building was erected in the outskirts of Jyväskylä, a town with 135,000 people, 270 km north of Helsinki. Connected by a concrete pedestal with parking spaces and storage rooms, 150 apartments in three stand-alone buildings with slightly angled facades and gently sloping pitched roofs will be constructed in two phases by late 2017 in cooperation with the town planning authority. This pilot project aims to create affordable, high-quality, eco-friendly dwellings for tenants, who buy in with a modest down payment and become owners after 20 years of rent payments. The development plan was specially adapted to enable high density. The amount of land taken up by the buildings on the hilly plot was minimised to the greatest extent possible in order to preserve a small grove of trees on the west side and thus create an outdoor area with welcoming qualities. Otherwise, the property is surrounded by wide streets. The buildings respond to the different sides in their form and material: On the “green” side, partially glazed loggias or balconies emerge from the facade, which enliven it and at the same time enlarge the living rooms of the smaller apartments. This facade is made of untreated larch, while the spruce cladding facing the streets is painted dark. The structures are highly compact. This is achieved by orienting each of the apartments only to the east or west and adding a central corridor with interestingly designed and illuminated air spaces over the entire height of the building. Support structure and prefabrication The project is characterised by its innovative use of room modules: Each apartment contains a module with a bedroom, living room and loggia on the facade side, while a second module on the inside contains the bathrooms, kitchens and other rooms. The corridor ceilings lie like a bridge between these two modules. Installations are integrated into the wall facing the shared hallway, allowing independent maintenance from outside. The room modules,

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Residential complex in Jyväskylä

made of spruce plywood, bear the vertical and horizontal loads. Hollow steel-reinforced concrete ceilings span the parking spaces in the base area. The prefabricated modules come equipped with interior fittings and a facade that includes a wind seal. The wooden cladding is mounted subsequently as prefabricated elements. The first construction phase took only six months, an essential benefit given Finland’s climatic conditions.

Fire safety The walls of the apartments and stairwells are clad in plasterboard. The surface of the wood remains visible on the ceilings of the apartments and stairwells, adding character to a space that would otherwise be entirely white. Cross laminated timber is used here as a support structure as well as a floor covering. A sprinkler system is part of the fire safety concept.

Building characteristics Number of storeys Gross floor area 1st – 8th storey Basement and parking Construction costs Construction time (timber): Production of modules Assembly on site Total construction time

8 5,335 m2 1,495 m2 Approx. EUR 11 million 5 months 2 months 6 months

Plan Scale 1:2,500 Sectional view • Floor plans Scale 1:500 1 2 3 4

Entrance Hallway Airspace Living area

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Example 05

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Floor slab: Flooring: oak parquet 15 mm, screed 40 mm Impact sound insulation with underfloor heating 30 mm Cross laminated timber panel 140 mm Cavity insulation: glass wool 50 mm Air space 77 mm, cross laminated timber panel 80 mm Facade: Wood shell: spruce, painted/larch, untreated 28 mm Wooden substructure with rear ventilation 50 mm Glued laminated timber 100 mm Parapet element: aluminium frame with glass filling Aluminium sliding windows Wooden sliding windows with triple-glazing, without threshold Floor structure, loggia: Sealing, plywood panel in the gradient, wedge battens Cross laminated timber panel 140 mm Cavity insulation: glass wool 50 mm Cross laminated timber panel 80 mm Sealing of the joint between the room modules Floor slab above basement: Flooring: oak parquet 15 mm, screed 40 mm Impact sound insulation with underfloor heating 30 mm Cross laminated timber panel 140 mm Cavity insulation 100/50 mm, airspace Hollow core slab prefabricated concrete Roof construction: Sealing: bitumen, OSB panel 18 mm, Battens with rear ventilation, Heat insulation: blow-in insulation 450 mm, Cross laminated timber 80 mm Floor slab above underground garage: Flooring: oak parquet 15 mm, screed 40 mm Impact sound insulation with underfloor heating 30 mm Cross laminated timber panel 140 mm Cavity insulation 100/50 mm, airspace Reinforced concrete floor 800 mm

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Residential complex in Jyväskylä

Building structure showing room modules

Apartment comprising two joined room modules

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Example 06

Residential complex Ansbach, DE 2013 Architects: Deppisch Architekten, Freising Michael Deppisch Team members: Johannes Dantele (project leader), Simon Huber, Christian Klessinger, Andreas Kopp Structural engineers: Planungsgesellschaft Dittrich, Munich

aa

Concept In a highly heterogeneous environment, two opposing residential buildings and outbuildings form an enclosed four-sided complex with a quiet central courtyard. The graduated height of the buildings responds to the environment and accentuates the ensemble. The residential complex is the result of a competition and was specially promoted as energy-efficient housing. Both 16-metre-deep, non-basemented, very compact and clearly structured residential buildings have around 2,400 m2 of total living space and 37 apartments with eight different layout variations.

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A simple support structure and centrally arranged sanitary cores enable high flexibility thanks to changeable inner walls. All public facilities are located on the ground floor facing the courtyard. The apartments on the upper floors either extend from front to back or are corner apartments and therefore always receive light from at least two sides. The lintel-free windows and bright jamb claddings ensure maximum use of daylight with energy-optimised window sizes in the facades. The kitchens within are illuminated by windows facing the stairwell, which receives daylight via a glazed roof. A compact volume in combination with a highly insulated,

homogeneous building shell made it possible to meet the KfW-40 residential energy efficiency target.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber, including facade) Total construction time

4 3,667 m2 EUR 4.34 million 4 months 13 months

Residential complex in Ansbach

Sectional view • Floor plans Scale 1: 500 14

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Courtyard Sand play area Bench Arbour (to be turned into common area) Heating Pellet storage Electrical room Bicycles Rubbish area Vestibule Washroom Pushchairs Storage rooms Platform elevator Elevator (optional) Airspace

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Example 06

Support structure The load-bearing structure comprises walls and ceilings made of spruce plywood. The ceiling elements penetrate the outer shell on the longitudinal side, resulting in a very simple continuous balcony construction. Thanks to the structural-physical properties of wood, there is no danger of condensate formation; a groove on the underside of the ceiling panel prevents moisture from moving from the outside to the inside of the wood and reduces thermal bridges. This also makes it easy to create the required airtight connection. The outer walls consist of prefabricated wooden frame elements with 28 cm of mineralwool core insulation. The windows as well as the outer cladding, which is made of preweathered and therefore maintenance-free horizontal boarding of local silver fir, were installed on-site. The outward-facing ground floor facades of the four-storey building are made of sandblasted exposed concrete, as are the outbuildings. The three timber upper storeys thus rest on a robust base, which also encloses the ensemble. Inside, the walls are clad with gypsum fibreboard and painted white, while the doors and windows are made of clear varnished spruce. The hollow wooden window frames sit deep in the jamb for aesthetic reasons and for better protection from the weather. The windows are triple-glazed and have insulated frames to prevent thermal

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bridges. The roof construction also features cross laminated timber elements, which are visible from inside, with 32 cm of roof insulation. Fire safety The different heights of the two residential buildings mean that the buildings fall into different classes, each with its own structural fire safety requirements, which affected the choice of materials for the facade. The Bavarian building code usually requires flame-retardant exterior cladding for the fourth storey and above. To ensure that both structures could have the same timber shell, the four-storey building was designed with a non-combustible concrete base on the ground floor to compensate. This limits the flammable surface to three storeys and reduces the risk of arson. Still, K260 encapsulation with highly fire-retardant insulation was required for the exterior walls. In addition, the ceiling panels for the balconies, which pass uninterrupted from the inside to the outside, act as a type of firewall on the long sides, as they separate the outer walls of each storey from the storeys above and below. In addition, on all windows, the circumferential jamb claddings were designed with a thickness of 6 cm to provide fire resistance of F 30 and prevent flames from leapfrogging from the room to the rear ventilation cavity. This made it possible to dispense with fireprotection panels on the front sides of the

building. To compensate for the visible cross laminated timber ceilings, which are not permitted under the current building code, a building-wide networked smoke-alarm system was installed in each apartment. The small size of the residential units, each of which has a maximum area of 100 m2, and the solid timber construction of the ceilings, which have no cavities, also helped this part of the design meet regulations.

Residential complex in Ansbach

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Vertical section Scale 1:20 1 Photovoltaic system (60,000 kWh/a > own consumption) 2 Roof construction: sealing membrane with fleece underneath, EPS thermal insulation 50 –130 mm, EPS thermal insulation 160 mm Emergency waterproofing / vapour barrier Cross laminated timber panel: spruce 160 mm 3 Drip tray, painted black /grey 4 Jamb: three-layer spruce, clear-glazed 30 mm 5 French windows with hollow frame, spruce, clear glazed; ventilation opening at top, self-regulating, sound-absorbing with triple glazing, argon-filled Uf = 0.91 W/m2K, Ug = 0.50 W/m2K Threshold: barrier-free 6 Handrail: flat steel 75/10 mm 7 Balustrade: silver fir, pre-weathered, patinated 30 mm on steel-tube substructure, anthracite, | 40/40 mm 8 Balcony floor construction: larch, untreated, 30 mm solid structural timber, conical 60/100 –120 mm, protective mat, sealing membrane Impact sound insulation EPS 20 – 50 mm Emergency seal: elastomer bitumen membrane Cross laminated timber panel, spruce 180 mm 9 Floor slab: Mosaic parquet: solid oak, oiled, 10 mm Heating screed 65 mm, separating layer of PE foil

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Impact sound insulation: mineral wool 40 mm Bonded chipping infill 80 mm Emergency seal: elastomer bitumen membrane Cross laminated timber panel, spruce 180 mm Encapsulation (K230): fire-rated plasterboard 18 mm, cross laminated timber panel: spruce 90 mm; thermal insulation: mineral wool 60 mm Cross laminated timber panel, spruce 90 mm Encapsulation (K230): fire-rated plasterboard 18 mm Cladding: plasterboard 12.5 mm Fire protection strips: mineral wool, non-flammable, airtight connection, groove (underside of cross laminated timber ceiling), insulated Facade: boarding of white fir, pre-weathered, patinated 20 mm, battens 40/50 mm Facade membrane: vapour-permeable Prefabricated wood frame element Encapsulation (K260): fire-rated plasterboard 2≈ 18 mm; thermal insulation: mineral wool 2≈ 140 mm/posts: solid timber 60/280 mm OSB panel 15 mm Encapsulation (K260): fire-rated plasterboard 2≈ 18 mm (inner layer mounted on site) Courtyard pavement: asphalt, sand-coloured Base: precast reinforced-concrete element, sandblasted Perimeter insulation: rigid polystyrene foam 100 mm

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Example 07

Terraced houses Munich, DE 2011 Architects: Bucher-Beholz Architekten, Gaienhofen Ingo Bucher-Beholz, Martin Frey Team members: Isabelle Honeck, Marc Jöhle Structural engineers: Helmut Fischer, Bad Endorf

Concept The terraced house complex in Munich’s Riem neighbourhood consists of six short rows of four vertically oriented housing units, the floor plans of which are largely flexible. Only the position of the stairs, the two upright supports opposite the stairs, and the sanitary installations are fixed. The layouts were created using lightweight walls or closets, and planners were able to adapt them to the individual requirements of the 24 different clients with relatively little effort. While this resulted in a variety of spaces inside, the outside of the rows of buildings is rigidly structured with closed wall surfaces covered with black slate contrasting with glazed or open surfaces. Support structure The houses feature wood-steel hybrid construction, with a delicate steel skeleton of rectangular tube supports (70/70/4 mm) and IPE beams (140/70 mm) combined with ceiling elements made of three-layer panels and load-bearing crosswalls made of panel walls. The steel skeleton divides the 5-metre crosswalls into spans of 2 and 3 metres. This allows for extremely slender ceiling cross sections of 50 or 75 mm, which minimises material requirements. The system allows for ceiling openings and air spaces with no costly replacements and, by extension, flexible room design on all storeys. The ceiling panels and the lower flange of the steel girders are flush and exposed on the underside, so the support structure can still be distinguished. Transverse reinforcement for the rows is provided by the framed sections in the residential partitions, while longitudinal reinforcement comes from crossed steel cables that are integrated in the closed exterior walls on the upper two storeys and remain visible on the ground floor in front of a large window element with fixed glazing.

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Vestibule Living room Kitchen Terrace Underground garage entrance Room Loggia Bedroom Studio Guest room

Terraced houses in Munich

Economics The hybrid style of construction and the resulting reduction in building material made it possible to keep construction costs very low, at EUR 1,650 /m2 (cost groups 300 and 400), despite high energy and construction standards. This method offers a way to make timber competitive for everyday construction duties. Prefabrication and assembly Beams, upright supports and steel transposition in the plane of the exterior walls are integrated in the prefabricated panel elements. This allowed the connections of steel and wood components as well as the continuous

course of component layers to be precisionmanufactured under controlled conditions. On the construction site, the elements were then connected to the rest of the steel skeleton and the ceiling panels were inserted into the primary structure.

Horizontal section Scale 1:20

Energy concept The highly insulated building shell, triple glazing and controlled ventilation with heat recovery minimise the heating-energy demand of the middle houses to 15 kWh/m2a and that of the end houses to 20 kWh/m2a. Two pellet boilers provide heat for the six rows of houses.

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Slate plates, battens 50/30 mm Rear ventilation 20 mm Housewrap Thermal insulation 220 mm Vapour barrier Gypsum fibreboard 15 mm Timber window, oak with triple insulated glazing Building partition: Framed timber element, on both sides: Gypsum fibreboard 15 mm Frame 100/60 mm filled with thermal insulation Three-layer panel 30 mm with sound insulation 30 mm in between Fixed window, triple insulated glazing Upright support, steel tube | 70/70/4 mm

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Example 07

Vertical sections Scale 1:20 1

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Roof structure: Extensive vegetation 100 mm, waterproofing Thermal insulation 300 mm, vapour barrier Three-layer panel 75 mm Timber window, oak with triple insulated glazing Timber planks 70/40 mm Substructure 60 mm Granulated rubber matting 10 mm, waterproofing Vacuum thermal insulation 30 mm, vapour barrier Three-layer panel 50 mm Facade structure: Slate plates Timber battens 50/30 mm

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Counter battens 20 mm Housewrap Thermal insulation 220 mm Vapour barrier Gypsum fibreboard 15 mm Steel profile, IPE 140/70 mm Upright support, steel tube | 70/70/4 mm Floor slab: Floor covering 10 mm Heating screed 60 mm, separating layer Impact sound insulation 80 mm Three-layer panel 50 mm Partition, framed timber element on both sides, thermally insulated by gypsum fibreboard 15 mm Timber frame 100/60 mm, three-layer panel 30 mm, with sound insulation 30 mm in between

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Terraced houses in Munich

1 Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

3 3,744 m2 EUR 6.36 million 12 months 24 months

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Example 08

Residential development above car park Munich, DE 2016 Architects: Florian Nagler Architekten, Munich Team members: Tobias Pretscher, Patrick Fromme, Benedikt Rauh, Laura Kwanka Timber construction: Huber + Sohn, Bachmehring Structural engineers (timber): Franz Mitter-Mang, Waldkraiburg Structural engineers (reinforced concrete): r.plan Büro für Bauplanung, Chemnitz

Concept “We need more affordable housing – and fast!” The Dantebad car park redevelopment project was devised against this backdrop. Little stood in the way of the redevelopment: The property belonged to the city of Munich, the parking spaces were not permanently assigned, and all those involved had an interest in implementing the project quickly and to a good standard of quality. The result is a building with a total of five storeys, one of which was needed as an exposed storey over the parking spaces. The more than 100-metre-long structure blends in well with the architectural environment, which is character-

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ised by large residential buildings, and it helps to better enclose the existing outdoor spaces. The apartments are accessed via balconies leading from the stairwells. In front of every third apartment, the access balcony has been extended to form a small niche that can be furnished and which serves as a meeting place for residents. 86 of the 100 apartments are studio apartments, while the remaining 14 units have one-and-a-half bedrooms. The apartments were built for eligible households of different income levels as well as officially recognised refugees, who have it particularly hard on the high-priced Munich housing market. As an additional offer for residents,

there are common areas, a laundry café, and a rooftop terrace with play areas, deckchairs and space to grow vegetables and herbs. Support structure In order to maintain most of the existing parking spaces, a construction of reinforced concrete columns and beams was erected first, and the actual residential development was then built in timber on top of that. The building only touches the ground via two stairwells and the two head buildings, where building services, storage and rubbish rooms are housed. The load-bearing interior walls and ceilings are made of apartment-sized plywood elem-

Residential development above car park in Munich

ents. The ceilings remain visible on the room side, and the walls have a double layer of gypsum fibreboard on both sides to provide the necessary soundproofing. The outer walls are made of framed wood and insulated with 20 cm of mineral fibre to meet the requirements of the 2016 Energy Saving Ordinance. The building’s exterior also reveals its timber structure. Differently designed facades with frames and panels made from rough-sawn wood make the construction process visible and give the building a quiet rhythm through their even repetition. The colourful facades fit naturally into the urban environment.

Plan Scale 1:2,000 Sectional view • Floor plans Scale 1:750 Building characteristics Number of storeys Gross floor area

Construction costs Construction time (timber) Total construction time

1 2 3

5 4,630 m2 (a) 722 m2 (b) 192 m2 (c) EUR 8.4 million 2 months 7 months

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Portico /access Studio apartment Plumbing unit, prefabricated Common areas Storage area 1.5-bedroom apartment Accessible apartment

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Example 08

Prefabrication The building’s reinforced concrete structure was cast on site, while the timber structure features a high degree of prefabrication. After the external walls and apartment partitions were installed, the prefabricated bathrooms, protected against the weather, were lowered into the residential units by a crane and closed with the wooden ceiling. Once the access balcony of prefabricated concrete elements was completed shortly after that, the storey was finished and construction of the storey above could begin.

Layout of the two apartment types Scale 1: 100

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This method of construction, as well as the fully equipped bathroom modules that were installed on site, reduced the required on-site assembly time to a minimum. This was the only way the project could be completed within the short planning and construction window between April and December. Fire safety The building falls into class 4, which requires the upper storeys to be fire-resistant for 60 minutes. The reinforced concrete “table” at the car

park level has a fire-resistance period of 90 minutes to protect the residential floors above it from the fire load of the cars parked below. The access balconies are also made of nonflammable materials. The two stairwells guarantee two structurally independent escape routes. Like the elevator shaft, they are made of reinforced concrete on the ground floor and of solid wood on the upper storeys. They have a layer of plasterboard on both sides, so they are considered to be substitute firewalls with a fire-resistance time of 60 minutes.

Residential development above car park in Munich

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Vertical section, facade Scale 1:20 1 Roof structure: extensive vegetation or gravel surface, Drainage element 40 mm, protective mat 6 mm Sealing: bitumen double-layered, EPS insulation in gradient 20 – 200 mm Thermal insulation PU 60 mm, latex-bonded chipping infill 60 mm Vapour barrier (emergency seal), cross laminated timber ceiling 140 mm 2 Boarding: Larch, textured, painted dark blue 19 mm, horizontal battens 35 ≈ 80 mm Vertical battens 16 ≈ 80 mm, cross laminated timber 100 mm 3 Triple glazed, insulated, in wood frame 4 Standard floor slab: Floor covering: linoleum 2.5 mm, putty substrate preparation 2 mm Cement screed 55 mm; separating layer: PE foil 2≈ 0.2 mm Impact sound insulation: mineral fibre 40 mm; latex-bonded chipping infill 100 mm; cross laminated timber ceiling, industrial grade 140 mm 5 Galvanised sheet steel cover; element frame: Larch, sawn 100 ≈ 100 mm 6 Cladding for element joint: larch, textured, painted dark blue, 19 mm 7 Faceplate: larch, rough-sawn, painted red 210 ≈ 40 mm 8 Roller shutter housing, plastic slats 9 Floor slab, 1st floor: Floor covering: linoleum 2.5 mm, putty substrate preparation 2 mm Cement screed 55 mm; separating layer: PE foil 2≈ 0.2 mm Impact sound insulation: mineral fibre 20 mm Thermal insulation EPS 40 mm, vapour barrier Thermal insulation EPS 120 mm, reinforced concrete floor 250 mm 10 Paving slabs 50 mm, chipping bedding 30 mm, supporting layer 182 mm Drainage element 40 mm, protective mat 6 mm Sealing: bitumen double-layered, EPS insulation in gradient 20 – 200 mm Thermal insulation PU 60 mm, latex-bonded chipping infill 60 mm Vapour barrier (emergency seal), cross laminated timber ceiling 140 mm 11 Balustrade, galvanised steel 12 Prefabricated reinforced concrete component 13 Prefabricated reinforced concrete component, PMMA-coated 140 – 210 mm 14 Glued laminated timber 200/160 mm 15 Insulation strips 16 Suspended thermal insulation 120 mm Wood-wool slab, non-flammable 15 mm

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Example 09

Addition of further storeys and conversion to a residential and commercial building Zurich, CH 2013 Architects: burkhalter sumi architekten, Zurich Team members: Steffen Sperle, Célia Rodrigues Structural engineers (solid construction): Dr. Lüchinger + Meyer Bauingenieure, Zurich Structural engineers (timber): Makiol+Wiederkehr, Beinwil am See Landscape architects: Klötzli Friedli Landschaftsarchitekten, Berne

Concept The area was used as a gravel pit until 1892 when a station and reloading point were built here for the Sihltal railway line. Prior to the conversion, the two-storey, 11-metre deep warehouse and service building for a local mass transit business from the 1960s was all that remained in operation; the rest of the area served as a car park. As part of a comprehensive revitalisation project, additional storeys were added to the existing building and two new buildings were erected. The decision was made to add the additional storeys because the basement of the existing structure housed relay stations required for railway operations, and moving them would have entailed disproportionately high costs. However, a lightweight style of construction was the only feasible way to add height to the existing structure. A twostorey steel skeleton added in the 1980s was dismantled. The support axes clearly divide the b floor plan into uninterrupted fields with kitchen / dining/living areas running from front to back and areas with interlocking side rooms and wet areas. This created studio, one-bedroom and three-bedroom apartments with the aim of ensuring a diverse mix of residents. The building is only recognisable as a timber construction on second glance: A homogenising layer of plaster covers the existing building and the newly added storeys; only the darkly painted cantilever arms of the balconies hint at the timber structure underneath.

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Addition of further storeys and conversion to a residential and commercial building in Zurich

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Support structure In the existing structure, a grid of reinforced concrete beams spaced five metres apart distributes the loads from the roof and ceilings to the outer walls. This grid repeats in the new storeys: Beams made of glued laminated timber run through the depth of the building, with one or two installation joints depending on the wall connection, and form projecting supports for the balconies. These beams rest on supports made of the same material, which are integrated in the apartment walls. These upright supports grow wider towards their base due to the increasing loads, but only on one axis, so as to allow for the same wall thicknesses on all storeys (Fig. “Static load transfer system”, p. 201). Between the beams, there are 275-mm-thick box ceilings with threelayer panel cladding. These act as a reinforced ceiling panel. The load from the additional storeys is transferred to the outer walls using Å-beams. Although these appear to rest on the existing reinforced concrete beams, they are statically separated to compensate for the difference in height between the existing ceilings concreted in the gradient. The reinforced concrete cores of the two lifts and the two stairwells stabilise the building. Closed exterior wall areas are non-structural panel assemblies. Prefabrication First, the concrete access cores were poured on site. The timber construction was completed within five weeks of this. The ceilings were delivered as structural elements, while the wall elements, in which the main beams are integrated, were delivered with their plasterboard cladding.

Building characteristics Number of storeys (timber) Gross floor area Construction costs Construction time (timber): Prep work (bottom structure with steel supports above pre-existing structure) Erecting timber structure Total construction time

4 5,127 m2 About EUR 9.6 million

3 weeks 5 weeks 16 months

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Example 09

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Addition of further storeys and conversion to a residential and commercial building in Zurich

Fire safety Load-bearing timber components have a fire resistance rating of 60 minutes for load-bearing capacity and 30 minutes for room closure and heat shielding. All surfaces are encapsulated in non-combustible building materials. The balconies have no fire protection requirements, so the timber construction can remain visible there. However, they effectively prevent flames from leapfrogging between storeys. In areas without balconies, the facade is made of noncombustible material.

Static load transfer system Vertical sections Scale 1:20 1 Roof structure: Extensive vegetation, filter substrate and drainage 120 mm, protective layer, PP foil 10 mm Roof membrane, two-ply 10 mm Thermal insulation in gradient 60 –140 mm Thermal insulation 140 mm, vapour barrier 3.5 mm Three-layer panel 27 mm, frame of joists 220 mm Three-layer panel 27 mm, battens in between, Thermal insulation 50 mm, plasterboard 2≈ 12.5 mm Plaster, painted 5 mm 2 Gravel fill 40 mm, drainage mat 8 mm Waterproofing, two-layer 10 mm Three-layer panel 27 mm, frame of joists 190 – 220 mm Three-layer panel, painted 27 mm 3 Roof drain 4 Facade: frame element, double steel sheet folded about 5 mm, joining with black rubber backing, with hex socket flat head screw fastened to three-layer panel via spacer 5 Lift and slide timber door, spruce, painted, with triple insulated glazing 6 Waterproofing, sound insulation element Vapour barrier on inside 7 Timber floor frame with battens to compensate for sloping beams, recycled rubber mat 10 mm Waterproofing, two-layer 10 mm Three-layer panel 27 mm, frame of joists 190 – 220 mm Three-layer panel, painted 27 mm 8 Floor slab: Parquet 15 mm, anhydrite floor 55 mm, separating layer, PE foil, impact sound insulation 20 mm Garden slabs /gravel fill 40 mm, separating layer, fleece Three-layer panel 27 mm, frame of joists 220 mm, filled with thermal insulation 60 mm Three-layer panel 27 mm, battens with spring clips 60 mm, between them thermal insulation 40 mm Plasterboard 2≈ 12.5 mm, plaster, painted 5 mm 9 Sun protection, vertical venetian blinds, scrim 10 Flat steel, hot-dip galvanised, coated 35 ≈ 5 mm 11 Balcony partition: Form-board panel, painted 10 mm 12 Plaster, painted 5 mm, thermal insulation, mineral fibre 180 mm, concrete wall (pre-existing) 350 mm 13 Apartment partition: Plaster, painted 1.5 mm, plasterboard 2≈ 12.5 mm Stud structure, metal, filled with thermal insulation 50 mm, gypsum fibreboard 15 mm Three-layer panel 27 mm, stud structure, timber, filled with thermal insulation 180 mm Three-layer panel 27 mm, stud structure, metal, filled with thermal insulation 50 mm Plasterboard 2≈ 12.5 mm, plaster, painted 1.5 mm 14 Main beams, glued laminated timber, spruce / fir 540/180 mm 15 Threaded rod, welded 16 Cavity insulation 80 mm, gypsum fibreboards 15 mm Glued laminated timber 94/340 mm as ceiling support Steel beams, HEA 600 17 Concrete ceiling, pre-existing

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Example 10

Renovation of a residential building Augsburg, DE 2012 Architects: lattkearchitekten, Augsburg Frank Lattke Team members: Markus Hölzl, Esther Strahl Structural engineers: bauart Konstruktions GmbH, Munich Landscape architects: emminger&nagies, Augsburg

Concept As one of nine projects, the 60-apartment building on Grüntenstraße was to be modernised while occupied as part of a pilot project called e% Energy-efficient Housing. The project was launched by Bavaria’s supreme building authority with the aim of exceeding the requirements of the 2009 Energy Saving Ordinance, which was in force at the time, by 40 % while also providing unrestricted access for all. The construction phase was supposed to go as quickly and smoothly as possible for the tenants, which meant that the focus was on a suitable construction process, given that the construction efforts included not only the build-

202

ing shell but a complete renovation of the bathrooms and water connections in the kitchens. Appropriate information management and coordination with residents was therefore essential. The buildings were given a new shell of prefabricated timber panel elements with painted cladding made from rough-sawn boards. The existing balconies were converted to sunrooms as extensions of the living space that buffer residents against the weather and against noise coming from the large street on the building’s southern side. The building shell’s high degree of prefabrication allowed the construction time to be reduced to a minimum.

The six-storey building was not barrier-free, as the entrance was half a storey lower than the ground floor level and the lift only stopped on the mezzanine storeys. As part of the modernisation, the site was raised to street level and an accessible vestibule was created. A new lift opens on the access balcony for each storey. Support structure A self-supporting facade of large, prefabricated and insulated timber panel elements stands in front of the brickwork of the exterior wall. Vertical loads from the dead weight are conveyed directly to a strip footing that has been concreted in front of the basement wall.

Renovation of a residential building in Augsburg

Building characteristics Number of storeys Gross floor area

6 7,124 m2 (before) 7,730 m2 (after) EUR 5.9 million 5 months 14 months

Construction costs Construction time (timber) Total construction time

aa

(before renovation)

bb

The horizontal stress resulting from wind suction and pressure is transferred to the existing reinforced concrete ceiling, storey by storey. To achieve this, a block of timber was fastened to the full length of the front edge of the ceiling with heavy-duty dowels and the facade elements were screwed onto it. The windows were replaced from the inside to the outside. First, notches were cut in the jamb’s masonry rebate, which was then broken off in order to subsequently lift the window frame outward. The new windows sit flush with the inner edge of the timber panel elements and connect to the shell opening. The inner jamb was created using a double layer of plasterboard. The new blind frame has an airtight connection at the first layer. The reinforced concrete balconies in the existing structure, with cantilevered ceilings and side walls embedded in the masonry walls, form a large thermal bridge. Key to the renovation concept was preserving the balconies and remodelling them only by removing the parapets and part of the side walls to create sunrooms with large sliding glass doors. As a result, the apartments gain both space and light. At the same time there are energy benefits. For example, all cantilevered concrete components are now inside the building shell. In addition, the sunrooms serve as a weather buffer. Cold, fresh air entering the wall through vents during the winter can warm up before it passes into the apartment through air intakes in the top of the window frame. It is then extracted by an exhaust system via the kitchens and bathrooms. Thanks to the new timber loggias that have been inserted between the sunrooms, the residents still have a balcony as well.

(after renovation)

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Example 10

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Fire safety With regard to fire safety requirements, a distinction was made between the existing load-bearing primary structure and the new, non-load-bearing building shell. The existing structure of walls and ceilings in masonry and reinforced concrete meets REI 90 and REI 90 M requirements. The additional facade elements used to energetically upgrade the building are non-load-bearing exterior walls. They are used neither to reinforce the building nor to transfer loads from other components. As a result, the only requirement to be met was that of the fire resistance time of W 30 B components. This allowed timber to

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be used to construct the upright supports of the panel elements and the cladding on all six storeys. Gypsum fibreboard with a thickness of 15 mm was used to close the prefabricated facade elements on the outside and at the element joints. To prevent flames from penetrating the construction at the window connections, the jambs have a timber cross section of 60/200 mm and are clad on all sides with gypsum fibreboard. The cavity between the timber panel elements and the existing masonry wall was completely filled with cellulose fibre insulation to prevent uncontrollable convection and fire transfer. The building was clad with normal, flammable, ventilated, alternatenotched boards while still complying with fire safety goals: The boards are 24 mm thick, the notches have 20 mm of overlap, and the screws extend more than 20 mm into the substructure. Sheet steel firestops were set into the horizontal joints between the vertical elements to prevent fire from spreading from storey to storey through the ventilation cavity behind the cladding. The 1.5-mm-thick steel firestops fit snugly into the joints in the gypsum fibreboard and are screwed to the timber panel element substructure with screws set 300 mm apart.

Horizontal section • Vertical sections Scale 1:20 1 Alternate-notched boards, spruce, visible screws, rough-sawn, painted white 28 mm, timber substructure with rear ventilation 30 mm, counter battens, OSB strips 10/120 mm, facade sheet, vapour-permeable, gypsum fibreboard 15 mm, solid construction timber, spruce 60/200 mm, in between thermal insulation, cellulose fibre 200 mm, OSB panel 10 mm, compensation plane 50 mm Pre-existing: plaster 10 mm, masonry 365 mm 2 Plaster 10 mm, plaster base board 60 mm, solid construction timber 60/160 mm, in between thermal insulation cellulose fibre 160 mm, OSB panel 10 mm, installation plane 50 mm Pre-existing: plaster 10 mm, masonry 365 mm plaster 10 mm 3 Exterior wall air vent 4 Timber-aluminium window including flush-mounted sunblind box with triple insulated glazing 5 PVC window (removed) 6 Timber window with ventilation element and triple insulated glazing 7 Roof structure: waterproofing, bitumen, single layer 5 mm Pre-existing: waterproofing, bitumen, single layer 5 mm, Insulation PUR 120 mm, reinforced concrete 170 mm 8 Attic, steel sheet, galvanised 1.5 mm 9 Floor slab, pre-existing 10 Loggia: linoleum 5 mm, trowel application 5 mm Pre-existing: tiles 10 mm, cement screed 75 mm, bitumen, reinforced concrete 160 –120 mm 11 Fall protection, steel parapets 12 Alternate-notched boards, spruce 24 mm Substructure, spruce 30/50 mm, counter battens OSB panel 12 mm, housewrap 0.5 mm Gypsum fibreboard 15 mm, solid construction timber, spruce 120 mm, OSB panel 10 mm 13 Timber grate, larch, untreated, gradient compensation 40 – 60 mm, waterproofing, plastic 5 mm Glued laminated timber, visible quality 51 mm 14 Fire-protection panel, steel 1.5 mm 15 Foundation, site-mixed concrete with shear connector

Renovation of a residential building in Augsburg

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Example 11

Zollfreilager housing complex Zurich, CH 2016 Architect: Rolf Mühlethaler Team members: Thomas Moser (project leader), Chantal Amberg, Julia Grommas, Marion Heinzmann, Sandra Stein, Jonas von Wartburg, Simon Wiederkehr Structural engineers (solid construction): Ingenta Ingenieure + Planer, Berne Structural engineers (timber): Indermühle Bauingenieure, Thun

Concept On the site of the former customs warehouse in Albisrieden in Zurich, a new residential district comprising around 190 apartments has been built. The units are divided between three solid multi-storeys made of reinforced concrete and three rows of timber buildings each of six storeys. Continuous balconies give the timber buildings a strong horizontal structure that mediates between the large scale of the buildings themselves and the small scale of the apartment facades. Window widths and the depths of balcony zones vary depending on their geographic direction and are designed in accordance with an ambitious energy concept

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A B C

(Minergie-P-eco). The deep balconies offer weather protection for the wood facade made of pressure-treated spruce and create differentiated outdoor areas. Staircase cores from front to back made of reinforced concrete provide access to two apartments on each level – a principle that repeats itself on every storey. The apartments in the two northern building rows (A and B) consist of a series of neutraluse rooms that are accessed via a large interior room. They have no hallways. Apartments in the southern building row (building C) are centred around an open cooking /dining / living area.

Support structure The clarity and consistency of each layout is reflective of the different support structures. The ceilings of buildings A and B rest on the longitudinal facades and on two middle walls that run parallel to those facades. The ceilings of building C span the longitudinal facades and rest on interior walls that form a regular crosswall structure. In both cases, the ceilings are made of dowel laminated timber elements and OSB panels provide reinforcement. Although the buildings have six storeys, vertical loads are successfully transferred via interior and exterior walls made of prefabricated timber panel elements.

Zollfreilager housing complex in Zurich

Plan Scale 1:5,000 Axonometries, load distribution compared Sectional view • Floor plans Scale 1:500 1 2 3 4 5 6 7 8 Buildings A and B

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Living / dining / kitchen Bedroom Apartment foyer Bathroom Plant room Access Vestibule Underground garage entrance Bicycle room

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Example 11

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In order to prevent subsidence against the reinforcing concrete cores of the stairwells, the timber panel elements are designed without a top plate and a bottom plate. The upright supports of these storey-high elements have their end-grain surfaces facing one another, which prevents transverse compression. The linear supports of the ceilings form L-shaped wall purlins, which are inserted in a recess in the upright supports. Assembly process The timber structure was assembled after the reinforced concrete staircases were completed. Load-bearing and non-load-bearing walls and the ceilings lying on top of them were installed one storey at a time. The timber panel elements of the exterior walls were prefabricated, including their interior cladding, windows, substructure of the facade and exterior lintel shutters. The facade cladding is made of prefabricated panels that were installed on site just like the dowel laminated timber ceilings with their OSB reinforcement panels. The floor structure and suspended ceiling were built on site.

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Zollfreilager housing complex in Zurich

Vertical sections, longitudinal facade with balcony Buildings A, B and C Scale 1:20 1

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Roof structure: Extensive vegetation Infill 128 – 328 mm Protection/drainage/filter layer 20 mm Waterproofing, plastic membrane Thermal insulation, EPS in gradient 10 –190 mm Thermal insulation, EPS 140 mm, dividing strip, mineral wool, vapour barrier, loosely laid Ribbed ceiling: OSB panels 22 mm glued to Ribs (a = 650 mm) 80/220 mm Cavity for installations/ventilation 68 mm Cavity insulation with spring clips for acoustic decoupling, suspended 50 mm Plasterboard, painted 15 mm Sun protection, veranda: Fabric awning (one piece per apartment) Hand crank with lateral guide cables Eaves board, bearer, silver fir, pressure-treated, double-oiled 24 mm, beams, glued laminated, Silver fir, glued laminated, pressure-treated, double-oiled b = 140 mm Sun protection, compact venetian blinds with slats and side guide rails Timber window, spruce, with triple insulated glazing Protective stain, brown, Ug = 0.6 W/m2K Facade supports, glued laminated timber, silver fir, pressure-treated, double-oiled with different dimensions: ground floor 160 mm /1st – 4th storey 140 mm / 5th storey 120 mm with front plate, round, steel, rustproof 5 mm, inserted into bearer Partition, veranda: Silver fir, pressure-treated, single-oiled Drip tray, aluminium, paint coating dark brown, eaves board, silver fir pressure-treated, single-oiled, rough-sawn 24 mm Floor structure, veranda, 2nd – 5th storey: Boards, silver fir, pressure-treated, planed / sanded 27 mm, battens 27 mm, mitred blocks 51– 81 mm Elastomer bed (impact sound) 20 mm Waterproofing, plastic membrane, mechanically fastened Glued laminated board in gradient 1.5 %, Soffits, gloss-stained 94 mm Floor structure, upper storeys: Flooring, parquet, solid oak, on-edge 15 mm screed with underfloor heating 53 mm Separating layer, sound impact insulation with kraft paper 27 mm, infill, bonded (installation level) 30 mm OSB panel as ceiling disc for reinforcement 15 mm, dowel laminated timber ceiling 180 mm Gypsum fibreboard (fire protection) 18 mm Cavity for installations/ventilation 50 mm Cavity insulation suspended using spring clips (soundproofing) 50 mm Plasterboard, painted 15 mm Floor structure, ground floor: Flooring, parquet, solid oak, natural, on-edge 15 mm, screed with underfloor heating 53 mm separating layer, impact sound insulation 27 mm Infill, bonded (installation level) 30 mm Reinforced concrete 250 mm Thermal insulation, EPS with cement-bound Wood-wool acoustic panel 200 mm Blind board above cassette and timber window, silver fir, pressure-treated, single-oiled, 27 mm Steel batten railing, metal, powder-coated Battens, round Ø 15 mm Facade structure (no installations in exterior walls): Cladding, silver fir, pressure-treated (tongue-andgroove) 22 mm in frame, silver fir, pressure-treated, single-oiled, solid 50 ≈ 50 mm Rear ventilation 33 mm, facade membrane, polyester fleece Gypsum fibreboard 15 mm Wood studs / thermal insulation, mineral wool 360 mm OSB panel (airtight layer), joining, masked 15 mm, gypsum fibreboard 18 mm Plaster, painted white 1 mm

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Example 11

2

Building characteristics Building A Number of storeys Gross floor area Construction time (timber) Total construction time Building C Number of storeys Gross floor area Construction time (timber)

6 9,500 m2 11.5 months (including fabrication) 36 months

Total construction time

6 10,554 m2 12 months (including fabrication) 36 months

Buildings A, B and C Construction investment volume

About EUR 330 million

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4

Plaster, painted white 1 mm Timber window, spruce, painted, with triple insulated glazing Ug = 0.7 W/m2K, Uf = 1.1 W/m2K Apartment partition (non-load-bearing): Gypsum fibreboard 12.5 mm, gypsum fibreboard 10 mm Stud structure, metal 75 ≈ 0.6 mm Cavity insulation 70 mm, cavity 20 mm Cavity insulation 70 mm Stud structure, metal 75/0.6 mm Gypsum fibreboard 10 mm Gypsum fibreboard 12.5 mm Electrical outlets in airtight boxes made of plasterboard 2≈ 12.5 mm

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Kampa administration building in Aalen

Kampa administration building Aalen, DE 2014 System development and design: Florian Nagler Architekten, Munich Construction: Kampa GmbH, Aalen Josef Haas, Johann Wellner Structural engineering, fire safety planning and building physics: bauart Konstruktions GmbH, Lauterbach

Concept The headquarters of this manufacturer of prefabricated houses has been designed, like the products it sells, as a prototype for an adaptable construction system. The system allows geometric variations on a defined building type and is suitable for five to eightstorey buildings. The distance between transverse axes can be between 2.50 and 3.20 metres, while the depth of the building can range between 12 and 13.50 metres. The seven-storey building described here has a depth of 12.50 metres and uses a 2.50metre grid. The basement is dedicated primarily to the substantial building services technology. The ground floor comprises a spacious foyer, a conference room and a canteen. The five floors above provide areas for exhibiting products and prototypes, and they also house the company’s offices and meeting rooms. Support structure The support structure of this administration building is an all-timber construction that rests on a basement made of reinforced concrete. The building is essentially designed as a skeleton structure made of glued laminated timber. Single-span beams rest transversely on notches in the upright supports. The remaining residual cross section of the upright supports is sufficient for directly transmitting the vertical load from one support to another. The rigid ceiling panels and the roof are made of cross laminated timber, as are the access cores and sanitary cores, which, in addition to handling load transfer, reinforce the building in the longitudinal direction. Transverse reinforcement is provided by four wall panels made of cross laminated timber. Traction anchors that transfer forces from strong winds are installed in the eight upright supports that connect to these wall panels. To minimise the number of these complex connections, the upright supports extend through three storeys.

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Example 12

Building characteristics Number of storeys Gross floor area Total construction costs Construction time (timber) Total construction time

Fire safety The load-bearing timber components in the building are dimensioned to withstand 90 minutes of fire before burn-up. Small smoke and fire compartments and short escape routes to the two stairwells increase safety in the event of a fire, making it possible to dispense with both a sprinkler system and encapsulating the load-bearing components. Only the stairwells are clad with gypsum fibreboard, and only the stairs and landings are constructed as prefabricated reinforced concrete elements. The fire safety certificate was based on the Baden-Württemberg building code for 2010. Since the amendment of the state building code in 2015, timber structures

in Baden-Württemberg must be planned to comply with building class 5. Building services Under the load-bearing ceilings, multifunctional ceiling sails stretch between the beams. The sails are statically independent and therefore sound-insulated. Perforated plasterboard panels are mounted flush with the beams on the bottom on a wooden substructure. These prefabricated elements with integrated cable routing (electrical, heating, cooling) also ensure good room acoustics. A building shell that meets the passive house standard, northsouth orientation, controlled ventilation with 75 % heat recovery, seasonal ice storage with

7 3,386 m2 (plus basement) About EUR 6 million 6 months (including interior fittings) 10 months

685 m3 capacity in conjunction with heat pumps for heating and cooling, and a photovoltaic system on the roof of the building all enable energy gains while the building is in operation. Lift The lift shaft has a double-shell timber design. The outer shell is made of cross laminated timber covered on both sides with two layers of 18-mm-thick special plasterboard panels. The sound-insulated inner shell is made of 10-cmthick cross laminated timber and is unclad. This shaft was prefabricated in three parts as a multi-storey module. Structurally, it is largely independent of the outer shell, which sits on a basement footing made of reinforced concrete.

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Floor plans • Sectional view Scale 1:400 1 Reception / foyer 2 Conference room

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Canteen Exhibition areas Offices Meeting rooms

Kampa administration building in Aalen

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Upper facade element: Exposed formwork, timber 25 mm with cover moulding in different cross sections (35/44 mm and 47/44 mm), battens 40/60 mm, plasterboard (fire protection class A1) 15 mm Bolt work 80/300 mm, filled with thermal insulation, mineral wool 300 mm Support structure: Cross laminated timber 140 mm, both sides with two layers of plasterboard (fire protection class A1) encapsulation 2≈ 18 mm

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Lift shaft: Cross laminated timber 100 mm, prefabricated as three-storey module with no additional cladding Interior wall: Cladding 25 mm Sound insulation, mineral fibre 110 mm, Plasterboard strips 2≈ 18 mm Cross laminated timber 160 mm Steel angle connection for positional stability (two per element) Slotted plate Plasterboard, horizontal, continuous 25 mm OSB panel to form disc 22 mm Floor slab: Flooring, carpet 10 mm Screed 23 mm, separation layer Impact sound insulation 10 mm

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Glued laminated timber 150 mm Plasterboard 25 mm (fire protection class A1) Cavity 360 mm Substructure for suspended ceiling Plasterboard 2≈ 12.5 mm Mineral fibre insulation strips for acoustic decoupling Support structure, cross laminated timber 140 mm Transverse tension tie, screw 6≈ 120 mm Plasterboard strips (fire protection class A1) 30 ≈ 125 mm External tongue, plywood F 20/10 27 mm Pair of screws, crossed horizontally Elastomer cushion for acoustic decoupling Floor batten 80/160 mm, secured with screws Casing, plasterboard strips (fire protection class A1) 30 mm

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Example 13

Illwerke Zentrum Montafon Vandans, AT 2013 Architects: Architekten Hermann Kaufmann, Schwarzach Team members: Christoph Dünser, Stefan Hiebeler, Thomas Fußenegger, Michael Laubender, Guillaume Weiss, Ann-Katrin Popp, Benjamin Baumgartl Structural engineering: merz kley partner, Dornbirn

Concept Illwerke Zentrum Montafon (IZM) in Vandans is the new administration building for Austrian power company Illwerke, with over 10,000 m2 of floor space. Key requirements in designing the building were the static structure of the construction system with prefabricated ribbed ceilings and the intention to create similar conditions for all 270 workspaces. This restricted the depth of the building and made it necessary to extend the length to 120 metres. One third of the length of this clear-cut timber construction extends over the surface of the water of the adjacent compensating reservoir. The building code only permitted this because the lake is artificial. The floor plan concept responds to this by placing the staff canteen and visitor centre in this special location. The building forms the conclusion of the park in front of it, and approaching visitors can see its entire width. A generously sized canopy marks the entrance. The facade is divided into horizontal layers of parapets, ribbon glazing and canopies. The building’s length and its construction module act as its leitmotif. Construction The building has two access cores for horizontal reinforcement. These were made of concrete mainly for fire safety reasons and were poured on site. The entire ground floor, including the ceiling, is made of the same material. This was necessary because the building stands in a lake, which meant special seismic safety measures were required. Site-mixed concrete proved to be economically viable as well. The ceilings of the storeys above consist of 3-metre-wide and 8.10-metre-long prefabricated timber-concrete composite elements, which are designed as T-beams. The concrete slab is reduced to a thickness of 8 cm and therefore meets the required sound insulation and fire safety requirements (REI 90), with vibration behaviour that complies with the standard. After being mounted, the individual elements were combined to form a frictionlocked reinforced ceiling panel with the help of joint sealing compound and, in some places, screw joints. The pendulum supports on the facade are designed as double cross

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Illwerke Zentrum Montafon in Vandans

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Foyer Office Copy centre Lecture hall Kitchen Restaurant Open-plan office Meeting room Think tank Cellular office Copy room / plotter room Open kitchenette Break room

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Example 13

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sections measuring 2≈ 24 ≈ 24 cm. By using a reinforced concrete edge beam integrated in the ceiling element, the load can be transferred from the end-grain wood of the upper stanchion directly to the end-grain wood of the lower stanchion without the use of costly fasteners. Assembly The entire timber structure, including the prefabricated facades with untreated oak exterior cladding and the roof elements, was assembled in just six weeks. Even the prefabricated oak windows were installed at the same time that the timber structure was being assembled. This minimised the risk that the

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structure would be soaked during assembly and, in turn, the steps needed to protect the structure from weather. Fire safety The entire structure has been left visible and was built to fire classification REI 90. A sprinkler system was installed as a compensatory measure. This enabled all of the aboveground storeys to form a single fire compartment, which was divided into several smoke compartments. Energy The building’s primary energy consumption is less than 30 kWh/m2a, and its heating

needs are 14 kWh/m2a (passive house standard). This is supplied entirely by the power plant’s waste-heat system, while cooling energy is supplied using cold water from the surrounding reservoirs.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

5 11,497 m2 EUR 26 million net 6 weeks 17 months

Illwerke Zentrum Montafon in Vandans

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Building assembly sequence LCT system (LifeCycle Tower One, Dornbirn, predecessor building and first eight-storey timber building in Austria) IZM system Assembly sequence in detail Isometry of the support system Timber-concrete-composite ribbed ceiling, vertical section Span 8.50 m, element width 2.70 – 3.00 m

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Wall element consisting of three pairs of upright supports with parapet Timber-concrete-composite ribbed ceiling Window module Canopy Supports made of glued laminated timber 2≈ 240 ≈ 240 mm Reinforced concrete C30/37 d = 80 mm with polypropylene fibres Timber ribs e = 860 mm

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Example 13

Facade Horizontal sections Vertical sections Scale 1:20 1

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Tempered glass 6 mm Rear ventilation 46 mm Cement-bonded chipboard 16 mm Thermal insulation, mineral wool 130 mm OSB board 18 mm Upright support, glued laminated timber, spruce 2≈ 240 ≈ 240 mm Fixed timber window, solid oak with triple glazing Timber window, solid oak with triple glazing Ug = 0.5 W/m2K Canopy console HEA 140 mm Alternate notches boards, untreated oak 27 mm Horizontal battens 40/60 mm Vertical battens 40/60 mm Chipboard, cement-bonded with glued joints 16 mm Frame construction, glued laminated timber 59/340 mm, in between thermal insulation, mineral wool 340 mm Air resistance level, vapour barrier OSB panel with glued joints (vapour barrier) 18 mm Thermal insulation, mineral wool (installation level) 77 mm Parapet backboard, chipboard, oak, veneered 19 mm Roof structure: extensive vegetation 100 mm Roof waterproofing Thermal insulation EPS 2≈140 mm Gradient insulation 0 –140 mm, vapour barrier Timber-concrete-composite ribbed ceiling: Reinforced concrete 80 mm; rib, glued laminated timber, spruce 240/280 mm Suspended ceiling: heating and cooling panel, perforated sheet with laminated acoustic fibre mat, textured lacquer Attic cladding, copper sheet Timber boarding 27 mm Battens 40/40 mm, counter battens 40/40 mm Wind seal: paper, gypsum fibreboard 16 mm Timber structure / thermal insulation, mineral wool 170 mm, vapour barrier OSB panel 18 mm, roof waterproofing Canopy: copper sheet 0.6 mm Seal: bitumen, three-ply Chipboard 24 mm, squared timber 120/60 mm Timber boarding, oak 20 mm Sun blinds Chipboard, oak, veneered 24 mm Floor slab: carpet with acoustic underlay Mineral-based panel, fibre-reinforced 38 mm Installation layer 125 mm with cavity insulation, Mineral fibre 30 mm Timber-concrete-composite ribbed ceiling: Reinforced concrete 80 mm Rib, glued laminated timber, spruce 240/280 mm Suspended ceiling: sound insulation 50 mm Fibre mat, silver fir 30/40 mm

Illwerke Zentrum Montafon in Vandans

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Example 14

Office building St. Johann in Tirol, AT 2015 Architects: architekturWERKSTATT, Breitenbach am Inn Team members: Bruno Moser, Florian Schmid, Thomas Schiegl Structural engineers: dibral, Alfred R. Brunnsteiner, Natters Timber construction: Holzbau Saurer, Höfen

Concept The winning design idea for a series of buildings for wood-based materials manufacturer Fritz Egger was to use Egger OSB 4 TOP boards with maximum dimensions of 2.80 ≈ 11.40 metres, the size of which resulted in a grid for the building and the prefabricated ceiling and wall elements. As a result, the distance between the upright supports and the wall height is equal to the board width of 2.80 metres. The building at the company’s headquarters in St. Johann consists of two parallel four-storey structures, which are connected and accessed via a covered atrium between them. From the outside, however, one cannot see that the building is divided into three sections because projecting circumferential ceilings with staggered larch wood slats join the structures together. The building stands out through consistent, precise implementation of the construction system in combination with a highly distinctive, eye-catching design against an Alpine backdrop. Support structure The basement houses an underground garage, a gym and adjoining rooms and is made of sitemixed concrete up to the top edge of the ceiling. Prestressed beams enable the 11.40-metre span of the main grid. All of the above-ground storeys, which comprise the foyer, canteen, seminar space and office space, are constructed entirely from timber. The ceilings – box elements filled with chipped wood and made of glued laminated timber ribs and glued OSB panels on both sides with integrated cable runs (ventilation, heating, cooling) – rest on upright glued laminated timber supports. Only the edge elements on the building’s longitudinal sides rest partly on reinforced, prefabricated framed timber elements with installation conduits. This allows the structure to be completely beamfree. The five-storey elevator shaft, the connecting bridges in the atrium, and the projecting staircases are made of five or seven layers of press-glued OSB panels. The load-bearing OSB surfaces are glazed white, so they remain visible in the building. The company’s own products were used to construct and finish almost all of the building.

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Office building in St. Johann in Tirol

Sectional view • Floor plan Scale 1: 500 1 Entrance 2 Reception 3 Atrium 4 Stairwell / emergency exit 5 Training / seminar area 6 Office 7 Storage / Building services 8 Kitchen 9 Break area 10 Canteen 11 Scullery 12 Dining room bb

Fire safety A perfectly coordinated design plan and fire safety plan enabled the visible wood surfaces in the building as well as the wooden central staircase in the atrium. Several compensatory measures play a key role here: Three stairways in and around the atrium reduce the length of escape routes to just 25 metres. The entire building is divided into a total of four fire zones: the basement, the ground floor with the atrium, and the combined upper floors of each wing. For this reason, the ceiling above the ground floor was given a double layer of gypsum fibreboard with a fire rating of REI 90. The circumferential overhang serves as a firewall here and continues in the upper storeys mainly for design reasons and cleaning purposes. Sprinklers installed in the cantilever ceiling panels of the atrium function as a kind of water curtain to prevent flames from leapfrogging horizontally between the wings of the building. A fully integrated fire alarm system guarantees early fire detection and quickly alerts firefighters. The fire safety concept is supplemented by fire-resistant fittings in the atrium as well as high visibility in the office wings, which have glass partitions and height limits for furniture.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

4 9,940 m2 n/a 5 months 12 months

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Example 14

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Office building in St. Johann in Tirol

Modular system The wood-based materials manufacturer’s headquarters is the latest in a series of four buildings that have been built in Romania, Austria and Germany. They are based on a modular timber-construction system that was created for a competition and that does not restrict flexibility of use despite its strict grid. Adjustments are possible in terms of the geometry as well as to meet architectural, functional, building physics and building code requirements, although there are limitations on adapting to narrow sites given the relatively large basic grid. The system’s modularity allows large quantities of the same elements to be produced on an industrial scale. To achieve this, the cross sections of the elements were designed for their respective maximum load case, and the efficiency of production managed to compensate for the partial over-dimensioning that resulted. The atrium between the office wings uses the same module grid to avoid the need for special lengths and components.

Vertical section Scale 1:20 1 Roof construction: Sealing, EPDM, mechanically fastened Thermal insulation, rockwool 2≈ 140 mm Vapour barrier, bituminous membrane Aluminium, laminated 4 mm Prefabricated roof structure: OSB panel 22 mm on wedge battens OSB 4 TOP panel, press-glued 6≈ 30 mm Beam, glued laminated timber 530/200 mm Installation conduits in the intermediate space OSB 4 TOP panel, white glazed 30 mm 2 Canopy: Sealing, EPDM OSB panel 22 mm on wedge battens OSB 4 TOP panel, press-glued 5≈ 30 mm Beam, glued laminated timber 500/100 mm OSB 4 TOP panel, clear glazed 30 mm 3 Timber-aluminium windows with triple glazing LSG 12 + internal gap 14 + toughened safety glass 6 +

4

5 6

internal gap 14 + toughened safety glass 8 mm Floor slab above ground floor: Floor covering, laminate with impact sound insulation 10 mm OSB panel, tongue-and-groove 18 mm Wood-fibre insulation panel, tongue-and-groove 32 mm OSB 4 TOP panel 30 mm glued on Beam, glued laminated timber 200/520 mm, between them installation conduits Chipping infill 60 mm OSB 4 TOP panel 30 mm, plasterboard 2≈ 20 mm, Suspension / installation conduits 500 mm OSB 4 TOP panel, white glazed 18 mm Heat outlet Fire safety ground floor to top storey: Slatted frame, larch, untreated Sealing, synthetic membrane, EPDM 1.8 mm OSB panel 30 mm, glued on Beam, glued laminated timber 100/300 – 320 mm OSB 4 TOP panel, press-glued,

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Soffit, clear glazed 4≈ 30 mm Copper sheet, sealing, OSB panel 30 mm Facade: Battens, larch, vertical 85/44 mm Battens, larch, rhomboid, planed 85/44 mm Facade membrane, vapour-permeable as wind paper Wood-fibre insulation panel (fire-resistant), tongue-and-groove 32 mm Timber beams 60/280 mm, between them thermal insulation, rockwool 2≈ 140 mm OSB 4 TOP panel, white glazed 22 mm Floor construction: Floor covering, laminate with impact sound insulation 10 mm OSB panel 22 mm, OSB panel 30 mm Vapour barrier, one layer, glued Battens 60/140 mm between them thermal insulation, mineral wool Levelling layer approx. 30 mm Base slab, reinforced concrete 300 mm

223

Example 15

Wood Innovation and Design Centre Prince George, CA 2014 Architects: Michael Green Architecture, Vancouver Team members: Michael Green (project leader), Mingyuk Chen, Carla Smith, Seng Tsoi Design team: Kristalee Berger, Alfonso Bonilla, Jordan van Dijk, Guadalupe Font, Adrienne Gibbs, Jacqueline Green, Asher deGroot, Soo Han, Kristen Jamieson, Vuk Krcmar-Grkavac, Alexander Kobald, Sindhu Mahadevan, Maria Mora Structural engineers: Equilibrium Consulting, Vancouver Concept The Wood Innovation and Design Centre (WIDC) of the University of North British Columbia at Prince George is a pilot project for multi-storey timber construction in Canada with nearly 5,000 square metres of floor space. It is considered a high-rise because the floor of the top storey is about 25 metres above the ground, well above the high-rise threshold of 22 metres. The building serves as a centre for researchers, scientists, engineers and architects who teach and carry out research on modern timber construction. It was built as part of Canada’s Tall Wood programme, a government-led initiative to promote large and tall timber structures. The lower three floors of the seven-storey building, which is just under 30 metres tall, are used by the university for its master’s programme in timber construction. The upper floors provide office space for the timber industry and for governmental organisations in the

forestry and timber sector. The architect’s goal was “to celebrate wood as a building material, to make it tangible everywhere and to show its beauty both externally and internally”. The aim was also to develop a prototype for an innovative yet very simple and replicable construction system for tall buildings that would provide an impetus for new developments in timber construction. Support structure The construction system is a skeletal structure based on a square grid measuring about 8 ≈ 8 metres, with a central access core providing reinforcement to the structure. The entire support structure including the core is made exclusively of various Canadian coniferous woods. Composite constructions were avoided to allow for easy demolition and end-of-life recycling. Attached to the visible glued laminated timber upright supports (36 ≈ 36 cm in the lower storeys and 30 ≈ 30 cm in the upper

storeys) are the main beams, which were also left visible and are between 60 and 100 cm high depending on the load. This transfers the load from the upper support directly to the lower support and prevents transverse compression and subsidence. Lying on the main beams are two layers of alternating cross laminated timber elements, still visible, with thicknesses of 10 or 17 cm and widths of about 120 to 160 cm. The resulting cavities are used as installation zones. These are effectively acoustically closed at the ceiling. Impact sound insulation is provided by carpet on a soft underlay. Canadian regulations made it possible to largely dispense with special measures for airborne sound insulation, apart from plasterboard suspended in the lower installation zone.

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Floor plans Sectional views Scale 1:500 Plan Scale 1:2,000

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Entrance Exhibition area Café Access Auditorium

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Research lab Office Electrical Plant room Waste and

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recycling room Deliveries Bicycles Office (tenantdeveloped)

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Wood Innovation and Design Centre

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Example 15

Fire safety Thanks to a specially designed fire protection concept, the entire construction could remain visible inside and did not have to be encapsulated. It is dimensioned to withstand 60 minutes of fire before burn-up. Sprinklers offer additional protection. The wooden post-andbeam facade is mostly glazed, alternating with opaque elements made of natural or precharred horizontal boards. External sun blinds were omitted. Prefabrication The building’s degree of prefabrication was not very high, due to Canadian timber construction companies’ limited experience in this area. The structure was erected first, and then the facades were built, which meant that intensive weather protection measures were needed during the construction phase. The building is an important contribution in the area of large-scale structures made entirely of wood, using dry materials, and it impresses visitors with a unique atmosphere achieved through meticulous attention to detail.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

226

7 4,820 m2 EUR 11.4 million 5 months 15 months

Wood Innovation and Design Centre

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Roof construction: Sealing, bitumen, two layers Thermal insulation, mineral wool, bitumen-coated 100 mm Thermal insulation PIR 2≈ 50 mm Gradient insulation EPS approx. 100 –140 mm Vapour barrier, plywood board 25 mm Plywood board 19 mm Cross laminated timber, seven layers 239 mm Battens with intermediate space 19/40 mm, acoustic mat Sound insulation 24 mm Beams, glued laminated timber 320/500 mm Upright support, glued laminated timber 320/320 mm Glare protection: timber slats (horizontal) Curtain-wall facing: aluminium sheet Thermal insulation, mineral wool 80 mm Post-and-beam facade, wood and aluminium with triple glazing Heating and utilities conduit Installation space: plywood board 2≈ 13 mm Installation conduits Sound insulation, fibreglass panel 2≈ 25 mm Floor slab (regular floor): Flooring, carpet 9 mm Impact sound insulation 7 mm Cross laminated timber, three layers 99 mm Cross laminated timber, five layers 169 mm Beams, glued laminated timber 220/500 mm Facade: Timber boarding, cedar, heat-treated, with flamed or natural surface, in different widths 30 mm Substructure, plywood strip, weatherproof 13 mm Timber strip, horizontal 10 mm, vapour barrier Wood fibreboard 13 mm, thermal insulation 165 mm Wood fibreboard 18 mm, plasterboard 16 mm Installation space: wood plank 89/40 mm Hollow metal rail, spring-mounted Plasterboard 2≈ 16 mm Sound insulation, fibreglass panel 50 mm Sprinkler Base slab, reinforced concrete Base: thermal insulation, hard foam with latexmodified concrete coating Steel angle bracket fixed in base slab, sealing

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Example 16

Office building Clermont-Ferrand, FR 2014 Plan Scale 1:3,000 Floor plans Scale 1:750

Architect: Bruno Mader, Paris Team members: M. Guzy, C. Grispello, E. Ranalletti, A. Veyssier, A. Bertrand, J. Varela Site manager: Atelier 4, Clermont-Ferrand Structural engineers (timber): Sylva-Conseil, Clermont Ferrand Structural engineers (solid construction): Sibat, Paris

1 2 3 4 5 6 7 8 9

Concept The polygonal shape of this imposing fivestorey administration centre with 18,000 m2 of floor space fits in well with its urban surroundings. A net-like facade structure supports the sculptural appearance, and the building’s different levels of public accessibility are reflected in different building materials. Two storeys in the concrete base house public areas such as the entrance hall, the assembly hall and other spaces for public services. Above it are three storeys made of wood, which are home to offices and various authorities that are not open to the public. The main access route through the building leads through three glass-covered, naturally ventilated courtyards planted with conifers, which the offices face. The project is a showcase for sustainable construction in the region, being highly energy-efficient and, thanks to its use of renewable materials, also resource-efficient. For example, the support structure is made of Douglas fir from Auvergne, where this tree has been selectively planted since the 1950s. As additional benefits, this saves CO2 emissions through short transport routes and provides local added value. Support structure On top of a two-storey concrete base stands a three-storey wooden frame that remains visible through the protective glass shell surrounding it. Upright supports made from glued laminated Douglas fir arranged in a grid of 2.50 metres extend up three storeys, and slotted steel sheets are used to fasten the visible beams to these supports. The building is stabilised by the diagonal stanchions in the facade and by the concrete central zone with office units, side rooms, stairs and lifts. In the courtyards, the supports are located behind the building’s shell – in contrast to the outer facades, where the construction is between the insulating layer and the outer glass skin and effectively appears as a design element. This means the main beams penetrate the building’s thermal shell, which, thanks to the properties of timber, can be done without condensation. The inner walls are built from panels. The ceiling elements, which lie on the main beams, are made of 14.60-cm-thick

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Entrance hall Reception Coatroom Catering Break room Storage Office Open office zone Inner courtyard, greened

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Meeting room Assembly room Control room, interpreter’s booth Mailroom Copy room Incoming deliveries Cloakroom Pre-archiving Archive Documentation Press room Representatives’ reception area Dining area

Office building in Clermont-Ferrand

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cross laminated timber elements that stretch over 16 metres and are prefabricated and assembled with a parapet element. Each of the slabs is bolted tight to prevent shearing, which allows them to act as a disc to absorb horizontal forces. The horizontal load is transferred to the concrete cores via dowelled edge beams. The entire support structure has a fire-resistance rating of 60 minutes.

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Indoor climate The ventilated double facade acts as a climatic and acoustic buffer zone. In the winter, it remains closed, reducing heat loss. When the outdoor temperature is 26 °C or above, the glass slats are opened to prevent excessive heat. On the outside of the three facades that receive direct sunlight, there are motorised blinds to protect against heat and glare. The courtyards are glass-covered and also act as thermal buffer zones. In the winter, this creates an intermediate temperature; in the summer, evaporation from the plants supports natural cooling, along with the fresh air flowing in through the glass slats on the facade and the openings in the roof. The glass slats are centrally controlled based on changes in temperature but can also be operated independently directly from the offices. The southern facades of the atria are shaded by plantings and translucent photovoltaic modules in the glass roof.

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7 Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

5 16,757 m2 EUR 45 million 6 months 28 months

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Example 16

Vertical section, street facade Scale 1:100 Vertical section, courtyard facade Scale 1:20

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Waterproofing, thermal insulation 60 mm beams, glued laminated timber, Douglas fir 138/765 mm Insulated glazing toughened safety glass 6 mm + internal gap 16 mm + 2≈ 5 mm laminated safety glass on a frame structure made of purlins, steel profile IPE 100 roof beams, glued laminated timber 2≈ 90/360 mm Steel profile, IPE 200 Reinforcement, tension rod, steel Ø 34 mm Facade cladding, steel sheet 1.5 mm Vapour barrier Edge beam, glued laminated timber, Douglas fir 138/1035 mm Support, glued laminated timber, Douglas fir 250/264 mm (F 60), fastened to reinforced concrete ceiling via steel corbel Timber-aluminium window with insulated glazing toughened safety glass 6 mm + internal gap 14 mm + toughened safety glass 4 mm Floor slab: Flooring, carpet 10 mm Plasterboard 3≈ 12.5 mm Sound impact insulation 15 mm Thermal insulation with honeycomb structure 30 mm Cross laminated timber ceiling, 5-layer 146 mm (fire resistance 60 minutes) Facade cladding, steel sheet 1.5 mm Vapour barrier OSB panel 10 mm Timber studs 46/155 mm, between them thermal insulation 155 mm, Vapour barrier Thermal insulation 60 mm Facade stiffening, laminated veneer lumber plate 22 mm every 2.50 metres (at each support axis) Horizontal reinforcement, square timber 60/155 mm Beams, glued laminated timber, Douglas fir 112/355 mm, fastened to masonry wall every 2.50 metres with a steel framing anchor Transverse beams, glued laminated timber 138/225 mm Edge beam, glued laminated timber, Douglas fir 185/495 mm

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Example 17

Community centre St. Gerold, AT 2009 Architects: Cukrowicz Nachbaur Architekten, Bregenz Andreas Cukrowicz, Anton Nachbaur-Sturm Team members: Stefan Abbrederis (project leader), Michael Abt, Christian Schmölz Structural engineers: M+G Ingenieure, Feldkirch

232

Community centre in St. Gerold

Plan Scale 1:2,000 Sectional views • Floor plans Scale 1:400 1 2 3 4

Group room Office Storage Kitchenette

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Coatroom Entrance Plant room Archive Store Exercise room Council room Mayor

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Concept Located on a steep southern slope above the collegiate church of Sankt Gerold in the Great Walser Valley, this community centre accommodates various public functions for the small town. A high retaining wall along the road forms a forecourt from which two storeys of the building can be seen. On the ground floor, there is a rural store and a multipurpose room, while the floor above is home to the local administration. The two storeys below the entrance take advantage of the steep hillside, with a preschool and a children’s playgroup with an outdoor area at the foot of the retaining wall. Apart from the

4

foundation slab and supporting wall, the fourstorey building is made entirely of timber. The support structure, outer cladding, fittings and furnishings made of fir form a homogeneous unit in which every detail is implemented in wood, up to and including the ventilation ducts. Support structure The four-storey building is a skeleton construction, the upright supports of which can be seen in the ribbon glazing on the mountain and valley side. The main beams lie in four axes in the exterior walls parallel to the slope and in the two interior walls next to the lift.

Ground floor

Ceilings of dowel laminated timber elements span between these beam axes. The solid wood supports and beams are integrated in the base course of the exterior wall construction and were already installed in the prefabricated storey-high panel elements. The lift shaft of cross laminated timber and the exterior walls reinforce the building. The roof is designed as a beamed ceiling. Environmental concept The Sankt Gerold community centre is a model of environmentally conscious construction. The building materials come from the forests of the Great Walser Valley and were processed by

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Example 17

Vertical sections Scale 1:20 1

local carpenters. Except for the lift shaft, solid wood was the only building material used; glued timber materials were not used. Wood fibre insulation and sheep’s wool were used as insulating materials. Although panel materials were largely ignored, the structure is based on the principles of modern timber buildings, with diagonal boarding replacing reinforcing panel materials in the wall structures and dowelled dowel laminated timber ceilings offering glue-free solid wood ceilings. Operating energy needs have been reduced to a minimum. With its highly insulated shell and ventilation with heat recovery, the building meets passive-house requirements. The exterior walls have a double layer of insulation –

one at the same level as the structural parts and an outer layer that covers the ceiling edges. The roof structure has three layers of insulation and was designed as a ventilated flat roof. Residual heat is provided by a geothermal heat pump. 2

3

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber frame) Total construction time

4 773 m2 EUR 1.9 million (net) 2 weeks 10 months

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234

Community centre in St. Gerold

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Roof structure: Bitumen membrane, two-layer, granular slate surface 5 mm Cladding, spruce, tongue-and-groove 27/100 mm Rear ventilation with timber substructure 500 mm Emergency roof, PE film, full-surface 2 mm Cladding, spruce, butt joint 27/100 mm Gradient formed with square timber 40 – 230 mm, filled with thermal insulation, wood fibre Square timber, spruce 180/100 mm filled with thermal insulation, wood fibre Timber beam 220/100 mm, filled with thermal insulation, wood fibre Cladding, spruce, tongue-and-groove 27/100 mm Vapour barrier, PE film, installation level 110 mm Acoustic insulation, sheep’s wool 30 mm Trickle protective membrane, black Battens, silver fir, untreated 40/36 mm Timber window, silver fir, sanded smooth with insulated triple glazing, float 6 + internal gap 16 +

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float 6 + internal gap 14 + laminated safety glass 2≈ 6 mm, Ug = 0.6 W/m2K, Window sill, silver fir, planed, solid Facade: Cladding, battens, silver fir, rough-sawn 30/50 –120 mm Substructure, battens, spruce, painted black 30/50 mm Counter battens/rear ventilation, spruce 30/50 mm Wind paper, black Prefabricated element: cladding, spruce, tongue-andgroove, diagonal 25/80 –150 mm Post, spruce 125/60 mm between them insulation, wood fibre Prefabricated element: cladding, spruce, tongue-andgroove, diagonal 25/80 –150 mm, post, spruce 200/60 mm between them insulation, wood fibre Cladding, spruce, tongue-and-groove, diagonal 25/80 –150 mm, vapour barrier, PE film Battens, spruce, between them: installation level 40/50 mm, thermal insulation, sheep’s wool Interior cladding, silver fir

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Tongue-and-groove 20/50 –120 mm Floor slab: strap floor, silver fir, rough-sawn, nailed, tongue-and-groove 27/80 –100 mm timbers 62 mm, between them loam building slabs Impact sound insulation, wood fibre 30 mm Dowel laminated timber timber, doweled 180 mm Installation level Soundproofing, sheep’s wool 40 mm Gypsum fibreboard 15 mm Installation level 36 mm Acoustic insulation, sheep’s wool 30 mm Trickle protective membrane, black Ceiling, silver fir, untreated 40/35 mm laid at distance Grate, oak, natural 30 mm Substructure, stainless steel tube | 25/25 mm Gradient compensation, plastic pad, black 5 – 25 mm Bitumen membrane, two-layer, torched 10 mm Insulation, foam glass 120 mm Vapour barrier, dowel laminated timber, doweled 100 mm

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Example 18

Secondary school Diedorf, DE 2015 Architects: ARGE “Diedorf” Architekten Hermann Kaufmann, Schwarzach and Florian Nagler Architekten, Munich Project leaders: Claudia Greußing, Stefan Lambertz Structural engineers: merz kley partner, Dornbirn Landscape architects: ver.de landschaftsarchitektur, Freising

Concept Schmuttertal secondary school’s new building for about 1,000 students is a research project and pilot project funded by the German Federal Environmental Foundation. Four buildings – two for classrooms, one for the administration and one for the gym – form a courtyard. These timber-clad volumes with their gently inclined roofs and integrated photovoltaic systems reference the agricultural buildings of the region and fit into the sensitive landscape of the Schmuttertal valley on the edge of a nature reserve known as the Augsburg western forests. Architecture’s very own resources help achieve the project’s ambitious sustainability and teaching goals. Versatile, open spaces

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offer room for independent collaborative learning and therefore reflect the new pedagogical concept of learning landscapes. Specially selected building materials and other materials guarantee a low-pollutant learning environment while bright rooms with visible wood construction create a pleasant atmosphere. Construction The clear organisation of the visible skeleton construction makes it possible to react flexibly to new teaching concepts now and in the future. Supports, beams and joists or rafters made of white-glazed glued laminated timber, each with its own dimensions, create a sense of unity across all of the buildings. Rows of

supports 2.70 metres apart create spaces with a basilica-like character. For areas with large spans, there are variations but no special solutions. Large glued laminated beams in a uniform design rhythm span the auditorium and the gym, with the purlins of the simple, visible roof structure set on top of them. The ceilings and the entire building shell, which meets the passive house standard, were prefabricated as large elements with a length of up to 12 metres, and the structural concrete topping for the timber-concrete composite ceilings was installed on site. Because there are no suspended ceilings, the installations are vertically oriented and integrated in the deep corridor walls of the classrooms.

Secondary school in Diedorf

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

3 16,046 m2 EUR 35.44 million 6 months 24 months

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Entrance / vestibule Auditorium Stage Library Cafeteria Kitchen Music room Art room

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Storage /archive Craft room Physics Biology Chemistry Assembly room Gym Mechanicals Schoolyard

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Example 18

Fire safety and energy concept Due to the minimised storey heights resulting from the chosen structures, the building falls into class 3, which requires it to be fire-resistant for just 30 minutes. Underlying the zero-energy concept, which also includes user-induced energy consumption, is the passive house concept and a photovoltaic system with more than 1,600 modules and 440 kWp that the architects managed to integrate in the large roof surfaces. Two pellet boilers and two buffer tanks with 7,500 litres each supply sufficient heat. Heat distribution and cooling is provided by underfloor heating and cooling. An ingeni-

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ous concept for using daylight reduces the consumption of electrical energy in combination with LEDs and fluorescent lamps. Ventilation losses are minimised by a ventilation system with heat recovery. All building materials were scrutinised to be sure they were free from pollutants (see “Interior air quality”, p. 30ff.). Acoustic elements made of lightweight wood-wool panels alternating with visible wooden surfaces characterise the interiors. The Federal Environmental Foundation evaluated whether the project had achieved its ambitious goals, in order to make the model useable for other schools as well.

Secondary school in Diedorf

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Vegetation mat 20 mm, extensive substrate 80 mm Drainage mat filled with substrate 40 mm, non-woven storage layer 10 mm EPDM membrane, root-proof, laid parallel to verge 1.3 mm Re-cover board, mineral wool 20 mm Timber battens 100/60 mm for securing EPDM membrane, between them thermal insulation, mineral wool, pressure-resistant 60 mm Thermal insulation, mineral wool, pressure-resistant 160 mm Timber battens fastened to rafters 100/160 mm, between them thermal insulation, mineral wool 160 mm Vapour barrier, full-surface, heat-welded, separation layer, bitumen membrane, nailed, laminated veneer lumber plate in edge area and support area 51 mm Rafters, glued laminated timber, spruce, glazed white 100/320 mm Main beams 240/2000 mm Facade element: cladding, vertical, spruce 30 mm, unplanned positioning, with different board widths (120, 160, 200 mm) Timber battens, horizontal 30/50 mm Structural element: timber battens, vertical 100/60 mm Wind paper, glued joinings wood fibreboard, permeable, waterproof 16 mm Studs, bar 60/120, horizontal Thermal insulation, mineral wool 120 mm Studs, bar 60/240, thermal insulation, mineral wool OSB panel (vapour retarder) 18 mm (sd ≥ 20 m) Interior fitting, deflector: Birch plywood panel, perforated 18 mm Glass fibre protective fabric, acoustic trickle protection fleece, acoustic insulation Screw structure, steel pipe 40 ¡ and 100/30/2 mm galvanised support structure, steel pipe ¡ 40/30/2 mm, galvanised mounting bracket 35/50/35/3.0 mm, galvanised, mounted on OSB panel with nail sealing tape Prefabricated parquet 15 mm (5 mm seam) Plywood panel 9 mm, plywood panel 12 mm, separating foil, PE 0.4 mm Plywood strip bed 18 mm, plywood strip bed 18 mm Heat chamber, standing timber, elastically supported 125 mm, underlay 18 mm Thermal insulation /underfloor heating 100 mm Moisture sealing 5 mm, primer Foundation slab, reinforced concrete (waterproof) 200 mm, thermal insulation XPS 80 mm Sub-base 50 mm, granular layer, anti-capillary 400 mm

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Example 18

Vertical section Middle axis and facade Scale 1:20 1

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Roof structure: Greening, extensive substrate 40 mm Drainage filled with substrate 40 mm Non-woven storage layer Waterproofing, EPDM root-proof 10 mm Thermal insulation, mineral wool 20 mm Timber battens, between them thermal insulation, mineral wool, pressure-resistant 60 mm Thermal insulation, mineral wool, pressure-resistant 160 mm Timber battens 100/160 mm, between them thermal insulation, mineral wool, pressure-resistant 160 mm Prefabricated roof element: Waterproofing Bitumen membrane Lightweight wood-wool panels in edge area and support area 50 mm (otherwise three-layer panel, spruce) Rafters, glued laminated timber, spruce, glazed white 100/360 mm Gutter, inside Sun protection Flat slats, aluminum, white Timber window, spruce, glazed white with insulated triple glazing 4 mm float + 18 mm internal gap + 4 mm float + 18 mm internal gap + 4 mm tempered safety

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glass /heat-soak-tested Window sill, outside, aluminum Facade element hung on exterior wall: Cladding, spruce, vertical, unplanned positioning, with different board widths 30 mm Substructure, timber battens, 40 ≈ 40 mm Exterior wall element: Timber battens, horizontal 40 mm Timber battens, vertical 110 mm Wind paper Wood fibreboard, permeable, waterproof 16 mm Supporting structure, spruce, filled with thermal insulation, mineral wool 140 mm Supporting structure, spruce, filled with thermal insulation, mineral wool 220 mm OSB panel (vapour retarder), glued joinings 18 mm Window sill, inside, three-layer panel, glazed white Room ventilation, displacement diffuser Built-in shelving, three-layer panel, spruce, glazed white 42 mm Interior wall structure: Gypsum fibreboard 12.5 mm OSB panel 18 mm Supporting structure, spruce 80/60 mm, filled with thermal insulation, mineral wool 80 mm

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OSB panel 18 mm Gypsum fibreboard 12.5 mm Ceiling slab: Mineral coating 5 mm Heating screed, perforated plate 85 mm Separation layer, PE foil Impact sound insulation 30 mm Levelling insulation 50 mm Separation layer PE foil, two-ply Reinforced concrete 98 –120 mm Ceiling element battens OSB panel 22 mm Frame of joists 2≈ 180/320 mm Filled with acoustic element: Thermal insulation, mineral wool 40 mm wood-wool acoustic panel, magnesite-bonded Fixed glazing, laminated glass made of 2≈ 12 mm float glass Edge beams, glued laminated timber 100/740 mm Foundation structure: Mineral coating 5 mm Heating screed, perforated plate 85 mm Separation layer, PE foil Impact sound insulation 30 mm Levelling insulation 50 mm Separation layer PE foil, two-ply Reinforced concrete 250 mm Thermal insulation 80 mm Ventilation channel

Secondary school in Diedorf

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Example 19

European School Frankfurt am Main, DE 2015 Architects: NKBAK, Frankfurt am Main Nicole Kerstin Berganski, Andreas Krawczyk Team members: Simon Bielmeier, Larissa Heller Structural engineers: Bollinger + Grohmann, Frankfurt am Main merz kley partner, Dornbirn

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Concept In Frankfurt, as in all growing German cities, there is currently a great need for classrooms. With the enlargement of the European Central Bank, the European School also reached the limit of its spatial capacity, and the additional space it needed had to be obtained quickly. The new building was only approved as a temporary building and had to be implemented within 17 months – from the planning application to the start of use. The extension offers space for 400 students aged 3 to 8, who are taught separately in a preschool and primary school. The modular construction method made it possible to meet the very ambitious schedule and

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the requirement for later reuse. The architects took advantage of the spatial potential of this construction method and combined the modules with corridor ceiling elements and glass facades to form differentiated sequences of rooms with alternating single and double-line access figures and a variety of connections to exterior spaces. The design allows for the future extension of the elementary school on the north side. Support structure and prefabrication The building is defined by module sizes of 3 ≈ 9 metres, which relate to the classroom depths. The load-bearing walls of the modules are made of cross laminated timber, while the

ceiling slabs of the corridors are suspended between the modules or placed on skeleton constructions made of glued laminated timber. The classrooms each consist of three modules, with 550 ≈ 220-mm bearers made of highly loadable beech laminated veneer lumber (LVL) spanning them longitudinally. Cross laminated timber ceilings and floors handle the span of 3 metres in the transverse direction. The use of beech LVL beams saved 8 cm of room height per storey compared to conventional spruce glued laminated timber. The consistent modular design made it possible to finish the weatherproof shell in just three and a half weeks starting from the foundation slab. The modules were prefabricated with

European School in Frankfurt am Main

Plan Scale 1:5,000 Sectional view • Floor plans Scale 1:500 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Main building Gym Sports field Container classrooms Primary school and preschool Main entrance Classrooms Teachers’ rooms Supply room Cafeteria Microwave station Storage Exercise room Group room for preschool Play hallway

interior surfaces, windows and building services. Only the foundation and the aluminium facade were assembled on site, in order to avoid unwanted joints and minimise the protective measures that would be necessary during transport. The wooden structure took a total of three months to build once the foundation slab was finished.

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Fire safety The engineers had to prove that the three-storey building could withstand fire for 30 minutes. An excellent escape route design with three staircases ensures that each classroom has two independent directions of escape at all times. This also made it possible to have visible wooden surfaces on the walls. Only in the stairwells did these surfaces have to be given a fire-protection coating. These areas were to be glazed anyway in order to fulfil a request for some colour and to facilitate orientation in the building.

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Building services Building services and the climate concept were deliberately kept simple. Legal requirements regarding heat transmission are met by moderate thermal insulation and triple glazing. The windows provide ventilation. Facades that receive strong solar radiation are equipped with external sun protection. The building is connected to the district heating network, and radiant heating systems are visibly mounted on the ceiling.

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3 1,215 m2 About EUR 1.9 million (net) 3 months 8 months

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Example 19

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European School in Frankfurt am Main

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cc Vertical sections • Horizontal section Scale 1:20 1 Roof structure: waterproofing, plastic membrane, Gradient insulation, EPS min. 120 mm, vapour barrier, Cross laminated timber 80 mm, thermal insulation, mineral wool 50 mm, wood-wool acoustic panel 25 mm Laminated veneer lumber (LVL) beam, beech 360/220 mm 2 Gutter, sheet metal 3 Aluminium sheet, lacquered 1 mm Wind paper, thermal insulation, mineral wool 120 mm 4 LVL beam, beech 360/120 mm 5 Timber-aluminium window with integrated guard rail in frame 6 Floor slab, classroom: Module 1: linoleum 2.5 mm, chipboard, glued 2≈ 16 mm, impact sound insulation panel 25 mm Cross laminated timber 80 mm, thermal insulation mineral wool 60 mm Module 2: cross laminated timber 60 mm, thermal insulation, mineral wool 60 mm, wood-wool acoustic panel 25 mm, LVL beam, beech 560/220 mm 7 Cross laminated timber 100 mm Acoustic insulation 50 mm Acoustic panel, perforated 8 Floor slab, hallway: Linoleum 2.5 mm, chipboard, glued 2≈ 16 mm impact sound insulation panel 25 mm Cross laminated timber 80 mm Installation space 265 mm Thermal insulation, mineral wool 60 mm Wood-wool acoustic panel 25 mm 9 Support, square timber 100/200 mm 10 Floor structure, ground floor: Linoleum 2.5 mm Chipboard, glued 2≈ 16 mm, vapour barrier Impact sound insulation panel 25 mm, cross laminated timber 80 mm Thermal insulation, mineral wool 80 mm Foundation slab, reinforced concrete 300 mm

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Module, prefabricated: 11 Timber-aluminium window with integrated guard rail in frame 12 Upright support, laminated veneer lumber, beech 120/360 mm 13 Cross laminated timber 80 mm, glazed white 14 LVL beam, beech 360/220 mm 15 Ceiling radiator 16 Wood-wool acoustic panel 25 mm Thermal insulation, mineral wool 50 mm Cross laminated timber 80 mm, vapour barrier 17 Chipboard, glued 2≈ 16 mm, impact sound insulation panel 25 mm, cross laminated timber 80 mm Thermal insulation, mineral wool 60 mm 18 LVL beam, beech 560/220 mm 22

On site: 19 Aluminium panel, lacquered 1 mm, wind paper Thermal insulation, mineral wool 120 mm 20 Cover, laminated veneer lumber, beech 21 Waterproofing, plastic membrane Gradient insulation, EPS min. 120 mm 22 Linoleum 2.5 mm dd

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Example 20

School complex Limeil-Brévannes, FR 2012 Architects: Agence R2K, Grenoble Véronique Klimine, Olavi Koponen Structural engineers (timber): Holzbau Amann, Weilheim Structural engineers (solid construction): Gaujard Technologie, Avignon

Concept Today’s largest timber school complex in France covers 9,500 m2 of floor space and accommodates around 1,000 children in 50 classes and day-care groups. To give each of the five institutions (three day-care centres, two elementary schools) its own identity, each was given its own playground, to which the classrooms and day-care rooms have direct access. Open passages illuminated from above connect the outdoor areas. The library and the school cafeteria, which serves as a multipurpose hall for the local community, are shared. Taking advantage of the large, 4-metre difference in height on the site, the new buildings are a maximum of three storeys despite the considerable building density. The flat roofs of the buildings on the lower portion of the site serve as courtyards and open spaces. The only vertical volume is the tall, triangular clock tower – the school building’s symbol. The entire building complex was to be completed within a year, which led the planners to choose timber construction. Incidentally, this also allowed their ambitious sustainability goals to be achieved.

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Support structure Apart from the lift shafts and the components that come in contact with the ground, which are made of concrete, the building is made entirely of wood – about 3,000 m3 of it. The ceilings, made of ribbed cross laminated timber (CLT) elements, lie on a system of timber panel walls, upright supports and glued laminated beams. CLT box elements were used for the roof. Various types of wood were used. Inside, the structural parts are made of glued laminated spruce and cross laminated spruce, while the 20-cmwide round supports outside are made of larch. The larch timber on the facade cladding was given a wave profile to make the material more tactile and more appealing to the senses. The terraces are made of thermally treated beech. Building characteristics Number of storeys Gross floor area Construction costs (including planning) Total construction time

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3 9,480 m2 EUR 18.6 million 14 months

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School complex in Limeil-Brévannes

Floor plan Scale 1:1,000 Sectional view Scale 1:500 1 2 3 4 5

Schoolyard Classrooms Vestibule Principal’s office Teachers’ rooms

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Library Multipurpose room Relaxation room Inner courtyard Exercise room Locker room Cafeteria Kitchen Deliveries

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Example 20

Indoor climate The buildings have mechanical ventilation with heat recovery. One third of the window surface in the classrooms can be opened manually. Projecting canopies and distinctive vertical slats made of painted perforated steel plate provide shade. However, these were only mounted in part of the upper storeys, and they do not cover the entire surface of the glazing. A skylight ribbon is shade-free and brings daylight deep into the classrooms. To limit heat input, the skylights were equipped with tinted glass. According to simulations, this reduces the frequency of excess temperatures (higher than 28 °C) to less than 2 % of annual operating hours.

Prefabrication and assembly Meticulous planning and logistics were needed to keep to this tight schedule. The decisive factor was having the timber construction company involved in the planning right from the start. The CLT ceiling elements with a span of up to 7 metres were supplied ex-works with a finished wood surface and a built-in room sound absorber, which made interior finishing work beneath the ceiling unnecessary in many areas of the building. The company was also able to install conduits in the cavities of the ribbed ceilings at the factory. A total of 108 tractor trailers then transported the prefabricated parts from Germany to the site in France where they were installed on a strict schedule.

Soundproofing and acoustics Since some classrooms are located below playgrounds, impact sound insulation was particularly important. First, the cavities in the ceiling elements were filled with chipped wood for noise reduction. The ceilings had already been equipped with acoustic profiles at the factory to improve the acoustics in the interior spaces. Behind a finely laminated surface of silver fir, sound is absorbed by wood fibre insulation.

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Roof structure: Waterproofing, plastic (polyolefin) OSB panel 22 mm Roof beams 200 – 320 mm (3 % gradient), filled with thermal insulation 200 – 320 mm OSB panel 15 mm, vapour barrier Box element, cross laminated timber (prefabricated) 210 mm Acoustic panel, cross laminated timber with integrated wood-fibre absorber 18 mm Battens, larch, half-round cut on outside, glazed grey, highly fire-resistant 81–134 mm /44 – 63 mm, counter battens Timber-stud wall 60/80 mm OSB panel 15 mm Waterproofing, plastic (polyolefin) Three-layer panel, spruce 19 mm Beam, glued laminated timber 180/320 mm, Support, glued laminated timber, spruce 200 mm Floor slab, interior: Flooring (soft) 10 mm Anhydrite floor 50 mm Wood fibreboard 10 mm Cross laminated timber 109 mm Cavity for ventilation and installations 719 mm Plasterboard 2≈ 12.5 mm Floor structure, exterior: Natural rubber 20 mm Concrete slabs 50 mm Paving support pads, height-adjustable, waterproofing OSB panel 22 mm Roof rafters with three-layer panel 40 mm Space between axes 625 mm, between them thermal insulation, cellulose, average in gradient 260 mm OSB panel 15 mm Vapour barrier Rib element, cross laminated timber 435 mm Acoustic panel, cross laminated timber, silver fir, with integrated wood-fibre absorber 18 mm Fall protection: Balustrade posts, steel profile 2≈ 8/100 mm, distance between axes 1.50 m Steel mesh, stainless Glass roof, post-and-beam construction with laminated safety glass 2 mm Shade element, wood slats 60/100 mm Beam, glued laminated timber 180/800 mm Beam, glued laminated timber 180/580 mm Floor structure, ground floor: Flooring 5 mm Flow screed 5 mm Reinforced concrete ceiling 200 mm Thermal insulation 100 mm Plank, beech, thermally treated 30 mm

School complex in Limeil-Brévannes

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Example 21

Renovation and new addition to a boarding school Altmünster, AT 2011 Architects: Fink Thurnher, Bregenz Team members: Josef Fink, Markus Thurnher, Sabine Leins, Carmen Schrötter-Lenzi Structural engineers (timber): merz kley partner, Dornbirn Structural engineers (solid construction): Mader & Flatz, Bregenz ‡ Pre-existing building

Concept The merger of an agricultural school and a home economics school brought a plan to train young farmers with additional job-supporting skills in trades and tourism closer to reality. The agricultural school was preserved as much as possible and extended to form a closed four-sided courtyard with an edge length of about 70 metres. This traditional style for the region underpinned the design concept of a rather internal orientation, while at the same time creating links to the impressive external landscape of lakes and mountains. The idea of a meandering access layout pursued this same goal with alternating links

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to the courtyard and the exterior, thereby not giving in to the monotony of a central hallway. Functions are essentially layered horizontally. A basement with an underground courtyard contains workshops and specialised classrooms. The middle entrance level is reserved for public areas such as an auditorium, canteen and two-storey gym. The upper level contains the main school area with classrooms, teachers’ rooms, administration and the residential rooms. Support structure The support structure pragmatically mixes wood, steel and concrete. The basement is

made of reinforced concrete because of the site’s slope. The upper storeys are designed as a skeleton construction in areas with large spans: The exterior walls contain square steel supports, while free-standing steel supports are concreted out for fire safety reasons. Steel beams connect the steel supports as continuous beams, and timber-concrete composite ceilings span the 5 – 8.50-metre-wide fields between them. A continuous 120-mm layer of concrete statically works in combination with the primary steel beams. The dowel-laminated timber layer below reacts to the changing spans with varying heights ranging from 120 to 240 mm. Reinforcement is provided by wall panels made of cross laminated timber.

Renovation and new addition to a boarding school in Altmünster

Plan Scale 1:3,000 Floor plans Scale 1:750

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Auditorium Gym Store Seminar area / trades Central cloakroom Canteen / serving room Dining area Internet café

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Kitchen Food storage area Teaching kitchen Residential area, double room Residential area, four-person room Inner courtyard Principal’s office / administration Library IT room Classrooms Teachers’ rooms

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In areas with smaller spans – the additions to the boarding school – a similar system is used. The same ceilings here rest directly on top of the walls, without a steel skeleton. In the roof, the primary beams are made of steel and the secondary beams are made of wood. Above them is stiffening cladding made of three-layer panels.

Building characteristics Number of storeys Gross floor area Construction costs Construction time (timber) Total construction time

3 12,948 m2 EUR 23.9 million About 2 months 28 months

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Example 21

Prefabrication The steel skeleton was assembled, pieceby-piece, on top of the basement, using sitemixed concrete. The concrete layer on the ceilings was added on site. The wall elements were prefabricated without cladding. While the facade cladding, which covers more than one storey in some places, as well as the suspended ceilings were delivered as elements in all the storeys, the interior cladding of the walls was built in the conventional manner on site. Almost all surfaces are made of local silver fir, mostly rough-sawn and untreated. Fire safety The basement of reinforced concrete meets REI 90 requirements, while the load-bearing parts (concrete-reinforced steel columns) in the two upper storeys meet REI 60 requirements. The roof is designed to meet REI 30 standards. Two escape stairwells in solid construction form the main escape routes for the entire building. The creation of a roughly 1,200 m2 fire compartment across three storeys made it possible to open the central stairwell near the main entrance. Encapsulated components were not required, nor was a sprinkler system.

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Renovation and new addition to a boarding school in Altmünster

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Facade: Cladding, silver fir 72/30 mm Battens and counter battens 60 mm Wind seal, UV-resistant 7 mm Cladding spruce 20 mm Timber-stud structure 80/370 mm, filled with thermal insulation, cellulose 370 mm Cladding, spruce 20 mm Vapour barrier 0.3 mm Plasterboard 12.5 mm (school) Installation level 40 mm Plasterboard 2≈ 12.5 mm (boarding school) and cladding, silver fir, untreated 20 mm (school) Support, timber in wooden rail wall Perforated plasterboard ceiling 12.5 mm Thermal insulation, sheep’s wool 50 m Suspension and carrier section 457 mm Roof construction: Extensive vegetation, substrate 100 mm Drainage 10 mm Waterproofing, bituminous membrane 2≈ 5 mm Waterproofing, bituminous membrane, self-adhesive, with interwoven glass fibre as heat shield 3 mm Thermal insulation, EPS in gradient 300 – 500 mm Vapour barrier, full surface, glued 3.8 mm Three-layer panel 40 mm Beam, glued laminated timber 360 mm Installation level 290 mm: Thermal insulation, sheep’s wool 30 mm Acoustic fleece 1 mm Suspended wood-slat ceiling, silver fir, untreated 30/30 mm Sun protection, textile, motorised Fixed glazing, timber window, fir with insulated triple glazing, with aluminium fixing profile, supported on two sides, vertical joints made of silicone Ceiling slab in upper storeys: strip floor, silver fir, untreated 27 mm Flooring sleepers, between them thermal insulation, EPS with underfloor heating 30 mm Impact sound insulation 40 mm Infill, expanded clay 53 mm Timber-concrete composite ceiling: Reinforced concrete 120 mm with dowel laminated timber element 200 mm Wooden space frame for suspended ceiling 290 mm Impact sound insulation, sheep’s wool 30 mm Acoustic fleece 1 mm Wood-slat ceiling, silver fir, untreated 30 mm Steel beam, HEB 200 with welded-on steel angle to transfer loads to the wooden rail wall Ceiling slab above ground floor: Strip floor, silver fir, untreated 27 mm Flooring sleepers, between them thermal insulation, EPS with underfloor heating 30 mm Impact sound insulation 40 mm Infill, expanded clay 100 mm Reinforced concrete 330 mm Installation level 260 mm: Impact sound insulation, sheep’s wool 30 mm Acoustic fleece 1 mm Suspended wood-slat ceiling, silver fir, untreated 30/30 mm Preparation for interior shades

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Example 22

Hotel Ammerwald Reutte in Tirol, AT 2009 Architects: Oskar Leo Kaufmann and Albert Rüf, Dornbirn Team members: Bernd Riegger (project leader), Matthias Reichert, Eva Hagmayer Structural engineers (timber): merz kley partner, Dornbirn Structural engineers (solid construction): Mader & Flatz, Bregenz

Architecture In the Ammergau Alps, the BMW Group operates the 3-star Hotel Ammerwald at 1,100 metres above sea level, primarily as a seminar centre for its employees. This L-shaped structure replaces a previous building. A competition led to the concept for this 93-room hotel, the public areas of which are functional and spacious, while the rooms are cosy due to their omnipresent wood surfaces, but at the same time modern due to the pared back design and integration of all their furnishing elements. The lower storeys encompass the shared spaces. Like the stairwells, they are made of reinforced concrete, which, in addition to construction factors, was chosen because of the depth of the snow in winter. The facade had to be robust, elegant, high-quality and low-maintenance, so a decision was made for stainless steel sheet, which reflects light and weather in many ways during the course of the year. However, it is still apparent from the outside that this is a timber building – the deep window niches, which are intended to be used as French balconies, clearly show the building material that makes up the interior. Construction The room modules rest on levelled hardwood sills with Sylomer cushions on a site-mixed concrete substructure. Three stair cores made of reinforced concrete guarantee safe escape routes. The room modules are made of cross laminated timber, which has been left visible on the inside. The 95-mm-thick load-bearing interior walls were installed on top of 140-mmthick floor panels, and a 60-mm-thick ceiling panel was then attached to the walls. This resulted in a stiffened, transportable room module with external dimensions of 4.50 ≈ 5.00 ≈ 3.00 metres, of which three were always stacked and decoupled with elastic Sylomer cushions to prevent structure-borne noise transmission. The central access area is also made of 160-mm-thick cross laminated timber panels, which rest elastically on the room modules and which use screed and plasterboard planking to meet fire safety and sound insulation requirements. The double-shell walls and ceilings as well as some direct plasterboard

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planking enabled compliance with the required airborne sound and impact sound insulation values. The walls and floors of the wet cells, including the shower, are also made of visible cross laminated timber panels, which are protected by a special transparent coating. For reasons of design and fire safety, the outer skin was designed in stainless steel. It could only be mounted on site, since sheet metal facades are not robust enough for transport and even the slightest damage would necessitate major repairs. Production A small carpentry company from the Bregenz Forest prefabricated all the room modules in its production facility. A production line was set up for this purpose, on which the 93 modules, pushed by hand, passed through twelve production stations where all the building services installations were installed, the surfaces finished and even the furnishings and curtains installed. The completely prefabricated rooms were temporarily stored and then transported to the site after completion of the building’s shell and stacked on top of each other within ten days. The ceiling panels of cross laminated timber for the long central hallway were placed on top of the modules on site. The plasterboard wall cladding for the access zones was also installed on site, as were the facades made of stainless steel sheet. The interfaces of the technology lines were also completed on site. The very high degree of prefabrication enabled a considerable reduction in construction time, which made production of the room wing weather-independent. Prefabrication also ensured the kind of quality that would not normally be achievable with conventional construction methods of on-site assembly, and it achieved this at a reasonable cost and with a high degree of manufacturing innovation. The extremely short production time of just 31 days for 93 room modules required sophisticated logistics that resembled industrial production in the automotive sector more than the work of craftspeople in conventional above-ground construction.

Hotel Ammerwald near Reutte in Tirol

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a Plan Scale 1:3,000 Sectional view • Floor plan Scale 1:750 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Entrance Lobby Restaurant Terrace Bar Dining hall Scullery Kitchen Deliveries Staff rooms Vehicle hall Building services Rubbish rooms Rooms

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Example 22

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5 8,175 m2 Around EUR 15 million 12 days 6 weeks 28 months

Hotel Ammerwald near Reutte in Tirol

Fire safety Some parts of the project conflict with current building code, so a separate fire safety concept was created. Since only non-combustible building materials are permitted for structural components in building class 5, the fire compartments were greatly reduced from the size allowed by law by dividing the room wings into three fire compartments of 800 m2 each (the law allows up to 1,200 m2) and shortening the length of escape routes to a maximum of 20 metres. The partition walls between the rooms have a fire resistance of 30 minutes (REI 30), the walls between the rooms and the corridor resist fire for 60 minutes (REI 60), while the floors and ceilings have a fire resistance of 90 minutes (REI 90). Wall and ceiling surfaces in the corridor area had to be noncombustible, so they were covered in plasterboard. A fire alarm system offering “complete protection” compensates for the timber construction method. Vertical section Horizontal section Scale 1:20 1 Roof structure: Gravel 60 mm Waterproofing, bitumen membrane, three-layer 11 mm Thermal insulation, PUR hard foam, no gradient 200 mm Vapour barrier Cross laminated timber panels, oiled on inside 140 mm 2 Timber casement door, larch, with thermally insulated glazing, tempered safety glass 6 mm + internal gap 16 mm + tempered safety glass 6 mm U = 1.1 W/m2K 3 Fall protection, balustrade, aluminium pipe, welded and lacquered 25/25/6 mm 4 French balcony: Stainless steel sheet 2 mm, smoothed Three-layer panel, larch 42 mm OSB panel 12 mm Thermal insulation, mineral wool 64 mm Vapour barrier Thermal insulation, insulated mineral wool 64 mm, installed on site (module joint) Vapour barrier Thermal insulation, mineral wool 64 mm OSB panel 12 mm Three-layer panel, larch 42 mm 5 Stainless steel sheet 2 mm, smoothed, with rear ventilation, installed on site 6 Square timber with Sylomer strips 12 mm 7 Floor slab: Coating, polyurethane resin 1 mm (in bath) Cross laminated timber panel 140 mm Air layer 30 mm (module joint) Impact sound insulation, mineral wool 50 mm Cross laminated timber panel, oiled on inside 60 mm 8 Panel joining with fish plate, three-layer panel with four rows of screws 27/160 mm 9 Roof panel /ceiling panel, installed on site 10 Cladding, plasterboard, installed on site 11 Room partition: Cross laminated timber panel, oiled on inside 95 mm Plasterboard 12.5 mm Thermal insulation, mineral wool 50 mm Air layer, 15 mm (module joint) Plasterboard 12.5 mm Cross laminated timber panel, oiled on inside 95 mm 12 Wind paper Thermal insulation, mineral wool, three-layer 380 mm Vapour barrier Cross laminated timber panel, oiled on inside 72 mm

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Authors Hermann Kaufmann born 1955 Univ.-Prof. Dipl.-Ing. certified architect Studied architecture at the Technical University of Innsbruck and the Technical University of Vienna 1981 –1983 Employed at office Hiesmayr in Vienna Founded own architectural firm in Schwarzach, Vorarlberg in an office shared with Christian Lenz, with a focus on sustainable building and the possibilities of modern (multi-storey) timber construction 1995 –1996 Guest lecturer for Timber Construction at the Liechtenstein Engineering School (LIS) 1998 Visiting professor at Graz University of Technology 2000 Visiting professor at the University of Ljubljana since 2002 Professorship of Architectural Design and Timber Construction at the Technical University of Munich (TUM)

Stefan Krötsch born 1973 Junior Prof. Dipl.-Ing. certified architect 1994–2001 Studied architecture at the Technical University of Munich and the Wrocław University of Science and Technology in Wrocław, Poland 2001– 2003 Employed at bogevischs buero, Munich 2003 – 2005 Project manager at Söldner und Stender Architekten, Munich  2005 – 2013 Architekturbüro Stefan Krötsch in Munich 2008 – 2014 Academic Council at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich since 2009 Braun Krötsch Architekten in partnership with Florian Braun since 2015 Junior professor, head of the newly founded Department of Tectonics in Timber Construction, Faculty of Architecture at the Technical University of Kaiserslautern (TUK)

Stefan Winter born 1959 Univ.-Prof. Dr.-Ing. 1980 –1982 Carpenter training 1982 –1987 Studies of Civil Engineering at the Technical University of Munich and the Technical University of Darmstadt 1987–1990 Research assistant at the Institute of Steel Construction and Materials Mechanics and at the Institute of Concrete Construction at the Technical University of Darmstadt 1990 –1993 Director at the Institute of Carpenters, Darmstadt 1993 Founded engineering company bauart Konstruktions GmbH & Co. KG, with headquarters in Lauterbach and branches in Munich, Darmstadt and Berlin 1993 – 2003 Specialist consultant for the information service Informationsdienst Holz in Hesse 1998 doctorate at the Technical University of Darmstadt, dissertation topic “Structural behaviour of steelconcrete composite columns out of high tensile steel StE 460 under normal temperature and fire conditions” since 2000 publicly appointed and sworn expert for timber construction at the Gießen-Friedberg Chamber of Industry and Commerce (IHK) 2000 – 2003 Chair of Steel and Timber Construction, University of Leipzig 2001– 2010 Shareholder at MFPA Leipzig GmbH since 2003 Full professor of Timber Structures and Building Construction at the Technical University of Munich since 2006 check engineer for structural analyses in the timber construction field, Bavaria 2009 – 2012 Finland Distinguished Professor (FiDiPro) at Aalto University, Helsinki

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since 2012 Chairman of the construction standards committee Department 04 “Timber Construction”, member of the DIN Standards Committee Building since 2014 Chairman of the European standards committee CEN TC 250 / SC 5 Eurocode 5 – Timber construction – Design and Execution

Heinz Ferk born 1961 Dipl.-Ing. 1990 Degree in civil engineering with honours, Graz University of Technology 1991–1996 University assistant at the Institute for Structural Engineering, Graz University of Technology 1996 Founded engineering office for building physics since 1998 Lecturer at the Graz University of Technology since 2000 Head of the Laboratory for Building Physics at the Graz University of Technology since 2004 Head of European notified accredited testing laboratory 2006 – 2014 Deputy director of the Institute for Structural Engineering, Graz University of Technology since 2014 Deputy director of the Laboratory for Structural Engineering (LKI)

Sonja Geier born 1973 Dipl.-Ing. 1991– 2000 Studied architecture at the Graz University of Technology 2006 Course in International Project Management at the Vienna University of Economics and Business 1992 – 2008 Work and project management at various architectural and civil engineering firms 2008 – 2012 International and national research projects at AEE INTEC in the area of sustainable buildings and timber construction since 2012 International and national research projects at the Lucerne University of Applied Sciences and Arts – Engineering and Architecture in the area of timber construction and planning processes

Annette Hafner born 1971 Prof. Dr.-Ing. certified architect 1990 –1997 Studied architecture at the Technical University of Munich and ETSAB Barcelona 1998 – 2004 Architect in London and Munich 2004 – 2014 Research assistant at the Chair of Timber Structures and Building Construction, Prof. Winter and head of Certification Body ZQ MPA BAU, Technical University of Munich 2012 Doctorate at the Department of Civil Engineering and Surveying, Technical University of Munich since 2014 Junior professor at the Chair of Resource Efficient Building at the Ruhr-University Bochum, Department of Civil and Environmental Engineering

Wolfgang Huß born 1973 Prof. Dipl.-Ing. Architect 1994 – 2000 Studied architecture at the Technical University of Munich and ETSA Madrid, graduated 2000 2000 – 2007 Employed architect at SPP Munich 2007 – 2016 Teaching and research assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich since 2013 firm hks  architekten (Huß Kühfuss Schühle) since 2016 Professor of Industrialised Construction and Production Technology, Faculty of Architecture and Civil Engineering, Augsburg University of Applied Sciences

Holger König born 1951 Dipl.-Ing. certified architect, book author 1971–1977 Studied architecture at the Technical University of Munich Working for environment and health in the building sector for over 30 years

Maren Kohaus born 1975 Dipl.-Ing. certified architect Studied architecture at the Technical University of Dortmund, Technical University of Munich, ETSA Madrid 2001– 2008 Employed at Allmann Sattler Wappner Architekten, Munich 2008 – 2012 Member of the Executive Board at Allmann Sattler Wappner Architekten, Munich since 2012 Research assistant /Academic Council at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich since 2012 work as a freelance architect 2015 – 2016 Lecturer at the Technical University of Munich

Frank Lattke born 1968 Dipl.-Ing. certified architect, Association of German Architects (BDA) Carpentry training, studied architecture at the Technical University of Munich and ETSA Madrid since 2003 own firm in Augsburg 2002 – 2014 Research assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich Teaching and research activity: TES EnergyFacade (WoodWisdom ERA Net) smartTES (WoodWisdom ERA Net) 2014 – 2017 Project partner in the leanWOOD research project

Lutz Müller born 1969 1989 –1992 Carpentry apprenticeship in Munich 1995 –1999 Studied architecture at the Konstanz University of Applied Sciences 1999 – 2001 Employed at Prof. Wolfgang Lauber und Prof. Steidle + Partner, Munich 2001– 2005 Employed at RRP Architekten, Munich 2005 – 2014 Project manager at agmm Architekten, Munich 2007 Research assistant at the Professorship of Building in the Tropics, Prof. Dr. Wolfgang Lauber, Konstanz University of Applied Sciences 2007– 2009 Graduate studies under Prof. Hans Kollhoff at the ETH Zurich 2011– 2014 Studied art history at the Ludwig Maximilian University of Munich 2015 Employed at Henn Architekten, Munich since 2015 Assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich since 2016 Employed at Gassmann Architekten, Munich

Anne Niemann born 1976 Dipl.-Ing. certified architect 1996 – 2002 Studied architecture at the Technical University of Munich, ETSA Madrid and Ben-Gurion University of the Negev 2003 – 2009 Partner at Niemann Ingrisch Architekten, Munich

2006 German Academy Rome Villa Massimo: fellowship at Casa Baldi, Olevano Romano, Italy 2008 – 2014 Assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich 2009 – 2013 Partner at m8architekten, Munich since 2014 Research assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich since 2017 Research assistant at the Chair of Architectural Design and Construction, Prof. Florian Nagler, Technical University of Munich

Gerd Wegener born 1945 Univ.-Prof. Dr. Dr. habil. Drs. h.c. TUM Emeritus of Excellence 1993 – 2010 Full professor of Wood Science and Wood Technology and Head of Holzforschung München (HFM) at the Technical University of Munich over 400 wide-ranging publications on forestry and wood science visiting professorships and expert reviewer around the world numerous awards and distinctions

Daniel Rüdisser born 1974 Dipl.-Ing. certified technical physicist and building physicist Work on research projects on the topic of heat, humidity and climate at the Laboratory for Building Physics, Graz University of Technology. Owner of the engineering office HTflux, which focuses primarily on developing building physics software

Christian Schühle born 1971 Dipl.-Ing. certified architect 1995 – 2002 Studied architecture at the Technical University of Munich 2000 – 2005 Employed at Herzog & de Meuron in Munich and Basel since 2007 own architecture firm, since 2013 hks  architekten (Huß Kuehfuss Schühle) since 2010 Research assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich

Manfred Stieglmeier born 1962 M Eng architect 1982 –1991 Studied architecture at the Academy of Fine Arts Munich, University of Applied Sciences Munich 1987–1998 Employed at various Munich architecture firms, including Auer + Weber among others 1999 – 2000 Partner at Schmidhuber + Partner 2007– 2009 Graduate studies in timber construction for architects at the Rosenheim University of Applied Sciences since 2000 own firm in Munich with focus on timber construction since 2009 Research assistant at the Professorship of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich

Martin Teibinger born 1972 Dipl.-Ing. Dr. techn Combination studies in the timber industry at the University for Soil Culture and Structural Engineering at the Technical University Vienna Doctorate at the Technical University Vienna For over 20 years, active in the Construction Technology Department at Holzforschung Austria since 2006 Head of the Department of Building Physics Research, appraisal and publication activities in the fields of building physics, fire protection and multistorey timber construction since 2016 Sworn and court-certified expert Lecturer and teacher in the fields of building physics, timber construction and fire protection as university lecturer, university of applies sciences lecturer and technical college teacher

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Glossary Acetylation Chemical modification of wood using acetic anhydride to prevent infestation by wood-destroying fungi or insects, reduce the timber’s moisture absorption and minimise swelling and shrinking. It makes sections of timber exposed to weather and moisture much more durable. Airborne sound Sound transmitted by air. Airtight layer Airtight layer in a structural component (usually the building envelope) between different temperature levels to prevent air convection through and in the structural component. Prevents energy losses caused by warm interior air escaping out of the component and damage to the structural component from moisture due to the permeation of warm, moist interior air and condensation of moisture on cold surfaces. Airtight layers in interior structural components primarily have the function of preventing the transmission of airborne noise and obstructing smoke and fire. They are usually identical with the vapour seal / vapour barrier. Often made of airtight, composite wood-based boards that inhibit diffusion (OSB, 3-ply or parallel strand lumber) with joints between boards glued to make an airtight surface. Airtightness Buildings now have to be very airtight to prevent heat losses, damage due to moisture and sound transmission. A building’s airtightness should be tested during construction and /or renovation (with a blower door test and measures to locate leaks). A continuous airtight layer in the building envelope or between building sections will ensure airtightness. Anisotropy Directional dependency of certain physical properties. In timber construction, this usually refers to wood’s varying properties in parallel with its fibres and perpendicular to them. Annual heating requirement A measurement of the amount of heat in kilowatt-hours per square metre per year (kWh/m2a) required to maintain a pleasant interior temperature. It is based on a balance of the heat gains and losses occurring in a building. Battens Defined in DIN 4074-1 as sawn timber up to 40 mm thick and up to 80 mm wide; roof battens: 24/48, 30/50, 40/60 mm. Beam Horizontal linear element in a slab structure, usually in a layer of frame of beams or joists. Individual beams or joists or primary parts of a frame structure are referred to as beams. Block or log-cabin construction Wall structure made of horizontally layered, linear cross sections (often solid timber or squared timber, historically also logs) braced by corner joints. Blower door test Test that measures the airtightness of building envelopes and identifies leaks by creating positive and negative pressure in the building. An important tool in determining a building’s quality. Board Sawn lumber up to 40 mm thick and over 79 mm wide (DIN 4074-1). DIN 4070-1 specifies rough-sawn board thicknesses as 16, 18, 22, 24, 28 and 38 mm. Bottom diagonal brace Angled joining member installed by a carpenter between a bottom plate and a stud (see top diagonal brace) to stabilise a frame. A top diagonal brace sits up under a

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roof beam, while a bottom diagonal brace sits below on a bottom plate. The installation of top diagonal braces is more common than bottom diagonal braces. Bottom plate Horizontal member at the bottom of the framework of a timber frame, stud frame, framing or panel construction wall or a horizontally laid bottom support beam in a timber structure. Usually squared solid wood or glulam, sometimes also hardwood or parallel strand lumber for absorbing higher compressive loads (see also crosspiece, crosspiece compression).

Composite structure Structural component or structural element whose loadbearing capacity is based on the intrinsic interaction of various individual parts, e.g. a wooden slab structure with a top layer of concrete as the tensile and compressive zone of a composite timber-concrete slab or the ribs and planking of a box slab element.

Box beam Beam or girder with a square, hollow cross section consisting of a top flange, a bottom flange and two webs. They can be made of boards, panel materials or glulam.

Condensation Transition of material from a gaseous to a liquid state. In construction, condensation formation usually refers to a cooling of interior air in a structural component or on cool surfaces. Condensation forms when the temperature falls below the dew point, and it can cause damage to a structural component and hygiene problems (mould). Condensation usually results from leaks in the building envelope’s airtight layer or in and around thermal bridges.

Box slab / Box slab element Slab structures consisting of box slab elements. The elements are made of slender ribs that follow the slab’s main span direction. Combined with the edge beams to form a frame, they are joined to the planking, making them structurally effective. From a structural perspective, the individual components make up a composite element, a box.

Construction method / technique Generalisable construction principle for a building’s support structure (e.g. frame or crosswall construction), materials (e.g. timber or hybrid construction), degree of prefabrication and assembly (e.g. panel or module construction) or structural use of materials (e.g. lightweight or solid construction).

Building Information Modelling (BIM) Method of optimising construction work processes using a digital three-dimensional model of the building over its entire life cycle, from planning through to dismantling.

Convection The word “convection” generally refers to transport in a flow, in construction usually to the transport of heat and / or water vapour. Convection of interior air through a building envelope can result in considerable energy loss and produce large quantities of condensation in structural components. Water vapour convection can result in much larger amounts of condensation than water vapour diffusion causes.

CAD (Computer Aided Design) Computer-aided design and planning. CAM (Computer Aided Manufacturing) Computer-aided manufacturing. Carbon store Storage of carbon as a material. Timber products store carbon temporarily because a tree absorbs carbon dioxide (CO2) from the atmosphere as it grows and stores it as carbon (C) until the wood is burnt, when the carbon is released as CO2. Cellulose Cellulose is the main constituent of wood and, together with lignin and hemicellulose, forms the structural substance of cell walls and the raw material used for making paper. One frequent application for cellulose in timber construction is in cellulose insulation, which can be installed as blown-in insulation in the cavities of panel construction elements. It is an inexpensive and high quality ecological material. Chipboard / Particle board Board made of bonded wooden chips or particles. Bonding agents used include glue, synthetic resin or cement. Climate neutrality / Climate neutral Processes are described as “climate neutral” when no gases that impact the climate are released or the amount of gas emitted is conserved elsewhere in the process, i.e. emissions do not change the atmospheric balance of gases. This evaluation is based on emissions of climaterelevant gases, especially CO2 (measured in GWP 100). CNC (Computerised Numerical Control) Electronic process used to control tooling machines, which are able to automatically process complex parts with high precision. Industrial looms were the precursors of today’s CNC machines. CNC milling machines Tooling machines that use modern control technologies to automatically make parts, including complex forms, with great precision. Most milling machines can be fitted by means of tool changers with various milling machine tools, saw blades, drills and other special tools. Column In timber construction, often used as a synonym for a pillar or post.

Counter battens Battens installed perpendicular to the main support battens, making it possible to use horizontal battens to construct a continuous rear ventilation cavity. Cross laminated timber – CLT Planar structural elements made of an odd number of layers of boards up to 40 cm thick that are laid crosswise and glued together. Various manufacturers supply different formats. Crosspiece / Crosspiece compression Structural components exposed to loading perpendicular to the direction of their fibres. Wood’s load-bearing capacity is more than three times as strong in the direction of its fibres than perpendicular to its fibres. A crosspiece is unfavourable from a static and structural point of view in load-bearing structural components in taller buildings (three floors and higher) and should not be used, because subjecting wood to compressive forces perpendicular to its fibres causes it to subside, which can lead to problems with rigid structural components and sections (e.g. reinforced concrete staircases). Density Wood’s proportion of mass to volume (g/cm3 or kg/m3) at a specific temperature and humidity. Its density varies depending on the wood’s moisture content. Normal density is determined at 20 °C and 65 % humidity after storage, while “oven-dry” wood is absolutely dry (0 % wood moisture content). Dew point Short for “dew point temperature”. Condensation can form in structural components when the temperature falls below this point. The dew point temperature depends on the ambient air temperature and humidity. Diffusion Physical process of complete mixing of various substances until their particles are evenly distributed. In construction, diffusion usually refers to the material transport of water vapour through an exterior structural component when interior air is moist and outside air is dry in winter. Condensation can form in structural components that are not properly built, so the diffusion resistance of layers

of exterior structural components should decrease from the inside towards the exterior. Dowel laminated timber Material used to make structural components consisting of boards or beams (squared timber) that are stacked, nailed or doweled together (with hardwood dowels). Slabs made of horizontal dowel laminated timber elements are called glued dowel laminated timber slabs. Drying, artificial or technical Drying or curing in artificial climatic conditions, usually in a chamber kiln or flow channel. It can result in much lower final moisture levels and shorter drying times than natural or open-air drying. Drying, natural or open-air Drying or curing of wood without using artificially produced thermal energy or dehumidification, a gentle drying method carried out mainly in well-ventilated rooms or outside, protected from the weather. Usually used for pre-drying. Depending on the degree of drying required, it can take 6 months to 2 years. Elastic modulus (E modulus) The measure of a substance or object’s resistance to elastic deformation under mechanical stress or loading in its elastic deformation range. Encapsulation Fire protection panelling with a protection period specified in minutes (capsule criterion, e.g. K2 30 or K2 60). Encapsulation limits the temperature on the side not directly exposed to fire to T ≤ 300 °C for the period specified, thereby preventing wood from burning and adding to the fire load. Encapsulating panelling should also prevent fire from penetrating into structures made of panel construction elements with insulated or uninsulated cavities. End grain wood Wood with a cut surface perpendicular to the direction of its fibres. End grain wood absorbs moisture very well through capillary action, so it requires particular protection in structural components exposed to weathering. Compressive forces between structural components can be optimally transferred through joints in end grain wood surfaces without compression on crosspieces. Energy source, fossil Energy sources containing carbon, such as oil or brown coal, which formed in the Earth’s geological past. Energy source, renewable Renewable energy sources like wood are continuously renewed (e.g. from forestry) when the energy source is used sustainably, so they are permanently available. Exposed surface quality Refers to a structural element’s suitability for use in its exposed form in the finished structure. Facade, not rear-ventilated Exterior wall structure in which the facade surface is joined to the insulating layer with no gap, e.g. a composite thermal insulation system or sandwich element (DIN 68 800-2).

the insulating layer and facade surface. Condensation can run off from the rear ventilation cavity and an exchange of air occur through an opening at the bottom end of it. Finger joint Longitudinal joint between two solid wood or wood-based material structural components, a further development of the scarf joints used to join boards and beams since prehistoric times. A finger joint is usually also glued. Its tensile strength derives from the increased surface of the glued joint, which slopes slightly in the same direction as the wood’s fibres. Finger-jointed structural components have relatively high flexural or bending strength. When they are made in optimum production and quality assurance conditions, they can achieve almost the load-bearing capacity of structural components made of solid timber grown naturally in one piece. Fire resistance Stipulated period during which a structural component so designated retains its load-bearing (R) and /or spaceenclosing (E) and/or insulating (I) functions in the event of fire. Fire-resistant seal / Fire stop Prevents the uncontrolled spread of fire (e.g. in shafts, rear ventilation cavities). Floor boards Boards at least 21 – 50 mm thick and relatively wide (from 80 mm). DIN EN 13 629 defines floor boards less than 40 mm thick as boards and thicker ones as planks. Footfall or Impact sound Airborne sound caused by structure-borne impact sound in an adjoining space, e.g. when a slab vibrates because of someone walking or jumping on it. Formaldehyde Formaldehyde (systematic chemical name: methanal) is a gaseous substance at room temperature. Its low boiling point (-19 °C) means that it belongs by definition not to the group of VOCs, but to the group of V VOCs (very volatile organic compounds, which vaporise at a boiling point < 0 to 50 … 100 °C). Formaldehyde has been used to make and process industrial products for almost 150 years. In 2016 the EU classified it as carcinogenic in animal experiments (1B). Frame construction Construction method in which loads are supported by a load-bearing structure, a frame consisting of columns and beams. The building envelope and inner panelling is independent of the load-bearing structure. They can be either made on the building site or be prefabricated, nonload-bearing wall elements. Framework Structure made of linear structural elements, e.g. stud walls, frame structure, spatial frameworks and panel construction wall structures made of linear members (studs, bottom plate, top plate), box slab or box slab elements. Girder Linear, horizontal element laid on supports erected at various points that transfers vertical loads to columns or walls.

Heartwood The inner core of a tree trunk that is surrounded by concentric rings of sapwood, often distinguished by its darker colour. Unlike sapwood, it does not transport water or nutrients. Hollow box Slab structure consisting of ribs and structurally effective planking (see box slab). Hybrid building Structures made of different construction materials can be combined in a single building, such as a reinforced concrete access core (for emergency exits, building bracing) integrated into a timber building or a timber element facade on a reinforced concrete frame structure. Hybrid construction method / technique Hybrid structural components or elements made of different materials can be systematically used in a single structure, e.g. steel beams in cross laminated timber slab elements. Hybrid structural component Various materials are combined to make some horizontal or vertical structural components. The best-known example is the composite timber-concrete slab. Indoor climate A term referring to all the conditions in a space that can impact the well-being and performance of its users. These conditions are influenced by air temperature, humidity and airspeeds, the content of contaminants in the air, the temperatures of the room’s surfaces and its lighting situation. Inhomogeneity The inhomogeneity of wood refers to the irregularity of its mechanical, structural and physical properties due to factors such as knotholes, resin pockets, uneven fibre orientation and varying densities and strength. One of the goals in sorting solid wood and manufactured woodbased materials into types such as solid structural timber, dowel laminated timber elements, layered and veneered, fibre and chip and shaving materials is to ensure that the resulting timber product will be homogeneous. Intumescent products Intumescent products foam up to close off any openings when they are subjected to heat loads, thereby preventing smoke and toxic gases (fire safety) from passing through them. Laminated veneer lumber – LVL Wood-based material made of several compounded layers of veneers. The veneers are laid in layers with their fibres crossing at 90° angles and usually glued together with phenol-formaldehyde resin to form a water-resistant bond. Leaks Airtight layers may leak (usually through joints between structural components or ducts and breaches made to install fittings etc.) despite having good measured airtightness values, resulting in damage to exterior structural components. A blower door test should always include measures to locate leaks. This test uses a positive and negative pressure differential in the building to enable builders to find and repair any leaks.

Facade, rear-ventilated Exterior wall structure in which there is an uninterrupted vertical rear ventilation cavity with an appropriate cross section (usually 2 cm; see DIN 68 800-2) between the insulating layer and facade surface, through which large amounts of air flow through openings with a suitable cross section (usually at least 50 % of the rear ventilation cavity) in the top and bottom ends due to the chimney effect.

Glued laminated timber / Glulam Linear cross sections made of glued boards (layers or veneers) laid in the same direction, normally 40 mm thick up to 30 cm wide, height of the cross section not glued is approx. 200 cm, and boards can be up to 65 metres long depending on the manufacturer. The maximum radius of curved glulam beams depends on the thickness of their layers.

Life-cycle assessment – LCA A life-cycle assessment is an established method for quantifying the environmental effects of a product or building. It makes it possible to compare the environmental effects of various products and environmental parameters of different types of buildings. The information it yields is key in highlighting timber’s positive effects on the climate and it can be crucial to take it into account in making decisions.

Facade, ventilated Exterior wall structure in which there is an uninterrupted vertical rear ventilation cavity with an appropriate cross section (usually 2 cm; see DIN 68 800-2) between

Grey energy Energy used in the manufacture, storage, transport, installation and disposal of materials, structural components and buildings.

Lightweight construction Structures built using materials and components with a low volume or own weight or a widely spaced support structure (e.g. timber or steel frame).

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Lignin The structural substance of wood that, with cellulose and other constituents, forms the cell walls in wood. The breakdown of lignin by UV radiation turns wood brown.

Plank Sawn timber over 40 mm thick and at least three times as wide as it is thick (DIN 4074-1). DIN 4070-1 specifies rough-sawn plank thicknesses of 44, 48, 50, 63, 70 and 75 mm.

Mass able to store energy Alternative term for areic effective thermal capacity (as defined in E DIN EN ISO 13 786:2015-06). It describes a structural component’s ability to absorb and release thermal energy as temperature fluctuates over a 24-hour cycle. This is especially relevant for thermal insulation in summer, when it can be used to reduce or prevent overheating.

Planking Planar panelling on a substructure, sometimes with a load-bearing or bracing function, e.g. panelling or planking on the ribs of a panel construction wall.

MDF board Medium density fibreboard is made using a dry process and with the addition of a synthetic bonding agent.

Post Vertical elements running from the top plate to the bottom plate in a stud frame wall, frame wall or panel construction wall. Mostly used as squared timber made of solid wood, laminated veneer lumber, glued laminated lumber or as Å-beams to minimise thermal bridges in highly thermally insulated constructions.

Natural durability Resistance or natural resilience to pests that can damage wood. DIN EN 350-2 categorises wood’s resistance to destructive fungi in the following resistance classes: 1 = very durable, 2 = durable, 3 = fairly durable, 4 = not very durable, 5 = not durable and classifies its resistance to insects as D = durable, S = susceptible, SH = heartwood also susceptible.

Plus-energy house, Plus-energy standard Buildings that produce more energy annually than is required to operate the building.

Pressure impregnation Method of pressing a preservative impregnating agent into wood in a vessel under high pressure to impregnate sapwood as evenly and deeply as possible.

Oriented strand board – OSB Structured board made of oriented, long, thin wood shavings (strands) usually with good load-bearing ability, available in different thicknesses and variations (impregnated, with bevelled or tongue-and-groove edges). Originally made of by-product from the veneer and plywood industries.

Primary energy Energy content of a primary energy source, e.g. energy content of the oil in the Earth. The energy ultimately available for use (e.g. as heating oil in the tank of a building to be heated) is calculated by subtracting all the energy required for supplying it (extraction, transport and processing).

Panel construction Panel construction is a further development of a North American post construction method consisting of a loadbearing structure made of linear members (stud frame) and bracing planking on one or both sides. Panel construction elements are now largely prefabricated. This book mainly uses the term “panel construction” instead of the other often-used term “frame construction” (in keeping with DIN 1995-1-1).

Primary energy requirement A building’s primary energy requirement is a figure calculated from a building’s final energy requirements and the primary energy factor, which will be different depending on the type of fuel/energy source (wood pellets = 0.2; gas = 1.3).

Panel load-bearing capacity Loading or stress imposed on a planar structural component perpendicular to its plane. Panelling and cladding Planar structures made of boards for cladding, panelling or planking timber structures. Parallel strand lumber – PSL Wood-based material made of several layers of veneers bonded together. In contrast to laminated veneer lumber, the veneers’ fibres are usually layered in parallel and glued with water-resistant phenol-formaldehyde resin. Passive house, Passive house standard Energy standard for buildings that can produce a comfortable indoor climate without a separate heating and air conditioning system. Annual heating requirement according to the PHPP (Passive House Planning Package) is max. 15 kWh/m2a; annual primary energy requirement (heating, hot water, household electricity) is max. 120 kWh/m2a. Demands on the building envelope: opaque exterior structural component with U  2 to 1,500 m) and vapour seals (sd > 1,500 m). Solid structural timber Finished timber that meets high demands in terms of its moisture content (15 % ± 3 %), cut type (free of heartwood or with heartwood separate) and surface finish (planed, bevelled). Solid structural timber can be finger-jointed (major inhomogeneities are eliminated) to make longer lengths available. Solid timber construction Block or log cabin type construction or dowel laminated timber element structures made of large-format panel materials such as cross laminated timber or glulam etc. Solid timber Wood with its structure unchanged as it has grown, in contrast to wood-based materials, which are made by reducing wood to small pieces that are bonded together. Squared timber Lumber with a cross section at least 40 mm wide (b) and a height (h) of b ≥ h ≥ 3 b (DIN 4074-1). Squared timber stock measures 60/60 mm to 160/180 mm. Structural component Static-structural, geometrically self-contained part of a building, e.g. exterior and interior walls, floor and ceiling slabs, floor slab and roof. Structural components can be single pieces or made up of prefabricated structural elements. Structural element Prefabricated component of a structural element, e.g. prefabricated panel construction element as part of an exterior wall, prefabricated dowel laminated timber slab or panel element as part of floor or ceiling slab etc. Structure-borne sound Sound created by the stimulation or excitation of solid bodies, partly emitted as airborne sound. Studs Vertical elements running from the top plate to the bottom plate in the stud frame of timber framing, framework or panel construction wall. Usually made of squared solid wood, parallel strand lumber, glulam or web beams and used to minimise thermal bridges in highly insulated structures. Support Linear, vertical, load-bearing structural component, e.g. a vertical element in a frame structure or support for a beam. Swelling and Shrinking Wood is hygroscopic; it swells when it absorbs moisture and shrinks when it releases it, so its dimensions and form change. These changes are much greater perpendicular to the direction of its fibres than they are longitudinal to the direction of its fibres. Extensive swelling and shrinking can result in gaps, cracks, warps or bulges. Swelling / Shrinkage values Figures measuring the changes in wood’s length or volume, caused by swelling or shrinking. These are expressed as percentages that describe the wood’s

reaction when it is in a dry state (and swells) or in a wet state (and shrinks). Swelling and shrinkage values are specified for the material’s three main cutting directions. Changes to length or in the direction of wood’s fibres are slight, while changes in the radial direction, in the direction of the wood’s rays, are 10 to 20 times greater and in the tangential direction 15 to 30 times greater. Wood swells to its maximum only when its fibres are completely saturated. Thermal comfort Thermal comfort is a result of the interior air temperature, the temperatures of surfaces enclosing spaces, the transmission of heat by floor surfaces, airspeed and relative humidity of interior air. Individual users’ perception of comfort also depends on their activity, clothing, age, state of health and habits. Thermal energy storage capacity The amount of energy that a building material can store in a specific period. Wood has significant thermal energy storage capacity because of its good ratio of thermal conductivity to density. Thermal lift The different density of warm and cold air causes differences in pressure. In winter, this leads to growing internal pressure being exerted on a building envelope as the building’s height increases. This increases the risk of interior air penetrating the structure (e.g. around ceiling joints or windows) and causing condensation to form inside structural components. Timber frame preparation, assembly and joinery Processing of timber in the preparation and prefabrication of timber structural elements, normally in a factory, e.g. cutting to size, creation of joints, folding and grooving, production of frames for panel construction elements. Timber framing A further development of the medieval half-timbered construction, with structures no longer braced by means of diagonal stays or top or bottom diagonal braces but by planking on a framework. Studs, the vertical, load-bearing elements in a framework, have a square, slender cross section. Timber framing construction Reimport and further development of North American frame construction in Central Europe. Timber framing construction resembles panel construction, but there is a conceptual distinction to avoid it being associated with the prefabricated housing industry. This book uses the term "panel construction" almost exclusively. Timber preservation, chemical Treating wood with biocides can help to prevent it being destroyed by fungus or insects. Use of these chemicals is regulated in the relevant standards (e.g. DIN 68 800-3). Chemical preservatives should be as sparingly used as possible because disposing of such chemically treated timber can be costly, complex and detrimental to the environment. Timber preservation, physical The durability of wood and wood-based materials can be improved by means of thermal treatment, for example.

structural component (post, column, stud) at the top of each storey (e.g. in a stud wall). See also bottom diagonal brace. Top plate Top horizontal member in a timber frame or panel construction wall. It has the function of horizontally bracing the structure, transferring horizontal shear forces through the stays and vertical forces through the uprights /studs into the bottom plate or foundations. A top plate also supports the framework of joists and beams (as a support for rafters, it is also called a roof beam or purlin). Total energy balance A measurement of the amount of energy required for constructing, using and then dismantling a building. Total volatile organic compounds – TVOCs The total of all the VOCs measured in interior air. Trimmer beam or joist Linear elements for deflecting loads in the frameworks of beam, ribbed and box ceilings, in frame construction and panel construction walls, and in roof structures. Tube-in-tube system Building support structure that consists of two concentric layers of a load-bearing or bracing walls joined by structural slabs. U value The thermal transmission coefficient (U value) describes the flow of heat through 1 m2 of a structural component that occurs at a temperature difference of 1° Kelvin. The physical unit is W/m2K. Vapour barrier (somewhat permeable) Layer in a structural component (usually building envelope) between different temperature levels with a high sd value (> 2 m up to 1,500 m) to reduce water vapour diffusion through the component. Installed on the room side of thermal insulation to protect against damaging condensation in structural components and against moisture penetrating into thermal insulation and causing structural damage. Often made of airtight, diffusion-resistant wood-based material boards (OSB, 3-ply board or LVL) with joints between panels glued to make them airtight. The vapour barrier usually also serves as an airtight layer. Vapour barrier, moisture-adaptive The vapour barrier’s diffusion resistance varies depending on the ambient humidity and material. In a dry ambient atmosphere (an interior in winter), it will have a higher sd value (up to sd = 10 m). When humidity levels are higher (e.g. in summer), its diffusion resistance will fall (to sd = 0.2 m).

The bottom flange absorbs tensile forces and the top flange absorbs compressive forces resulting from the beam’s bending moment, while the web is mainly subjected to shear forces. Weathering Lignin is broken down by moisture and exposure to UV radiation. This changes wood’s colour but does not destroy its substance. Moisture can turn a naturally aged timber facade grey or black, while it will darken to brown or black in strong sun and a dry climate. Windproofing A permeable layer that is tightly glued on or applied, e.g. synthetic fleece, soft fibreboard panel or plaster on the cold side of thermal insulation, that prevents outside air from permeating the insulation, cooling and causing heat loss. Windproofing also augments the effect of an airtight layer by preventing excessive negative or positive pressure in the insulating layer, which can result in convection between interior air and the insulating layer. Windproof layers are often built as a second water-bearing layer. Wood-based materials Materials that are produced by reducing wood to small pieces and bonding it to form structured elements, usually through gluing or pressing. Wood fibreboard Planar wood-based material made of pressed, compacted wood fibres of varying thicknesses and strengths. MDF board (medium density fibreboard) is the most commonly used soft fibre or hard fibreboard. Wood’s moisture content Proportion of water in wood in relation to dry mass, expressed as a percentage. Wood is hygroscopic and reacts to fluctuations in humidity. Depending on the wood’s thickness, it can take some time to reach a balanced state (sorption equilibrium). Wood should be dried before processing, to give it levels of moisture that approximate the levels in its subsequent surroundings so that only periodic fluctuations in climate will affect the wood, and any changes in form due to swelling and shrinking will be kept to a minimum. Wood with a moisture content of more than 20 % is at risk of fungal infestation, so it must be protected from becoming too moist, mainly by implementing structural measures. Typical wood moisture content levels: newly harvested wood approx. 60 %, timber stored outside 15 –18 %, exterior cladding protected from the weather 15 – 20 %, exterior cladding not protected from the weather 18 – 24 %, unheated interiors 10 –12 %, heated interiors 6 – 8 %.

Vapour seal (not at all permeable) Layer in a structural component (usually an external structural component) between different temperature levels with a very high sd value (>1,500 m) to reduce vapour diffusion through the component. Installed on the room side of thermal insulation to protect against destructive condensation in components and against moisture from penetrating insulation and causing structural damage. Usually bitumen sheeting with a layer of aluminium. It also serves as an airtight layer.

Timber preservation, structural Structural and geometric measures to keep wood and wood-based materials dry (e.g. covering wood with suitable panelling, protecting it from the weather with a roof overhang, keeping it away from areas exposed to splashing water, mechanically separating it from moisture that could reach it through capillary action by installing separating layers etc.). Examples of such structures are listed in the standard on structural timber preservation measures for buildings (DIN 68 800-2).

Volatile organic compounds – VOCs Volatile organic compounds is the collective term for organic substances containing carbon that vaporise easily and so are volatile, meaning that they become gaseous at low temperatures, e.g. room temperature.

Top diagonal brace Bracing diagonal element in a framework between a horizontal (roof beam, top plate, beam) and a vertical

Web beam Beam usually with an Å-shaped cross section. Its geometry is divided into a top flange, bottom flange and web.

Water vapour diffusion resistance μ Resistance of a building material to penetration by water vapour in relation to the diffusion resistance of motionless air (μ = 1).

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DIN standards The EU has passed directives on a number of products to ensure the safety and health of their users. These directives must be incorporated into binding laws and statutory regulations in member states. The directives themselves do not contain any technical details, only fundamental binding specifications. The relevant technical values are specified in related technical rules and in harmonised European standards (EN standards). Technical rules provide practical guidance and auxiliary tools for everyday work. They are not legal regulations but offer help in making decisions, form guidelines for correct technical procedure and /or render the contents of directives concrete. Anyone can apply technical rules in their work. They only become legally binding (e.g. in building law) when they are incorporated into laws, statutory regulations or codes or when the binding character of specific standards between the parties is stipulated in a contract. Technical rules include DIN standards, VDI directives and works referred to as codes of practice (e.g. Technical Rules for Hazardous Substances – TRGS). Standards are divided into in product, application and testing standards and often deal only with a specific group of materials or products. Standards are based on appropriate methods for testing and researching individual materials. The newest version of a standard, which should reflect the technological state-of-the-art, is always the applicable one. A new or revised standard is made available for public discussion in the form of a draft standard before being adopted as standard. A standard’s title reveals its origins and scope. DIN plus a number (e.g. DIN 4108) is a standard of mainly national significance (drafts are prefixed with an E and pre-standards with a V). DIN EN plus a number (e.g. DIN EN 335) identifies the German edition of a European standard that has been adopted unchanged from the European standards organisation CEN. DIN EN ISO (e.g. DIN EN ISO 13 786) designates a national, European and worldwide scope. A European standard is drafted based on an ISO (international standards organisation standard) and then adopted as a DIN standard. DIN ISO (e.g. DIN ISO 2424) indicates the adoption of an ISO standard unchanged as a national standard. The following list is a selection of standards representing the state of the art (May 2017). Only standards specifications sheets with the latest date of issue from DIN (the German Institute for Standardisation) are binding. Voluntary agreements on strict compliance with standards that are not required in building law and additional features and requirements must be agreed on individual contracts. Statements made in contracts that all standards must be complied with are meaningless and can no longer be made in future contracts. To avoid inconsistencies, parties must definitively stipulate which standards must be complied with and which details of standards should apply in each requirements category. DIN 4074-1:2012-06 Strength grading of wood – Part 1: Coniferous sawn timber DIN 4074-5:2008-12 Strength grading of wood – Part 5: Sawn hard wood DIN 4102-1:1998-05 Fire behaviour of building materials and building components – Part 1: Building materials; concepts, requirements and tests DIN 4102-4:2016-05 Fire behaviour of building materials and building components – Part 4: Synopsis and application of classified building materials, components and special components DIN 4108 Supplement 2:2006-03 Thermal insulation and energy economy in buildings – Thermal bridges – Examples for planning and performance DIN 4108-2:2013-02 Thermal protection and energy economy in buildings – Part 2: Minimum requirements to thermal insulation DIN 4108-3:2014-11 Thermal protection and energy economy in buildings – Part 3: Protection against moisture subject to climate conditions – Requirements and directions for design and construction

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DIN 4108-7:2011-01 Thermal insulation and energy economy in buildings – Part 7: Air tightness of buildings – Requirements, recommendations and examples for planning and performance DIN 4109 Beiblatt 2:1989-11 Sound insulation in buildings; guidelines for planning and execution; proposals for increased sound insulation; recommendations for sound insulation in personal living and working areas DIN 4109-1:2016-07 Sound insulation in buildings – Part 1: Minimum requirements DIN 20000-1:2013-08 Application of construction products in structures – Part 1: Wood based panels DIN 20000-7:2015-08 Application of construction products in structures – Part 7: Structural finger jointed solid timber according to DIN EN 15497 DIN 68800-1:2011-10 Wood preservation – Part 1: General DIN 68800-2:2012-02 Wood preservation – Part 2: Preventive constructional measures in buildings DIN 68800-3:2012-02 Wood preservation – Part 3: Preventive protection of wood with wood preservatives DIN 68800-4:2012-02 Wood preservation – Part 4: Curative treatment of wood destroying fungi and insects and refurbishment DIN EN 300:2006-09 Oriented Strand Boards (OSB) – Definitions, classification and specifications; German version EN 300:2006 DIN EN 301:2013-12 Adhesives, phenolic and aminoplastic, for load-bearing timber structures – Classification and performance requirements; German version EN 301:2013 DIN EN 312:2010-12 Particleboards – Specifications; German version EN 312:2010 DIN EN 316:2009-07 Wood fibreboards – Definition, classification and symbols; German version EN 316:2009 DIN EN 338:2016-07 Structural timber – Strength classes; German version EN 338:2016 DIN EN 350:2016-12 Durability of wood and wood-based products – Testing and classification of the durability to biological agents of wood and wood-based materials; German version EN 350:2016 DIN EN 622-4:2010-03 Fibreboards – Specifications – Part 4: Requirements for softboards; German version EN 622-4:2009 DIN EN 622-5:2010-03 Fibreboards – Specifications – Part 5: Requirements for dry process boards (MDF); German version EN 622-5:2009 DIN EN 634-1:1995-04 Cement-bonded particleboards – Specifications – Part 1: General requirements; German version EN 634-1:1995 DIN EN 634-2:2007-05 Cement-bonded particleboards – Specifications – Part 2: Requirements for OPC bonded particleboards for use in dry, humid and external conditions; German version EN 634-2:2007 DIN EN 635-2:1995-08 Plywood – Classification by surface appearance – Part 2: Hardwood; German version EN 635-2:1995 DIN EN 635-3:1995-08 Plywood – Classification by surface appearance – Part 3: Softwood; German version EN 635-3:1995 DIN EN 636:2015-05 Plywood – Specifications; German version EN 636:2012 + A1:2015 DIN EN 975-1:2011-08 Sawn timber – Appearance grading of hardwoods – Part 1: Oak and beech; German version EN 975-1:2009 + AC:2010 DIN EN 1611-1:2002-11 Sawn timber – Appearance grading of softwoods – Part 1: European spruces, firs, pines, Douglas firs and larches (including amendment 1:2002); German version EN 1611-1:1999 + A1:2002 DIN EN 1912:2013-10 Structural timber – Strength classes – Assignment of visual grades and species; German version EN 1912:2012 + AC:2013 DIN EN 1991-1-1:2010-12 Eurocode 1: Actions on structures – Part 1-1: General actions – Densities, self-weight, imposed loads for buildings; German version EN 1991-1-1:2002 + AC:2009

DIN EN 1991-1-1/NA:2010-12 National Annex – Nationally determined parameters – Eurocode 1: Actions on structures – Part 1-1: General actions – Densities, self-weight, imposed loads for buildings DIN EN 1995-1-1:2010-12 Eurocode 5: Design of timber structures – Part 1-1: General – Common rules and rules for buildings; German version EN 1995-1-1:2004 + AC:2006 + A1:2008 DIN EN 1995-1-2:2010-12 Eurocode 5: Design of timber structures – Part 1-2: General – Structural fire design; German version EN 1995-1-2:2004 + AC:200 DIN EN 1995-1-2/NA:2010-12 National Annex – Nationally determined parameters – Eurocode 5: Design of timber structures – Part 1-2: General – Structural fire design DIN EN 12 369-1:2001-04 Wood-based panels – Characteristic values for structural design – Part 1: OSB, particleboards and fibreboards; German version EN 12 369-1:2001 DIN EN 13 168:2015-04 Thermal insulation products for buildings – Factory made wood wool (WW) products – Specification; German version EN 13 168:2012 + A1:2015 DIN EN 13 171:2015-04 Thermal insulation products for buildings – Factory made wood fibre (WF) products – Specification; German version EN 13 171:2012 + A1:2015 DIN EN 13 353:2011-07 Solid wood panels (SWP) – Requirements; German version EN 13 353:2008 + A1:2011 DIN EN 13 501-1:2010-01 Fire classification of construction products and building elements – Part 1: Classification using data from reaction to fire tests; German version EN 13 501-1:2007 + A1:2009 DIN EN 13 501-2:2016-12 Fire classification of construction products and building elements – Part 2: Classification using data from fire resistance tests, excluding ventilation services; German version EN 13 501-2:2016 DIN EN 13 986:2015-06 Wood-based panels for use in construction – Characteristics, evaluation of conformity and marking; German version EN 13 986:2004 + A1:2015 DIN EN 14 080:2013-09 Timber structures – Glued laminated timber and glued solid timber – Requirements; German version EN 14 080:2013 DIN EN 14 081-1:2016-06 Timber structures – Strength graded structural timber with rectangular cross section – Part 1: General requirements; German version EN 14 081-1:2016 DIN EN 14 279:2009-07 Laminated Veneer Lumber (LVL) – Definitions, classification and specifications; German version EN 14 279:2004 + A1:2009 DIN EN 14 374:2016-07-Draft Timber structures – Laminated veneer lumber (LVL) – Requirements; German and English version EN 14 374:2016 DIN EN 15 026:2007-07 Hygrothermal performance of building components and building elements – Assessment of moisture transfer by numerical simulation; German version EN 15 026:2007 DIN EN 15 251:2012-12 Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics; German version EN 15 251:2007 DIN EN 15 283-1:2009-12 Gypsum boards with fibrous reinforcement – Definitions, requirements and test methods – Part 1: Gypsum boards with mat reinforcement; German version EN 15 283-1:2008 + A1:2009 DIN EN 15 425:2017-05 Adhesives – One component polyurethane (PUR) for load-bearing timber structures – Classification and performance requirements; German version EN 15 425:2017 DIN EN 15 497:2014-07 Structural finger jointed solid timber – Performance requirements and minimum production requirements; German version EN 15 497:2014 DIN EN 15 804:2014-07 Sustainability of construction works – Environmental product declarations – Core rules for the product category of construction products; German version EN 15 804:2012 + A1:2013

DIN EN 15 978:2012-10 Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method; German version EN 15 978:2011 DIN EN 16 449:2014-06 Wood and wood-based products – Calculation of the biogenic carbon content of wood and conversion to carbon dioxide; German version EN 16 449:2014 DIN EN ISO 717-2:2013-06 Acoustics – Rating of sound insulation in buildings and of building elements – Part 2: Impact sound insulation (ISO 717-2:2013); German version EN ISO 717-2:2013 DIN EN ISO 10 456:2010-05 Building materials and products – Hygrothermal properties – Tabulated design values and procedures for determining declared and design thermal values (ISO 10 456:2007 + Cor. 1:2009); German version EN ISO 10 456:2007 + AC:2009 DIN EN ISO 14 044:2006-10 Environmental management – Life cycle assessment – Requirements and guidelines (ISO 14 044:2006); German and English version EN ISO 14 044:2006 SIA 102:2014-11; SN 50 8102:2014-11: Regulations governing architects’ services and fees SIA 112:2014; SN 50 9112:2014 Model construction planning – Agreed standards SIA 265:2012 Timber Structures

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Rahm, Peter: Die Vorfabrikation mit Bauelementen – ein verkanntes Potenzial. In: Die Baustellen 10/2015, p. 32– 36 Rosenberger, Michael; Weigl, Norbert (pub.): Über Nutzen und Würde von Wald und Holz. Überlegungen zur Verantwortung im Umgang mit einer zentralen Lebensgrundlage. Munich 2014 Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-Basisdaten für Bauprodukte aus Holz. Arbeitsbericht aus dem Institut für Holztechnologie, No. 01/2012; pub. by Johann Heinrich of the Thünen-Institute. Hamburg 2012 Rüter, Sebastian: Projection of Net-Emissions from Harvested Wood Products in European Countries – For the period 2013 – 2020. Arbeitsbericht aus dem Institut für Holztechnologie und Holzbiologie No. 2015/1, Johann Heinrich of the Thünen-Institute. Hamburg 2015 Salthammer, Tunga; Marutzky, Rainer: Bauen und Leben mit Holz, Informationsdienst Holz – spezial, March 2013 Sathre, Roger; O’Connor, Jennifer: Meta-analysis of greenhouse gas displacement factors of wood product substitution. In: Environmental Science & Policy 13, 2010, p. 104 –114 Schankula, Arthur: Vorgefertigtes Bauen mit Holz. In: Detail 06/2012, p. 662– 669 Scheer, Claus; Andresen, Kurt: Holzbau-Taschenbuch, vol. 1, Grundlagen, Entwurf, Bemessung und Konstruktionen. Berlin 1995 Scheer, Claus; Peter, Mandy: Holz Brandschutz Handbuch. Published by Informationsdienst Holz together with the Deutsche Gesellschaft für Holzforschung e. V. Berlin 2009 Schindler, Christoph: Ein architektonisches Periodisierungsmodell anhand fertigungstechnischer Kriterien dargestellt am Holzbau. Dissertation. ETH Zurich, 2009 Schittich, Christian: Vorfertigung – High-Tech und Handarbeit. In: Detail 06/2012, p. 588 – 593 Schmidt, Hans: Vom neuen Bauen: Industrialisierung des Bauens: aus der Wegleitung des Kunstgewerbemuseums der Stadt Zurich. In: Das Werk: Architektur und Kunst = L'oeuvre : architecture et art, 15th volume, 1928, p. 34–37. Accessible online at: www.e-periodica. ch/cntmng?pid=wbw-002:1928:15::808 Schulze, Dieter: Wohnbauten in Fertigteilbauweise (Baujahre 1958 –1990). Stuttgart 1995 Staib, Gerald, Dörrhöfer, Andreas, Rosenthal, Markus: Elemente + Systeme modulares Bauen: Entwurf, Konstruktion, neue Technologien. Munich 2008 Steiger, Ludwig: Basics Holzbau. Revised and updated new edition. Basel 2013 Stein, René et al.: Konstruktionskatalog Fassadenelemente für Hybridbauweisen. Technical University of Munich, 2016 (unpublished) Steurer, Anton: Entwicklung im Ingenieurholzbau. Der Schweizer Beitrag. Basel 2006 Studiengemeinschaft Holzleimbau e. V. (pub.); Mestek, Peter; Werther, Norman; Winter, Stefan: Bauen mit Brettsperrholz. Informationsdienst Holz. Holzbau Handbuch. Reihe 4, Teil 6, Series 1. April 2010 Technical University of Munich, Chair of timber construction and structural design; Winter, Stefan; Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln / -details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse. 4 August 2014 Teibinger, Martin; Dolezal, Franz; Matzinger, Irmgard; Holzforschung Austria (pub.): Deckenkonstruktionen für den mehrgeschossigen Holzbau. Vienna 2014 Teibinger, Martin; Matzinger Irmgard; Holzforschung Austria (pub.): Bauen mit Brettsperrholz im Geschoßbau – Fokus Bauphysik. Vienna 2013 Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz; Holzforschung Austria (pub.): Bauen mit Brettsperrholz im Geschoßbau – Fokus Bauphysik. Planning brochure. 2nd revised edition. Vienna 2014 Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz; Holzforschung Austria (pub.): Holzrahmenbauweise im Geschossbau – Fokus Bauphysik. Planning brochure. Vienna 2014

The European Cement Association: CEMBUREAU, Cement & Concrete: Key facts & figures 2014 The International Aluminium Institute: Historical Aluminium Inventories (1973 – 2014). London 2014 Federal Environment Agency (pub.): Berichterstattung unter der Klimarahmenkonvention der Vereinten Nationen und dem Kyoto-Protokoll 2012 – Nationaler Inventarbericht zum Deutschen Treibhausgasinventar 1990 – 2010. 08/2012 Verband Holzfaser Dämmstoffe e. V. (pub.) Förster, F.; Mosch, M.; Wiegand, T.: Holzfaserdämmstoffe, Eigenschaften – Anforderungen – Anwendungen. Informationsdienst Holz. Holzbau Handbuch. Reihe 4 Baustoffe, Teil 5 Dämmstoffe, Series 2. December 2007 Wehrmann, Wiebke; Torno, Stefan: Laubholz für tragende Konstruktionen. Zusammenstellung zum Stand von Forschung und Entwicklung. Cluster-Initiative Forst und Holz in Bayern GmbH (pub.). Freising 2015 Westphal, Tim; Hermann, Eva Maria: BIM Building Information Modeling I Management – Methoden und Strategien für den Planungsprozess. Beispiele aus der Praxis. Munich 2015 Winter, Stefan; Merk, Michael: Verbundforschungsprojekte Holzbau der Zukunft – Teilprojekt TP 02 – Brandsicherheit im mehrgeschossigen Holzbau. Technical University of Munich, Chair of timber construction and structural design. Munich 2009 Winter, Wolfgang: Wiederentdeckung des Holzbaues im urbanen Kontext – das Beispiel Wien. In: Standards der Zukunft. Wohnbau neu gedacht. pub. by Roland Burgard. Vienna 2008, p. 86 –103

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Image credits The authors and publisher would like to sincerely thank everyone who contributed to this book's production by providing images, granting permission to reproduce their work, and supplying other information. All the diagrams in this book were created especially for it. The authors and their staff created those graphics and tables for which no other source is credited. Photos for which no photographer is credited are architectural or work photos or come from the archive of DETAIL magazine. Despite intensive efforts, we have been unable to identify the copyright holders of some images, but their entitlement to claim copyright remains unaffected. In these cases, we would ask you to contact us. Figures refer to illustration numbers.

Preface

Gataric Fotografie

Part A

Life-cycle assessment A 4.1 sps÷architekten, Thalgau A 4.2 From: Kaufmann, Hermann; Nerdinger, Winfried (pub.): Bauen mit Holz – Wege in die Zukunft. Munich, London, New York 2016, p. 52 A 4.3 Hafner, Annette, Schäfer, Sabrina: Methodenentwicklung zur Beschreibung von Zielwerten zum Primärenergieaufwand und CO2-Äquivalent von Baukonstruktionen zur Verknüpfung mit Grundstücksvergaben und Qualitätssicherung bis zur Entwurfsplanung. Deutsche Bundesstiftung Umwelt, Aktenzeichen 31943/01 A 4.4 Annette Hafner A 4.5 From: Kaufmann, Hermann; Nerdinger, Winfried (pub.): Bauen mit Holz – Wege in die Zukunft. Munich, London, New York 2016, p. 47 A 4.6 Stefan Müller-Naumann

B 1.18

B 1.20 a

Structural components and elements B 2.1, 2.2 Matthias Kestel B 2.8 STEICO SE B 2.16 proHolz Polaris B 2.22 Finnforrest B 2.27 Bernd Borchardt B 2.31, 2.37 Mathias Kestel B 2.42 Ökoberatung G. Bertsch B 2.49 Binderholz GmbH B 2.53 Peter Cheret B 2.57 Architekten Hermann Kaufmann

Part C C

A

Christian Schittich

The development of multi-storey timber construction A 1.1 From: Weston, Richard: Utzon – Inspiration, Vision, Architektur. Kiel 2001, p. 48 A 1.2 HGPhotography A 1.3 mykyotomachia.com A 1.4 Sergio Somavilla A 1.5 Bernard Gagnon A 1.6 Neckar-Magazin, Esslingen / Neckar A 1.7 Peter Bonfig A 1.8 Bernd Borchardt A 1.9 Roland Pawlitschko A 1.10 TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann A 1.11 Waugh-Thistleton Architects A 1.12 Artec Arkitekter A 1.13 RLP Rüdiger Lainer + Partner Wood as a resource A 2.1 Friedrich Böhringer A 2.2 Tourist Information Einbeck A 2.3 Munich Stadtmuseum, Graphics / Paintings collection A 2.4, 2.5 Gerd Wegener / Ralf Rosin, Holzforschung München A 2.6 TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann A 2.7, 2.8 Ralf Rosin, Holzforschung Munich A 2.9 From: Kaufmann, Hermann; Nerdinger, Winfried (pub.): Bauen mit Holz – Wege in die Zukunft. Munich, London, New York 2012, p. 17 A 2.10 Michael Christian Peters / Pollmeier Massivholz Solid wood and wood-based products A 3.1a–d Heyer, Hans-Joachim, Werkstatt für Photographie, University of Stuttgart A 3.1e SWISS KRONO A 3.1f proHolz A 3.1g Holzabsatzfonds, Bonn A 3.1h Mathias Kestel A 3.1i – l Holzabsatzfonds, Bonn A 3.1m Mathias Kestel A 3.1n ARGE Holz, Düsseldorf A 3.1o – q Holzabsatzfonds, Bonn A 3.1r Mathias Kestel A 3.2 In: Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-Basisdaten für Bauprodukte aus Holz. Arbeitsbericht aus dem Institut für Holztechnologie, No. 2012/1; published by Johann Heinrich of the Thünen Institute. Hamburg 2012

268

Interior air quality – the influence of timber construction A 5.1 Adolf Bereuter A 5.2 In: Leitwerte für TVOC in der Innenraumluft. Compiled by the ad hoc working group under the auspices of the Federal Environmental Agency. Dessau 2007 A 5.3 In: Wikipedia A 5.4 From: Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und Pflanzliche Baustoffe. Wiesbaden 2012, p. 26 A 5.5 From: Bauen und Leben mit Holz. pub. by Informationsdienst Holz. March 2013, p. 23 A 5.6 From: Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und pflanzliche Baustoffe. Wiesbaden 2012, p. 33 A 5.7 TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann A 5.8 In: Thünen Institute and Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und pflanzliche Baustoffe. Wiesbaden 2012, p. 32 A 5.9 TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann A 5.10 TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann A 5.11 In: Paulitsch, Michael; Barbu, Marius C.: Holzwerkstoffe der Moderne. LeinfeldenEchterdingen 2015, p. 418 A 5.12 Stefan Müller-Naumann A 5.13 From: König, Holger: Baustoffe – Lebenszyklusanalyse als Planungsinstrument. In: Djahanschah, Sabine; Kaufmann, Hermann; Nagler, Forian (pub.): Schmuttertal-Gymnasium. Architektur – Pädagogik – Ressourcen. DBU Bauband 1. Munich 2016, p. 84 A 5.14 In: Raumluftqualität – Grundlagen und Massnahmen für gesundes Bauen. Published by Lignum. Zurich 2013, p. 27

Part B B

Eckhart Matthäus / lattkearchitekten

Structures and support structures B 1.1 Darko Todorovic B 1.7 a Architekten Hermann Kaufmann B 1.7 b, 1.10 Bernd Borchardt B 1.15 a proHolz Polaris B 1.15 b Bernd Borchardt B 1.15 c Architekten Hermann Kaufmann B 1.17 ETH Zurich

TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann Margherita Spiluttini, © Architekturzentrum Vienna, Collection

ARTEC

Protective functions C 1.1 abcmedia – Fotolia C 1.2 In MBO (2012) C 1.3 In DIN 4102-2 and DIN EN 13 501-2 C 1.4 In Deutsches Institut für Bautechnik: Bauregelliste – Bauregelliste A, Bauregelliste B und Liste C. Issue 2015/2 C 1.5, 1.6 Technical University Munich C 1.7 In EN 1995-1-2 C 1.9 Stefan Winter C 1.10 Dianna Snape C 1.11 Emma Cross photographer C 1.16 a From: Zeumer, Martin; El Khouli, Sebastian; John, Viola: Nachhaltig konstruieren. Munich 2014 C 1.17 Huber & Sohn GmbH & Co. KG, Bachmehring C 1.18 Midroc, Photo: Martin Johansson C 1.19 a Photo: Bosch C 1.19 b Hilti, Kaufering C 1.20 David Borland C 1.21, 1.22 Stefan Winter C 1.23 Christian Schittich C 1.24 Stefan Winter C 1.25 Holzforschung Austria /Grüll C 1.26 Thomas Madlener C 1.27 Stein, René; Schneider, Patricia; Kleinhenz, Miriam et al.: Fassadenelemente für Hybridbauweisen – Vorgefertigte, integrale Fassadenelemente in Holzbauweise zur Anwendung im Neubau hybrider Stahlbetonhochbauwerke (unpublished). Chair of timber construction and structural design, Chair of energy-efficient and sustainable planning and construction and chair of massive construction. Technical University Munich 2016 Thermal insulation for summer C 2.1, 2.2 From: Ferk, Heinz; Rüdisser, Daniel et al., proholz Austria (pub.): Sommerlicher Wärmeschutz im Klimawandel – Einfluss der Bauweise und weitere Faktoren. In: att.zuschnitt. Vienna 2016 C 2.3, 2.4 Daniel Rüdisser / Laboratory of construction physics at TU Graz C 2.5, 2.6 From: Ferk, Heinz; Rüdisser, Daniel et al., proholz Austria (pub.): Sommerlicher Wärmeschutz im Klimawandel – Einfluss der Bauweise und weitere Faktoren. In: att.zuschnitt. Vienna 2016 The layer structure of building envelopes C 3.1 Bruno Klomfar C 3.2 In: Informationsdienst Holz und www.dataholz.com

C 3.4 C 36

C 3.7 C 3.8 C 3.9 C 3.16 a

C 3.16 b

C 3.17 a

C 3.17 b

C 3.20 C 3.22 C 3.28

Huber & Sohn GmbH & Co. KG, Bachmehring In: Winter, Stefan; Merk, Michael: Verbundforschungsprojekte Holzbau der Zukunft – Teilprojekt TP 02 – Brandsicherheit im mehrgeschossigen Holzbau. Technical University Munich, Chair of timber construction and structural design. Munich 2009 Adolf Bereuter Michael Meuter Bernd Borchardt In accordance with DIN 68 800-2, A7; in: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 In accordance with DIN 68 800-2, A4; in: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 In accordance with DIN 68 800-2, A5; in: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 In accordance with DIN 68 800-2, A2; in: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 Bernd Borchardt In DIN 68 800 or www.dataholz.com RADON photography / Norman Radon

The layer structure of interior structural components C 4.1 Ed White Photographics C 4.8 Köhnke, Ernst Ulrich: Schallschutztechnische Ausführungsfehler an Holzdecken, Beitrag zum 4 HolzBauSpezial: Akustik und Brandschutz im Holz- und Innenausbau (ISB 2013) Bad Wörishofen 2013 Building technology – some special features of timber construction C 5.1 Kiefer Holzbau GmbH & Co. KG, Stockach C 5.2 Informationsdienst Holz, Düsseldorf C 5.3 Manfred Mühe C 5.6 Informationsdenst Holz, Düsseldorf C 5.7 Eisedicht, Rinteln C 5.10 Kaiser GmbH & Co. KG, Schalksmühle C 5.11 Holzforschung Austria C 5.12 Informationsdienst Holz, Düsseldorf C 5.21, 5.22 Stefan Winter

Part D D

Courtesy of the University of British Columbia

Planning D 1.1 TU Munich, Professor of Design and Timber Construction, Univ. Prof. DI Hermann Kaufmann D 1.5 Gumpp & Maier, Binswangen D 1.9 a Merz Kley Partner D 1.9 b Achitekten Hermann Kaufmann D 1.9 c Kaufmann Bausysteme Timber production D 2.1 BDF / Vennenbernd, Bad Honnef D 2.2 Hajotthu, CC BY-SA 3.0 D 2.3 AxelHH, Wikipedia D 2.4, 2.5 Hans Hundegger AG D 2.7 Wenmann Holzbausystemtechnik GmbH D 2.8 a Renggli AG – Schötz, Switzerland D 2.8 b, c Weinmann Holzbausystemtechnik GmbH

Prefabrication D 3.1 RADON photography / Norman Radon D 3.2 Huber & Sohn GmbH & Co. KG D 3.3 b lattkearchitekten D 3.4 b Darko Todorovic / Cre D 3.5 b Ignacio Martinez D 3.7 RADON photography / Norman Radon D 3.11 thomasmayerarchive.de D 3.13 b Vielstädte Holzbau GmbH & Co. KG D 3.13 d Stefan Müller-Naumann D 3.13 f Architekten Hermann Kaufmann D 3.14 a Architekten Hermann Kaufmann D 3.15 Ignacio Martinez Solutions for modernising buildings D 4.1 lattkearchitekten D 4.2 Gumpp & Maier, Binswangen D 4.4 Bruno Klomfar D 4.5 Dominik Reipka D 4.6 Martin Lukas Kim D 4.11 Alexander Gempeler D 4.20 Eckhart Matthäus / lattkearchitekten

p. 226 bottom p. 228, 230, 231 p. 232, 233, 234 bottom, 235 top p. 235 bottom p. 236, 239 –241 p. 237, 238 p. 242, 244 p. 245 p. 246 –248 p. 250, 251, 253 p. 252 p. 254, 255 left, 256 top, 257

Green Architecture, Vancouver) Courtesy of Forestry Innovation Investment @ photo.Abbadie.Herve Hanspeter Schiess Cukrowicz Nachbaur Architekten Carolin Hirschfeld Stefan Müller-Naumann thomasmayerarchive.de RADON photography / Norman Radon Lignotrend, Weilheim-Bannholz / Fotografie Uwe Röder, Bischweier Walter Ebenhofer Fink Thurnher Architekten Adolf Bereuter

Part E E

Mikko Auerniitty

Joints in detail p. 161 Gataric Fotografie p. 162 Hanspeter Schiess p. 163 Pietro Savorelli p. 164 Adolf Bereuter p. 165 RADON photography / Norman Radon Project examples p. 166 p. 167

KK Law; naturally:wood Courtesy of Seagate Structures. Photographer: Pollux Chung p. 168 bottom Stefen Errico p. 169 top left Neil Taberner p. 169 top centre Neil Taberner p. 169 top right Stefen Errico p. 170 –173 Bernd Borchardt p. 174, 175, 177 Pietro Savorelli p. 176 proHolz Polaris p. 178 top Michael Meuter p. 178 bottom Jakob Schoof p. 179 Giuseppe Micciché p. 180, 181 top pool Architekten p. 181 bottom Giuseppe Micciché p. 182, 183, 185 Mikko Auerniitty p. 184 Juha Pakkala p. 186 –188 Sebastian Schels p. 189 Deppisch Architekten p. 190, 191, 193 Florian Holzherr p. 192 Bucher-Beholz Architekten p. 194 top Eva Schönbrunner p. 194 bottom, 195, 196 Stefan Müller-Naumann p. 198 left Sihltal Zürich Uetliberg Bahn SZU AG, www.szu.ch p. 198 right burkhalter sumi architekten p. 199 Unirenova (Stephanie Künzler) p. 200 top Pino Ala p. 200 bottom Heinz Unger p. 201 burkhalter sumi architekten p. 202 top, 203 lattkearchitekten p. 202 bottom Eckhart Matthäus p. 204 Guido Koeninger, Firma Keimfarben p. 206 –210 Gataric Fotografie p. 211–213 KAMPA GmbH 214, 215, 218 Bruno Klomfar 217 left, centre Thomas Giradelli 217 right Darko Todorovic p. 220 –223 Christian Flatscher p. 224 –225, 227 Ed White Photographics ©2015 p. 226 top Photography by MAG (Michael

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Index A access core ∫ 41, 43, 46, 149 acetylated timber ∫ 85 added storeys ∫ 150ff., 198 added storeys / adding of one or more storeys with a new facade ∫ 154 additional exterior insulation ∫ 94 additional insulation ∫ 94f. additional interior insulation ∫ 94 additive manufacturing ∫ 139ff., 147 additives ∫ 18, 21ff., 66f. adhesives ∫ 18, 21ff., 66 air-conditioning systems ∫ 87 air exchange ∫ 81, 90f. airborne sound insulation ∫ 83 airborne sound reduction index ∫ 82f., 101 airtight layer ∫ 97ff., 123, 125, 260 airtightness ∫ 80, 85ff., 98, 120, 260 analysis of the building ∫ 150f. anisotropy /anisotropic ∫ 54f., 260 annual energy consumption ∫ 85 apertures ∫ 122ff. automated method ∫ 138 automated production ∫ 147 award and cooperation model ∫ 132, 135 B bar-shaped / linear materials ∫ 20f., 39 basic noise level ∫ 82 beam ∫ 39, 53, 56 beam breakthroughs ∫ 122 beam ceiling ∫ 58, 67 beam ceiling without adhesives / adhesive-free construction methods ∫ 39, 51, 58, 66 beam geometry ∫ 56 beams ∫ 48 beech laminated veneer lumber ∫ 48, 55, 63, 67, 242ff. beech /beechwood ∫ 19, 22f., 51, 55, 63 bending or flexural strength ∫ 18ff. block / log-cabin construction ∫ 10, 39, 260 blower door test ∫ 80, 98, 260 blown-in insulation ∫ 80 board layers ∫ 54, 63 bonded metal inserts ∫ 64f. bonding agent ∫ 18, 21ff. box beams ∫ 56 box ceiling ∫ 60, 68ff., 199ff., 220 box elements ∫ 38, 246 bracing ∫ 46f., 51f., 54f., 57, 62f. bracing elements ∫ 46f. building inspection authorities, approval ∫ 54f., 132 building assembly ∫ 107, 142ff. building classes ∫ 73f., 76 building envelope ∫ 92, 143, 154 building information modelling (BIM) ∫ 135, 260 building materials classes ∫ 73 building regulations ∫ 137, 154, 156 building technology ∫ 122ff., 137 buildings very comfortable in summer ∫ 102 bulk density, density ∫ 18, 21ff., 75, 79, 260,, butterfly table ∫ 140 C cable sheathing ∫ 126 CAM data ∫ 26, 135 carbon content ∫ 18ff. carbon footprint ∫ 24, 27f. carbon sequestration, carbon storage ∫ 24ff., 120, 260

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carbon sink ∫ 24 carpenters’ joints ∫ 52, 60, 142 carpentry ∫ 142 cascading or multiple use ∫ 18, 27f. cavity floor ∫ 116 cavity insulation ∫ 115, 118 ceiling structures ∫ 58 cellulose ∫ 85, 260 cement-bonded particle board, chipboard ∫ 19, 22f. charring rates ∫ 18ff., 75 chemical timber preservation ∫ 84, 260 chimney stack effect ∫ 78, 81 chipboard ∫ 19, 22 climate neutrality ∫ 25f. CNC timber frame ∫ 134, 139ff., 142 CNC-milling ∫ 54, 60, 135, 260 CO2 storage ∫ 67f. CO2-equivalent ∫ 24 CO2 /carbon sink ∫ 7, 103 colour treatments /coating ∫ 85 column ∫ 39 combination of materials ∫ 41 combustibility ∫ 72ff. composite effect ∫ 39, 41, 60f., 64 composite element ∫ 60 composite /combined timber-concrete structure ∫ 38, 43f. compressive strength ∫ 45 concrete ∫ 42f. concrete top layer, layer of concrete ∫ 42f., 64 concrete construction ∫ 47 condensation ∫ 79ff., 95ff., 105, 260 conserving the logs ∫ 138 construction moisture ∫ 138 construction and assembly planning ∫ 132 construction phase, risk of damage from moisture ∫ 143 construction product standards ∫ 18 construction products regulation ∫ 82 contract award ∫ 133 convection ∫ 79f., 87, 260 crane ∫ 140 creep behaviour ∫ 49 cross laminated timber ∫ 19ff., 54, 62, 146f., 160, 164, 170ff., 176, 183, 188, 197, 211, 224ff., 229ff., 242ff., 250ff., 254ff., 260 cross laminated timber ceiling ∫ 62, 69 cross laminated timber wall ∫ 54, 66, 101f., 164 crossed layers ∫ 63 crosspiece compression ∫ 43, 45, 260 crosspieces ∫ 52, 260 curved surfaces ∫ 54 D damage from rot ∫ 126 damage from moisture, construction phase ∫ 143 damp rooms ∫ 126f. decoupling ∫ 45, 83, 118, 120 design phase ∫ 130, 146f. design planning ∫ 134, 137, 144 diaphragm beam ∫ 53f. diffusion ∫ 79f. diffusion-resistant coatings ∫ 82 digital process chain ∫ 135ff. direction of fibres ∫ 51, 54f., 63 dismantling ∫ 65 double and triple laminate beams ∫ 19ff. double floor ∫ 116 double wall ∫ 119 Douglas fir ∫ 20ff. dovetail joint ∫ 52, 64f., 147 dowel laminated timber ∫ 39, 260 dowel laminated timber ceiling ∫ 57, 66ff., 171f., 179, 208, 234, 252ff. dowel laminated timber structure

∫ 38ff., 179ff. dowel laminated timber wall ∫ 51, 66 dowel-type fastener systems ∫ 64f. dowelling ∫ 51 drainage level ∫ 81, 95 drip edge ∫ 85 E earthquake resistance ∫ 10, 44, 47f., 150, 176 ecological considerations ∫ 103f. economic factors ∫ 102f. edge beams ∫ 60 efficient use of resources ∫ 25f. elastomer bearings ∫ 120 electrical equipment ∫ 123f. emergency escape route ∫ 73 encapsulation criterion ∫ 75 enclosing a construction site ∫ 81 ergonomic working conditions ∫ 140ff. evaluation of the basics ∫ 134 expanded metal plates glued in ∫ 65 exposure to weather ∫ 84 extension / renovation roof truss ∫ 153f. extension ∫ 143 exterior cladding layer ∫ 94 exterior insulation, flat roof ∫ 104 exterior wall structure ∫ 85 exterior wall with insulation in interstices ∫ 96f. F facade cladding ∫ 78 facade of a renovated building ∫ 148 facade ventilation ∫ 78, 81, 85 fibre-based materials ∫ 18, 22, 38 filled with grouting ∫ 45 finely sawn surface ∫ 85 finger-jointed / finger-jointed solid timber ∫ 19f., 261 fire alarm ∫ 77 fire barrier ∫ 97 fire load ∫ 74 fire outbreak, fire development phase ∫ 74 fire performance ∫ 18ff. fire protection cladding ∫ 75 fire resistance ∫ 54, 72ff., 261 fire-resistance class ∫ 74, 76 fire-resistant seal ∫ 95, 261 fire safety ∫ 42ff., 72ff., 95, 101, 114, 123ff., 137 fire safety compartments ∫ 123ff. firestop ∫ 125f. flank adhesion ∫ 54 flanking sound transmission ∫ 121 flat roof ∫ 97, 104ff. flat roofs with insulation in interstices ∫ 100 flat steel elements set in sawn ∫ 65 flexural stiffness ∫ 47 floor covering ∫ 145 floor structures ∫ 115 flow resistance ∫ 80 footfall / impact sound (insulation) ∫ 82, 100, 110ff., 114f., 124, 261 formaldehyde ∫ 31f., 261 formwork, planking ∫ 58f., 84 frame construction ∫ 10f., 40f., 46, 160, 162, 165, 262 framework ∫ 39, 61, 261 framing station ∫ 139f. frictional connection ∫ 53 full service general contractor model ∫ 132 functional tendering ∫ 132, 135 fungal infestation ∫ 138 G gantry system ∫ 139 German Energy Saving Ordinance (EnEV) ∫ 85f.

German Model Building Code (Musterbauordnung – MBO) ∫ 72 Glaser method ∫ 79 global warming potential ∫ 18ff., 24 glued laminated timber / glulam ∫ 19ff., 52, 169, 199, 217, 224ff., 236ff., 246ff., 250ff., 261 glued laminated timbers ∫ 33 glued laminated timber ribs ∫ 220f. gluing ∫ 51, 57, 60 greenhouse gas emissions ∫ 24ff. H half-timbered construction ∫ 11, 52, 114 hard firestops ∫ 126 hardwood ∫ 7, 15ff., 48, 52, 75, 81 hardwood dowels ∫ 51, 54, 57, 66 heat transmittance coefficient / thermal resistance ∫ 86 High-rise building, buildings up to high-rise height ∫ 12, 46, 73ff., 77ff., 97, 102 hollow box ceiling ∫ 60, 261 hollow mould ∫ 54f. horizontal loads ∫ 155 hybrid construction methods ∫ 41f., 64, 149, 156, 261 hygroscopic ∫ 81 I Å-beams ∫ 52, 261 impact sound reduction level ∫ 83 implementation planning ∫ 131, 134, 137 in-plane effect, plate function ∫ 44, 66 indirect support ∫ 42, 45 individual boards ∫ 51, 57 indoor, interior climate ∫ 30, 102, 105 industrial manufacture, industrialised production ∫ 38, 148 industrial prefabrication ∫ 139 industrialisation ∫ 141, 148 infill ∫ 145 information models ∫ 136 inhomogeneities ∫ 51, 54f., 57 inner lining ∫ 100 inspection openings ∫ 126f. installation layer ∫ 94, 101, 125 installation shaft ∫ 125 installations in ceilings ∫ 124 installations in exterior walls ∫ 123 installations in partition walls ∫ 123ff. installations in roofs ∫ 125 insulating layer ∫ 99 insulation ∫ 85f. insulation blower ∫ 141 integrative planning approach ∫ 133, 135 interior air emissions ∫ 33, 35 Interior air quality ∫ 30 interior walls ∫ 118 intumescent material ∫ 126ff. J joinery ∫ 140ff., 261 jointing ∫ 106, 121, 148f. joints ∫ 97, 120ff., 126, 156, 160ff. joints between elements ∫ 53, 55, 145, 147 joints between elements, butt joints ∫ 62, 145, 147f. joists ∫ 39 K kiln-dried wood ∫ 140 Kyoto Protocol ∫ 24f. L ladder beams ∫ 52 laminated materials ∫ 20f., 52

laminated beams ∫ 20 laminated veneer lumber (LVL) ∫ 19, 22, 38, 52, 55f., 60, 63, 242ff. laminated veneer lumber ceiling ∫ 63 laminated veneer lumber slab ∫ 63f. laminated veneer lumber wall ∫ 55, 63 layer structure ∫ 92, 99, 113 layers ∫ 127 leaks ∫ 80, 97, 127, 262, leftover material / waste ∫ 54, 143f. levelling fill ∫ 115 libraries of structural components ∫ 136 life-cycle assessment ∫ 24f., 27f., 262 lightweight structural elements ∫ 38f. lightweight timber beams /supports ∫ 19ff. lightweight wood wool board (WW) ∫ 19, 22 lignin ∫ 85 linear elements ∫ 144f. linear members ∫ 38ff., 144, 147 linear support ∫ 68 lintel ∫ 52ff., 262 lintel beams /parapet transoms ∫ 51ff. load transfer ∫ 102, 152ff. load transfer facade ∫ 155f. load-bearing capacity ∫ 56 load-bearing layer ∫ 115 load-bearing, outside ∫ 94, 101, 118 loggia ∫ 104f., 155 logs ∫ 15 long span lumber (LSL) ∫ 19, 22f. low-energy house ∫ 86 lower flange ∫ 56 lumber ∫ 15 M making it more homogeneous, homogenisation ∫ 55 masonry construction ∫ 44f. mass able to store energy ∫ 88ff., 262 material requirements ∫ 67f. measure to protect structures from the weather ∫ 143 measurements ∫ 144, 151 medium density fibreboard (MDF) ∫ 22 milling robot guided by computers ∫ 14, 52 modernisation facade, modernisation of building ∫ 148f., 154, 202ff. modernising buildings ∫ 150ff. modular construction ∫ 154ff., 242ff. modulus of elasticity ∫ 48, 263 moisture ∫ 126 moisture leaks ∫ 80f. moisture content ∫ 18, 79, 82, 138 moisture protection ∫ 79ff. moisture-adaptive vapour barrier ∫ 100, 105 mould ∫ 81, 86 multifunction bridge ∫ 139, 141 N nailing ∫ 51, 57 natural cooling ∫ 90 natural fire tests ∫ 97 O openings ∫ 51f., 54, 58, 122ff., 137f., 154ff. oriented strand board (OSB) ∫ 19, 22, 38, 51f., 58f., 60 overheating ∫ 88ff. overlapping ∫ 62 P panel construction ∫ 39, 45, 52, 58, 93, 103, 123, 161f., 202, 224, 236, 246, 250ff., 262 panel construction element ∫ 139ff. panel processing centre ∫ 139 parapet ∫ 54

passive house / passive house standard ∫ 26f., 86, 263 people with particular sensitivities ∫ 33 permeable foil ∫ 84, 97 perp-to-grain compressive strength ∫ 45 perpendicular tensile strength ∫ 45f. pests, insects ∫ 84, 138 photo-oxidation ∫ 85 pipe and cable routing ∫ 122f. pipe couplings ∫ 65 planar elements ∫ 145 planar building materials ∫ 38 plane ∫ 38ff. plank slab ∫ 39 planking ∫ 39, 51ff., 100, 262, planning phase ∫ 131ff., 136 planning period ∫ 131 plate rigidity ∫ 51 plinths ∫ 41 plus-energy house ∫ 86 polyfunctionality ∫ 92f., 97, 106f. porous panels ∫ 19, 22 positive bond ∫ 64 post-in-ground structures ∫ 11 pre-tensioned structures ∫ 47f. precision ∫ 140, 142 prefabrication ∫ 103, 107ff., 130, 137, 142ff., 150f. prefabrication methods ∫ 147f., preliminary design phase ∫ 131 preliminary planning ∫ 134, 137 prestressed beam ∫ 56 primary energy consumption / requirements ∫ 26f., 262 process chains, digital ∫ 135ff. production ∫ 138ff. production processes ∫ 141 profile ∫ 51, 57 proportion of glue /glue ratios ∫ 55, 67 protect structures from weather ∫ 94 protecting the structure ∫ 151 protective plank ∫ 84 protective functions ∫ 72ff., 92, 98 prototype character ∫ 142 R raw material industry ∫ 138 rear-ventilated facade structure ∫ 95ff., 101, 262 rear-ventilated facades ∫ 94f., 97f., 101 rear-ventilated flat roof ∫ 104 recycling ∫ 78, 84 reinforcement ∫ 64f. relative humidity ∫ 81f., 85 renovation ∫ 58, 143, 149, 151ff. ribbed slab ∫ 39 ribs ∫ 60f., 262, rigidity ∫ 54 risk of fire starting ∫ 72 room cubicle module ∫ 54, 127, 130, 145ff., 150, 164, 262 rotary-cut veneers ∫ 55 S sagging behaviour ∫ 42 saving time in the construction phase ∫ 143 sawmill ∫ 138 screed ∫ 81f., 87, 145 screw joint ∫ 53, 60, 62 screws ∫ 64f. screws as well as adhesives ∫ 52 sd value ∫ 97ff., 104, 263 sealing layer ∫ 81 sealing systems ∫ 126 second water-bearing layer ∫ 97, 263 secondary emergency escape route ∫ 73, 76f. shading ∫ 88 shaft (wall) ∫ 125f.

shear stiffness ∫ 153 shear stress ∫ 123 shear-resistant joints /connections ∫ 42, 56, 64 shielded from driving rain ∫ 81, 85 shrinking ∫ 54, 263 single walls ∫ 119f. single-ply sheeting ∫ 19ff. slab effect ∫ 44 slab supports ∫ 43f. slab’s span direction ∫ 63 slabs ∫ 38ff. slabs bordering on outside space ∫ 104 sloping roof structures ∫ 97, 105 soft firestop ∫ 126 solar radiation ∫ 90 solid structural timber, solid construction timber ∫ 19ff., 52, 56, 261 solid timber /solid wood structures / building /construction ∫ 39ff., 93f., 102, 107, 124ff., 263 solid wood ∫ 18ff., 51, 58, 263 solid wood structural components ∫ 39 sorting ∫ 138 sound absorption ∫ 118 sound insulation ∫ 117, 146f. sound reduction index ∫ 100 sound transmission ∫ 147 soundproofing ∫ 42, 69, 100, 115 span ∫ 54, 60, 263 spatial acoustics ∫ 82, 263 spatial geometry ∫ 137 sprinkler system ∫ 72, 77ff., standardisation ∫ 141f. steel cable ∫ 48 steel components ∫ 44ff. steel-reinforced concrete ceiling ∫ 69 steel-reinforced concrete construction ∫ 45 steel-reinforced concrete cores ∫ 46f. storing for several years ∫ 138 strand, chip and fibre-based materials ∫ 22 strands ∫ 22 strongness ∫ 48 structural component layers ∫ 97 structural components ∫ 50ff., 137 structural components classes ∫ 73 structural elements ∫ 50ff., 263 structural height, low ∫ 57 structural physics / building physics ∫ 122ff., 137 structural planning ∫ 44 structural timber preservation ∫ 83 structure-borne sound insulation ∫ 82, 263 structures insulated on the outside ∫ 93, 98f., 104 stud frame ∫ 52f., 139, 263 substitution ∫ 25, 28 subtractive manufacturing ∫ 139f., 147 support ∫ 155 support at various points ∫ 61ff., 68 support situation ∫ 60, 62f. support structure ∫ 28, 38ff., 50 suspension, decoupling for sound transmission purposes ∫ 117 swelling ∫ 51, 54, 263 T technical building equipment ∫ 122ff. temporary roof ∫ 151, 153 tendering, functional ∫ 132, 135 tensile strength ∫ 45 thermal conductivity ∫ 18ff., 102 thermal bridge ∫ 86f., 93, 100, 107, 148, 151, 156 thermal insulation in summer ∫ 87ff. thermal insulation in winter ∫ 86f. thermal insulation system ∫ 85, 94, 98, 102ff.

thermowood ∫ 84 thicknesses of structural elements ∫ 86 three-ply laminate sheeting ∫ 19ff., 51, 58ff. timber industry ∫ 15 timber construction company ∫ 140ff. timber framing ∫ 7, 11, 39, 262 timber structural engineers ∫ 135 timber-concrete slabs ∫ 40ff., 45, 57, 64, 68ff., 149, 165, 173ff., 214, 236 timber / wood preservation ∫ 72, 83ff., 263 tongue-and-groove joint ∫ 60 tongue-and-groove formwork ∫ 59 tool head ∫ 140 total volatile organic compounds ∫ 31, 263 transmission heat losses ∫ 86 transport ∫ 27, 95, 144ff. transverse formwork ∫ 58f., 66 transverse stress ∫ 123 trickle protection ∫ 115f. trimmer joists / trimmers ∫ 51f., 57ff., 263 trimming machines ∫ 147 trussed beam ∫ 56 tube-in-tube systems ∫ 47, 263 U U value (heat transmittance coefficient) ∫ 86, 98, 110ff., 263 upper flange ∫ 56 upright support, glued laminated timber ∫ 166ff. use classes ∫ 84 V vacuum lifting devices ∫ 140 vapour barrier ∫ 100ff., 104, 263 vapour-permeable planking ∫ 98f. varnish ∫ 85 veneered plywood ∫ 19, 22f. veneers ∫ 22 ventilated ∫ 85 ventilated and rear-ventilated exterior wall cladding ∫ 95f., 97f., 100f. ventilation ducts ∫ 124 verification of vibration levels ∫ 45 vertical battens ∫ 84, 263 vertical loads ∫ 155 vibration behaviour ∫ 42 visible timber structural elements ∫ 75ff., 79 volatile organic compounds ∫ 31, 263 volume flow ∫ 81 W wall planes ∫ 47, 49 walls that form part of fire safety compartments ∫ 123f. water and heating pipes and cables ∫ 124 water dissipation layer ∫ 81, 97ff. water vapour diffusion resistance ∫ 18ff., 263 weather-independent work ∫ 254 weighted impact sound level ∫ 82 wet storage ∫ 138 window installation ∫ 156 window rail ∫ 52ff. windproof layer ∫ 80, 92, 97f., 263 wood as a resource ∫ 7, 14ff. wood types ∫ 20, 22 wood-based materials /products ∫ 18, 263 wood-based panel ∫ 75 wood-destroying fungi ∫ 79, 84 wood-steel hybrid construction ∫ 190 wood’s moisture content ∫ 79, 84, 261 workshop conditions ∫ 142f.

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The authors and the publisher would like to thank the following institutions for supporting the 1st German language edition:

www.stmelf.bayern.de

www.zimmerer-bayern.com

www. proholz.at

MANUAL of Multi-Storey Timber Construction Wood is a visually attractive material with a tactile appeal, it is sustainable, renewable and usually readily available. The notion that wood can also be used almost without limit in multi-storey timber construction is however a recent one and requires a creative application of previously practised construction methods. Modern timber construction has been freed of its classic categories, such as timber frame construction etc., so various building methods can be combined within a single project as needed, which opens up a range of entirely new possibilities for timber architecture. This book focuses on multi-storey timber construction and provides architects, engineers and timber experts with essential expertise on new systems and construction methods, ranging from design and planning, through prefabrication, right up to assembly on site. It sets out the mutual understanding that everyone involved in the project needs to effectively cooperate in an integrated planning and construction process and offers readers the technical knowledge required to advocate persuasively for modern timber construction.

The authors: Hermann Kaufmann Stefan Krötsch Stefan Winter Heinz Ferk Sonja Geier Annette Hafner Wolfgang Huß Holger König Maren Kohaus Frank Lattke Lutz Müller Anne Niemann Daniel Rüdisser Christian Schühle Manfred Stieglmeier Martin Teibinger Gerd Wegener

ISBN 978-3-95553-394-6

DETAIL Business Information GmbH, Munich www.detail-online.com

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