Expert Knowledge-based Inspection Systems: Inspection, Diagnosis, and Repair of the Building Envelope [1st ed.] 9783030424459, 9783030424466

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Jorge de Brito Clara Pereira José D. Silvestre Inês Flores-Colen

Expert Knowledge-based Inspection Systems Inspection, Diagnosis, and Repair of the Building Envelope

Expert Knowledge-based Inspection Systems

Jorge de Brito Clara Pereira José D. Silvestre Inês Flores-Colen •

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Expert Knowledge-based Inspection Systems Inspection, Diagnosis, and Repair of the Building Envelope

123

Jorge de Brito CERIS, Instituto Superior Técnico University of Lisbon Lisbon, Portugal

Clara Pereira CERIS, Instituto Superior Técnico University of Lisbon Lisbon, Portugal

José D. Silvestre CERIS, Instituto Superior Técnico University of Lisbon Lisbon, Portugal

Inês Flores-Colen CERIS, Instituto Superior Técnico University of Lisbon Lisbon, Portugal

ISBN 978-3-030-42445-9 ISBN 978-3-030-42446-6 https://doi.org/10.1007/978-3-030-42446-6

(eBook)

© Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

This book constitutes the capstone of a line of research about expert inspection systems for individual building elements. It builds on that research and presents a broader approach for the building envelope. That approach is not simply a sum of the information collected for individual types of non-structural building elements and materials used in the building envelope. It tries to summarise the complexity of several building elements and materials in a harmonised system of inspection, dealing with pathology in a comprehensive manner, trying to balance conciseness and particular characteristics. That philosophy also extends to diagnosis methods that may be useful to be performed on-site to help characterise the defect and confirm its causes, and to repair techniques, which in the course of action a surveyor may recommend to the decision-maker. Performing building inspections in a systematised manner potentiates obtaining more reliable results. Those results, as the basis of application of predictive maintenance strategies, for instance may promote more effective maintenance operations. The authors intend to encourage a more standardised approach to building inspection, as opposed to a case-based approach. Periodically inspecting buildings allows detecting pathological phenomena at an early stage, hence more likely to be circumscribed and easier to repair. If the frequency of inspection is adapted to the needs of the building and to the required levels of performance of building elements, and inspection results reflect on adequate repair techniques, then the durability of building elements and the general in-use quality level of the building will increase. Planned maintenance should be seen as the key-approach to keep the physical performance levels of building elements according to the required standards. Then, more accurate building inspections may contribute to prolong the service life of the building stock, avoiding the construction of new buildings, hence decreasing the consumption of resources and construction and demolition waste.

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Preface

This book is aimed at professionals in the building sector that are looking for a methodology to inspect buildings. Although a specific inspection system for the building envelope is proposed, the authors intend to inspire the development of other building inspection systems whose contents are according to the needs, knowledge and experience of the readers, using the proposed methodology. Lisbon, Portugal

Jorge de Brito Clara Pereira José D. Silvestre Inês Flores-Colen

Acknowledgements The authors gratefully acknowledge the support of the Fundação para a Ciência e a Tecnologia (FCT) to the project PTDC/ECM-COM/5772/2014 “Service Life Prediction for a risk-based Building Management System”. The authors would also like to acknowledge the support of FCT through the second author’s Ph.D. scholarship SFRH/BD/ 131113/2017. Finally, the authors would like to acknowledge the support of FCT to the research centre Civil Engineering Research and Innovation for Sustainability (CERIS), based at Instituto Superior Técnico, University of Lisbon.

Contents

1 Buildings’ Management . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Building Envelope . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Maintenance and Inspection . . . . . . . . . . . . . . . . . . 1.4 Overview of Building Inspection Systems . . . . . . . . 1.4.1 Expert Individual Inspection Systems . . . . . 1.5 From Individual Elements to the Building Envelope . 1.6 Book Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2 Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Natural Stone Claddings . . . . . . . . . . . . . . . . . . . . . 2.2.1 Materials Used in Natural Stone Claddings . 2.2.2 Design of Natural Stone Claddings . . . . . . . 2.2.3 Execution of Natural Stone Claddings . . . . . 2.3 Adhesive Ceramic Tiling . . . . . . . . . . . . . . . . . . . . . 2.3.1 Materials Used in Adhesive Ceramic Tiling . 2.3.2 Design of Adhesive Ceramic Tiling . . . . . . . 2.3.3 Execution of Adhesive Ceramic Tiling . . . . 2.3.4 Quality Control at the Execution Stage . . . . 2.4 Wall Renders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Materials Used in Wall Renders . . . . . . . . . 2.4.2 Design of a Wall Render . . . . . . . . . . . . . . 2.4.3 Execution of Wall Renders . . . . . . . . . . . . . 2.5 Painted Façades . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.1 Materials Used in Painted Façades . . . . . . . 2.5.2 Design of Painted Façades . . . . . . . . . . . . . 2.5.3 Execution of Painted Façades . . . . . . . . . . .

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2.6

Etics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.1 Components of ETICS . . . . . . . . . . . . . . . . . . . . 2.6.2 Design of an ETICS Cladding . . . . . . . . . . . . . . 2.6.3 Execution of ETICS Claddings . . . . . . . . . . . . . . 2.7 Architectural Concrete Surfaces . . . . . . . . . . . . . . . . . . . . 2.7.1 Materials Used in Architectural Concrete Surfaces 2.7.2 Design of Architectural Concrete Surfaces . . . . . . 2.7.3 Execution of Architectural Concrete Surfaces . . . . 2.8 Door and Window Frames . . . . . . . . . . . . . . . . . . . . . . . 2.8.1 Materials Used in Door and Window Frames . . . . 2.8.2 Design of Door and Window Frames . . . . . . . . . 2.8.3 Execution of Door and Window Frames . . . . . . . 2.9 External Claddings of Pitched Roofs . . . . . . . . . . . . . . . . 2.9.1 Materials Used in External Claddings of Pitched Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9.2 Design of External Claddings of Pitched Roofs . . 2.9.3 Execution of External Claddings of Pitched Roofs 2.10 Flat Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10.1 Materials Used in Flat Roofs . . . . . . . . . . . . . . . 2.10.2 Execution of Flat Roofs . . . . . . . . . . . . . . . . . . . 2.11 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 Pathology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Proposed Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Classification of Defects . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Defects of Physical Nature . . . . . . . . . . . . . . . . . 3.2.2 Defects of Chemical Nature . . . . . . . . . . . . . . . . 3.2.3 Defects of Mechanical Nature . . . . . . . . . . . . . . . 3.2.4 Other Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Occurrence of Defects in Building Elements and Materials 3.4 Classification of Probable Causes . . . . . . . . . . . . . . . . . . 3.4.1 Design Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Execution Errors . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 Mechanical Actions . . . . . . . . . . . . . . . . . . . . . . 3.4.4 Environmental Actions . . . . . . . . . . . . . . . . . . . . 3.4.5 Use and Maintenance Errors . . . . . . . . . . . . . . . . 3.5 Occurrence of Causes of Defects in Building Elements and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Defects–Causes Correlation . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Defects–Probable Causes Correlation Matrix . . . . 3.6.2 Inter-defects Correlation . . . . . . . . . . . . . . . . . . . 3.7 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Diagnosis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Proposed Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Classification of Diagnosis Methods . . . . . . . . . . . . . . . . . 4.2.1 Assisted Sensory Analysis . . . . . . . . . . . . . . . . . . 4.2.2 Electrical Methods . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Thermo-Hygrometric Methods . . . . . . . . . . . . . . . 4.2.4 Sound and Acoustic Methods . . . . . . . . . . . . . . . . 4.2.5 Nuclear Methods . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.6 Hydric Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.7 Mechanical Methods . . . . . . . . . . . . . . . . . . . . . . 4.2.8 Pressure Methods . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.9 Colour Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.10 Chemical Methods . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Application of Diagnosis Methods in Building Elements and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Defects–Diagnosis Methods Correlation . . . . . . . . . . . . . . . 4.4.1 Correlation Matrix . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Building a Defects–Diagnosis Methods Correlation Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5 Repair Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Proposed Methodology . . . . . . . . . . . . . . . . . . . . 5.2 Classification of Repair Techniques . . . . . . . . . . . 5.2.1 Surface of the Cladding . . . . . . . . . . . . . 5.2.2 Cladding System . . . . . . . . . . . . . . . . . . 5.2.3 Change in the Bearing Structure/Substrate 5.2.4 Singularities . . . . . . . . . . . . . . . . . . . . . . 5.3 Use of Repair Techniques in Building Elements and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Defects–Repair Techniques Correlation . . . . . . . . 5.4.1 Correlation Matrix . . . . . . . . . . . . . . . . . 5.4.2 Building a Defects–Repair Techniques Correlation Matrix . . . . . . . . . . . . . . . . . 5.5 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 Elements to Support the Inspection Procedure 6.1 Proposed Methodology . . . . . . . . . . . . . . 6.2 Defect Files . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Structure of a Defect File . . . . . . 6.2.2 Example of a Defect File . . . . . . 6.3 Atlas of Defects . . . . . . . . . . . . . . . . . . .

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6.3.1 Structure of the Atlas of Defects . . . . . . . . 6.3.2 Example of a Page of the Atlas of Defects 6.4 Diagnosis Methods Files . . . . . . . . . . . . . . . . . . . . 6.4.1 Structure of a Diagnosis Method File . . . . 6.5 Repair Techniques Files . . . . . . . . . . . . . . . . . . . . 6.5.1 Structure of a Repair Technique File . . . . . 6.5.2 Example of a Repair Technique File . . . . . 6.6 Inspection Forms . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.1 Structure of an Inspection Form . . . . . . . . 6.6.2 Example of an Inspection Form . . . . . . . . 6.7 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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7 Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Coffee House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Characterisation of the Building and Its Surroundings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Data on Building Elements and Their Degradation Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Detached House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Characterisation of the Building and Its Surroundings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Data on Building Elements and Their Degradation Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Museum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Characterisation of the Building and Its Surroundings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Data on Building Elements and Their Degradation Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Analysis of the Inspection Procedures . . . . . . . . . . . . . . . . 7.6 Advantages and Limitations of Using an Inspection System 7.7 Examples of How to Convey Information . . . . . . . . . . . . . 7.8 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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8 The Way Forward . . . . . . . . . . . . . . . . . . . 8.1 Introduction . . . . . . . . . . . . . . . . . . . . 8.2 Development of a Software Tool . . . . . 8.3 Integration with Service Life Prediction 8.4 Integration with Maintenance Planning . 8.5 Objectives-Based Customisation . . . . . 8.6 Region-Based Customisation . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . .

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About the Authors

Jorge de Brito is a Full Professor at Instituto Superior Técnico, University of Lisbon since 2009. He graduated in Civil Engineering in 1982, completed his Master’s Degree in Structural Engineering (pathology of concrete structures) in 1987 and his Ph.D. in Civil Engineering (bridge management systems) in 1993. He was the head of the research centre Civil Engineering Research and Innovation for Sustainability (CERIS) from 2017 until 2018. Prof. Jorge de Brito is a member of the following international commissions: W80 (CIB)—presently co-coordinator; W86 (CIB)—presently coordinator; W115 (CIB); TC RAC (RILEM); and WC7 (IABSE). He is also a member of the IABSE, FIB, CIB, IABMAS and RILEM international organisations. Prof. Jorge de Brito has published seven international books, including “Methodologies for Service Life Prediction of Buildings” and “Handbook of Concrete Bridge Management”. Clara Pereira is a Ph.D. Student at Instituto Superior Técnico, University of Lisbon since 2017. She graduated in Architecture in 2008 and completed her Master’s Degree in Construction and Rehabilitation (characterisation and pathology of secondary schools’ buildings) in 2012. Clara Pereira is a member of the CIB SC-DECivil (at Instituto Superior Técnico, University of Lisbon). José D. Silvestre is an Assistant Professor at Instituto Superior Técnico, University of Lisbon since 2012. He graduated in Civil Engineering in 2002, completed his Master’s Degree in Construction (expert inspection system of adhesive ceramic tiling) in 2005 and his Ph.D. in Civil Engineering (life cycle assessment applied to construction materials and building assemblies) in 2012. Prof. José D. Silvestre is a member of the W115 (CIB) international commission. He was the President of the Portuguese Technical Committee CT171 “Sustainability of construction works” between 2017 and 2019. CT171 is a mirror group of the CT350 of the European Committee for Standardization (CEN).

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About the Authors

Inês Flores-Colen is an Associated Professor at Instituto Superior Técnico, University of Lisbon since 2016. She graduated in Civil Engineering in 1996, completed her Master’s Degree in Construction (maintenance of building elements) in 2002 and her Ph.D. in Civil Engineering (in-service performance of rendered facades for predictive maintenance) in 2009. Prof. Inês Flores-Colen is a member of the following international commissions: W70 (CIB) and W86 (CIB)—secretary of W86 (CIB) commission since June 2019. She is a member of the Portuguese Technical Committee CT192 for “Facility Management”.

List of Figures

Fig. 2.1 Fig. 2.2 Fig. 2.3 Fig. 2.4 Fig. 2.5 Fig. 2.6

Fig. 2.7 Fig. 2.8 Fig. 2.9

Fig. 2.10

Fig. 2.11

Fig. Fig. Fig. Fig.

2.12 2.13 2.14 2.15

Blocks of limestone rock in a quarry (a) and quarry for the extraction of limestone in a natural park (b) . . . . . . . . Different types of joints in natural stone claddings . . . . . . . . . Open joints in a natural stone cladding: a general view; b close-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Staining emphasising the perimeter of natural stone plates . . . Natural stone cladding with ventilation holes: a general view; b close-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sections of: a a dowel anchorage system; and b a Keil-type technology undercut anchorage system. 1—natural stone plate; 2—panel bracket; 3—slotted anchor sleeve with internal thread; 4—screw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two types of kerf anchor clips’ profiles . . . . . . . . . . . . . . . . . Different types of natural stone finishes: a scratched; b bush-hammered; c polished . . . . . . . . . . . . . . . . . . . . . . . . . Early staining in a natural stone cladding associated with the adhesive material: a general view; b close-up; c back face of removed stone plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Expansion joint filled with mastic. 1—substrate; 2—bedding material; 3—tiles; 4—expansion joint filling material; 5—silicone cord; 6—mastic . . . . . . . . . . . . . . . . . . . . . . . . . . Representation of the application of adhesive ceramic tiling using a thick or a thin bed. 1—substrate; 2—spatter-dash (render layer); 3—render; 4—traditional mortar layer; 5—traditional mortar applied on the back face of tiles; 6—elastic joint; 7—adhesive material; 8—movement joint; 9—tile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Composition of paint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water repellence versus permeability to water vapour . . . . . . Paint pellicle formation process . . . . . . . . . . . . . . . . . . . . . . . Scheme of the components of ETICS . . . . . . . . . . . . . . . . . . .

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26

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26 27

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31

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List of Figures

Fig. 2.16 Fig. 2.17

Fig. 2.18 Fig. 2.19 Fig. 2.20

Fig. Fig. Fig. Fig.

2.21 2.22 2.23 2.24

Fig. 2.25 Fig. 2.26 Fig. 2.27

Fig. 2.28

Fig. 2.29

Fig. 2.30 Fig. 2.31

Examples of types of finishes for ETICS: a mixed binder coating; b stone plates; and c adhesive ceramic tiling . . . . . . . Thermal bridge in a system with insulation between two masonry leaves and prevention of thermal bridges in ETICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison between thermal gradients of walls without and with ETICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reinforcement of joints between starting and lateral profiles . Bonding of the reinforcement mesh directly on the substrate before placing the starting profile (a) and reinforcement mesh folded and bonded over the thermal insulation boards using mortar (back-wrapping) (b) . . . . . . . . . . . . . . . . . . . . . . . . . . . Illustration of the execution of the peripheral cord at 45° . . . . Simplified effect of wind loads in a building façade . . . . . . . . Mechanical fastening of wall plugs . . . . . . . . . . . . . . . . . . . . . Arrangement of insulation boards with unaligned joints (a) and L-shaped boards around a window (b) . . . . . . . . . . . . Pattern of fastening marks in an architectural concrete surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Architectural concrete surface with: a smooth finish (a); mid-relief (b); and sunk relief (c) . . . . . . . . . . . . . . . . . . . . . . Location of the different types of shims in different types of door and window frames (from left to right, top to bottom: fixed window, casement window, hopper window, awning window, European tilt and turn window, pivot window, sliding window, vertical sliding window). C1—bearing shims; C2—side shims; C3—safety shims . . . . . . . . . . . . . . . . . . . . . Different types of joints between the glazing units and rails (from left to right: open joint, closed joint, joint with exterior glass stop fastened with nails or screws and self-draining joint). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mastics and sealing accessories used in door and window frames: a acrylic bitumen; b sealing rubbers; and c sealing tape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Elements of a wall opening (a) and basic components of a door or window frame (b) . . . . . . . . . . . . . . . . . . . . . . . . Different types of windows. a—fixed window; b—casement windows; c—hopper window; d—awning window; e—European tilt and turn window; f—vertical pivot window; g—horizontal pivot window; h—sliding window; i—double-hung window; j—jalousie window . . . . . . . . . . . . .

..

66

..

69

.. ..

70 75

. . . .

. . . .

75 76 78 78

..

79

..

89

..

91

. . 103

. . 103

. . 105 . . 106

. . 109

List of Figures

Fig. 2.32

Fig. 2.33

Fig. 2.34 Fig. 2.35

Fig. 2.36

Fig. 2.37 Fig. 2.38 Fig. 2.39

Fig. 2.40 Fig. 2.41

Fig. 2.42 Fig. 2.43 Fig. 2.44 Fig. 2.45 Fig. 2.46 Fig. 2.47

Fig. 2.48

Fig. 2.49

Different types of doors. a—side-hung door; b—folding door; c—revolving door; d.1—encased sliding door; d.2—surface hung sliding door . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steps in the execution of wood door and window frames: a gluing wood profiles; b installing sealants; and c ironmongery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steps in the execution of aluminium door and window frames: a sealing profiles; b fastening profiles; and c ironmongery . . . Heritage building with the pitched roof cladded with clay-slate tiles (a) and building with the external cladding of the pitched roof in clay-slate tiles (b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . Different types of ceramic roof tiles. a—interlocking roof tile; b—Marseille roof tile; c—interlocking flat roof tile; d—Monk and Nun roof tiles; e—Roman roof tiles; f—flat roof tile . . . . Example of a pitched roof with Monk and Nun tiles . . . . . . . Inclusion of polypropylene strips in the corrugated profiles of fibre-cement sheets for better resistance . . . . . . . . . . . . . . . Different types of metallic roof claddings: a copper roof cladding; b zinc roof cladding; c curved metallic roof cladding; d trapezoidal metallic sheet roof cladding; and e moulded metallic sheet roof cladding mimicking ceramic roof tiles . . . Composition of bitumen and aluminium sheet coated steel plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of fastening criteria for ceramic roof tiles with interlock in a roof with a slope higher than 150% (a), and for flat ceramic roof tiles in a roof with a slope higher than 175% (b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of clay-slate tiles over a wood deck using nails and clamps (a) and over wood battens using nails (b) . . . . . . . . . . Alignment and beginning of application of interlocking ceramic tiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flat tiles with aligned (a) and misaligned joints (b) . . . . . . . . Minimal overlay of micro-concrete tiles according to the roof slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Direction for applying fibre-cement sheets . . . . . . . . . . . . . . . Applying bituminous strips as a watertightness complement in the transverse (a) and longitudinal (b) overlays of metallic roof claddings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrangement of fastening elements of metallic and plastic roof claddings. a—Fastening to structure elements; b—fastening to underlaying cladding sheets . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of ways of adhering plastic roof claddings elements together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xv

. . 110

. . 111 . . 112

. . 114

. . 116 . . 118 . . 122

. . 123 . . 133

. . 139 . . 141 . . 142 . . 143 . . 144 . . 145

. . 146

. . 147 . . 148

xvi

Fig. 2.50

Fig. 2.51

Fig. 2.52

Fig. 2.53 Fig. 2.54

Fig. 3.1 Fig. 3.2 Fig. 3.3 Fig. 3.4

Fig. 3.5

Fig. 3.6

List of Figures

Comparison of the temperature profile (warm weather case) in (a) a traditional flat roof and in (b) an inverted flat roof (data from DuPont [2019b]). 1—protection layer; 2—waterproofing layer; 3—thermal insulation layer; 4—bearing structure . . . . . Design details of tail-ends of waterproofing in parapet walls (general cases): a protected tail-end and b unprotected tail-end. 1—wall render; 2—brick masonry; 3—tail-end strip of APP modified bitumen membrane; 4—heavy protection layer; 5—separation layer; 6—APP modified bitumen waterproofing membrane; 7—primer (bituminous emulsion) or vapour-barrier (if necessary); 8—bearing structure; 9—sealant; 10—aluminium flashing profile; 11—tail-end strip of self-protected APP modified bitumen membrane . . . . . . . . . . . Design detail of the adequate tail-end in doorsills (general case). 1—doorsill with a drip edge, laid on a bed of mortar; 2—metal flashing; 3—waterproofing layer; 4—pavers on paver pedestals; 5—thermal insulation (thickness in accordance with thermal regulations); 6—vapour-barrier; 7—shaping layer; 8—bearing structure; 9—thermal break to avoid a thermal bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design detail of a coping in stone or precast concrete of a parapet wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design detail of an expansion joint in a flat roof (general case). 1—neoprene cord; 2—tail-end strip of self-protected APP modified bitumen membrane; 3—tail-end strip of APP modified bitumen membrane; 4—heavy protection layer; 5—separation layer; 6—APP modified bitumen waterproofing membrane; 7—primer (bituminous emulsion) or vapour-barrier (if necessary); 8—shaping layer; 9—bearing structure . . . . . . Examples of defects of physical nature: a A-A1 leakage damp; b A-A2 surface damp; c A-A3 dirt . . . . . . . . . . . . . . . . . . . . . Examples of defects of physical nature: a A-A4 colour changes; b A-A5 peeling; c A-A6 disaggregation . . . . . . . . . . Examples of defects of chemical nature: a A-B1 biological growth; b A-B2 vegetation growth; c A-B3 efflorescence . . . . Examples of defects of chemical nature: a A-B4 bulging; b A-B5 corrosion on the current surface; c A-B6 corrosion in metallic fastening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of defects of mechanical nature: a A-C1 mapped cracking; b A-C2 oriented cracking on the current surface; c A-C3 fracture on the current surface . . . . . . . . . . . . . . . . . . Examples of defects of mechanical nature: a A-C4 splintering adjacent to edges; b A-C5 scaling of the finishing coat; c A-C6 deep wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 162

. . 165

. . 165 . . 166

. . 167 . . 190 . . 191 . . 192

. . 193

. . 194

. . 194

List of Figures

Fig. 3.7

Fig. 3.8 Fig. 3.9

Fig. 3.10

Fig. 3.11

Fig. 3.12

Fig. 3.13

Fig. 3.14 Fig. 3.15

Fig. 3.16 Fig. 3.17 Fig. 3.18 Fig. 3.19 Fig. 3.20 Fig. 3.21 Fig. 3.22 Fig. 3.23 Fig. 3.24

Examples of defects of mechanical nature: a A-C7 flatness deficiencies; b A-C8 material gap; c A-C9 detachment of the wall render . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of defects of mechanical nature: a A-C10 loss of adhesion; b A-C11 bending of metallic fastening element . . . Examples of other defects: a A-D1 flaws in tail-end elements; b A-D2 misalignment of cladding elements; c A-D3 finishing defects/discontinuities in architectural concrete surfaces . . . . . Examples of other defects: a A-D4 finishing colour flaws in painted façades; b A-D5 finishing texture flaws in painted façades; c A-D6 degradation of the filling material of current joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of other defects: a A-D7 loss of filling material in current joints; b A-D8 inadequate operation of expansion joints in flat roofs; c A-D9 insufficient overlap of the claddings elements in roofs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of other defects: a A-D10 gaps in door and window frames; b A-D11 absent or damaged hinges or locks in door and window frames; c A-D12 ponding/insufficient slope in roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of other defects: a A-D13 inadequate operation of elements of the rainwater drainage system; b A-D14 deficient capping adjacent to flat roofs; c A-D15 incorrect or deficient interventions in claddings of pitched roofs . . . . . . . . . . . . . . . Incorrect detailing of a window-sill in an ETICS façade. . . . . Defects in an architectural concrete surface that were probably caused by the application in unfavourable weather conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deformation of the bearing structure of a pitched roof . . . . . . Ceramic roof tiles of a pitched roof affected by strong wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Efflorescence in an architectural concrete surface . . . . . . . . . . Vegetation growth in a façade associated with the lack of cleaning of debris on horizontal surfaces . . . . . . . . . . . . . . . . Two-dimensional correlation matrix between defects and causes of defects, as defined by de Brito et al. (1994) . . . . . . Schematic three-dimensional defects–causes correlation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interpreting the three-dimensional correlation matrix . . . . . . . Possible analysis sequences allowed by a three-dimensional matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Proportions of the three-dimensional matrix between defects and probable causes of defects within the building envelope inspection system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xvii

. . 195 . . 195

. . 196

. . 197

. . 198

. . 198

. . 199 . . 208

. . 212 . . 214 . . 216 . . 222 . . 226 . . 234 . . 235 . . 235 . . 236

. . 237

xviii

Fig. 3.25 Fig. 3.26 Fig. 4.1

Fig. 4.2 Fig. 4.3

Fig. 4.4

Fig. 4.5

Fig. 4.6

Fig. 4.7

Fig. 4.8

Fig. 4.9 Fig. 4.10

Fig. 4.11

Fig. 4.12

Fig. 4.13

List of Figures

Associating defects through causes to build an inter-defects correlation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic three-dimensional inter-defects correlation matrix . Example of assisted sensory analysis method “D-A3 Assessment of the slope, flatness, orthogonality and alignments”: a inclinometer; b spirit level . . . . . . . . . . . . . . . Example of assisted sensory analysis method “D-A4 Tell-tale gauge and gypsum testimonies”: using a tell-tale gauge . . . . . Examples assisted sensory analyses (method “D-A5 Crack width ruler and crack-measuring microscope”): a use of a crack width ruler; b illustration of the use of a crack-measuring microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of assisted sensory analysis method “D-A6 Mechanical strain gauge”: drawing of a digital mechanical strain gauge and a steel calibration bar . . . . . . . . . . . . . . . . . . Examples of electrical methods: a diagram of “D-B1 Eddy currents”; b use of a magnetometer in a reinforced concrete column (“D-B4 Magnetometry”) . . . . . . . . . . . . . . . . . . . . . . . Examples of thermo-hygrometric methods: a use of a surface moisture meter (“D-C1 Measurement of the ambient and/or surface temperature and humidity”); b moisture meter with long probes (“D-C2 Measurement of in-depth humidity”) . . . Examples of use of the thermo-hygrometric method “D-C3 Infrared thermography”: a thermographic camera; b thermogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of sound and acoustic methods: a illustration of the use of ultrasound probes in a wall cladding (“D-D1 Ultrasound”); b use of a rubber hammer (“D-D2 Percussion”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diagram of “D-E1 Nuclear method” . . . . . . . . . . . . . . . . . . . . Example of the hydric method “D-F1 Watertightness test”: schematic view of both the flat roof with a water surface 2.5 cm thick and a top floor room, whose ceiling shows subsequent signs of leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of hydric methods: a schematic view of performing “D-F2 Water jet”; b schematic view of performing “D-F3 submersion of the base of window frames” . . . . . . . . . . . . . . Examples of hydric method “D-F4 Initial surface absorption test (ISAT) and Karsten-tube”: a scheme of the typical assembly of the ISAT; b Karsten-tube apparatus . . . . . . . . . . Examples of use of the mechanical method “D-G1 Sphere impact, grid cutting, scratching and abrasion tests (Martinet Baronnie)”: a sphere impact test; b grid cutting test . . . . . . . .

. . 246 . . 247

. . 260 . . 261

. . 262

. . 263

. . 264

. . 267

. . 268

. . 272 . . 274

. . 275

. . 276

. . 277

. . 279

List of Figures

Fig. 4.14

Fig. 4.15 Fig. 4.16

Fig. 4.17 Fig. 4.18

Fig. 4.19 Fig. 4.20 Fig. 4.21

Fig. 5.1

Fig. 5.2 Fig. 5.3

Fig. 5.4

Fig. 5.5

Fig. 5.6

Examples of the mechanical method “D-G6 Pull-off test”: a core drilling machine; b illustration of an hydraulic pull-off equipment; and c and d two other different types of hydraulic pull-off equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of pressure method “D-H1 Ventilator test”: schematic view of the assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of colour methods: a drawing of a generic colour meter (“D-I1 Colour meter”); b use of the NCS colour scale (“D-I2 Munsell system or NCS scale colour specification”) . . Examples of use of the chemical method “D-J2 Test strips and field kit”: a test strip and comparison scale; b field kit . . . . . . Two-dimensional correlation matrix between defects and diagnosis methods as defined by de Brito (1992) and Branco and de Brito (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic three-dimensional defects–diagnosis methods correlation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interpreting the three-dimensional defects–diagnosis methods correlation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Proportions of the three-dimensional defects–diagnosis methods correlation matrix within the building envelope inspection system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of: a dust caused by repair works in the narrow streets of a city’s historical centre; and b a building’s scaffolding covered with protection net . . . . . . . . . . . . . . . . . . Example of use of repair technique “R-A1 Cleaning”: high-pressure air jet to clean natural stone . . . . . . . . . . . . . . . Example of “R-A2 Application of a protective coat (paint, varnish, water-repellent, antifungal, biocide)”: illustration of application of a hydrophobic product on a cladding surface and its effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of locations where fibreglass mesh should be used when applying repair technique “R-A11 Replacement or reapplication of the cladding/glazing (partially or completely)” . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of using fibreglass mesh in the whole surface of a rehabilitated render while applying repair technique “R-A11 Replacement or reapplication of the clad-ding/glazing (partially or completely)” . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of repair technique “R-A12 Application of a new (adequate) cladding/finishing coat over the existent/replacement”: application of one of the new coats of paint in a façade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xix

. . 280 . . 282

. . 283 . . 284

. . 288 . . 289 . . 289

. . 290

. . 306 . . 309

. . 315

. . 318

. . 321

. . 323

xx

Fig. 5.7

Fig. 5.8 Fig. 5.9

Fig. 5.10

Fig. 5.11

Fig. 5.12

Fig. 5.13 Fig. 5.14

Fig. 5.15

Fig. 5.16

Fig. 5.17

Fig. 5.18 Fig. 5.19 Fig. 5.20

List of Figures

Example of an attempt to repair a cracked stone plate with repair technique “R-A13 Treatment of cracks or other holes in the cladding”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of “R-B4 Application/repair/replacement of the vapour barrier”: scheme of a non-ventilated pitched roof . . . . Example of “R-B11 Change/replacement/repair of the fastening system or correction of the holes in the plates or substrate”: in a riveted metallic roof cladding, introduction of a self-tapping screw next to a loose rivet . . . . . . . . . . . . . . Example of “R-C3 Application/replacement of the shaping or levelling layer”: diagram of the replacement levelling layer of a flat roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of repair technique “R-C4 Repair of dead cracks in the substrate and reapplication of the cladding”: diagram of the different stages (from top to bottom) of the repair process, beginning with the crack already exposed . . . . . . . . . . . . . . . . Example of “R-D2 Replacement/repair of current joints’ filling material and/or joints cleaning”: illustration of removing the degraded joint filling material . . . . . . . . . . . . . . . . . . . . . . . . . Example of elastic joints in a renewed adhesive ceramic tiling façade (“R-D4 Joint thickness increase or joint insertion”) . . . Example of use of repair technique “R-D6 Application/repair/replacement/cleaning of drainage systems/plumbing” by redrawing the drainage system and replacing hoppers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example of misuse of repair technique “R-D7 Removal of corroded or damaged metallic elements, with hole and notch filling (if applicable)”: area from where a corroded metallic element was removed, leaving rust behind and a sloppy hole filling job . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Examples of use of profiles in the perimeter (b) and corner (a) of adhesive ceramic tiling, according to “R-D9 Protecting or smoothing protruding corners or edges” . . . . . . . . . . . . . . . Examples of: a using gutters in rehabilitated eaves as preconised by repair technique “R-D14 Correction of geometrical construction details”; and b drip detail in a window sill but without extending over the side of the window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two-dimensional correlation matrix between defects and repair techniques as defined by Branco and de Brito (2004) . . Schematic three-dimensional defects–repair techniques correlation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interpreting the three-dimensional defects–repair techniques correlation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 325 . . 329

. . 330

. . 332

. . 332

. . 334 . . 335

. . 336

. . 337

. . 338

. . 339 . . 343 . . 344 . . 345

List of Figures

Fig. 5.21

Fig. 6.1 Fig. 6.2 Fig. 6.3 Fig. 6.4

Fig. 6.5 Fig. 6.6 Fig. 6.7

Fig. 6.8 Fig. 6.9 Fig. 6.10 Fig. 6.11

Fig. 6.12 Fig. 6.13

Fig. 6.14 Fig. 6.15 Fig. 6.16 Fig. 6.17 Fig. 6.18

Proportions of the three-dimensional defects–repair techniques correlation matrix within the building envelope inspection system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Header, description and field of application of the file of defect “A-B6 Corrosion in metallic fastening or tail-end elements” . Probable causes and possible consequences of the file of defect “A-B6 Corrosion in metallic fastening or tail-end elements” . Aspects to inspect and diagnosis methods of the file of defect “A-B6 Corrosion in metallic fastening or tail-end elements” . Classification parameters, urgency of repair and repair techniques of the file of defect “A-B6 Corrosion in metallic fastening or tail-end elements” . . . . . . . . . . . . . . . . . . . . . . . . Complete file of defect “A-B6 Corrosion in metallic fastening or tail-end elements” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page of the atlas of defects corresponding to defect “A-C5 Wear or scaling of the finishing coat”. . . . . . . . . . . . . . . . . . . Header, type of method, objectives, materials and equipment needed, field of application and photographs of the file of diagnosis method “D-J2 Test strips and field kit” . . . . . . . . . . Description of the file of diagnosis method “D-J2 Test strips and field kit” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages, limitations and references of the file of diagnosis method “D-J2 Test strips and field kit” . . . . . . . . . . . . . . . . . . Complete file of diagnosis method “D-J2 Test strips and field kit” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Header, location, type, equipment and materials needed and field of application of the file of repair technique “R-A6 Creation of pathways”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Description of the file of repair technique “R-A6 Creation of pathways” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Estimated labour and target time, estimated cost, expected results, critical areas and references of the file of repair technique “R-A6 Creation of pathways” . . . . . . . . . . . . . . . . . Complete file of repair technique “R-A6 Creation of pathways” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sections of the inspection form for a header and for weather conditions data at inspection time . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form for information on the building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form for environmental exposure data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form for information on each building element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xxi

. . 346 . . 359 . . 359 . . 360

. . 361 . . 362 . . 367

. . 368 . . 369 . . 369 . . 370

. . 372 . . 373

. . 373 . . 374 . . 376 . . 377 . . 377 . . 378

xxii

Fig. 6.19 Fig. 6.20

Fig. 6.21 Fig. 6.22 Fig. 6.23

Fig. 6.24 Fig. 6.25 Fig. 6.26 Fig. 6.27 Fig. 7.1 Fig. 7.2 Fig. 7.3

Fig. 7.4 Fig. 7.5 Fig. 7.6 Fig. 7.7

Fig. 7.8 Fig. 7.9

Fig. 7.10

List of Figures

Sections of the inspection form for general maintenance data, maintenance data on specific building elements and notes . . . Sections of the inspection form to identify detected defects, determine their level of urgency of repair and characterise them . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form to identify the probable causes of detected defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form to identify the adequate diagnosis methods for each detected defect . . . . . . . . . . . . . . . Sections of the inspection form to propose repair techniques for each detected defect and to place photographs of the detected defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cover page of the inspection form . . . . . . . . . . . . . . . . . . . . . First part of the inspection form . . . . . . . . . . . . . . . . . . . . . . . Second part of the inspection form, in this case, for the characterisation of an architectural concrete surface . . . . . . . . Third part of the inspection form, in this case, to characterise the degradation of an architectural concrete surface . . . . . . . . Section of the inspection form with general data about the conditions at inspection time . . . . . . . . . . . . . . . . . . . . . . . . . . General view of the coffee house building . . . . . . . . . . . . . . . Sections of the inspection form with general data about the building’s environmental exposure characteristics and maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General view of the adhesive ceramic tiling surfaces . . . . . . . Section of the inspection form with data on the characteristics of one of the adhesive ceramic tiling surfaces . . . . . . . . . . . . View of the degradation of the joint filling material in the adhesive ceramic tiling surfaces . . . . . . . . . . . . . . . . . . . . . . . Sections of the inspection form with data on the defects detected on the green adhesive ceramic tiling surface, including: urgency of repair, specific characteristics, and identification of probable causes, diagnosis methods and repair techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vegetation growth in the lower area of the façade cladded with adhesive ceramic tiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analysed architectural concrete surfaces in the coffee house: a partial view of the surface on the main façade; b surface on the side façade; and c partial view of the surface on the rear façade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form with data on the characteristics of one of the architectural concrete surfaces . . . . . . . . . . . . . .

. . 379

. . 380 . . 380 . . 381

. . 381 . . 382 . . 383 . . 385 . . 386 . . 398 . . 399

. . 400 . . 402 . . 403 . . 404

. . 405 . . 414

. . 415 . . 416

List of Figures

Fig. 7.11

Fig. 7.12

Fig. 7.13 Fig. 7.14 Fig. 7.15 Fig. 7.16 Fig. 7.17 Fig. 7.18 Fig. 7.19

Fig. 7.20 Fig. 7.21 Fig. 7.22 Fig. 7.23 Fig. 7.24 Fig. 7.25 Fig. 7.26 Fig. 7.27

Fig. 7.28

Fig. 7.29 Fig. 7.30

Section of the inspection form with data on the detected defects and their urgency of repair referring to the architectural concrete surface in the front façade. . . . . . . . . . . . . . . . . . . . . Defects in architectural concrete surfaces: a wear in the front façade; and b efflorescence in the rear façade; both photographs also show signs of biological growth . . . . . . . . . Section of the inspection form with data on the characteristics of one of the window frames . . . . . . . . . . . . . . . . . . . . . . . . . Appearance of the lower frame profiles of the casement window in the front façade . . . . . . . . . . . . . . . . . . . . . . . . . . . Aerial view of the coffee house (adapted from Google Images and Maxar Technologies 2019) . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form with data on the characteristics of the main flat roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accumulation of pine cones and needles in the main flat roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General view of the inspected house . . . . . . . . . . . . . . . . . . . . Partial views of the inspected natural stone claddings in the detached house: a front façade (northwest); b side façade (northeast); c side façade (southwest) . . . . . . . . . . . . . . . . . . . Section of the inspection form with data on the characteristics of the natural stone claddings in the front façade . . . . . . . . . . Diamond-shaped adhesive ceramic tiles showing defects . . . . Section of the inspection form with data on the characteristics of the wall renders in the southwest façade . . . . . . . . . . . . . . Section of the inspection form with data on the characteristics of the southwest painted façade . . . . . . . . . . . . . . . . . . . . . . . Oriented cracking in the southwest façade (highlighted in green) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of the inspection form with data on the characteristics of the external cladding of the pitched roof . . . . . . . . . . . . . . Accumulation of debris in the pitched roof . . . . . . . . . . . . . . . Partial views of the inspected natural stone claddings at the museum: a front façade (southeast); and b side façade (north) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General views of the ETICS surfaces inspected in the museum: a recessed surface on the front façade (east); b main surface of the front façade (southeast); and c side façade (north) . . . . Section of the inspection form with data on the characteristics of one of the ETICS surfaces . . . . . . . . . . . . . . . . . . . . . . . . . Surface moisture, dirt, colour changes, oriented cracking and flaws in a tail-end in the main ETICS surface of the front façade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xxiii

. . 417

. . 419 . . 421 . . 422 . . 424 . . 425 . . 426 . . 427

. . 428 . . 429 . . 430 . . 432 . . 433 . . 434 . . 436 . . 437

. . 438

. . 439 . . 441

. . 442

xxiv

Fig. 7.31

Fig. 7.32

Fig. 7.33

Fig. 7.34

Fig. 7.35

Fig. 7.36

Fig. 7.37

Fig. 7.38

Fig. 7.39

List of Figures

Partial view of the main surface of the front façade with oriented cracking highlighted in blue and efflorescence stains circled in red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inspected door frame in the main entrance of the museum: a general view; and b detail of a loose sealant of the glazed surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inspected flat roof: a partial view with a railing on the left; and b the roof drain without a dome strainer, additionally showing vegetation growth around the drain and biological growth on the surface of the concrete paving slabs . . . . . . . . . . . . . . . . . Set of pictures illustrating an ETICS surface: a general view; b detail of the lower tail-end with visible cracking; c detail of the intersection with a parapet wall with visible cracking; d rectangle-shaped cracked area with efflorescence; and e gap in the base and finishing coats . . . . . . . . . . . . . . . . . . . . . . . . Absolute frequency of recommendation of each type of diagnosis method (a) and relative frequency of recommendation of each type of diagnosis method according to the number of detected defects (b) . . . . . . . . . . . . . . . . . . . Estimated urgency of repair of each type of defect detected in the sample. 0—imminent danger, contingency measures needed; 1—need of immediate intervention; 2—need of intervention in the short-term; 3—need of intervention in the long-term; 4—no urgent need, assess in the next inspection . . Relative frequency of occurrence of the groups of causes. C-A —design errors; C-B—execution errors; C-C—mechanical actions; C-D—environmental actions; C-E—use and maintenance errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relative contribution of the groups of causes to the occurrence of each group of defects. A-A—defects of physical nature; A-B—defects of chemical nature; A-C—defects of mechanical nature; A-D—other defects; C-A—design errors; C-B—execution errors; C-C—mechanical actions; C-D—environmental actions; C-E—use and maintenance errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relative frequency of recommendation of repair techniques in the 22 observations of defect “A-A3 Dirt and accumulation of debris”. R-A1—cleaning; R-A2—application of a protective coat (paint, varnish, water-repellent, antifungal, biocide); R-A12—application of a new (adequate) cladding/finishing coat over the existent/replacement; R-D14—correction of geometrical construction details . . . . . . . . . . . . . . . . . . . . . . .

. . 443

. . 444

. . 445

. . 450

. . 453

. . 454

. . 455

. . 455

. . 456

List of Figures

Fig. 8.1

Fig. 8.2

Fig. 8.3

xxv

Provisional diagram of the building inspection software tool. (a) digital interface for building inspection processes; (b) digital interface for the production of reports; (c) execution of building inspection processes; (d) execution of reports’ production processes; (e) processes to access the building inspection system; (f) processes to update the building inspection system; (g) datablocks with the inspection system information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 Translated screenshot (from Portuguese) of the first developments of the software tool: identification of a new inspection and weather conditions. . . . . . . . . . . . . . . . . . . . . . . . 461 Translated screenshot (from Portuguese) of the first developments of the software tool: characterisation of an inspected building element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

List of Tables

Table 1.1 Table 2.1 Table 2.2 Table 2.3 Table 2.4

Table 2.5 Table 2.6 Table 2.7 Table 2.8 Table 2.9

Table 2.10 Table 2.11 Table 2.12 Table 2.13 Table 2.14 Table 2.15 Table 2.16

Expert building inspection systems developed at IST-UL . . Classification of rocks (adapted from Tyrrell [1978] and Siegesmund and Török [2014]) . . . . . . . . . . . . . . . . . . . . . . Important characteristics of natural stone (Siegesmund and Dürrast 2014; Siegesmund and Török 2014) . . . . . . . . . Functional requirements of natural stone claddings for façades (Lucas 2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Description of the most common types of finish for natural stone (García-del-Cura et al. 2008; Camposinhos 2014; Marble Institute of America 2016) . . . . . . . . . . . . . . . . . . . . Minimal height of the notches of trowels used in large size tiles (Cass 2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Admixtures (Rixom and Mailvaganam 1999; Aggoun et al. 2008; Flores-Colen and de Brito 2015) . . . . . . . . . . . . . . . . Additions (Flores-Colen and de Brito 2015) . . . . . . . . . . . . External claddings of the building envelope (adapted from Lucas [2011]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison between a traditional render and a non-traditional (one-coat) render (Hernández-Olivares and Mayor-Lobo 2011; Flores-Colen and de Brito 2015) . . . . . . Main characteristics of pigments (adapted from Talbert [2008] and Eusébio and Rodrigues [2009, 2016]) . . . . . . . . Main types of vehicles in paint (Talbert 2008; Eusébio and Rodrigues 2009; CEN 2014c) . . . . . . . . . . . . . . . . . . . . . . . Estimated partial costs of painting works (Nogueira 2008) . Examples of accessories for ETICS . . . . . . . . . . . . . . . . . . . Summary of the essential requirements defined for ETICS and respective tests (EOTA 2013) . . . . . . . . . . . . . . . . . . . . Treatment measures for substrates (adapted from Sto Corp. [2009]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Primer examples for substrate preparation . . . . . . . . . . . . . .

..

7

..

18

..

20

..

23

..

28

..

41

.. ..

44 44

..

45

..

48

..

53

.. .. ..

55 57 66

..

68

.. ..

73 74 xxvii

xxviii

Table 2.17 Table 2.18 Table 2.19 Table 2.20 Table 2.21 Table 2.22 Table 2.23 Table 2.24 Table 2.25 Table 2.26 Table 2.27 Table 2.28 Table 2.29 Table 2.30 Table 2.31 Table 2.32 Table 2.33 Table 2.34 Table 2.35 Table 2.36 Table 2.37 Table 2.38 Table 2.39

List of Tables

Wood species commonly used in door and window frames (Sousa 2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Initial type test for external windows and pedestrian doors (adapted from Pinto and Fernandes [2011]) . . . . . . . . . . . . . Types of external claddings of pitched roofs . . . . . . . . . . . . Main characteristics of clay-slate tiles (Levine 1993) . . . . . . Main characteristics of Marseille roof tiles (CTCV 1998; LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of interlocking roof tiles (CTCV 1998; LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of Monk and Nun roof tiles (LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of Roman roof tiles (CTCV 1998; LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of flat roof tiles (CTCV 1998) . . . . . . . Main characteristics of interlocking flat roof tiles (CS Coelho da Silva SA 2016) . . . . . . . . . . . . . . . . . . . . . . Main characteristics of micro-concrete roof tiles (Argibetão 2009; LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of flat fibre-cement roof tiles (Cembrit 2018; Eternit 2019a) . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of corrugated fibre-cement roof sheets (Cembrit 2017, 2019; Eternit 2019b) . . . . . . . . . . . . . . . . . . Metallic materials used in the external cladding of pitched roofs and their minimal thickness . . . . . . . . . . . . . . . . . . . . . Main characteristics of steel roof claddings (EDAR 2018; LNEC 2018; Mundiperfil 2019) . . . . . . . . . . Main characteristics of aluminium roof claddings (Zappone 2000; EDAR 2018; LNEC 2018) . . . . . . . . . . . . . Main characteristics of copper roof claddings (Bragança et al. 2003; EDAR 2018) . . . . . . . . . . . . . . . . . . Main characteristics of zinc roof claddings (VMZINC 2016; Rheinzink 2017; EDAR 2018; LNEC 2018) . . . . . . . . . . . . Distance between bearing points for polymethacrylate sheets’ roofs (INDAC 2015) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of polymethacrylate roof sheets (INDAC 2015; LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of polycarbonate roof sheets (Sabic 2013; Dagol 2016a, b; Onduline 2019) . . . . . . . . . . . . . . . . Main characteristics of glass fibre reinforced polyester roof sheets (LNEC 2018; Onduline 2019) . . . . . . . . . . . . . . . . . . Main characteristics of PVC roof sheets (Palram 2013; H&F Manufacturing Corporation 2018; LNEC 2018) . . . . . . . . . .

..

98

. . 107 . . 113 . . 114 . . 117 . . 117 . . 118 . . 119 . . 119 . . 120 . . 121 . . 122 . . 122 . . 124 . . 125 . . 126 . . 127 . . 128 . . 129 . . 130 . . 130 . . 131 . . 132

List of Tables

Table 2.40 Table 2.41 Table 2.42

Table 2.43

Table 2.44 Table 2.45 Table 2.46 Table 2.47 Table 2.48 Table 2.49

Table 2.50 Table 2.51 Table 2.52

Table 2.53 Table 2.54 Table 3.1 Table 3.2 Table 3.3

Table 3.4

xxix

Main characteristics of sandwich panels for roof claddings (Irmalex 2015; Painel 2000; Alaço 2019a, b) . . . . . . . . . . . . Main characteristics of asphalt shingles for roof claddings (GAF 2019; Onduline 2019) . . . . . . . . . . . . . . . . . . . . . . . . Main characteristics of metallic tiles and slates coated with mineral granules for roof claddings (Decra Metal Roofing 2015; Boral Steel 2018, 2019) . . . . . . . . . . . . . . . . . . . . . . . Minimum slope of pitched roofs with ceramic tiles in Portugal (slope in centimetres per metre of horizontal projection) (CTCV 1998) . . . . . . . . . . . . . . . . . . . . . . . . . . . Overlay according to exposure of the roof for ceramic tiles without interlock (CTCV 1998) . . . . . . . . . . . . . . . . . . Fastening of cover and channel tiles according to wind loads and the slope of the roof (adapted from CTCV [1998]) . . . . Overlay of fibre-cement sheets according to the roof slope (LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Different fastening systems for metallic roof claddings . . . . Top overlay according to the roof’s slope for plastic roof claddings (LNEC 2018) . . . . . . . . . . . . . . . . . . . . . . . . Basic requirements (The European Parliament and The Council of the European Union 2011) and components of a flat roof . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of traditional waterproofing materials (adapted from Lopes [2010]) . . . . . . . . . . . . . . . . . . . . . . . . Classification of non-traditional waterproofing materials (adapted from Lopes [2010]) . . . . . . . . . . . . . . . . . . . . . . . . Technical specifications of the most commonly used insulation materials in the building sector (adapted from Lopes [2010], ImperMachado [2014], DuPont [2019a], Fibrosom [2019], and Viero [2019]) . . . . . . . . . . . . . . . . . . Functional and economic requirements of flat roofs (adapted from Lopes [2010]) . . . . . . . . . . . . . . . . . . . . . . . . Available options to consider at the design stage of a flat roof (adapted from Lopes [2010]) . . . . . . . . . . . . . . Classification of defects in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . Defects–building elements/materials matrix in a global inspection system for the building envelope . . . . . . . . . . . . . Classification of probable causes in the category “design errors” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of probable causes in the category “execution errors” in a global inspection system for the building envelope (part 1 of 2) . . . . . . . . . . . . . . . . . . . . . .

. . 134 . . 134

. . 135

. . 138 . . 139 . . 140 . . 145 . . 146 . . 148

. . 150 . . 151 . . 153

. . 158 . . 160 . . 161 . . 189 . . 200

. . 202

. . 204

xxx

Table 3.5

Table 3.6

Table 3.7

Table 3.8

Table 3.9 Table 3.10

Table 3.11

Table 3.12

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Table 4.5

List of Tables

Classification of probable causes in the category “execution errors” in a global inspection system for the building envelope (part 2 of 2) . . . . . . . . . . . . . . . . . Classification of probable causes in the category “mechanical actions” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of probable causes in the category of “environmental actions” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of probable causes in the category “use and maintenance errors” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . Probable causes–building elements/materials matrix in a global inspection system for the building envelope . . . . . . . Excerpt of the defects–probable causes correlation matrix in a global inspection system for the building envelope (layer for natural stone claddings) referring only to environmental actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Excerpt of the inter-defects correlation matrix in a global inspection system for the building envelope (layer for natural stone claddings) referring only to defects of physical and chemical nature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Excerpt of the inter-defects percentage correlation matrix in a global inspection system for the building envelope (layer for natural stone claddings) referring only to defects of physical and chemical nature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of diagnosis methods in the category assisted sensory analysis in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of diagnosis methods in the categories electrical methods and thermo-hygrometric methods in a global inspection system for the building envelope . . . . . . . Classification of diagnosis methods in the categories sound and acoustic methods, nuclear methods and hydric methods in a global inspection system for the building envelope . . . . Classification of diagnosis methods in the category mechanical methods in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of diagnosis methods in the categories pressurization methods, colour methods and chemical methods in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 205

. . 205

. . 206

. . 207 . . 228

. . 239

. . 244

. . 245

. . 260

. . 264

. . 271

. . 278

. . 281

List of Tables

Table 4.6 Table 4.7

Table 5.1

Table 5.2

Table 5.3

Table 5.4

Table 5.5 Table 5.6

Table 6.1 Table 7.1 Table 7.2

xxxi

Diagnosis methods–building elements/materials matrix in a global inspection system for the building envelope . . . . . . . Excerpt of the defects–diagnosis methods correlation matrix in a global inspection system for the building envelope (layer for wall renders) referring only to thermo-hygrometric, sound and acoustic, nuclear, hydric and mechanical methods . . . . . Classification of repair techniques in the category “surface of the cladding” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of repair techniques in the category “cladding system” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of repair techniques in the category “change in the bearing structure/substrate” in a global inspection system for the building envelope . . . . . . . . . . . . . Classification of repair techniques in the category “singularities” in a global inspection system for the building envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Repair techniques–building elements/materials matrix in a global inspection system for the building envelope . . . . Excerpt of the defects–repair techniques correlation matrix in a global inspection system for the building envelope (layer for external claddings of pitched roofs), referring only to defects of physical, chemical and mechanical nature and to repair techniques in categories “surface of the cladding” and “change in the bearing structure/substrate” . . . . . . . . . . . . . . Structure of a page of the atlas of defects . . . . . . . . . . . . . . Area of inspected façade building elements according to the orientation of the façade . . . . . . . . . . . . . . . . . . . . . . . Area of inspected building elements according to the type of building element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 286

. . 292

. . 304

. . 328

. . 331

. . 333 . . 340

. . 348 . . 366 . . 451 . . 452

Chapter 1

Buildings’ Management

Abstract The construction, operation and maintenance, and end of life stages compose the life-cycle of buildings. The operation and maintenance stage, comprising the service life of buildings, may be associated with more than half of their life-cycle costs. Given that importance, it is essential to plan maintenance to optimise costs and keep acceptable performance levels of the buildings, postponing the end of the service life. Within a building, its envelope is paramount to withstand external aggressions and guarantee minimum comfort levels for the occupants. But buildings are complex systems composed of several different assemblies/materials, which increases the uncertainty levels of planning and performing building maintenance. To deal with that uncertainty, predictive maintenance relies on the planned and systematised collection and analysis of information on building elements to adapt maintenance actions accordingly. Inspection systems provide the methodology and tools for that collection and analysis of information. Various inspection systems have already been developed, some more focused on divulging information, others trying to provide customised diagnosis, and others with a solid and broad information structure. Among those, a set of identically structured inspection systems for individual elements of the building envelope was selected as the basis for developing a global inspection system.

1.1 Background In general terms, the life of a system comprises the following phases (Wübbenhorst 1986): initiation, planning, realisation, operation, and disposal/salvage. ISO/TR 15686-11:2014 (International Organization for Standardization [ISO] 2014) transposes these phases to the specificity of a building system, defining the life-cycle of a building as consecutive connected stages, encompassing construction, operation and maintenance and the end of life, which includes decommissioning, deconstruction and disposal. According to Islam et al. (2015), based on the outcomes of Australian, European and North American life-cycle costs studies, the operation and maintenance stages may represent up to 54% of the costs of a building’s life-cycle, depending on the assumptions and boundaries of the studied systems. Such economic impact of © Springer Nature Switzerland AG 2020 J. de Brito et al., Expert Knowledge-based Inspection Systems, https://doi.org/10.1007/978-3-030-42446-6_1

1

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1 Buildings’ Management

the operation and maintenance stages emphasises their importance and the relevance of optimising costs and performance through maintenance plans. The operation and maintenance stages comprise the service life of a building, which is the period during which the building or its parts meet or exceed the performance requirements (ISO 2014). So, the establishment of (more or less demanding) performance requirements by the stakeholders is critical to determine the end of the service life. When the minimum performance requirements are not met, the building may enter the end of life stage, unless changes are made to re-establish its performance levels. Performance requirements may refer to several categories of performance acting isolated or in combination, such as physical and functional performance (Shohet et al. 2003; Then et al. 2004; Shohet and Paciuk 2006; Lavy 2011; Lai and Yuen 2019). Additionally, performance requirements may change throughout the service life of a building, determining the end of life due to obsolescence, as the building cannot meet or no longer be adapted to meet the new requirements (ISO 2011). Functional, technological and economic obsolescence are defined by ISO 15686-1:2011 (ISO 2011) as the main types of obsolescence, which are considered broad enough to comprise changing social contexts, aesthetics, laws and environmental requirements (Flanagan et al. 1989; Flores-Colen and de Brito 2010a). Physical deterioration is one of the ways by which a building may stop fulfilling minimum performance requirements, hence reaching the end of its service life. Deterioration is a gradual phenomenon associated with physical, chemical and mechanical degradation agents and with the natural ageing process (Silva et al. 2016a). Design and construction errors and use conditions can potentiate the effects of the degradation agents, increasing the rate of deterioration. On the other hand, maintenance may slow down deterioration and prolong the service life of a building, as it minimises the effects of deterioration agents, thus enabling the building to perform its required functions (ISO 2014). In the context of this book, deterioration and degradation are seen as near synonymous. While deterioration refers to “the process of becoming progressively worse” (Lexico 2019a), degradation refers to “the condition or process of degrading or being degraded” (Lexico 2019b). Going deeper into the meaning of degradation, in the context of building maintenance and inspection, degrade may refer to (Lexico 2019c): (i) “lower the quality of; cause to deteriorate”; or (ii) “break down or deteriorate chemically”. Given these definitions by a trustworthy source, the authors consider that degrade implies becoming worse and deterioration implies lowering the quality of something, hence considering the definitions interchangeable in the broad context of maintenance and inspection. Maintenance operations may be (Flores-Colen and de Brito 2010a): preventive, executed at regular intervals; predictive, based on the results of planned inspections; or reactive, correcting unexpected failures, usually, as an emergency. Thus, inspection procedures are framed within the operation and maintenance stage of the life-cycle of a building as a way of improving the accuracy of maintenance operations. Building inspection is a procedure that measures the real degradation condition of building elements through observation and testing, allowing maintenance operations to be

1.1 Background

3

performed accordingly. Otherwise, maintenance is done following degradation estimates or a standard expected service life (Huffmeijer et al. 1998; Blom et al. 2010; Straub 2012).

1.2 Building Envelope The building envelope separates the interior of a building from the outside atmosphere and surroundings (Structural Engineering Institute and American Society of Civil Engineers 2000). It is composed of several elements working together to separate and filter the external conditions for interior comfort (Watt 2007; Silva et al. 2016b). As the envelope surrounds and protects building occupants like a skin, it must be robust, resilient and adaptable to succeed. For instance, in emergencies, such as windstorms, the performance of the building envelope is crucial, as damage in the building escalates after the failure of the first envelope component and losses dramatically increase if the building envelope is breached (Minor 2005). Minimum building envelope requirements vary according to the context of the building, including the climate. For instance, in the USA, building codes in southern climates tend to have less strict thermal insulation requirements than in northern climates (Horne and Hayles 2008). Additionally, considering that the most substantial portion of energy requirements in a building’s life-cycle resides in the operation stage, the behaviour of the building envelope can considerably influence the energy performance of a building (Yohanis and Norton 2006). The condition of the building envelope affects the whole building, as defects in the building envelope directly contribute to the decrease of performance in terms of functional requirements, such as waterproofing, while also negatively influencing others, like thermal insulation (Building Research Establishment [BRE] 1988). The building envelope may be further categorised into roofs, walls, fenestration (doors and windows) and foundations. Often, the performance of the building envelope is conditioned by the intersection between these categorised systems or by their endings. This book focuses on external claddings of roofs and façades and door and window frames.

1.3 Maintenance and Inspection Effectively managing a building implies implementing a maintenance plan to optimise costs while preserving performance levels (Madureira et al. 2017). Developing a maintenance plan involves the detailed knowledge of the building elements, including their behaviour, estimated service life, maintenance needs, degradation mechanisms and their most frequent defects. Then, the strategies implemented in the plan may be proactive (preventive or predictive) or reactive (Palmer 2006).

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Preventive maintenance strategies act before the occurrence of significant changes in building elements, thus avoiding unexpected defects and extra-work through regular actions. It is a strategy based on the theoretical behaviour of the building (FloresColen and de Brito 2010a, b). As for predictive maintenance strategies, they are based on the assessment of maintenance needs in periodic planned inspections. The inspection results provide the degradation condition of each building element and maintenance operations are performed accordingly. Vast knowledge on the in-service behaviour of building elements is required for an accurate diagnosis (Pitt 1997). The reactive strategy, based on corrective actions, responds to advanced degradation in cases of emergency, which occasionally endanger the life of users. The maintenance of buildings may be particularly complex when compared to factory produced equipment. The place where a building is made, the construction site, is always different and influenced by variable conditions (e.g. topography, weather agents, and plot size), as well as by construction site workers, who mostly differ along construction phases and from building to building. Furthermore, the design is specifically developed for each built object and, consequently, the construction procedures have to adapt to that design specifications, achieving a tailor-made building composed of several different materials, with different origins, behaviours, and degradation patterns. Given the complexity of buildings, there is a high uncertainty degree associated with the adequate moment to perform maintenance actions and with the load and type of suitable activities. As predictive maintenance strategies are based on the collection of information on the degradation condition of building elements, adapting maintenance activities to the deterioration detected in buildings, they deal with the uncertainty of building maintenance through systematised data gathering. Still, a balanced maintenance plan should combine several strategies to fulfil its objectives (Chartered Institution of Building Services Engineers 2008). Regardless of the particulars of the plan, inspection activities are fundamental in various stages. For instance, when developing a maintenance plan for existing buildings, the first step is to perform a detailed inspection of the building to identify every building element and determine their real degradation condition. Additionally, whether in new or existing buildings, inspections are part of proactive maintenance actions, using inspection results to adjust the periodicity of interventions according to observed degradation conditions. The accuracy of inspection results influences the nature and extent of repair actions, hence affecting their effectiveness and associated costs. So, inspection procedures should be as unbiased as possible. The systematisation of inspection activities is expected to improve the objectiveness of procedures and the gathering of information to strengthen the diagnosis results. The implementation of an inspection system within a building maintenance plan should standardise the procedures, organising the collection of information, homogenise the technical language, improve communication, and make inspection activities more agile and the whole inspection less dependent on the surveyors’ knowledge and experience, reducing the uncertainty of in situ diagnoses. As a consequence, inspection results are expected to be more reliable.

1.4 Overview of Building Inspection Systems

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1.4 Overview of Building Inspection Systems Ferraz et al. (2016) collected a set of relevant building pathology assessment systems from the literature. That set includes the Defect Action Sheets (BRE 2001), Anomalies Repair Forms (Paiva et al. 1985), Cases of Failure Information Sheet (CIB W86 1993), Building Pathology Sheets (Agence Qualité Construction 2015), Construdoctor (Ribeiro and Cóias e Silva 2003), Learning from Mistakes (de Angelis and Ferro 2004), Patorreb (Freitas et al. 2007), Web-based Prototype System (Fong and Wong 2009), Maintainability Website (Chew 2010), and the Building Medical Record (Chang and Tsai 2013). These systems are similar in terms of data acquisition about defects as they (i) describe the defect, (ii) determine its probable causes, and (iii) recommend diagnosis and repair methods. Some of the systems are based on defect files (Paiva et al. 1985; CIB W86 1993; BRE 2001), marking the beginning of the systematic analysis of building pathology. More recent systems using information technology started divulging defect files in websites (de Angelis and Ferro 2004; Freitas et al. 2007; Agence Qualité Construction 2015), but still lacked case-specific repair solutions. Also using information technology, two systems (Ribeiro and Cóias e Silva 2003; Chang and Tsai 2013) provide online diagnoses based on the information given in a form, which is analysed by experts. However, without first-hand access to occurrences, the reliability of the expert’s conclusions may be compromised. Fong and Wong’s (2009) approach, in turn, chooses to share the knowledge of experts to assist decision-making. Finally, the Maintainability Website (Chew 2010) offers a defects library, a manual of building materials and classification system of diagnosis and repair methods highly based on images. Still, rational connections between defects, materials and diagnosis and repair methods are absent from this website (Ferraz et al. 2016). More recently, in the context of an automation trend in construction, Lee et al. (2016) proposed an inspection methodology that connects data about building defects to building information model (BIM) environments, offering an information flow from the detection of a defect to those responsible for its occurrence, expecting to avoid future errors through the dissemination of information on the pathological phenomena. This method focuses on the structure of degradation and repair information, emphasising the importance of an exact record including repair materials used, affected building elements and their characteristics, rooms where defects were detected, costs and time spent, root causes (to direct the flow of information to those responsible), and a short description of the defect complemented with photographs and drawings. Bortolini and Forcada (2018) also proposed a building inspection system, which is directed at the assessment of the structural, physical and equipment performance of existing buildings. Such system considers the entire building and the interdependence of its parts, determining a three-step process: building characterisation; determination of defects in building elements and systems through an organised visit to the building, using lists of main expected defects per building element; and assessment of severity, according to a proposed severity rating, and recommendation of maintenance actions.

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For the second stage, Bortolini and Forcada (2018) suggest the use of information and communication technology tools, like the one developed by Macarulla et al. (2012), to take pictures tagged with predetermined keywords.

1.4.1 Expert Individual Inspection Systems Following the path set by the first systems of building pathology assessment, a research team at Instituto Superior Técnico (IST), Universidade de Lisboa (UL), has developed a series of knowledge- and experience-based inspection, diagnosis and repair systems for individual non-structural building elements (Table 1.1). These systems were designed around the purpose of providing objective information so that more rational maintenance decisions could be made. The expert inspection, diagnosis and repair systems developed at IST-UL classify and define the typical defects, probable causes, diagnosis methods and repair techniques in the considered building element. In correlation matrices, they also determine how defects are associated with probable causes, diagnosis methods and repair techniques, additionally establishing an inter-defects correlation matrix. Furthermore, detailed files strengthen the inspection systems with the characterisation of each type of classified defect, diagnosis method and repair technique. For the structured collection of data on-site, these inspection systems include an inspection form. Finally, each expert inspection system was validated in an inspection campaign of a significant sample of building elements. Only considering building envelope elements (Table 1.1), the expert inspection systems developed at IST-UL are the basis of the global inspection system proposed in this book.

1.5 From Individual Elements to the Building Envelope With the starting point in a set of nine expert inspection systems with an identical structure, each referring to a type of building element used in building envelopes (façades and roofs), the global inspection system was devised. First, all the elements constituting the expert inspection systems were collected and organised. Then, a harmonisation process started, beginning with the development of homogenised classification lists of defects, probable causes, diagnosis methods and repair techniques incorporating all the defects, probable causes, diagnosis methods and repair techniques considered in the individual systems through a merging process (Pereira et al. 2018). Based on the new homogenised classification lists, three harmonised correlation matrices were developed: defects–probable causes; defects–diagnosis methods; and defects–repair techniques. The new global correlation matrices include the dimension of the building element, which considers

1.5 From Individual Elements to the Building Envelope

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Table 1.1 Expert building inspection systems developed at IST-UL References

Building elements

Validation sample

In the global inspection system?

Silvestre and de Brito (2009, 2010, 2011)

Adhesive ceramic tiling

155 surfaces in 64 buildings

Yes

Garcia and de Brito (2008)

Epoxy resin industrial floor coatings

29 floorings in 23 buildings

No

Neto and de Brito (2011, 2012)

Natural stone claddings

128 surfaces in 59 buildings

Yes

Delgado et al. (2013, 2018)

Wood floorings

98 floorings in 35 buildings

No

Gaião et al. (2011, 2012)

Gypsum plasterboard walls

121 walls in 21 buildings

No

Pereira et al. (2011, 2014)

Gypsum plaster coatings

119 surfaces in 23 buildings

No

Garcez et al. (2012a, b)

External claddings of pitched roofs

207 roofs in 164 buildings

Yes

Sá et al. (2014, 2015)

Wall renders

150 surfaces in 55 buildings

Yes

Amaro et al. (2013, 2014)

External thermal insulation composite systems

146 surfaces in 14 buildings

Yes

Pires et al. (2015a, b)

Painted façades

105 surfaces in 41 buildings

Yes

Santos et al. (2017a, b)

Door and window frames

295 frames in 96 buildings

Yes

da Silva et al. (2017a, b)

Architectural concrete surfaces

110 surfaces in 53 buildings

Yes

Walter et al. (2005), Conceição et al. 2017, 2019)

Flat roofs

105 roofs in 105 buildings

Yes

Carvalho et al. (2018, 2019)

Vinyl and linoleum floorings

101 floorings in 6 buildings

No

the correlation matrices of the individual systems adapted to the new global classification lists. Based on the new defects–probable causes correlation matrix and on the methodology defined by Silvestre and de Brito (2009), a global inter-defects correlation matrix was also developed. With the skeleton of the global inspection system assembled, it was then possible to create defects, diagnosis methods and repair techniques files containing detailed information about each component of the classification lists. The structure of the files results from harmonising the structure of those from the individual inspection systems, where most of the information was already collected, adapted to the new global classification lists. A literature survey filled any missing data.

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Finally, based on the inspection forms of the expert inspection systems, a global inspection form was developed. Its initial sections, referring to the building and its surroundings, integrate the information requested in the individual systems. Then, the sections specifically referring to the features and degradation of the building elements were multiplied in parallel sections, each containing the fields suggested in the individual inspection forms but with a unified form format. After the completion of the global system, a qualitative validation was performed. It consisted of an inspection campaign of the building envelope of a small sample of current buildings, working as a test of the use of the global inspection system and resulting in a limited number of revisions. This campaign is out of the scope of this book. Instead, a demonstration of the use of the proposed inspection system in case studies is made.

1.6 Book Overview This book is organised in eight chapters, as follows: • This chapter, Chapter 1, frames building inspection within a building’s life-cycle, highlighting its relevance for the operation and maintenance stage, emphasises the importance of the building envelope, provides a concise review of building inspection systems, and outlines the methodology of development of the proposed global inspection system for the building envelope; • Chapter 2 presents the technology associated with each type of building element included in the scope of the proposed building inspection system. The materials, design and execution of nine types of building elements are described as a way to better understand their degradation mechanisms; • Chapter 3 is dedicated to building pathology, proposing a classification list of defects and another of probable causes. Defects are grouped into defects of physical, chemical and mechanical nature and other defects, while design errors, execution errors, mechanical actions, environmental actions and use and maintenance errors groups allow organising the probable causes. The relationship between each defect and cause is identified in a correlation matrix between defects and probable causes, which is the basis for an inter-defects correlation matrix. Examples of application of the concepts and challenges of developing the mentioned components of the building inspection system are discussed throughout the chapter; • Chapter 4 concerns the diagnosis methods, presenting them in a proposed classification list. Destructive and non-destructive methods that can be performed in situ are within the list’s scope, but laboratory tests are excluded. Ten categories of diagnosis methods are defined: assisted sensory analysis, electrical, thermo-hygrometric, sound and acoustic, nuclear, hydric, mechanical, pressure, colour, and chemical methods. A correlation matrix between defects and diagnosis methods is presented;

1.6 Book Overview

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• Chapter 5 addresses repair techniques and, considering the advantages of classification lists, one is proposed. Repair techniques used on the surface of claddings, in cladding systems, in bearing structures or substrates and in singular points of the building envelope are presented. A defects–repair techniques correlation matrix is put forward, establishing the adequate ways of dealing with the occurrence of different types of defects in building elements; • Chapter 6 refers to elements of the inspection system used to support inspection procedures. Examples of files of defects, diagnosis methods and repair techniques are presented as a means of communication of knowledge. An atlas of defects, an illustrated version of the criteria to determine the urgency of repair of defects included in the files of defects, is also presented. The inspection form used for fieldwork is proposed; • Chapter 7 is dedicated to demonstrate the use of the proposed inspection system in three case studies: a coffee house, a detached house and a museum. For that purpose, summaries of the results of the inspections are presented following the structure of the information collected using the inspection system. Then, a brief guide for the use of the inspection system in fieldwork is provided. Taking the case studies’ experience into account, the advantages and limitations of using such system are analysed. Additionally, considering the need to communicate inspection results, examples of pictures, tables and charts to present findings are shown; • Chapter 8 presents research paths for future works that may bring the proposed inspection system to new and more advanced levels of development. • Each chapter includes a list of references.

References Agence Qualité Construction (2015) Fiches pathologiebâtiment (Building pathology files). http:// www.qualiteconstruction.com/outils/fiches-pathologie.html. Accessed 19 Jan 2017 Amaro B, Saraiva D, de Brito J, Flores-Colen I (2014) Statistical survey of the pathology, diagnosis and rehabilitation of ETICS in walls. J Civ Eng Manag 20:511–526. https://doi.org/10.3846/ 13923730.2013.801923 Amaro B, Saraiva D, de Brito J, Flores-Colen I (2013) Inspection and diagnosis system of ETICS on walls. Constr Build Mater 47:1257–1267. https://doi.org/10.1016/j.conbuildmat.2013.06.024 Blom I, Itard L, Meijer A (2010) Environmental impact of dwellings in use: maintenance of façade components. Build Environ 45:2526–2538. https://doi.org/10.1016/j.buildenv.2010.05.015 Bortolini R, Forcada N (2018) Building inspection system for evaluating the technical performance of existing buildings. J Perform Constr Facil 32:04018073. https://doi.org/10.1061/(ASCE)CF. 1943-5509.0001220 Building Research Establishment (1988) Common defects in low-rise traditional housing. Building Research Establishment, Watford, United Kingdom Building Research Establishment (2001) Defect action sheets—The complete set. Building Research Establishment Press, London, United Kingdom

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Carvalho C, de Brito J, Flores-Colen I, Pereira C (2018) Inspection, diagnosis, and rehabilitation system for vinyl and linoleum floorings in health infrastructures. J Perform Constr Facil 32:04018078. https://doi.org/10.1061/(ASCE)CF.1943-5509.0001229 Carvalho C, de Brito J, Flores-Colen I, Pereira C (2019) Pathology and rehabilitation of vinyl and linoleum floorings in health infrastructures: Statistical survey. Buildings 9:116. https://doi.org/ 10.3390/buildings9050116 Chang C-Y, Tsai M-D (2013) Knowledge-based navigation system for building health diagnosis. Adv Eng Informatics 27:246–260. https://doi.org/10.1016/j.aei.2012.12.003 Chartered Institution of Building Services Engineers (2008) Maintenance engineering and management. A guide for designers, maintainers, building owners and operators, and facilities managers. Chartered Institution of Building Services Engineers, London, United Kingdom Chew MYL (2010) Maintainability of facilities: for building professionals. World Scientific, Singapore CIB W86 (1993) Building pathology: a state-of-the-art report. International Council for Research and Innovation in Building and Construction, Delft, The Netherlands Conceição J, Poça B, de Brito J et al (2019) Data analysis of inspection, diagnosis, and rehabilitation of flat roofs. J Perform Constr Facil 33:04018100. https://doi.org/10.1061/(ASCE)CF.1943-5509. 0001252 Conceição J, Poça B, de Brito J et al (2017) Inspection, diagnosis, and rehabilitation system for flat roofs. J Perform Constr Facil 31:04017100. https://doi.org/10.1061/(ASCE)CF.1943-5509. 0001094 da Silva C, Coelho F, de Brito J et al (2017a) Statistical survey on inspection, diagnosis and repair of architectural concrete surfaces. J Perform Constr Facil 31:04017097. https://doi.org/10.1061/ (ASCE)CF.1943-5509.0001092 da Silva C, Coelho F, de Brito J et al (2017b) Inspection, diagnosis, and repair system for architectural concrete surfaces. J Perform Constr Facil 31:04017035. https://doi.org/10.1061/(ASCE)CF.19435509.0001034 de Angelis E, Ferro A (2004) Impararedaglierrori: un archivioaperto di casi di guasto a supporto di progetto e gestione di sistemitecnologiciedilizi (Learning from mistakes: an open archive of cases of failure to support project and management of building technology systems). Regione Lombardia, Milan, Italy Delgado A, de Brito J, Silvestre JD (2013) Inspection and diagnosis system for wood flooring. J Perform Constr Facil 27:564–574. https://doi.org/10.1061/(ASCE)CF.1943-5509.0000342 Delgado A, Pereira C, de Brito J, Silvestre JD (2018) Defect characterization, diagnosis and repair of wood flooring based on a field survey. Mater Constr 68:1–13. https://doi.org/10.3989/mc.2018. 01817 Ferraz GT, de Brito J, de Freitas VP, Silvestre JD (2016) State-of-the-art review of building inspection systems. J Perform Constr Facil 30:04016018. https://doi.org/10.1061/(ASCE)CF.19435509.0000839 Flanagan R, Norman G, Meadows J, Robinson G (1989) Life cycle costing: theory and practice. BSP Professional Books, Oxford, United Kingdom Flores-Colen I, de Brito J (2010a) A systematic approach for maintenance budgeting of buildings façades based on predictive and preventive strategies. Constr Build Mater 24:1718–1729. https:// doi.org/10.1016/j.conbuildmat.2010.02.017 Flores-Colen I, de Brito J (2010b) Discussion of proactive maintenance strategies in façades’ coatings of social housing. J Build Apprais 5:223–240. https://doi.org/10.1057/jba.2009.21 Fong PSW, Wong K-C (2009) Knowledge and experience sharing in projects-based building maintenance community of practice. Int J Knowl Manag Stud 3:275–294. https://doi.org/10.1504/ IJKMS.2009.028841 Freitas VP de, Alves SM, Sousa M (2007) Um contributo para a sistematização do conhecimento da patologia da construçãoem Portugal—www.patorreb.com (A contribution to the systematisation of the knowledge on construction pathology in Portugal—www.patorreb.com). In: 2.o Congresso

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Nacional de Argamassas de Construção. Associação Portuguesa dos Fabricantes de Argamassas de Construção (APFAC), Lisboa Gaião C, de Brito J, Silvestre J (2011) Inspection and diagnosis of gypsum plasterboard walls. J Perform Constr Facil 25:172–180. https://doi.org/10.1061/(ASCE)CF.1943-5509.0000149 Gaião C, de Brito J, Silvestre JD (2012) Technical note: Gypsum plasterboard walls: inspection, pathological characterization and statistical survey using an expert system. Mater Constr 62:285– 297. https://doi.org/10.3989/mc.2011.62210 Garcez N, Lopes N, de Brito J, Sá G (2012a) Pathology, diagnosis and repair of pitched roofs with ceramic tiles: statistical characterisation and lessons learned from inspections. Constr Build Mater 36:807–819. https://doi.org/10.1016/j.conbuildmat.2012.06.049 Garcez N, Lopes N, de Brito J, Silvestre J (2012b) System of inspection, diagnosis and repair of external claddings of pitched roofs. Constr Build Mater 35:1034–1044. https://doi.org/10.1016/ j.conbuildmat.2012.06.047 Garcia J, de Brito J (2008) Inspection and diagnosis of epoxy resin industrial floor coatings. J Mater Civ Eng 20:128–136. https://doi.org/10.10617/(ASCE)0899-1561(2008)20:2(128) Horne R, Hayles C (2008) Towards global benchmarking for sustainable homes: an international comparison of the energy performance of housing. J Hous Built Environ 23:119–130. https://doi. org/10.1007/s10901-008-9105-1 Huffmeijer FJM, Hermans MH, Van Egmond HCM (1998) Levensduur van bouwproducten – Praktijkwaarden (Service-life of construction products – Practical values), 2nd edn. SBR, Rotterdam, The Netherlands International Organization for Standardization (2014) ISO/TR 15686-11:2014 Buildings and constructed assets—service life planning—Part 11: Terminology. International Organization for Standardization, Geneva, Switzerland International Organization for Standardization (2011) ISO 15686-1:2011 Buildings and constructed assests—service life planning—Part 1: General principles and framework. International Organization for Standardization, Geneva, Switzerland Islam H, Jollands M, Setunge S (2015) Life cycle assessment and life cycle cost implication of residential buildings—a review. Renew Sustain Energy Rev 42:129–140. https://doi.org/10.1016/ j.rser.2014.10.006 Lai JHK, Yuen PL (2019) Identifying key performance indicators for facilities management in hospital buildings. In: CIB world building congress 2019. Hong Kong SAR, China, p WC0016 Lavy S (2011) A literature review on measuring building performance by using key performance indicators. In: Architectural engineering conference (AEI). Oakland, CA, USA, pp 406–417 Lee D-Y, Chi H, Wang J et al (2016) A linked data system framework for sharing construction defect information using ontologies and BIM environments. Autom Constr 68:102–113. https:// doi.org/10.1016/j.autcon.2016.05.003 Lexico (2019a) Deterioration | Meaning of deterioration. In: LEXICO powered by OXFORD. https:// www.lexico.com/definition/deterioration. Accessed 16 Dec 2019 Lexico (2019b) Degradation | Meaning of degradation. In: LEXICO powered by OXFORD. https:// www.lexico.com/definition/degradation. Accessed 16 Dec 2019 Lexico (2019c) Degrade | Meaning of degrade. In: LEXICO powered by OXFORD. https://www. lexico.com/definition/degrade. Accessed 16 Dec 2019 Macarulla M, Forcada N, Casals M, Kubicki S (2012) Tracking construction defects based on images. In: Gudnason G, Scherer R (eds) European conference on product and process modelling. CRC Press, Reykjavik, pp 723–729 Madureira S, Flores-Colen I, de Brito J, Pereira C (2017) Maintenance planning of facades in current buildings. Constr Build Mater 147:790–802. https://doi.org/10.1016/j.conbuildmat.2017.04.195 Minor JE (2005) Lessons learned from failures of the building envelope in windstorms. J Archit Eng 11:10–13. https://doi.org/10.1061/(ASCE)1076-0431(2005)11:1(10) Neto N, de Brito J (2011) Inspection and defect diagnosis system for natural stone cladding. J Mater Civ Eng 23:1433–1443. https://doi.org/10.1061/(ASCE)MT.1943-5533.0000314

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Neto N, de Brito J (2012) Validation of an inspection and diagnosis system for anomalies in natural stone cladding (NSC). Constr Build Mater 30:224–236. https://doi.org/10.1016/j.conbuildmat. 2011.12.032 Paiva JV de, Carvalho EC, Silva AC e (1985) Patologia da construção. In: 1.o Encontro sobre Conservação e Reabilitação de Edifícios de Habitação. LNEC, Lisboa, pp 1–95 Palmer RD (2006) Maintenance planning and scheduling handbook, 2nd edn. McGraw Hill, New York, NY USA Pereira A, Palha F, de Brito J, Silvestre JD (2014) Diagnosis and repair of gypsum plaster coatings: statistical characterization and lessons learned from a field survey. J Civ Eng Manag 20:485–496. https://doi.org/10.3846/13923730.2013.801918 Pereira A, Palha F, de Brito J, Silvestre JD (2011) Inspection and diagnosis system for gypsum plasters in partition walls and ceilings. Constr Build Mater 25:2146–2156. https://doi.org/10. 1016/j.conbuildmat.2010.11.015 Pereira C, de Brito J, Silvestre JD (2018) Global inspection, diagnosis and repair system for buildings: managing the level of detail of the defects classification. In: Villegas L, Lombillo I, Blanco H, Boffil Y (eds) Rehabend—construction pathology, rehabilitation technology and heritage management. University of Cantabria, University of Extremadura, Cáceres, Spain, pp 572–579 Pires R, de Brito J, Amaro B (2015a) Statistical survey of the inspection, diagnosis and repair of painted rendered façades. Struct Infrastruct Eng 11:605–618. https://doi.org/10.1080/15732479. 2014.890233 Pires R, de Brito J, Amaro B (2015b) Inspection, diagnosis, and rehabilitation system of painted rendered façades. J Perform Constr Facil 29:04014062. https://doi.org/10.1061/(ASCE)CF.19435509.0000534 Pitt TJ (1997) Data requirements for the prioritization of predictive building maintenance. Facilities 15:97–104. https://doi.org/10.1108/02632779710160612 Ribeiro T, Cóias e Silva V (2003) Anomalies in buildings—“Construdoctor’s case studies.” In: 2nd international symposium on building pathology, durability and rehabilitation. Laboratório Nacional de Engenharia Civil (LNEC), Lisbon, Portugal, pp 221–230 Sá G, Sá J, de Brito J, Amaro B (2014) Inspection and diagnosis system for rendered walls. Int J Civ Eng 12:279–290 Sá G, Sá J, de Brito J, Amaro B (2015) Statistical survey on inspection, diagnosis and repair of wall renderings. J Civ Eng Manag 21:623–636. https://doi.org/10.3846/13923730.2014.890666 Santos A, Vicente M, de Brito J et al (2017a) Analysis of the inspection, diagnosis, and repair of external door and window frames. J Perform Constr Facil 31:04017098. https://doi.org/10.1061/ (ASCE)CF.1943-5509.0001095 Santos A, Vicente M, de Brito J et al (2017b) Inspection, diagnosis, and rehabilitation system of door and window frames. J Perform Constr Facil 31:04016118. https://doi.org/10.1061/(ASCE)CF. 1943-5509.0000992 Shohet IM, Lavy-Leibovich S, Bar-On D (2003) Integrated maintenance monitoring of hospital buildings. Constr Manag Econ 21:219–228. https://doi.org/10.1080/0144619032000079734 Shohet IM, Paciuk M (2006) Service life prediction of exterior cladding components under failure conditions. Constr Manag Econ 24:131–148. https://doi.org/10.1080/01446190500184535 Silva A, de Brito J, Gaspar PL (2016a) Methodologies for service life prediction of buildings. With a focus on façade claddings. Springer, Switzerland Silva L, Flores-Colen I, Vieira N et al (2016b) Durability of ETICS and premixed one-coat renders in natural exposure conditions. In: Delgado JMPQ (ed) New approaches to building pathology and durability. Springer, Singapore, pp 131–158 Silvestre JD, de Brito J (2011) Ceramic tiling in building façades: inspection and pathological characterization using an expert system. Constr Build Mater 25:1560–1571. https://doi.org/10. 1016/j.conbuildmat.2010.09.039 Silvestre JD, de Brito J (2010) Inspection and repair of ceramic tiling within a building management system. J Mater Civ Eng 22:39–48. https://doi.org/10.1061/(ASCE)0899-1561(2010)22:1(39)

References

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Silvestre JD, de Brito J (2009) Ceramic tiling inspection system. Constr Build Mater 23:653–668. https://doi.org/10.1016/j.conbuildmat.2008.02.007 Straub A (2012) Using the factor method to get realistic service lives of applied building components. In: Michell K, Bowen P, Cattell K (eds) Joint CIB W070, W092 & TG72 international conference: delivering value to the community. Department of Construction Economics and Management, University of Cape Town, Cape Town, South Africa, pp 672–680 Structural Engineering Institute, American Society of Civil Engineers (2000) Guideline for condition assessment of the building envelope Then DS-S, Tan T-H, Chau C-K (2004) An integrated asset performance framework for operational buildings—preliminary results of focus group validations in Hong Kong and Australia. In: Then DS-S, Jones K, Kinks J (eds) CIB W70 international symposium. Facilities Management and Maintenance: Human Elements in Facilities Management—Understanding the Needs of Our Customers. International Council for Research and Innovation in Building and Construction, Hong Kong SAR, China, pp 239–250 Walter A, de Brito J, Lopes JG (2005) Current flat roof bituminous membranes waterproofing systems—inspection, diagnosis and pathology classification. Constr Build Mater 19:233–242. https://doi.org/10.1016/j.conbuildmat.2004.05.008 Watt DS (2007) Building pathology. Principles and practice, 2nd edn. Blackwell Publishing, Oxford, United Kingdom Wübbenhorst KL (1986) Life cycle costing for construction projects. Long Range Plann 19:87–97. https://doi.org/10.1016/0024-6301(86)90275-X Yohanis YG, Norton B (2006) Including embodied energy considerations at the conceptual stage of building design. Proc Inst Mech Eng Part A J Power Energy 220:271–288. https://doi.org/10. 1243/095765006X76009

Chapter 2

Technology

Abstract Considering that the development of a building inspection system should have a specific scope, and that, within that scope, a broad knowledge of the building elements is advised, a set of nine building elements and claddings is presented. In this case, the technology associated with each building element or cladding included in the proposed building inspection system is approached. For each one, the materials, the design and the execution are developed from a general perspective, as a means of better understanding the building pathology associated with each type of building element or cladding.

2.1 Introduction Understanding the technology of claddings and building elements is essential to better perceive pathological processes that may occur. First, the properties of the materials used help to comprehend reactions between materials and aggressive agents, for instance. Design requirements establish the main concerns that should be considered at this stage. Finally, knowing the adequate execution procedures supports the understanding of limitations associated with on-site constraints. If designers, prescribers and labour have a better knowledge of the technology associated with each building element, many defects may be avoided. In this chapter, the technology of natural stone claddings, adhesive ceramic tiling, wall renders, painted façades, external thermal insulation composite systems (ETICS), architectural concrete surfaces, door and window frames, external claddings of pitched roofs and flat roofs is approached. The technology associated with each type of building element is presented according to the Portuguese approach to such technological challenges, framed within European and International standards.

© Springer Nature Switzerland AG 2020 J. de Brito et al., Expert Knowledge-based Inspection Systems, https://doi.org/10.1007/978-3-030-42446-6_2

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2.2 Natural Stone Claddings Natural stone has been used in construction for a long time. Nowadays, natural stone is still very common in buildings, although now being mainly used as cladding. Besides the durability that is normally associated with natural stone, it is also a cladding that associates good technical and visual properties. Natural stone claddings raise the value of buildings while representing the first layer of protection against weather-related agents. Technological progress in the ornamental stone processing industry has been reflected in thinner plates, as well as in improvements in different types of finishes. Still, results are not always as good as expected. The design stage is very important, taking the properties of the materials into account, as well as the location of the building and the exposure to aggressive agents.

2.2.1 Materials Used in Natural Stone Claddings The origin of each type of rock is different, influencing the behaviour of stone plates. The properties of natural stone should be known, but they cannot be manipulated. According to Campanella and Mateus (2003), natural stones for buildings should show compact grain, be free from fracture planes, gaps, veins, chips, foreign substances and any other defects that may influence their homogeneity and resistance. Additionally, natural stone plates should have dimensions adapted to the application solution and provide adequate resistance to loads. The use of marly stones should be avoided, as well as the use of any kind of natural stone whose properties change under the action of environmental agents and running water. Still, instead of a motive for rejection, the presence of some heterogeneities in some types of rock may be a devaluing or valuing factor, according to each situation.

2.2.1.1

Raw Material

Rock is a cohesive aggregate of minerals or solid substances resulting from natural processes. In the construction industry, natural stone is distinguished from artificial stones, like concrete. The value of stone is determined by the quality and amount of stone available in a rock body and by the distance between quarries and manufacturing plants. The demand is also a determining factor to estimate the value of natural stone. It is often determined by subjective and transitory visual criteria, associated with colour and texture.

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Classification of Natural Stone Knowing the process that resulted in some type of natural stone helps to understand its properties and behaviour. The characteristics of rocks determined by their development process are relevant for building application purposes. It should be mentioned that the natural development conditions that resulted in a specific rock depend on the geographical location and on the specific conditions on a given period, which will not occur repeatedly. According to the origin of rocks, they are classified into three categories: igneous or magmatic rock, sedimentary rock and metamorphic rock. Igneous or magmatic rock results directly from the consolidation, cooling and crystallisation of magma, at a specific depth from the Earth’s crust, or on the surface, due to volcanic action. Igneous rocks have a generically crystalline appearance, whose structure depends on the cooling depth. Granite, syenite and basalt are examples of igneous rocks. Granite and syenite consolidated at a great depth, while basalt consolidated on the surface. Sedimentary rock results from the (i) deposition of fragments from the disaggregation of pre-existing rocks due to various agents and from the (ii) precipitation of loose substances in the air or water. Sedimentary rocks may be easily identified by the frequent presence of fossil remains and by well-defined overlapping layers. Metamorphic rock results from changes in existing rocks, whether igneous, sedimentary or even metamorphic, that alter their mineralogical composition and structure due to high temperatures, pressure or water. Marble and gneiss are two types of metamorphic rocks. Igneous and metamorphic rocks compose about 95% of the volume of the lithosphere. Still, most of the rocks that appear on the Earth’s surface are sedimentary rocks (Marques et al. 2006). Table 2.1 shows a detailed classification of natural stone.

Characteristics of Natural Stone Natural stone refers to every rock that may be obtained in blocks or plates with adequate dimensions for building purposes, maintaining their properties. The most common types of stone used in buildings are (Siegesmund and Török 2014): • Clay-slate: with low thickness planar foliation and waterproof; • Sandstone: composed of sediments of rocks that are aggregated, showing good workability; • Basalt: presents high density, capacity and hardness; • Limestone: shows high strength, although it is easy to cut; • Granite: shows good resistance under adverse weather conditions; • Marble: results from metamorphic changes in limestone; • Syenite: similar to granite, without quartz, hence showing better workability; • Shale: highly crystalline structure but with lower strength than clay-slate.

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Table 2.1 Classification of rocks (adapted from Tyrrell [1978] and Siegesmund and Török [2014]) Class

Sub-class

Development process

Types of rock

Characteristics

Igneous

Intrusive

Cooling inside the Earth’s crust

Granite

Rock of variable grain size, composed of quartz (20–40%), feldspar (15–55%) and mica (14–56%). The colour of granite varies according to the minerals that compose it. For instance, it may be black or white if black or white mica is present, respectively. Micaceous granites may change with moisture or the atmosphere’s carbon dioxide, resulting in disaggregation. Still, granites have excellent mechanical resistance, polish-ing durability and resistance to temperatures around 500 °C

Syenite

Different from granite due to the lack of quartz. Syenite has better workability than granite

Gabbro

Rock with coarse grain, without quartz, generally dark green (continued)

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Table 2.1 (continued) Class

Sedimentary

Metamorphic

Sub-class

Development process

Types of rock

Characteristics

Nepheline syenite

Syenite with feldspathoids. It may be used as granite, but with the inconvenient of possible changes in feldspathoids

Intermediate extrusive

Cooling at low depth.

Porphyry

It has a similar composition to granite, but with changes due to developing at a lower depth

Extrusive

Cooling at the Earth’s surface

Basalt

Dark colour, dense, compact, with excellent mechanical resistance

Clastic

Deposition of debris from other rocks.

Sandstone and breccia

They may be disaggregated, compacted due to pressure or agglomerated by a natural cement

Deposition of muds, silts and other sediments

Shale

It typically has a laminated structure and is fissile (tendency to split into thin parallel layers)

Chemical

Deposition of salts that occur in water

Limestone

Mainly composed of calcite and aragonite, very susceptible to erosion processes

–

Changes in other classes of rocks due to pressure, temperature or water

Marble

Composed of crystallised calcite and other minerals, like mica and graphite. Good resistance to environmental agents

Clay-slate

Foliated rock

20 Table 2.2 Important characteristics of natural stone (Siegesmund and Dürrast 2014; Siegesmund and Török 2014)

2 Technology Type of characteristic

Characteristic

Structural

Mineralogical composition Chemical composition Texture Petrographic composition

Aesthetical

General appearance Colour and colour variations Micro-fracturing Veins Agglomerates Stains and strips

Technological

Compressive strength Flexural strength Apparent density Water absorption Open porosity Freeze resistance Resistance to anchorage Thermal linear expansion coefficient Abrasion wear Resistance to impacts

Each type of natural stone presents structural, aesthetical and technological characteristics that are responsible for its appearance and durability, for instance. Due to the large variety of natural stone, the characteristics mentioned in Table 2.2 should be known ahead to help the selection process.

Manufacturing Process The manufacturing process is decisive for the final properties of natural stone products. These products should be measured, assessed and analysed according to a predefined sample plan applied at each manufacturing stage. In quarries, the extraction process is complex, as the best extraction direction should be defined for better results. Blocks of rock from quarries (Fig. 2.1, part a) are transformed by specialised companies, which saw the block, manufacturing plates cut and finished with adequate equipment. Blocks are sawn considering the structure of the rock. This stage is very important to avoid subsequent flatness defects, cracks or mechanical resistance issues.

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b

a

Fig. 2.1 Blocks of limestone rock in a quarry (a) and quarry for the extraction of limestone in a natural park (b)

Environmental Impact of Extracting the Raw Material Extraction activities have a negative effect associated with (i) the tasks that need to be performed, (ii) rejected and unused materials and (iii) abandoned quarries. The location of quarries often lacks planning (Fig. 2.1, part b) and even explored areas are frequently underused. Extraction activities need to find balanced solutions that include rational and planned mining, considering the actual demand needs, and the preservation of the environment. Rock deposits should be known in detail, as well as economic benefits and environmental impact costs.

2.2.1.2

Natural Stone Joints

The design of natural stone claddings should consider the execution of joints (Fig. 2.2). Joints between stone plates absorb deformations associated with loads, thermal actions or water absorption. In general terms, stone joints should be at least 5 mm. The type of joint and filling material should be selected according to the expansion coefficient of stone, thickness, and exposure and required waterproofing levels. Joints may be open or filled. Open joints represent a discontinuity/void in the cladding surface. Filled joints are sealed with mortar or mastic to make them watertight. If natural stone claddings are mechanically fastened and have an air gap (cavity walls), joints need to be open (Fig. 2.3). If the cladding does not have an air gap, joints should be waterproof and filled, generally with resin-modified mortar. Joints filled with rigid mortar or mineral products are prone to crack, resulting in leakages. Sealants for the joints of natural stone claddings may be elastomers or porous mastics. Elastomer sealants include acrylic, polysulphides, silicones and polyurethane. Porous mastics may be resinous oils or butyl.

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Fig. 2.2 Different types of joints in natural stone claddings

a

b

Fig. 2.3 Open joints in a natural stone cladding: a general view; b close-up

Elastic vertical and horizontal joints (wider and deeper) should be designed, approximately, every three or four rows. They should be executed with mastic and go up to the substrate layer. Additionally, this type of elastic joints is also considered in the surface’s perimeter and in transition areas between different materials. The building’s expansion joints should be visible at the cladding level and have adequate treatment.

2.2.2 Design of Natural Stone Claddings The design stage is decisive to obtain durable and safe solutions. An adequate raw material should be selected, as well as adequate stone finish, substrate and joints.

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Natural stone cladding solutions should be detailed and complemented with comprehensive technical specifications, including clear specifications of the stone plates’ size, stone properties and fastening system.

2.2.2.1

Functional Requirements of Natural Stone Claddings

Besides the appearance of façades, façade claddings assume an important role in the watertightness of the building envelope, protecting masonry and structures, for instance. The main functional requirements of natural stone claddings are shown in Table 2.3. Table 2.3 Functional requirements of natural stone claddings for façades (Lucas 2008) Type of requirement

Functional requirements

Safety

Stability

Compatibility with the substrate

Geometrical compatibility

Tightness

Watertightness

Hygrothermal

Thermal insulation

Visual comfort

Flatness

In service safety Mechanical compatibility

Verticality Straight edges Regularity of the surface Homogeneous colour and glow Tactile comfort

Non-harsh facings

Hygiene

No deposition of dust or microorganisms

Dry facings Cleaning resistance Adaptation to regular use

Resistance to impact and abrasion Resistance to water actions Adhesion to the substrate Resistance to staining

Durability

Resistance to weather agents Resistance to chemical products in the air Resistance to erosion caused by solid particles in the air Resistance to the development of biological growth

Easy cleaning

–

Economy

–

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2.2.2.2

2 Technology

Classification of Façade Claddings

Granite, basalt, limestone, marble and clay-slate plates may be considered watertight claddings, as they may ensure the watertightness of the façade towards rainwater. These are discontinuous claddings with direct or indirect fastening to the substrate. On the other hand, natural stone claddings may also be considered a decorative cladding. Generally, the thickness of natural stone claddings is lower than 80 mm. Stone plates may have customised dimensions, still considering that each plate should be less than 1 m2 and, at least, 30 mm thick. Alternatively, stone plates may have standard dimensions, with length or width up to 800 mm and thickness up to 20 mm. These products may be applied on-site using mortars or mastics or indirect fastening, like clamps and an intermediate metallic structure.

Direct Fastening of Natural Stone Claddings Natural stone claddings may be adhesive or sealed to the substrate through the continuous superficial contact with the substrate’s surface. Adhesive fastening may be done using an adhesive mortar, with or without special resins, cementitious adhesive or an adhesive material without cement (normally mastic). Epoxy adhesives may also be used. Sealed fastening uses a hydraulic lime or cement-based mortar. Mortars should be able to resist sulphates and saponification. The binder should be stable and free from lumps and the sand should be washed. Direct fastening of natural stone claddings may be complemented with mechanical fastening to minimise the occurrence of defects. Direct fastening is limited by the weight and size of natural stone elements, the type of substrate, the presence of moisture in the substrate and the location of the cladding within the façade. Additionally, adhesive materials may cause staining in the stone plates, including specific types of stains due to the lack of ventilation, emphasising the perimeter of plates (Fig. 2.4). Moreover, incompatibilities between the stone and the substrate, caused by hygrothermal variations, result in detachment defects when direct fastening is used, as the adhesive material may not be able to absorb differential movements between the stone and the substrate.

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Fig. 2.4 Staining emphasising the perimeter of natural stone plates

Indirect Fastening of Natural Stone Claddings Indirect fastening for natural stone claddings may be done: (i) with local fastening points or (ii) using an intermediate structure, typically using metallic profiles, ensuring an air gap between the plates and the substrate. Although indirectly fastened natural stone claddings may be built using the best practices, the occurrence of leakages during their service life should be considered at the design stage. Hence, a second protection barrier should be created to avoid the entrance of water in the building envelope, using a ventilation and drainage system, simultaneously avoiding the occurrence of condensations (Camposinhos 2014). Those systems consist of executing ventilation and drainage pipes or flashings in the joints (fastened with adhesive material, not interfering with the fastening system) in every two floors. Using indirect fastening may be advantageous, as it allows differential movements between the cladding and the substrate and the air gap allows draining and ventilating the back face of stone plates, if adequately detailed (e.g. creation of ventilation holes) (Fig. 2.5). In this type of fastening systems, the durability of the natural stone cladding depends on the nature of the stone and on the type of fastening elements. The selection of the fastening system is done according to loads, type of stone and substrate and the possibility of including thermal insulation in the air gap. Three main types of indirect fastening systems are available: dowel anchorage (local fastening points), undercut anchorage (using an intermediate structure) and kerf anchorage (using an intermediate structure). Dowel anchorage (Camposinhos 2014) uses the insertion of dowel pins in holes. It is adequate for stone plates with a length up to 1 m. Fastening is provided by four dowel pins for each plate (two on top and two at the bottom, or two on each side) that are inserted in holes drilled

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a

b

Fig. 2.5 Natural stone cladding with ventilation holes: a general view; b close-up

a

b

Fig. 2.6 Sections of: a a dowel anchorage system; and b a Keil-type technology undercut anchorage system. 1—natural stone plate; 2—panel bracket; 3—slotted anchor sleeve with internal thread; 4—screw

in the thickness of the plate. The depth of the holes is about 2/3 of the thickness of the plate, also depending on the diameter of the dowel pin. Dowels are part of a system using perpendicular rods to connect the fastening system to the substrate (Fig. 2.6, part a). The undercut anchorage system provides a keying-type anchorage in the stone plate thickness. Essentially, two types of undercut anchorage are available (Camposinhos 2014): Fischer-type undercut anchors and crosswise slotted anchor sleeves with internal thread. Fischer-type anchors have a cone bolt, an expansion ring, a sleeve and an optional nut. These anchors are applied placing the anchor sleeve against the expansion ring, forcing it to expand in the undercut hole, hence locking inside

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Fig. 2.7 Two types of kerf anchor clips’ profiles

the stone plate. Undercut anchorage using crosswise slotted anchor sleeves with an internal thread consists of fitting the anchor in an undercut hole and then inserting the sleeve, which is deformed. The anchor sleeve expands when a screw is inserted in it, fitting the anchor in the undercut hole in the stone plate. This system is also known as Keil-type technology (Fig. 2.6, part b). The kerf anchorage system consists of using saw-cut grooves in the edge of stone plates, where kerf clips fit (Camposinhos 2014). Kerf clips are fastened to a bearing frame or directly to the substrate. Kerf clips may be continuous or discontinuous and, usually, they fit the bottom and top edges of the stone plates (Fig. 2.7). Kerf clips, as Fischer-type anchors, are usually made with stainless steel or aluminium.

2.2.2.3

Types of Finishes

Selecting a specific type of natural stone for a cladding often depends on the appearance of the finished product. In turn, the appearance depends on the colour of the stone, homogeneity and heterogeneity of its texture and on the finish.

a

b

c

Fig. 2.8 Different types of natural stone finishes: a scratched; b bush-hammered; c polished

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Finishes that may be applied on natural stones depend on the type of material and on its geological structure. Thus, some types of finish are better suited for specific types of natural stone. For instance, marble and granite, with high levels of crystallisation, are better suited for polished and honed finishes. The finish should not only be applied considering the final appearance of the stone product but also taking the resistance to aggressive agents into account. For instance, low porosity plates subject to flamed or polished finishes are waterproof. Coarse finishes, such as bush-hammering, significantly increase the exposed area of the natural stone plate, interfering with the effect environmental agents may have. Table 2.4 highlights some natural stone finishes. Usually, suppliers provide samples with the most adequate finishes for their range of natural stones. Rougher finishes are advised for applications outdoors, as the texture of the surface creates random paths for water, which, in smoother surfaces, causes staining. Table 2.4 Description of the most common types of finish for natural stone (García-del-Cura et al. 2008; Camposinhos 2014; Marble Institute of America 2016) Type of finish

Description

Diamond sawn

It is a finish obtained through sawing the stone using circular saws. The stone’s surface shows curved grooves

Polished (Fig. 2.8, part c)

The treated surface becomes smooth, glowing and reflecting light. A polished finish is obtained using rotary heads that rub the stone surface with abrasive materials with a progressively lower grain size. The last stage consists of rubbing with felt heads

Honed

The honed finish process is similar to that of a polished finish, but small grain size abrasives are not used. The surface is also smooth, but not glossy

Scratched (Fig. 2.8, part a)

This type of finish is obtained by making a set of parallel grooves in the stone surface. Grooves are generally concave or trapezoidal

Rubbed

Slightly smooth finish, similar to a honed finish

Sandblasted

It is obtained through the abrasive impact on the surface of a high-pressure water jet with silica sand. The surface has a fine homogeneous appearance

Flamed

This finish creates an irregular surface, relatively smooth, in granite stones. It is obtained using a blowtorch pointed at the surface at about 45°. Generally, the colour also changes

Cleft

This finish takes advantage of the natural layers of the stone structure, hence being more adequate for clay-slate and sandstone, for instance. When the stone is cut, the finish is naturally obtained

Bush-hammered (Fig. 2.8, part b)

The stone surface is struck with a bush-hammer, which is a type of hammer whose head consists of a set of pyramidal teeth. The bush-hammered finish may be finer or coarser, according to the size of the bush-hammer teeth

2.2 Natural Stone Claddings

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It should also be mentioned that common known changes in the stone may be used to intentionally obtain natural effects in the stone cladding when combined with a given finish.

2.2.2.4

Design Limitations

The use of natural stone as a façade cladding requires adequate design detailing. The choice of size, shape and finish should consider functional requirements, location, type of fastening system and the physical and mechanical properties of stone. Rainwater drainage systems, including the drainage of the façade, should be taken into account. The location of drainage plumbing inside the walls should be considered at the design stage and the elements should be installed before the stone cladding. The selection of a specific type of stone should be based on visual and technical criteria, and testing and calculations should be provided. Design specifications should include the material’s requirements and the expected loads, so that the material, complying with those specifications, fulfils its purpose safely. The height of a stone cladding on the façade may influence the type of fastening system used. The different types of anchorage should be designed considering the loads on the cladding, including its weight, impact and wind loads, and loads resulting from differential deformation. As for the size of the joints, the different expansion coefficients of the stone and of the substrate should be taken into account. The building’s expansion joints should be visible and treated also at the cladding level, and elastic joints should also be considered along the façade, besides adequate peripheral joints between different materials applied on the same surface.

2.2.2.5

Standards

Standardisation results in more homogeneous products, potentially with higher quality levels. In Europe, a large set of standards establishes different types of requirements for natural stone products, namely: • Terminology and denomination standards: – EN 12440:2017 Natural stone—Denomination criteria (European Committee for Standardization [CEN] 2017a); – EN 12670:2019 Natural stone—Terminology (CEN 2019a); • Test methods standards: – EN 1925:1999 Natural stone test methods—Determination of water absorption coefficient by capillarity (CEN 1999a); – EN 1926:2006 Natural stone test methods—Determination of uniaxial compressive strength (CEN 2006a);

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– EN 1936:2006 Natural stone test methods—Determination of real density and apparent density, and of total and open porosity (CEN 2006b); – EN 12370:1999 Natural stone test methods—Determination of resistance to salt crystallisation (CEN 1999b); – EN 12371:2010 Natural stone test methods—Determination of frost resistance (CEN 2010a); – EN 12407:2019 Natural stone test methods—Petrographic examination (CEN 2019b); – EN 13161:2008 Natural stone test methods—Determination of flexural strength under constant moment CEN 2008a); – EN 13501-1:2018 Fire classification of construction products and building elements—Part 1: Classification using data from reaction to fire tests (CEN 2018a); – EN 13364:2001 Natural stone test methods—Determination of the breaking load at dowel hole (CEN 2001); – EN 13373:2019 Natural stone test methods—Determination of geometric characteristics on units (CEN 2019c); – EN 13755:2008 Natural stone test methods—Determination of water absorption at atmospheric pressure (CEN 2008b); – EN 14066:2013 Natural stone test methods—Determination of resistance to ageing by thermal shock (CEN 2013a); – EN 14146:2004 Natural stone test methods—Determination of the dynamic modulus of elasticity (by measuring the fundamental resonance frequency) (CEN 2004a); – EN 14157:2017 Natural stone test methods—Determination of the abrasion resistance (CEN 2017b); – EN 14158:2004 Natural stone test methods—Determination of rupture energy (CEN 2004b); – EN 14579:2004 Natural stone test methods—Determination of sound speed propagation (CEN 2004c); – EN 14580:2005 Natural stone test methods—Determination of static elastic modulus (CEN 2005a); – EN 14581:2004 Natural stone test methods—Determination of linear thermal expansion coefficient (CEN 2004d); – EN 12326-2:2011 Slate and stone for discontinuous roofing and external cladding—Part 2: Methods of test for slate and carbonate slate (CEN 2011a); • Product standards: – EN 1467:2012 Natural stone—Rough blocks—Requirements (CEN 2012a); – EN 1468:2012 Natural stone—Rough slabs—Requirements (CEN 2012b); – EN 1469:2015 Natural stone products—Slabs for cladding—Requirements (CEN 2015a); – EN 12057:2015 Natural stone products—Modular tiles—Requirements (CEN 2015b);

2.2 Natural Stone Claddings

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– EN 12059:2008+A1:2011 Natural stone products—Dimensional stone work— Requirements (CEN 2011b); – EN 12326-1:2014 Slate and stone for discontinuous roofing and external cladding—Part 1: Specifications for slate and carbonate slate (CEN 2014a).

2.2.3 Execution of Natural Stone Claddings The execution of natural stone claddings should be especially careful, as many defects result from execution errors. So, the adequate use of materials, the correct fastening of elements, the use of specialised labour and complying with the project and technical specifications may be decisive factors for the success of a natural stone cladding throughout its service life. Additionally, coordination between the different actors at the construction site should be promoted.

2.2.3.1

Execution of Claddings Directly Fastened to the Substrate

As mentioned, direct fastening systems are not the best solution for natural stone façade claddings, mainly above 6 m high. Early degradation (Fig. 2.9) may be caused by the behaviour of the adhesive material, application conditions, moisture and preparation of the substrate and stone plates. When direct fastening is the chosen solution, the substrate should be prepared ahead. It should be cleaned, flattened and waterproofed with a traditional render, which should be kept damp for two weeks, avoiding quick drying. The render may have to be reinforced with adequate fibreglass mesh if stresses or differential movements are expected. Then, the stone plates are adhered or sealed, applying the adhesive or mortar, respectively. Mortar should be applied simultaneously on the back face of the stone plates (back-buttering) and on the substrate, while adhesives only require application on the substrate (Amaral et al. 2015). Application on the substrate is done by spreading the adhesive material (cementitious or not) on the substrate using an adequate notched trowel, creating a continuous and homogeneous bed of adhesive

a

b

c

Fig. 2.9 Early staining in a natural stone cladding associated with the adhesive material: a general view; b close-up; c back face of removed stone plates

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material. Then, the stone plates are applied on the substrate, pressing the plate so that the adhesive cords are crushed, ensuring that no voids remain between the substrate and the stone plate. All manufacturers’ recommendations should be followed. Movement joints should be executed between every plate, as well as elastic joints and expansion joints. Peripheral joints should also be executed in the transition between coplanar claddings and next to protrusions. In stone claddings directly fastened to the substrate, joints between stone plates should be at least 4 mm wide, depending on the size of the plates. As for hydrophobic treatments, in these cases, they should only be applied 30 days after applying the cladding. Additionally, waterproofing treatments should only be applied 48 h after raining, to avoid moisture in the plates.

2.2.3.2

Execution of Claddings Indirectly Fastened to the Substrate

As for the indirect fastening of natural stone claddings, the following sequence of tasks is executed: • Marking the location of fastening elements on the substrate; • Drilling any required holes and installing the fastening elements on the substrate; • Installing the plates, considering that fastening elements (e.g. dowels) are already installed in the stone plates; • Straightening and aligning the stone plates; • Removing any wedges; • Optionally filling joints. In indirectly fastened stone claddings, if the cladding elements are small (e.g. slates), joints may be overlaid.

2.2.3.3

Maintenance

Regular maintenance is advised in natural stone claddings, as it is a relevant factor for the performance and durability of the cladding. Simple planned works, such as cleaning, washing and inspecting the façade are useful to avoid expensive late repairs (Snethlage 2014; Amaral et al. 2015). These procedures help to identify prepathological signs that indicate possible degradation mechanisms, while an accurate diagnosis determines the best course of action to stop them. In most cases, washing the natural stone cladding with pressurised water is advised, followed by the application of a hydrophobic treatment to delay ageing signs (Amaral et al. 2015). Adequate means of access to the façade make maintenance works easier.

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2.3 Adhesive Ceramic Tiling Adhesive ceramic tiling is a commonly used cladding, especially in flooring solutions, bathrooms and kitchens, as it is easy to maintain, durable and relatively cheap (Stock 2004). Indoors, adhesive ceramic tiling is more advantageous than natural stone claddings in terms of water absorption, and staining and slip resistance. On the other hand, the performance of ceramic tiling in façades does not seem to be so competitive. For instance, in Singapore, the use of adhesive ceramic has been prohibited above the 4th floor, due to the high level of detected defects (Wong 2004). Still, the materials’ quality, as well as labour and execution may have influenced such results. To avoid problems, the technology of adhesive ceramic tiling should be divulged, including the properties of materials, for more conscious applications.

2.3.1 Materials Used in Adhesive Ceramic Tiling 2.3.1.1

Ceramic Tiles

Ceramic tiles for façade claddings are manufactured with a mixture of clay materials, such as clay and kaolin, and melting materials, such as sand and feldspar. Tiles may be manufactured using press forming or extrusion forming (Centro Tecnológi-co da Cerâmica e do Vidro [CTCV] 2003).

Classification of Ceramic Tiles The classification of ceramic tiles is determined by standard EN 14411:2016 (CEN 2016a), considering the level of water absorption and the manufacturing process. Group A tiles are extruded, and group B tiles are dry-pressed. Extruded tiles include extruded sandstone tiles, clinker tiles, terracotta tiles and rustic tiles. Drypressed tiles include porcelain tiles, porcelain sandstone tiles and azulejo. The different types of tiles may have essentially two types of finish: glazed or unglazed. Glazed tiles have a superficial vitrified coat, which is waterproof. Unglazed tiles do not have any kind of superficial coat. Both types of finish may be polished (CEN 2016a). Additionally, the glazing level of the ceramic paste directly influences the porosity and mechanical resistance of tiles. Porosity decreases as the glazing level increases and mechanical strength increases with glazing. A higher level of glazing may be obtained using finer clay grains while manufacturing the tiles.

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Quality Control of Manufacturing Quality control during the manufacturing process of ceramic tiles is done in sequential stages, following the process from raw materials supply up to testing the final product. When the production process ends, before ceramic tiles are ready to leave the factory, the final product is tested to control the compliance with standards. In Europe, standard test methods of ceramic tiles are included in EN ISO 10545 series (CEN 1996, 1997a, b, c, 1998a, 2012c, d, 2013b, 2014, 2015c, 2016b, 2018b, c, 2019d). These standards define the procedures do determine: dimensions and surface quality; water absorption, apparent porosity, apparent relative density and bulk density; modulus of rupture and breaking strength; impact resistance; resistance to deep abrasion (unglazed tiles); resistance to surface abrasion (glazed tiles); linear thermal expansion; resistance to thermal shock; moisture expansion; crazing resistance (glazed tiles); frost resistance; chemical resistance; resistance to stains; and small colour differences.

Environmental Impact The main environmental impacts resulting from the production of ceramic tiles refer to: • • • • •

The consumption of natural resources; Emissions to the atmosphere; Water consumption and liquid effluents; Production of waste; Noise emissions. Each of these types of impacts may be minimised with specific measures, namely:

• Exploring natural resources in a smart way, systematically benefiting affected areas; • Minimising the consumption of energy and exploring alternative renewable sources; • Minimising gaseous emissions and liquid effluents, and treating them; • Limiting the production of solid waste, including reusing or recycling in the productive cycle and using waste as an aggregate in the construction industry.

2.3.1.2

Adhesive Material for Ceramic Tiles

Ceramic tiles may be directly fastened to the substrate. For this purpose, two main solutions are available (Lucas 2003): traditional mortar and different types of adhesive material. Traditional mortar is applied as a thick bed, 5–20 mm, simultaneously smoothing the substrate. Still, the use of this solution represents a lower adhesion tension with the tile (i.e. adhesion occurs only physically) and is only adequate for

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highly porous substrates and tiles. In façades, traditional mortar should include a water repellent admixtures, to improve the resistance do water. Cementitious adhesive (hydraulic binders), dispersion adhesives (organic binders) and reaction resin adhesives (synthetic resins) are industrial materials that are applied as a thin bed, 2–5 mm. These adhesives may be applied directly on the substrate or over a screed layer (spatter-dash and base layer). The fundamental property that separates these industrial materials from traditional mortars is the ability to retain water. That ability allows thin bed applications to have the required amount of water to hydrate Portland cement (Medeiros and Sabbatini 1998). Adhesive materials should comply with EN 120004-1:2017 (CEN 2017c) and, for quality control purposes, with EN 120004-2:2017 (CEN 2017d), referring to test methods. Adhesive materials may have different compositions, each one more adequate for specific situations. In façades, bi-component cementitious adhesive, mixed binders’ cementitious adhesive, aluminous cementitious adhesive and dispersion adhesives are recommended.

2.3.1.3

Joints for Ceramic Tiles

The stereotomy of ceramic tiling requires including joints between elements, taking the width of joints into special account. Joint filling materials should be waterproof, resilient and compressible, and show good resistance to water, cleaning products, chemical attack and biological growth. Still, as ceramic tiles are waterproof, exchanges of moisture between the substrate and the surrounding environment must occur through the joints, which must be permeable to water vapour. Adhesive ceramic tiling should include movement joints between every tile, as well as elastic, expansion and peripheral joints. Movement joints should be dimensioned to absorb the expansion of tiles. Generally, in façades, extruded tiles should have, at least, 6 mm wide joints, while pressed tiles should have, at least, 4 mm wide joints. As extruded tiles may have larger expansion associated with moisture, they need to be laid with larger joints. The width of joints should also increase with the exposure aggressiveness of the cladding’s surrounding environment and with the tiles’ darker colours. Movement joints may be filled with two main groups of materials: cement grout and resin grout, as defined in EN 13888:2009 (CEN 2009a). Resin grout materials are manufactured with reaction resins. In façades, the use of cement grout with high resin content is advised and, in aggressive exposure conditions, bi-component epoxy grout is recommended. Elastic joints are meant to avoid cracking and the detachment of tiles due to stresses resulting from differential deformations of hygrometric nature in the substrate, bedding material and tiles. Elastic joints are more important the thicker the bedding material and the more aggressive the exposure environment (Lucas and Abreu 2011). Elastic joints are as deep as the bedding material, even including the screed layer. This type of joints divides the cladding into smaller areas, avoiding the cumulative action of the mentioned differential movements. Elastic joints should be,

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1

2

3

4

5

6

Fig. 2.10 Expansion joint filled with mastic. 1—substrate; 2—bedding material; 3—tiles; 4— expansion joint filling material; 5—silicone cord; 6—mastic

at least, 5 mm (usually 12 mm) thick and filled with a compressible material and a metallic or plastic profile. The surface of the joint should be filled with the material used for movement joints or with mastic, depending on the width. Expansion joints must be included in the cladding system. It is common to use mastics (Fig. 2.10) or prefabricated expansion joints reinforced with metallic or plastic profiles to fill this type of joints. The Young’ modulus of materials used to fill expansion joints should be in the products’ specifications sheet, so that designers are able to recommend a product that fits the expected expansion of the building’s bearing structure. Otherwise, the chosen product may degrade faster than expected (e.g. break, if a fragile material is chosen). In the perimeter of adhesive ceramic tiling surfaces, peripheral joints should be executed. Peripheral joints should be treated as elastic joints, but, in some cases, like corners, a metallic or plastic profile may be enough.

2.3.2 Design of Adhesive Ceramic Tiling The quality of the design of adhesive ceramic tiling is paramount for the durability of the cladding. The design should take structural factors into account, such as the deformability of the substrate, construction limitations associated with maintenance conditions, as well as service factors, such as the protection the cladding provides to the building envelope. The cladding’s exposure conditions, such as thermal shock, wind and pollution, should also be considered during the design process. The designer should accurately determine the stereotomy of the adhesive ceramic tiling, including the location and size of every type of joints, and specify the properties of materials and application techniques.

2.3.2.1

Design Limitations

In façades, the application of adhesive ceramic tiling should prevent any kind of human and material damages caused by the detachment of tiles. In buildings with

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three or more floors, at the ground level, some kind of architectural protection should be implemented to minimise possible damages resulting from the fall of tiles. As for the dimension of tiles, ceramic tiles should only be applied using adhesive materials if (CTCV 2003): • • • •

Tiles have a water absorption level lower than 0.5% and a surface up to 2000 cm2 ; Tiles have a water absorption level higher than 0.5% and a surface up to 3600 cm2 ; Terracotta tiles are used and their surface is up to 300 cm2 ; Terracotta slates are used and their surface is up to 231 cm2 .

The design of adhesive ceramic tiling should also take the properties of the substrate into account. First, the dimensional tolerances of the substrate should be considered. For instance, ceramic tiles should not be applied in a substrate composed of a metallic structure using adhesive materials, due to excessive deformations associated with this structural solution. Generally, adhesive ceramic tiling may be applied on walls and prefabricated panels of concrete and rendered masonry walls (with or without external thermal insulation). In façades with a linear reinforced concrete structure, the ideal stage for applying the cladding occurs after the building has been subjected to all service loads (Lucas and Abreu 2011). However, this is not usually possible. Hence, the deformation of the structure due to dead loads should be taken into account in the adhesive ceramic tiling design. So, horizontal elastic joints, normally located at the height of floor slabs, should be dimensioned considering such loads, which may correspond to vertical displacements of 12.5 mm per floor. As the surfaces defined by elastic joints should be approximately square, the distance between vertical elastic joints should take the floor height into account (Goldberg 2011), considering the position of façade openings and the colour of the tiles as well (darker colours may cause higher expansion of tiles).

2.3.2.2

Selection of Materials and Stereotomy

For each type of application of adhesive ceramic tiling, the selection of tiles should take their properties into account. In façades, the most important properties are frost resistance, moisture expansion and linear thermal expansion (CTCV 2003). Additionally, the ease of cleaning and low absorption of impurities may also be important properties for ceramic tiles applied in façades. As for the selection of bedding material, the type of connections that are established between the substrate, the adhesive material and the tile should be considered. When cement-based materials are used, connections are merely physical, consisting in the crystallisation of the cement hydration reaction products in the tile’s pores. This crystallisation allows the creation of anchorage points between the layers that compose the cladding. When the bedding material is mainly composed of resins, the connection between layers is done by electrostatic interactions, which ensure the stability of the cladding. In the case of adhesive materials composed of cement and resin, the connection is partially physical and chemical.

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In some application conditions, tiles may be back-buttered. That procedure is advised, for instance, for the application of tiles with a surface larger than 500 cm2 or with a water absorption level lower than 3%. Back-buttering consists in applying adhesive on the substrate and on the back face of tiles. Back-buttering makes it easier to crush the adhesive cords, maximises the contact area between the adhesive and the back face of tiles and absorbs some flatness defects of the substrate (Lucas and Abreu 2011). However, excessive thickness of the bedding layer should be avoided, and the higher cost of back-buttering, when compared with simple buttering, should be considered. During the service life of adhesive ceramic tiling, there is a transition point that corresponds to joints starting to actively work, due to loads on the cladding. The role of joints may avoid the occurrence of cracking, whether in the joint or in the tiles, and the detachment of tiles. Additionally, joints stop air and water leakage in the cladding, while constituting the privileged area for the release of water vapour. With these functions in mind, generally, the area of joints should correspond, at least, to 10% of the surface of the cladding (Goldberg 2011). Additionally, joint filling materials should have good workability, low drying shrinkage and good adhesion. Grout for adhesive ceramic tiling with the mentioned properties should successfully fulfil its requirements, allowing also the local adjustment of tiles and limiting the deformation of the cladding. Many defects in adhesive ceramic tiling are associated with an incorrect or absent definition of the type, size and materials of joints at the design stage. Some authors (Shohet and Paciuk 2004, 2006) refer that the service life of an adhesive ceramic tiling outdoors may be three to four times lower than expected when joints are not adequately designed. Analysing that type of data leads to the conclusion that the durability of adhesive ceramic tiling may only be ensured if joints are adequately designed and if the design specifications are followed during the execution stage. While designing an adhesive ceramic tiling cladding, areas subject to higher stresses should be anticipated and treated. The substrate’s screed may be reinforced, using, for instance, a fibreglass mesh, joints may be larger or elastic joints may be designed with smaller spacing between them. Additionally, thermal bridges should be treated, trying to ensure that, throughout the façade, the substrate has the same properties in terms of thermal conductivity, hence avoiding preferential areas of heat and water vapour transmission, which would result in the occurrence of condensations on the cladding’s surface or inside the wall, according to the environmental conditions. The top of façades is also a sensitive area for the occurrence of water leakages. This area may be associated with a parapet wall or with the eaves of the roof. As water leakage may lead to the occurrence of efflorescence and to the degradation of the bedding material, the top area of the façade should be studied and detailed at the design stage to ensure better durability of the cladding. The detail should determine the end of the adhesive ceramic tiling, the size and filling of the peripheral joint and the waterproofing solution. If metallic profiles are used, the adhesive material should provide good adhesion properties to metallic materials (Goldberg 2011).

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If the top of the façade is constituted by a capped parapet wall, the coping should have a drip detail to avoid water runoff and subsequent dirt stains on the cladding, as well as possible detachment of tiles, due to changes in the bedding material. Drip details should be considered in every protrusion of the façade, like windowsills. Façades may also have curved areas cladded with ceramic tiles. In those cases, rectangular tiles should be applied with the shortest edge parallel to the curve’s perimeter. Small square tiles, with edges of about 2.5 cm, may also be used to efficiently clad the façade’s curve. In façades with more than two storeys, means of access to the façade should be defined for future maintenance of the cladding. Hence, anchorage points or support equipment should be provided. If good access is provided, cleaning operations, inspections and local repairs are easier to take place at lower costs (no scaffolding required).

2.3.3 Execution of Adhesive Ceramic Tiling The execution of adhesive ceramic tiling, whether with a thin or thick bed, is composed of five main stages: preparation of the substrate, application of the bedding material, application of tiles, filling the joints and final cleaning. Between each stage, setting periods should be complied with, so that the first, and most significant, deformations of the materials take place. Setting periods depend on the properties of the materials, curing conditions, type, size and exposure conditions of the surface, as well on the flatness and cleanliness level of the substrate. If adhesive ceramic tiling is applied over a rendered substrate, the application of the cladding should only occur after four to six weeks (CTCV 2003; Lucas and Abreu 2011).

2.3.3.1

Preparation of the Substrate

In this stage, the dimensions and orthogonality of the substrate should be checked, so that the width and location of all joints are determined, trying to obtain a low number of cut tiles. Tile spacers should be used to precisely locate and dimension the joints. Vertical and horizontal alignments of the first rows should be marked with a nylon wire. Flatness defects on the substrate may require executing a screed layer or using a traditional mortar bed (thick bed method) (Lucas and Abreu 2011). If the substrate’s texture is too rough, the thick bed method may also be advised, even if the roughness increases adhesion. To apply adhesive ceramic tiling, the flatness assessment of the substrate with a 2 m batten should not result in differences larger than 5 mm. As for the assessment of verticality, with a 3 m plumb line, it should not reveal differences larger than 10 mm per floor.

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A very porous substrate requires previous treatment with a primer. On the other hand, a substrate with low water absorption only allows the chemical adhesion of the bedding material, limiting the range of products that may be used. The cleanliness of the substrate also influences the quality of adhesion. Hence, if necessary, the substrate should be previously cleaned with a pressurised water jet.

2.3.3.2

Application of the Bedding Material

This application stage should begin with the preparation and mechanical mixture of the adhesive material according to manufacturers’ recommendations. If a thick bed is used (Fig. 2.11), a 10–15 mm thick single layer of traditional mortar is applied, finished with a wooden batten and let to harden to bear the weight of the tiles. When it is hard enough, the back face of the tiles is covered with mortar. The thickness of this layer depends on the texture of the back face of tiles. Then, applying a slight pressure, the tiles are placed in the adequate position. If a thin bed is used (Fig. 2.11), after levelling the substrate, the adhesive material is applied on the substrate, considering the adequate thickness for each case. First, the

1

Fig. 2.11 Representation of the application of adhesive ceramic tiling using a thick or a thin bed. 1—substrate; 2—spatter-dash (render layer); 3—render; 4—traditional mortar layer; 5—traditional mortar applied on the back face of tiles; 6—elastic joint; 7—adhesive material; 8—movement joint; 9—tile

2.3 Adhesive Ceramic Tiling Table 2.5 Minimal height of the notches of trowels used in large size tiles (Cass 2004)

41 Size of the tiles

Minimal height of the trowel’s notches

20 cm × 20 cm

8 mm

25 cm × 25 cm

10 mm (back-buttering advised)

30 cm × 30 cm

12 mm (back-buttering advised)

≥40 cm × 40 cm

≥12 mm (back-buttering advised)

flat edge of a trowel is used, at 45°, so that the adhesive material forms a homogeneous layer. Then, the notched side of the trowel is used on the adhesive material, to form adhesive cords. Table 2.5 shows the advised size of the trowel’s notches for tiles larger than 20 cm × 20 cm. If back-buttering is advised, the adhesive material should also be applied on the back face of the tiles.

2.3.3.3

Application of Tiles

The application of tiles using a thick bed has already been described in Sect. 2.3.3.2. If a thin bed is used, the application of tiles should be done applying high pressure, crushing the adhesive cords so that a homogenous layer, without voids, is formed, ensuring the complete contact between the back face of the tile and the adhesive material. A rubber hammer may be used at this stage. The Tarver method (Cass 2004) is a procedure that helps to ensure complete contact between the back face of tiles and the adhesive material. It is a three-stage method. First, the tile is placed exactly in its position applying slight pressure. Then, the tile is moved and pressed in the perpendicular direction of the adhesive material cords, considering a distance of about 1 cord. Finally, the tile is moved back to its original (and final) position applying constant pressure. The application of tiles should comply with the adhesive open-time. Typically, when the adhesive material is no longer adequate for the application of tiles, a whitish pellicle is formed on the adhesive cords. From that moment on, the application of tiles should stop, and the adhesive material should be removed. In cases with highly porous tiles or very low relative humidity, the use of primers to improve the adhesion quality is advised (Lucas and Abreu 2011).

2.3.3.4

Filling the Joints

Tiles should be applied with straight and uniform joints, whose width depends on the type and shape of the tiles, as well as on loads. Movement joints are usually done using tile spacers, which ensure a homogeneous width. Tile spacers are usually in plastic and should be removed from the cladding before grouting. However, the use of tile spacers may result in the low-quality application of tiles, as the tile is only placed in its position, becoming harder to crush the adhesive cords, even if a rubber hammer is used.

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The joints should be filled at least 24 h after applying the tiles to ensure that the bedding material has dried. The grout should be applied with a rubber trowel, ensuring that all joints are filled equally. After the grout starts to dry, it should be inspected to ensure a perfect finish.

2.3.3.5

Final Cleaning

The residue of grouting materials should be cleaned with a damp sponge, using a diagonal movement. This operation should only occur after the cure of the grout, as recommended by the manufacturer.

2.3.4 Quality Control at the Execution Stage The quality control of the tiles’ adhesion should be done removing a recently applied tile, while the bedding material is still fresh, and observing the back face of the tile and the substrate. The contact area between the tile and the bedding material is, thus, checked. If a thin bed was used, the adhesive material cords should not be visible, and the adhesive material on the substrate should be a continuous and homogenous layer, completely covering the back face of the tiles. After the bedding material dries, a percussion test, using a rubber hammer, may be performed, checking the homogeneity of the bedding (Lucas and Abreu 2011).

2.4 Wall Renders Three types of wall render may be considered: traditional, current and non-traditional. However, this classification is not unanimous, as several different types of classification are used. In this context, two main groups may be considered: traditional and non-traditional renders, as the difference between traditional and current renders is the use of lime only in traditional renders, better for conservation and rehabilitation works.

2.4.1 Materials Used in Wall Renders A wall render mortar is generally composed of aggregates, water, binders, admixtures, additions and, in wall areas more susceptible to cracking, reinforcement meshes (Flores-Colen and de Brito 2015).

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Sand is the most common aggregate in wall renders and works as the skeleton of the mortar. The type of sand and its size grading influence the behaviour of mortars, having an important role in the quality of the render. Sand will decrease shrinkage, create volume, absorb water vapour and improve mechanical strength. The sand should not contain any organic matter or salts and should be washed as needed. Water is also essential while manufacturing mortars as it promotes the hydration of aggregates and the activation of binders, and provides workability for application purposes. The water used for manufacturing render mortars should be free from impurities, dissolved salts (that contribute to the appearance of efflorescence), organic matter and soil matter (which decreases mechanical strength). Water excessively pure should also be avoided as it may lead to the dissolution of lime (Day 2006). Binders are adhesive elements composed of fine powders that, kneaded with water, form a paste with binding properties whose hardening occurs through chemical reactions between the particles of powder, water and air. These elements are classified according to hardening and setting, namely: hydraulic binders, which, after hardening, keep their mechanical resistance and stability, even under water, like hydraulic lime and cement; and air binders, which, after hardening and setting, only keep their mechanical resistance and stability if not in direct contact with water, like gypsum and air lime (Flores-Colen and de Brito 2015). The most common binders are cement and hydraulic and air lime, as gypsum is a binder with more restricted use and that normally appears associated with indoor claddings. Admixtures and additions are products that can be incorporated in mortars with the objective of improving renders’ properties. Conceptually, an admixture and an addition are different as admixtures provide changes at a chemical level and additions at a physical level. The most common admixtures and additions are highlighted in Table 2.6 and Table 2.7, respectively. In wall areas more susceptible to cracking, reinforcement is embedded in the render, such as in wall openings, protrusions, corners and transition areas between different materials. The reinforcement is made with fibreglass, nervometal sheet, distended metal or welded steel wire meshes, which are generally embedded in the base layer of the render with the objective of: improving the tensile strength, avoiding cracking; ensuring the adhesion of the render to the substrate, avoiding cracking and detachment processes; and increasing the impact resistance. Fibreglass mesh should have anti-alkaline protection, while metal or wire meshes should have anti-corrosion protection.

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Table 2.6 Admixtures (Rixom and Mailvaganam 1999; Aggoun et al. 2008; Flores-Colen and de Brito 2015) Admixtures

Description

Plasticisers

Improve the workability of mortars increasing their viscosity and decreasing the needed amount of kneading water

Adhesion promoters

Improve adhesion without increasing the cement content, decreasing shrinkage and susceptibility to cracking (e.g. synthetic resins and polymers)

Water repellents or capillary reducers

Promote the capillary sealing, decreasing capillary water permeability

Water reducers

Decrease attraction forces between binder particles, making the paste more fluid and decreasing the needed amount of kneading water

Water retainers

Stop the premature desiccation of the paste, contributing to more complete hydration

Air-entrainers

Promote the homogeneous distribution of air in small bubbles, making the mortar more permeable, homogenous and workable, improving the resistance to freeze-thaw and to the action of salts, while contributing to decreasing exudation and cracking

Hardening accelerators

Accelerate the development of initial resistance

Setting accelerators

Make initial reactions faster, decreasing the setting time

Setting retarders

Make initial reactions slower, increasing the setting time

Antifreeze

Decrease the freezing point, avoiding the formation of ice crystals

Flocculants or thickeners

Decrease exudation

Fungicides, insecticides, bactericides and germicides

Stop the fixation of microorganisms in the mortar

Table 2.7 Additions (Flores-Colen and de Brito 2015) Additions

Description

Pigments

Allow obtaining coloured mortars

Fibres

Generally made of glass, resistant to alkali, of fibrillated or of cellulose polypropylene, which are meant to increase the tensile strength and the render’s ductility

Lightweight fillers

Decrease the render’s Young’s Modulus, resulting in very deformable renders

Natural and artificial pozzolans

Improve the resistance to sulphates and the silica-aggregates reaction

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2.4.2 Design of a Wall Render External claddings of the building envelope may be classified according to the role of the cladding (Lucas 2011). That classification is presented in Table 2.8 and allows showing the context where wall renders fit. Watertight claddings are different from waterproofing claddings, as watertight claddings should ensure a tight facing, even when cracking occurs. Waterproofing claddings significantly contribute to waterproof the wall, but alone they do not ensure the watertightness of the facing.

2.4.2.1

Functional Requirements

A wall render should comply with a set of functional requirements to ensure quality. The most important requirements are (Flores-Colen and de Brito 2015): • Appearance: the cladding should give the facing a pleasant appearance that conveys its quality and good condition; the visual appearance is associated with the colour and texture of the outermost layer of the cladding, which is visible; the appearance of the render is very important whether from a well-being and visual comfort point of view or from an economic point of view, as it influences the value of buildings; Table 2.8 External claddings of the building envelope (adapted from Lucas [2011]) Functional classification

Examples of external claddings of the building envelope

Watertight claddings

Natural stone plates mechanically fastened to the substrate, with an air gap Plates of other materials (e.g. plastic) mechanically fastened to the substrate, with an air gap Scale-like claddings (e.g. clay-slate tiles, clay tiles) Reinforced synthetic binder claddings

Waterproofing claddings

Traditional renders Premixed renders (one-coat or others) Mixed binders (hydraulic or synthetic) claddings Synthetic binder claddings

Thermal insulation claddings

Tiles/plates claddings with insulation in the air gap Claddings with insulating components (e.g. thermal renders) Claddings applied over insulation (e.g. ETICS)

Finish or decorative coats

Tiles/plates claddings mechanically fastened or bonded without an air gap (e.g. ceramic tiles, stone plates) Thick plastic coats Thin coats of mixed binders Painted coats

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• Workability and consistency: the mortar’s workability and consistency influence directly the quality of application of the render, the adhesion to the substrate, the efficiency of activities on-site and the final performance of the render; • Water retention: this functional requirement is about kneading water and translates the capacity of the mortar to retain it; this characteristic allows avoiding the evaporation and absorption of kneading water in the substrate, thus ensuring adequate hydration and curing conditions; • Permeability to water vapour: the permeability to water vapour ensures the evaporation of water from leakages, absorption or excessive kneading water, as soon as weather conditions permit the process, and allows adequate control of condensations and inner hygrometry through releasing water vapour generated inside the buildings; • Mechanical, impact and cracking resistance: a wall render should have acceptable levels of mechanical strength (capacity of the render to resist to internal and external stresses resulting from the effects of environmental conditions or from static or dynamic loads on the building; in other words, the capacity of the render to resist to stresses without rupture), impact resistance (capacity of the render to resist to the impact of a hard body, sharp or not, without any marks or without losses of material or performance damages) and cracking resistance (capacity of the render to resist tensile stresses due to shrinkage restrictions without opening cracks); • Durability: it is a functional requirement of any building element; the render should have a durability adequate to its location and function; the durability of a render is directly associated with the susceptibility to different pathological phenomena, location of the facing, climatic region, quality of the material, labour, execution techniques and care, type of finish, nature and condition of the substrate and planned maintenance executed throughout the render’s service life; • Adhesion and compatibility with the substrate: the adhesion of the cladding to the substrate is a fundamental requirement for a cladding, as, otherwise, it will not be able to perform adequately; the adhesion to the substrate has implications in waterproofing, cracking resistance and durability of the adopted construction solution; adhesion is processed by capillary penetration of kneading water in the substrate’s pores, dragging the finer elements of the mortar that, as they crystallise inside the pores, ensure bonding; in the case of non-traditional renders, resinbased admixtures may also be used to provide chemical adhesion; adhesion does not depend exclusively on the mortar, as it is highly influenced by the characteristics and type of substrate (e.g. roughness, absorption coefficient), as well as by preparation measures; the mortar should have mechanical, geometrical, physical and chemical compatibility with the substrate.

2.4.2.2

Standards

In Europe, a broad set of standards stipulate requirements and execution rules for renders. Standard EN 13914-1:2016 (CEN 2016c) specifies requirements and recommendations for the design, preparation and application of external renders.

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Regarding test methods, the family of standards EN 1015 (CEN 1998b, c, 2002a, b, 2004e, f, 2006c, d, e, f, g, h, 2016d, 2019e) specifies methods of test for mortars or masonry, including rendering mortars. Test methods are specified for: particle size distribution; sampling and preparation of test mortars; consistence, bulk density, air content, workable life and correction time, and water-soluble chloride content of fresh mortar, dry bulk density, flexural and compressive strength, and water absorption coefficient due to capillary action of hardened mortar; water vapour permeability and adhesive strength of hardened rendering and plastering mortars; and determining the compatibility of one-coat rendering mortars with substrates. As for the materials used in render mortars, a set of standards determines specifications for: factory-made renders based on organic and inorganic binders (CEN 2016e, 2017e); pigments (CEN 2014f); aggregates and lightweight aggregates (CEN 2013c, 2016g); cement (CEN 2011c); lime (CEN 2015d); and admixtures (CEN 2012e).

2.4.2.3

Comparison Between Traditional Renders and Non-traditional (One-Coat) Renders

Among practitioners, using a one-coat render is generally considered a more expensive solution, although that idea has been proved wrong. Even though one-coat systems have slightly higher initial costs than those of traditional renders, the costs have been converging. But the analysis should not be strictly economic. Thus, technical aspects presented by both solutions should be assessed, as well as specific limitations of the construction site/building. In Table 2.9, a comparison shows the main characteristics of each type of render.

2.4.3 Execution of Wall Renders 2.4.3.1

Traditional Renders

Traditional renders are prepared and dosed on-site with traditional techniques and technologies (manual preparation, with a concrete mixer or with a mechanical mixer and manual application), using components such as cement, lime, sand and some admixtures or additions. This type of cladding is made with three layers of different thickness, composition and content. From bottom to top: spatter-dash, base layer and finish layer. Each layer has specific characteristics considering the role it plays. Spatter-dash is the first layer of a traditional render and it is meant to promote the adhesion between the substrate and the cladding and homogenise (and decrease) the substrate’s water absorption. This layer should be 3–5 mm thick, rough and nonuniform, to maximise the mechanical connection and adhesion to the next layer. The mortar used for the spatter-dash should have a high content of binder (cement), a very fluid consistency, to prevent the substrate’s absorption from compromising the hydration of cement reactions, and high content of coarse sand.

High mechanical strength (flexural, compressive, capillary and soluble salts actions) and high chemical resistance towards sulphates

The paint coat works as a way of filling any possible cracking

Resistance

Pathology

There should be more care in application to avoid the appearance of cracking, as it is a single layer finish/cladding

Higher homogeneity; better adhesion to the substrate; better content control when mixing the raw materials; easier to handle as it does not dry as fast as one-coat renders; it does not require specialised labour; easier to apply in rehabilitation works; good chromatic homogeneity, even if painted with bright colours; good resistance to ageing due to environmental aggressions

It requires a higher renting period of scaffolding; it implies a longer application process, as the render itself is not a finish, needing painting; need of compatibility tests between layers

Disadvantages

Sanded: for smooth paint finishes

Due to the low quality of brickwork, one-coat systems should be light; it needs specialised labour in repair or maintenance; to comply with chromatic homogeneity, its application is more demanding; weather conditions are more relevant for the final appearance of the render; it is more porous, hence having higher probability of biological growth in façades with poor insulation

Quick to apply, as both cladding and coating are done in the same procedure; less labour needed; it does not require setting scaffolding twice; it does not have high maintenance needs; it clads, protects and decorates in a single application; not being a sealant, it gives the substrate enough waterproofing towards rainwater entrance, absorbing it during rainy periods and eliminating it as water vapour during dry periods

Projected stone Scratched, rustic, smooth or trowelling

Trowelling: to be finished with textured paint or polished finishes

Battened: for ceramic tiling or natural stone finishes

Both types of cladding are subject to the same types of failure and mechanical faults, such as cracking, blistering and detachments, or efflorescence, thermophoresis, stains and mould. To avoid mechanical action defects, it is advised, in both solutions, to use a fibreglass mesh with anti-alkaline treatment, which also provides better adhesion to the substrate

Advantages

Types of finish

16–15 kg/m2 /1 cm thick

19 kg/m2 /1 cm thick

Efficiency

It ensures every façade requirement: waterproofing, resistance, colour and texture

Dry mortar, formulated with hydraulic binders, silica aggregates and admixtures, using a satin, textured paint as a finishing coat, based in disperse polymers in aqueous phase, flexible and waterproof but permeable to water vapour

Composition

One-coat render Coloured cladding mortar composed of hydraulic binders, aggregates and admixtures/additions (fibres, setting regulators, water retainers, light fillers and pigments)

Façade render and paint coat

Parameter

Table 2.9 Comparison between a traditional render and a non-traditional (one-coat) render (Hernández-Olivares and Mayor-Lobo 2011; Flores-Colen and de Brito 2015)

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The base layer is the second one of a traditional render and it is meant to ensure flatness, verticality, smoothness and waterproofing. This layer should be 10–15 mm thick and show a regular surface. It has a low content of binder (cement) and water (to minimise cracking and to be more homogeneous and compact), and incorporates sand with a high content of coarse sand, ensuring waterproofing. It is important to control the content of lime as it will ensure the workability of the mortar and delay setting, allowing smoothing the surface. This layer should be stroked to improve its compactness, but not smoothened in such a way that the risk of cracking would increase due to rising of the binder to the surface. The finish layer is the third and last one of a traditional render and is meant to: protect preceding layers against impacts and wear; fill any cracking of the base layer; to ensure waterproofing of the facing, and give a pleasant appearance to the render. This layer is generally 5–10 mm thick, except in projection cases, which can be up to 3 mm thick. The mortar should be made with fine aggregates and low content of binder (cement), allowing the application of a thinner layer and less susceptible to cracking. In external renders, it is common to increase the content of lime to decrease cracking and avoid stains in the facing. Five steps are established for the application of the layers of a traditional render: preparation, application, battening, flattening and smoothing. The preparation stage includes cleaning the substrate, correcting imperfections, filling any voids in the substrate and correcting flatness defects incompatible with the cladding (Pinho 2008). Application refers to the three mentioned layers, with the following highlights: • Spatter-dash should be done over a damp substrate to avoid excessive absorption of kneading water; • Spatter-dash should not be followed by smoothing and, when weather conditions are dry, it should be periodically sprinkled with water to avoid premature desiccation; • The base layer should be applied over a damp spatter-dash but only after it has dried, hardened and gone through most of its initial shrinkage (at least 48–72 h, according to weather conditions and the nature of the binder); • The base layer is applied vigorously throwing mortar over the previous layer or, alternatively, vigorously pressing uniformly with a trowel to ensure better compactness conditions; • The finish layer is applied after the base layer has dried, hardened and gone through most of its initial shrinkage (at least 7–12 days, according to weather conditions and the nature of the binder); • The finish layer should be executed over a uniformly damp base layer, and the method of application varies according to the decorative finish. Battening, flattening and smoothing are the three last steps and are meant to give the finished facing a regular, flat surface with the desired texture. These steps should only be executed after the mortar dries and sets so that it resists each process. A period that allows the evaporation of the kneading water should be predicted, avoiding the occurrence of cracking and shrinkage afterwards.

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Non-traditional/One-Coat Renders

Non-traditional/one-coat renders are claddings made of premixed factory-made mortars based on hydraulic binders and applied in a single layer. This layer is projected over the wall in one or two coats and should have a final thickness of 20 mm. Despite one-coat renders being prepared to be applied using a single coat, if considered necessary (e.g. if flatness deficiencies are detected on the substrate), the render may be applied using a two steps process (i.e. two coats). If that methodology is selected, both coats have the same composition. The composition of one-coat renders is similar to that of traditional renders, based on binders like cement and lime mixed with mineral fillers, adequately selected and adjusted with admixtures and additions. This type of wall cladding is prepared on-site kneading water with a powder mix, premixed at the factory, which can be adjusted using admixtures and additions. Due to quality control, it is possible to obtain regular characteristics and better performance than traditional renders (workability, adhesion to the substrate, resistance to cracking and waterproofing). As this render is composed of a single layer, it should simultaneously perform as protection and decoration (these renders are usually pigmented, not needing a finishing coat of paint). As for application, it can be done manually or through projection. Mechanical application is used more often as it makes the application process quicker and simpler. The mechanical application process should be done from bottom to top in regular strips of mortar. If the application is done in two coats, the first should be executed using the technique of points and masters, so that a homogeneous thickness is obtained, of about 15 mm. After the first coat, the facing should be battened using a wooden batten to ensure a smooth and levelled surface. Within the next 24 h, and according to a set time of 2–5 h, the second coat should be applied. If the application is not done within this period, the facing should be humidified before applying the second coat (Flores-Colen and de Brito 2015). The finish should be executed after smoothing the surface and as soon as the second coat starts to harden. The finish varies according to the desired visual effect and refers to texture, as most of these claddings are already pigmented. If elastic joints are to be implemented, the negatives should be placed before setting begins. Non-traditional/one-coat renders that are not pigmented require the application of a finishing coat, like traditional renders, according to the intended visual effect.

2.4.3.3

Good Practice Rules

When good practice rules are put in place, they allow obtaining a cladding that complies with functional requirements, minimising the occurrence of defects. These are the most relevant: • The consecutive layers of a traditional render should comply with the rule of decreasing the cement content from the lower to the top layer, with the intent

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of improving cracking behaviour and facilitating the evaporation of absorbed rainwater; • Complying with pauses between the application of different layers allows layers/coats to have independent behaviours, minimising the effects of shrinkage and stopping it from spreading from one layer to another; this measure has aesthetical and waterproofing advantages; • Materials of render mortar should be stored on-site in a dry location, protected from damp and inclement weather; • The choice of an aggregate with uniform size distribution and adequate shape allows obtaining a more compact and resistant mortar, with lower needs of binder and water, and economically more attractive.

2.5 Painted Façades The research about paints may be approached considering: the complexity of this building material and its physical-chemical characteristics, components and rheology; painting schemes, taking the selection of products, different combinations and application into account; and the role paint plays in the behaviour of substrates. Additionally, the paint industry has evolved in such a way that, nowadays, the market is composed of thousands of products, with different formulae and functions, answering the diverse and growing demands building coatings must comply with.

2.5.1 Materials Used in Painted Façades Paint may be defined as a pigmented liquid, viscous or solid composition that is convertible after some time into a solid, coloured and opaque pellicle, when applied as a thin layer over an adequate surface, in the supplied state or after fusion, dilution or dispersion in volatile products (CEN 2014c). Alternatively, paint may be defined as a mixture essentially composed of pigments, extenders, vehicles and additives, which is applied as a thin layer, forming solid pellicles after drying (Eusébio and Rodrigues 2009). The composition of paint depends on the application for which it was designed, considering the type of substrate, the means and conditions of application, as well as the exposure conditions of the dry pellicle. The ratio between components depends on their nature, the desired properties for the pellicle, specific ends meant for the paint and economic factors. In this case, only paints applicable in wall renders are considered, but some may also be applied over concrete surfaces. Figure 2.12 summarises the components of paint. Concisely, each component may be described as follows (Eusébio and Rodrigues 2016): pigments provide colour and

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Fig. 2.12 Composition of paint

opacity to the pellicle; extenders help giving body to the paint; the binder (vehicle) connects the pigments particles and extenders and gives the pellicle its integrity and adhesion capacity; solvents and diluents provide the adequate consistency for the application; and additives provide specific properties.

2.5.1.1

Pigments

Pigments are solid substances, generally very fine and basically insoluble in the vehicle. They are used to prepare the paint, attributing opacity and colour or even other special characteristics. Additionally, pigments provide paint with good appearance, surface protection and special properties, such as anti-corrosive and mechanical resistance, gloss and resistance to chemical products and ageing. Pigments should bear the influences of where they are used, through manufacturing or weather exposure. They should also be compatible with the environment and be harmless for health, as well as having an adequate cost, considering pricing demands of materials where they will be used (Talbert 2008). Natural pigments were used for centuries, including coloured soil, oxides, sulphates, metallic sulphides and some vegetal and animal products. Now, most pigments are synthetic, i.e. they are industrially produced using the chemical reaction of specific compounds. Pigments may be categorised into organic and inorganic. The former are sensitive to temperature and combustible, and the latter (oxides or metallic salts) are incombustible and resistant to heat (Eusébio and Rodrigues 2009). The main characteristics of pigments are registered in Table 2.10. The amount of pigment in a paint may vary according to type and colours, within a range of 2–8%. It is not the higher or lower percentage of pigment or vehicle used that determines the quality of the product, but the balance between the function and the in-service conditions for which the product is formulated (Talbert 2008). However, considering that pigments have a heavy weight on the paint’s total cost, to obtain a specific opacity degree, it is preferable to optimise the spacing between particles, whether through a judicious size grading selection or through the incorporation of other paint components, like extenders.

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Table 2.10 Main characteristics of pigments (adapted from Talbert [2008] and Eusébio and Rodrigues [2009, 2016]) Characteristics of pigments

Description

Colour and colouring capacity

It depends on the chemical composition and on the selective absorption and reflexive capacities within a specific wavelength in the visible light spectrum. The colouring capacity is a measure of the pigment’s ability to attribute colour

Opacity and covering power

Opacity allows the paint to completely cover the substrate and is a function of the difference between the pigment’s and the dispersion medium’s refraction indexes. The higher that difference, the more covering power of the paint and the greater ability to eliminate colour or colour differences in the substrate

Size grading

The control of the particles of the pigment may influence gloss, opacity, consistency or the pigment’s suspension power

Ease of dispersion

Dispersion is great when each particle of pigment is separated from the remaining particles and completely wet by the vehicle. The presence of adsorbed water or gases on the pigment’s surface and the tendency to form agglomerates make dispersion more difficult. It also depends on the polarity of the surface of the particles, affinity with molecular groups of the binder and on the nature and concentration of solvents

Resistance to migration and separation

Lack of resistance to migration and separation may result in chalking, which may be due to crystalline content and shape of the pigment, as well as to the destruction of the binder

Chemical resistance

Some pigments are completely inert, but others may react with acid binders, which may lead to unwanted thickening. Some organic compounds may stay soluble, being dissolved in vehicles or solvents of subsequent coats, originating bleeding

Light stability

Light stability depends on the composition, purity, crystalline structure and exposure conditions of the pigment. Ultraviolet radiation is the main cause of photochemical changes in pigments and may cause colour changes

Various resistances

Pigments may have an active role in the cladding’s behaviour, like on absorption of ultraviolet radiation, fungicide action and anti-vegetation

2.5.1.2

Extenders

An extender is an inorganic substance in the form of particles, soluble or not, with low covering power, insoluble in the vehicle, and used as a paint component to provide specific properties.

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Like pigments, extenders may be of natural origin (such as natural barium sulphate, calcium carbonate, talc and sand) or synthetic (such as bentonite, precipitated calcium carbonate and artificial silica). Not providing great opacity or colouring capacity, extenders are used to give body to the paint, for economic (low cost when compared to pigments) and technical reasons. In fact, the size grading, specific surface and specific properties of some extenders may ease the manufacturing and application of paint, improving quality and durability of the paint finish by increasing waterproofing and elasticity, enabling the conservation of paint, besides providing thermal and acoustic insulation and fire resistance characteristics, for instance (Talbert 2008; Eusébio and Rodrigues 2009, 2016).

2.5.1.3

Vehicle

In the literature, the terms vehicle, vehicle system, binder and resin often appear as equivalents. The vehicle is the paint’s component responsible for forming a solid pellicle. It may be composed of one or more products. Besides forming the pellicle, the vehicle is also responsible for the adhesion to the substrate and for other related properties, such as resistance to blistering, cracking and peeling, hardness, chemical and mechanical resistance, resistance to washing and to chalking, as well as to environmental conditions, and permeability to water vapour and to liquid water. The vehicle is also responsible for fluidity, paint consistency, and level of gloss (Daniotti 2002; Talbert 2008; Eusébio and Rodrigues 2016). The main types of vehicle are concisely described in Table 2.11.

2.5.1.4

Additives

An additive is a substance, usually added in a small percentage to paint, with the intent of improving specific characteristics. It may be a liquid, viscous or solid powdery product, soluble in the vehicle and meant to improve the application conditions of the paint and the properties of the dry pellicle. When additives are powdery solids and insoluble in the vehicle, they are distinguished from extenders due to their content being below 5% of the paint mass (Eusébio and Rodrigues 2009). Additives are generally named according to their function, instead of according to their chemical composition, hence being classified as construction (bactericide, fungicide, algaecide, dryer, wetting, dispersant, thickener and stabiliser) or corrective (anti-skin, anti-foam and antiseptic) additives (Talbert 2008).

2.5.1.5

Solvents and Diluents

Solvents and diluents, also known as volatile vehicle, are the paint’s component that evaporates during the drying process. Solvents are liquids, which, in normal drying conditions of the applied paint, can dissolve the vehicle. Diluents are volatile

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Table 2.11 Main types of vehicles in paint (Talbert 2008; Eusébio and Rodrigues 2009; CEN 2014c) Vehicle

Description

Symbolic oils

Fat oil of vegetable or animal origin, which has the capacity of forming, in contact with air, a continuous, adhesive and elastic pellicle, when applied as a thin layer over a surface. Generally, symbolic oils are modified with resins through boiling, refining or dehydration processes, so that polymerisation and cross-linking are improved, as they are essential to forming the pellicle. Examples: linseed oil, tung oil, dehydrated castor oil and soy oil

Natural resins

Thermoplastic product of vegetable or animal origin, polymerised, water-insoluble and soluble in organic solvents, of varied chemical origin. Natural resins fuse and decompose by heating, but their composition generally varies according to the origin, needing treatment. Examples: copal, colophony, Chinese lacquer and Dammar resin

Artificial resins

Product of high molecular mass, coming from the chemical modification of fat oils, symbolic or not, natural resins or of a mix of these products, or even of synthetic resins, when the modifier agent has natural resins. Examples: alkyd resins modified with long-chain fat oils, ester, cellulosic and oleoresin gum and chlorinated rubber

Synthetic resins

Polymers of high molecular mass, resulting from the controlled chemical reaction between one or various substances of low molecular mass (monomers) with two or more reactive groups or double connections. From these substances, those soluble in water, in comparison, dry faster, do not have an odour, are applied easily, have good appearance and resistance to washing. Examples: acrylic, vinyl, styrene-butadiene, polystyrene, alkyd (without oil), polyurethane, epoxide, phenolic and polyester resins

Inorganic binders

Products usually combined with organic binders, in such a way to ensure stability, decrease permeability, increase resistance to chalking and adhesion, with the content below 5%. Examples: lime and silicates

Siloxane resins

Product with low binding capacity on its own, being usually combined with acrylic or styrene-acrylic dispersions and organic binders, such as lime, which improve some of its properties

New technologies

The increasing search for economical products, environmentally conscious and with improved durability reflects on the development of materials that show high resistance and improved characteristics, such as self-cleaning properties. Examples: nanocomposites and hydro-pliolite

liquids, partially or totally miscible with the vehicle, which are added to the paint during manufacturing or at the application stage to obtain the required application characteristics. The most common solvents and diluents are water (water-based paints), turpentine, hydrocarbons (solvent-based paints), oxygenated solvents (alcohols, ketones, ethers and esters) and chlorinated solvents (Talbert 2008; Eusébio and Rodrigues 2009). When the volatile vehicle evaporates, the pigments and the binder remain on the painted surface, constituting the solid part of a paint. In volume, the proportion of solids and liquids composing a painting product applied with a specific humid

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thickness determines the dry thickness after drying. Higher content of solids in the paint may lead to a thicker dry pellicle, with better opacity and durability (Eusébio and Rodrigues 2016). Solvents and diluents influence the properties of the painting product, such as its viscosity and dissolving ability, which also depend on the binder’s solubility. The volatility, determining the drying speed of paint, the odour of the liquid product, toxicity, flash point and cost of the painting product are also influenced by solvents and diluents (Talbert 2008). The paint industry is actively searching for innovation, focusing research and development efforts on decreasing the use of volatile organic compounds. This includes progressively abandoning solvent-based systems, such as paint formulated with acrylic and vinyl resins. Even though these types of paint show better chemical resistance, lower permeability to liquid water and atmospheric gases, waterbased paints present a good general performance, being competitive for cases not susceptible to chemical attack (Talbert 2008).

2.5.2 Design of Painted Façades In a commercial environment, the names of paints are confusing, at times, due to the various attributes that these may be characterising, from the type of vehicle to their function. For instance, it is current to wrongly use the name “plastic paint” or “emulsion paint” in water-based paints or with a synthetic binder. It is also common to find anti-mould or fungi paints that do not disclose their detailed composition. There is also some generalised terminology in the construction industry, such as “enamel paint”, referring to the type of finish, glossy and smooth, and “textured paint”, which have extenders with larger size grading, allowing obtaining a rough surface (Eusébio and Rodrigues 2016). Technically, in Europe, standard EN 1062-1:2004 (CEN 2004g) defines various available classifications for paint. According to the type of use, paints may be divided into preventive, decorative or protective. Paints may also be classified according to the nature of the binder, including, for instance, lime, cement and silicates paint, or acrylic, vinyl, alkyd and polyester resins paint. As for the dissolution or dispersion state of the binder in the paint, paints may be classified as soluble in water, soluble in solvent or solvent-free. Other classifications are available, like those referring to gloss, thickness of the dry pellicle, size of the largest grain and permeability to water vapour and liquid water. Besides those more common names, the standard indicates that coatings meant for masonry that have a special protective function may be assessed according to the following properties(CEN 2004g): • Capacity to resist static cracking; • Resistance to mould, fungi and algae; • Permeability to carbon dioxide;

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• Alkali resistance; • Thermal shock resistance. The choice of products, their composition and the way they interact with the substrate is a role that, nowadays, is frequently given to paint products’ retailers. Although designers know the requirements of the cladding (the type of substrate and cure, exposure, special performance needs), the great range of products in the market and the different combinations make the selection more and more difficult.

2.5.2.1

Design Criteria

The selection of a painting system implies analysing and taking into account various factors, including qualitative factors, in view of answering specific requirements. Additionally, different products may be applied for similar needs. However, not only the performance of each coating may be different, but the initial low cost may result in higher costs in the long term, namely due to maintenance and repair works. Nevertheless, some fundamental factors should be considered (Eusébio and Rodrigues 2009): • Use of the coating: decorative, protective and hygiene purposes, for instance; • Type of substrate: the physical-chemical nature of the substrate may influence the choice of the type of paint; • Type of environment: indoors or outdoors, rural, urban, maritime, industrial and special exposure conditions; • Special selection restrictions: toxicology, application conditions (for instance, drying time) and substrate conditions (for instance, a substrate with high moisture content); • Economy: global costs including materials’, preparation of the surface, application, accessibility, equipment’s and utilities’ costs, and the cost due to production losses; the weight of each stage of the execution process may be estimated, considering the initial cost of the painted façade (Table 2.12); • Durability demands: the service life of the coating and warranty periods of products. Table 2.12 Estimated partial costs of painting works (Nogueira 2008)

Item

Cost (%)

Application of the paint

25–60

Preparation of the surface

15–40

Cleaning

5–10

Auxiliary products

3–6

Paint

10–12

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Besides the mentioned factors, the chosen products should comply with specific demands, according to their purpose. In façade’s painting, these are the requirements (Eusébio and Rodrigues 2009): • • • • • • • • • • •

Durable protection of the substrate; Easy application; Low toxicity; Fast drying; Good resistance to washing; Pleasant decorative aspect; Good resistance to inclement weather; Good adhesion to the base coat; Colour stability; Chemical neutrality between the painted coat and the base coat; Good resistance to fungi, mould and algae.

There is also the need to separate painting schemes adequate for old buildings from those used in recent buildings, namely after the 1950s, when concrete largely replaced traditional building materials, in most countries. In old buildings, materials usually show very similar hygrothermal behaviour, due to similar coefficients of thermal expansion, high thermal inertia, absence of thermal bridges and structures highly permeable to water vapour. On the other side, waterproofing is minimal, whether in façades, roofs or foundations. Thus, water percolates freely through walls due to capillary phenomena. In these cases, selection criteria should also include ensuring the compatibility between new and pre-existing materials, whether in terms of behaviour or aesthetically. In more recent buildings, one should be aware that, to reach the level of current requirements, in terms of construction time, cost, comfort and accessibility, some other features may should be considered, such as: (i) the resistance to thermal expansion; (ii) thin-wall systems with low thermal inertia; (iii) the origin of thermal bridges between different materials; (iv) existence of high amount of water in the construction materials, mostly concrete and mortars, which, due to execution deadlines, does not get to evaporate totally, hindering the execution and compromising the durability of coatings. Still, no matter the age of the building, two functions need to be performed by coatings: water repellence and permeability to water vapour. Crossing these criteria, a matrix (Fig. 2.13) may be obtained, including the most advised binders considering the various permeability to water vapour and water repellence relationships for painted walls. It is found that products that show low permeability to water vapour and low water repellence are not advised for any type of wall coating. Indoor walls, not subject to weather effects, accept products with low water repellence but require high permeability so that the water vapour from indoors may be diffused by the materials and transported outdoors. When walls are well dried and there is no possibility of moisture appearing inside them, products with high water repellence and low permeability to water vapour offer good value for money. However, in the cases where

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Fig. 2.13 Water repellence versus permeability to water vapour

moisture is expected inside the walls and, mostly, in façades subject to environmental actions, products with high permeability to water vapour and high water repellence are the most adequate (Simões 2015).

2.5.2.2

Painting Schemes

The name “painting system” is tightly linked with the chemical nature of paints composing it and is independent of the number of coats. For instance, if all applied products are formulated with alkyd resins, it is said that the system is alkyd. When a combination of paints is considered, establishing all the thicknesses and the number of consecutive coats, the notion of painting system is restricted to painting scheme. Schemes may be monolayer, if constituted of a single layer of a paint product, or multilayer, if constituted of various layers. In this case, the layers should be chemically compatible and, in both cases, the system needs to be compatible with the substrate and vice versa (Simões 2015).Generally, schemes are composed of different types of products (Talbert 2008; Eusébio and Rodrigues 2009):

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• Stabilising solutions and sealants: to control the behaviour of the substrate, for instance, when it is particularly friable or has high moisture content; • Primers: contribute to the adhesion of the painting scheme and promote the bilateral chemical protection between the substrate and the paint; • Sublayers: smooth and disguise imperfections through increasing the thickness of the coating, which may also be their only function, besides ensuring a barrier effect of the painting scheme; • Finishing coat: gives the scheme its final colour, gloss, good characteristics of adaption to the surrounding environment and other special characteristics, depending on its formulation. In a painting scheme, the primer is frequently substituted by a highly diluted paint coat. As for façade painting, schemes are generally composed of a coat of primer, and two or three coats of finishing paint, if the finish is smooth. When a textured finish is desired, it is common to use a “smear” coat and one or two coats of textured paint.

2.5.3 Execution of Painted Façades 2.5.3.1

Preparation of Surfaces

All painting works should start with a careful assessment of the substrate, with special attention to the characteristics of the base material, namely soundness and superficial hardness of the material, superficial texture, cracks or warpage, dirt or exudations, degree of acidity or alkalinity and high moisture content. The preparation of the surface includes a set of operations that aim at obtaining a homogeneous surface, with adequate and known roughness, able to receive the painting work. The durability of the paining systems is strongly influenced by the care taken in this task. So, it is equally important recommending an adequate treatment of the surface and making sure that it is followed. So that paint adheres to the substrate correctly, it is indispensable to remove particles with low adhesion, namely dust and sand, scraps of paint and other contaminants. For that purpose, brooms, dusters, clean cloths and air jets may be used, although, sometimes, it is necessary to use abrasive equipment or rigid brushes. The render may also be cleaned through washing with clean water. However, this operation postpones remaining works, as it is fundamental that the surface is dried before applying paint. The drying period should not be less than 2 or 3 days, in this case. If damp cloths are used, the drying period may be about 1 or 2 days. In cases with dirt or grease highly ingrained in the substrate, they should be removed using clean water and adequate detergents, or even solvents (Eusébio and Rodrigues 2002).

2.5 Painted Façades

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Application Processes

Paint application processes vary mostly according to the dimension and shape of the surface, desired finish, application speed needed, designed thickness required and economic aspects. The application may be done manually or automatically, respectively if mainly labour is used in execution or equipment decreases that necessity. From the many manual paint application processes in façades, the following are highlighted (Eusébio and Rodrigues 2009): • Regular paint rollers, with long hair for elastomeric and textured paints and with short hair for the remaining water-based paints; • Sponge paint rollers, highly used in façades, due to the aesthetic effect that they provide and to execution swiftness; • Non-drip paint rollers, which avoid drips of very fluid paints, such as most waterbased paints; • Brushes, for small areas or detailing. From automated application methods, conventional pneumatic and airless guns are highlighted. They decrease the amount of air inside the paint, avoiding the occurrence of blisters and craters in the damp pellicle. After protecting all decorative elements, doors, windows, handrails and other details, the application should start from the top of the façade and the painting process should not be interrupted until the panel is complete.

2.5.3.3

Application Conditions

Environmental application conditions during the paint application process are, many times, responsible for the good or bad performance of the paint coating. Hence, the manufacturers’ recommendations should be judiciously followed, considering drying periods, and admitting that the painting application process is done in the following environmental conditions (Eusébio and Rodrigues 2002, 2009): • The environmental temperature should not be below 5 °C nor above 35 °C; • Exposure of the paint to strong sunlight should be avoided; • The relative humidity should not be above 85% and the wall render moisture content should be below 5%; • There should be no dust in the air, nor strong wind that deforms the pellicle during the drying period.

2.5.3.4

Drying Processes

The curing process may occur: by physical drying, i.e. the film is formed after the evaporation of the solvent, as in water dispersions, in which water evaporates; or by

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Fig. 2.14 Paint pellicle formation process

a polymerisation chemical reaction, in which there is a first stage of physical drying (Talbert 2008). The maladjustment of evaporation speed of the solvent may cause an inadequate physical drying that, in turn, causes application problems or subsequent defects. If drying is too fast, the levelling of the pellicle is faulty and may not penetrate the substrate’s pores, leading to a lack of adhesion between the paint system and the substrate. If drying is too slow, the painting may runoff in vertical surfaces and not cover the substrate adequately (Talbert 2008). When the pellicle is formed, the liquid stage of paint ends, and the paint coating is said to be in-service (Fig. 2.14).

2.6 Etics After the Second World War, with the partial loss of economic viability for using oil products for heating purposes, a system that would allow keeping thermal comfort conditions indoors was needed. In Sweden, in the 1940s, the first external thermal insulation system was developed, consisting of a layer of mineral wool over the building envelope, cladded with lime and cement render. After some experiments, the use of expanded polystyrene (EPS) was proposed, cladded with a reinforced render, which is the system used nowadays (Amaro et al. 2013). The first great expansion of ETICS’ use occurred in the 1950s, with its industrial development in Germany. In 1988, the European Union for technical approval in construction (UEAtc) created the first directives about the external thermal insulation system of walls using EPS. That was the first standardisation document referring to the application, use and assessment of ETICS. In 1992, a technical guide was created referring to the use of rock wool. Afterwards, the European Organization for Technical Approvals (EOTA) created a specific technical guide for ETICS—“ETAG 004 Guideline for European Technical Approval of External Thermal Insulation Composite Systems with Rendering” (EOTA 2013).

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2.6.1 Components of ETICS A cladding system like ETICS is composed of a set of layers overlaying the external walls of buildings. These layers follow a specific order, but materials may vary. Generally, the system is composed of a thermal insulation layer bonded to the substrate, that can also be mechanically fastened, over which a base coat incorporating a reinforcement mesh is applied. Finally, on the surface, a finishing coat is applied with or without the application of a primer, also known as key coat (Fig. 2.15).

2.6.1.1

Substrate

The substrate is the vertical or horizontal (or tilted) surface not exposed to rainwater on which the system is applied. It may be made with any material used to build façades. Still, existing painted façades or façades cladded with mineral or organic materials can only bear the application of bonded ETICS after adequate preparation of the substrate.

2.6.1.2

Adhesive Mortar

ETICS are bonded to the substrate, but can also be complemented with mechanical fastening. The adhesive mortar corresponds to the layer that connects the thermal insulation to the substrate. Its composition may vary between purely organic or purely mineral, but a mixed solution is more frequently used. The adhesive mortar may be a premixed powder to which water is added at the construction site according to the manufacturer’s recommendations. In other cases,

substrate adhesive mortar thermal insulation reinforcement mesh

base coat key coat (primer) finishing coat

Fig. 2.15 Scheme of the components of ETICS

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a paste may be supplied, to which a percentage of Portland cement needs to be added. According to the EOTA (2013), powder adhesive mortars that require adding a specific binder and ready to use pre-prepared pastes are also admitted.

2.6.1.3

Thermal Insulation

Thermal insulation is a prefabricated material that is applied as boards with a flat or notched contour. It is meant to increase the thermal resistance of the wall. According to The Minnesota Lath & Plaster Bureau (2001), the most common insulation material used in ETICS is EPS. However, there are other thermal insulation materials commonly used, namely extruded polystyrene (XPS), mineral wool and insulation cork board (ICB). A group of characteristics are common to every type of thermal insulation: low thermal conductivity, low water absorption and low elastic modulus (EOTA 2013; Mandilaras et al. 2014). This type of properties partially derives from the density of the insulation material—the denser the insulation material, the lower its permeability. The system’s thermal conductivity may also be decreased by adding graphite to the composition of EPS. Additionally, EPS may be altered to increase acoustic resistance by using elasticised EPS. Mineral wool assumes the role of thermal and acoustic insulation material. However, the acoustic insulation role loses efficiency if the remaining façade elements (namely doors and windows) are not adequately insulated. For this reason, as the adoption of mineral wool is more expensive, it should only be chosen when all systems are acoustically insulated. On the other hand, mineral wool shows advantages in terms of fire safety, avoiding the propagation of flames, thus protecting the building. The thickness of the insulation material is calculated according to the thermal efficiency that is desired and according to the material’s heat transfer coefficient. Additionally, the type of connection with the substrate should be determined. Generally, in a new building, bonding may be enough up to 20 m high. From that height onwards, mechanical fastening must be considered, as so if mineral wool, XPS and ICB are used. If the finishing coat is ceramic tiling, for instance, as the weight increases drastically, compared with rendered coats, mechanical fastening is needed throughout the whole façade.

2.6.1.4

Base Coat

The base coat is applied over the insulation material and has a small thickness (4– 6 mm) (Novotný 2016; Uyguno˘glu et al. 2016). Its composition is usually a mix of resin and cement, identical to the adhesive mortar used between the substrate and the insulation material (The Minnesota Lath & Plaster Bureau 2001). A reinforcement mesh is embedded in the base coat, thus requiring its application through consecutive coats. Generally, the reinforcement is in the middle of the thickness of the base coat. According to the EOTA (2013), the base coat provides mechanical strength to the system and protects it from the entrance of water. Its properties should include

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good adhesion to the insulation material, high cracking resistance, low capillary and resistance to perforation and impacts.

2.6.1.5

Reinforcement Mesh

As mentioned, the reinforcement of the system is embedded in the base coat. The reinforcement may be a squared mesh with 3–5 mm openings, generally in fibreglass (woven or thermally bonded) and with an anti-alkaline protection treatment. Although traditionally the reinforcement material is fibreglass, other materials are mentioned by the EOTA (2013), namely galvanised steel (with adequate thickness of a zinc coat) and plastic meshes. Carbon fibre is also currently used. The reinforcement mesh must: increase the mechanical resistance of the system to impacts; limit dimensional variations of the base coat; and ensure cracking resistance in the joints between thermal insulation boards. Moreover, a regular reinforcement mesh may be used, or it may be reinforced with another mesh to improve impact resistance.

2.6.1.6

Key Coat (Primer)

The key coat is composed of a primer, which is a product usually applied as a thin layer (similar to an opaque paint coat) over the base coat with the objective of preparing the system for the application of the finishing coat, by regulating absorption and improving adhesion between layers. The primer’s composition is based on resins in a water solution. The primer needs to be compatible with the alkalinity of the base coat. A key coat is not always used, as some manufacturers advocate that the compatibility between the finishing coat and the base coat is enough not to require any other product.

2.6.1.7

Finishing Coat

The most common finishing coat in ETICS consists of a paste applied with a trowel with thicknesses between 1 and 2.5 mm. The finish contributes to the protection of the system against inclement weather and has a decorative role. If the finishing coat complies with necessary functional requirements, it may be done with several materials. For instance, it may be a mineral or mixed binder coating, paints specifically formulated to this end (acrylic resins, siloxanes or silicates), stone plates, ceramic tiling or other adhesive claddings, or wood, metallic or glass plates (Fig. 2.16). Finishes should be previously tested and specified in the system’s technical approval document.

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b

a

c

Fig. 2.16 Examples of types of finishes for ETICS: a mixed binder coating; b stone plates; and c adhesive ceramic tiling

2.6.1.8

Accessories

ETICS are continuous systems applied on the façade. Still, in discontinuous areas, the thermal insulation function should not be compromised. Hence, accessories and products that allow keeping the system’s continuity were developed to be used in, for instance (Table 2.13): • Outside and inside corners; • Connections with building elements, such as windows; • Areas of discontinuity, such as joints between insulation boards, profiles or expansion joints. In the edges, resistant corners (in aluminium, stainless steel, fibreglass or polyvinyl chloride [PVC]) should be applied over the insulation board and then coated with the base coat to provide a homogeneous system surface. The inclusion of detail mesh in these profiles is recommended, providing extra resistance with the use of the double layer of reinforcement mesh. For connections with building elements, aluminium or stainless steel corner profiles (at the bottom and laterally, to bear the system), sills, flashings and copings should be used. The surface of these profiles, over which mortar is applied, should have a minimum width of 30 mm and present at least two rows of holes of about 6 mm diameter, corresponding to 15% of the surface. The use of galvanised steel Table 2.13 Examples of accessories for ETICS

Type of singularity

Accessory

Outside and inside corners

PVC corner profile with detail mesh Mesh with drip profile Coping profile

Connections with building elements

PVC corner profile Mesh with window profile Flashing

Discontinuities

Expansion joint profile

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is not advised for flashings, copings or visible profiles, as zinc (for flashing and copings) and anodised aluminium (for visible profiles) are recommended. Accessories for discontinuities have the objective of providing watertightness in these areas. The choice of material to fill joints depends on its chemical compatibility with the insulation material, but it is common to use elastomeric or plastic mastics, such as silicon, polyurethane or acrylic, and pre-compressed impregnated foam cords. For the building’s expansion joints, expansion joint profiles are available, admitting the substrate’s movement, and ensuring the continuity and watertightness of the system. Some other accessories are also necessary in some cases, such as wall plugs for mechanical fasteners, high-density EPS fastening blocks and PVC discs.

2.6.2 Design of an ETICS Cladding 2.6.2.1

Performance Requirements of an ETICS Cladding

Like any other building product, ETICS must comply with six essential requirements: mechanical strength and stability; fire safety; hygiene, health and environmental requirements; in-service safety; noise protection; and energy economy and heat retention. Each of these parameters has specific directives for ETICS (Table 2.14), defined by (EOTA 2013), but, as ETICS is a cladding system, requirements of mechanical strength and stability do not apply. In terms of fire safety, each commercial ETICS must be identified in terms of class of reaction to fire (from A1 to F), as defined by EN 13501-1 (CEN 2018a). As for hygiene, health and environmental requirements, the system should be able to stop water leakages inside the wall (condensation, air humidity or soil dampness, rainwater or snow). It should also bear current maintenance equipment on the façade without causing damages in the system (by rupture or perforation) and it should be able to withstand impacts. Additionally, the system should ensure that polluting and dangerous substances are not emitted for the exterior environment, respecting limit ratios defined by law. During the system’s service life, lack of adhesion problems should not occur between the layers nor between the system and the substrate. The ETICS should remain stable and resistant to normal loads, such as its own weight, wind loads, structural movements of the building, deformations due to shrinkage and temperature variation, among others. As for noise protection, the wall as a whole should fulfil this requirement, not the ETICS cladding. But in terms of energy economy and heat retention, the system should contribute to saving energy by decreasing needs of heating (during winter) and cooling (during the summer). Thermal resistance should be assessed case wise. All requirements should be fulfilled during an economically reasonable service life period and all components should preserve their properties during that period,

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Table 2.14 Summary of the essential requirements defined for ETICS and respective tests (EOTA 2013) Essential requirement

Assessment parameters

Tests

Mechanical strength and stability

–

–

Fire safety

Reaction to fire

Reaction to fire

Hygiene, health and the environment

Tightness

Hygrothermal behaviour Freeze-thaw behaviour

Impact resistance

Hard body shock test

Permeability to water vapour

Resistance to the diffusion of water vapour

Surrounding environment

Release of dangerous substances

Adhesion between layers

Adhesion between the base coat and the thermal insulation material

Resistance to perforation

Capillary test

In-service safety

Adhesion between the adhesive mortar and the substrate Adhesion between the adhesive mortar and the thermal insulation material Resistance to wind load

Tensile tearing-off of mechanical fasteners Static foam block test Dynamic suction load

Noise protection

–

–

Energy economy and heat retention

Thermal resistance

Thermal resistance

considering normal maintenance conditions. The EOTA (2013) also defines durability and in-service ability aspects for the system and its components in terms of thermal, humidity and shrinkage resistance. Preventive measures should be taken at the design stage to protect the system, such as applying reinforcement accessories in singularities.

2.6.2.2

Advantages and Disadvantages of an ETICS Cladding

ETICS fit within a large range of types of thermal insulation. Available thermal insulation solutions may vary from indoors insulation, insulation inside two masonry leaves

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and insulation applied on the outer surface of the building envelope, the group ETICS belong to. Considering other types of thermal insulation, the use of ETICS may be advantageous from different perspectives, but it may also be decisively inconvenient. Commercial catalogues of ETICS present long lists of the system’s advantages. However, it is necessary to distinguish the real advantages of the system from marketing strategies. As for functionality, ETICS show good results in terms of thermal inertia of the building. In fact, it contributes to less heat indoors during the summer and less cold during the winter, simultaneously contributing to the decrease of energy consumption for heating and cooling purposes (Fernandes et al. 2016). According to Bendouma et al. (2018), comparing with other thermal insulation systems applied on the outer surface of the building envelope, namely the bardage type or ventilated rain screen façade (external insulation façade cladding with an air gap partially filled with thermal insulation), ETICS show the advantage of a lower weight increase on the substrate and a lower thickness increase of the façade. Comparing with insulation inside two masonry leaves, or indoors insulation, ETICS have the advantage of uniform heat losses on the façade surface, due to its external continuity, avoiding thermal bridges and maintaining thermal inertia (Fig. 2.17). As mentioned, ETICS have a thin layer of reinforced render (reinforced base coat) that contributes to the tightness of the system due to its waterproofing properties, independent from the finishing coat used. Simultaneously, the reinforcement mesh contributes to lower cracking probability, preventing water leakage through cracks (Sulakatko et al. 2006). As the system is applied on the outer surface of the building envelope, it will lead to decreasing the temperature gradient that other layers of the wall are subjected to (Fig. 2.18) and, while increasing indoors temperature, internal values of saturation pressure increase, decreasing the probability of water vapour reaching those values and condensing. In other words, interstitial condensation decreases. Additionally, the application of ETICS from the outside also increases the range of possibilities for rehabilitation purposes.

Fig. 2.17 Thermal bridge in a system with insulation between two masonry leaves and prevention of thermal bridges in ETICS

summer temperatures

indoors

outdoors

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winter temperatures

Fig. 2.18 Comparison between thermal gradients of walls without and with ETICS

Still, as ETICS increase the thickness of the wall, in rehabilitation, some architectural incompatibilities may arise in areas between protruding and recessed elements (difficult accessibility). Additionally, the application of ETICS may be limited by weather conditions, flatness defects of the substrate and high sensitivity to wind loads in elevated areas, which may lead to tearing the system. According to Künzel et al. (2006), well designed and applied ETICS with an adequate maintenance plan have a service life similar to traditional masonry walls, i.e. about 60 years. For that to happen, the design detailing needs to be quite meticulous and application procedures adequate, as the system is very sensitive to errors at these stages. The tendency to develop microbiological growth and the mechanical vulnerability to impacts are two types of disadvantages in ETICS. According to Barreira and Freitas (2008), as the thermal insulation is applied on the outer surface of the building envelope, heat exchanges between building elements drastically decrease and the thin cover layer over the insulation has a very small thermal inertia. Thus, during the night, the superficial temperature of external facings is lower than the dew point, propitiating the occurrence of superficial condensation and increasing relative humidity. As 70 and 80% values of relative humidity are reached, the ideal conditions for the development of algae and mould are gathered, respectively. As for reaction to fire, the thermal insulation material traditionally used (EPS) has poor fire reaction properties. In fact, according to Mack (2014), EPS and XPS are combustible materials, whose softening point is around 100 °C and fusion point around 180 °C. Hence, these materials limit the class of resistance to fire of ETICS. The thermal insulation material must belong, at least, to class E-d2, as the general minimal classification of the system, for medium-height buildings, is B-s3,d0 (CEN

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2018a). Higher buildings have even more restrictive requirements in terms of class of resistance to fire (B-s2,d0 above 28 m in Portugal), generally restricting the insulation material to the use of mineral wool, whose class of resistance to fire is normally A1 or A2. Moreover, although solutions that improve the performance of ETICS towards impacts have been developed, one of their main disadvantages is still the ease of perforation of the system. As it is exposed to passers-by, the system may need maintenance actions more frequently than other types of wall, as perforations may limit its thermal capabilities. Simultaneously, the system has higher initial costs than other types of thermal insulation (up to twice the cost of a system with indoors thermal insulation) (Direcção Geral de Geologia e Energia 2004; Sustainable Energy Authority of Ireland 2018).

2.6.2.3

Types of ETICS

At first, the conventional system that was applied included reinforcement meshes of mineral origin and acrylic finishes. That set of materials showed moisture problems, which resulted in the presence of microorganisms and defects associated with the unwanted presence of water in the system. From 2004 onwards, 100% organic systems started to be used (without cement in mortars) and silicone appeared in the finishing coat, increasing its permeability and decreasing damp issues. Simultaneously, higher ductility and flexibility of the material decreased the system’s colour limitation issues and improved the impact resistance. In 2007, the development of carbon systems with silicone and carbon finish and carbon fibre reinforcement revolutionised ETICS, increasing the superficial resistance. This solution has some variants that exponentially improve the system’s resistance, namely adding carbon to the base coat and strengthening the reinforcement (Caparol 2014, 2016, 2017, 2018a, b, c; Alsecco 2018). Increasing the amount of carbon implies higher costs but does not imply increasing the system’s weight, thickness or labour cost. In 2009, by including incombustible reinforcement mesh in the system, it became more resistant to fire. For the consumer, the most limiting system’s property is the colour. In fact, as dark colours imply higher heat absorption, if the finish material is not adequately ductile and flexible, it may result in cracking and a set of associated defects (like water leakage). The use of ceramic tiling as finishing coat has been explored. According to Malanho and Veiga (2011), ceramic tiling contributes to creating more resistant systems but implies higher costs and a heavier solution. In general terms, traditional ETICS are those with EPS insulation, fibreglass reinforcement mesh and a simple and rough finish. Reinforced ETICS are those with

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double reinforcement. Resistant ETICS use carbon material to obtain better resistance (Caparol 2014, 2016, 2017, 2018a, b, c; Alsecco 2018), and ceramic ETICS (or stone) use adhesive tiling as the finishing coat.

2.6.3 Execution of ETICS Claddings When an external thermal insulation system is applied, some precaution should be taken in design details. In renovation or rehabilitation projects, additional measures should be taken analysing the substrate considering its bearing capacity and needed treatment. Any substrate meant for these types of systems should be flat; otherwise, additional fastening should be used according to any detected warpage. Still, warpage of the substrate affects the decision on the type of façade system to be used and on using a smoothing treatment coating; thus, the analysis of the substrate is paramount. Watertightness is also an essential requirement that should be thought of previously, considering the durability and good behaviour of the building in the long-term. To ensure better watertightness, façade elements should be considered at the design stage, before executing the system. Downpipes, air conditioning systems, joints, wall openings, window and doorsills, ventilation grids, balconies and terraces should be studied ahead to ensure that all connections are adequately watertight. Besides these, it is also important to be previously aware of the characteristics and shape of the roof’s tail-end, as well as any other singularity in the façade. On the other hand, to ensure higher work efficiency, scaffolding should be planed and set in advance, to ensure setting according to safety standards. All façade elements that have to be replaced or altered should be removed (cables, HVAC or electrical equipment, among others). Any existing downpipes should be removed, ensuring that rainwater drainage during the construction period is done away from the façade plane (Lucas 2011). The surrounding area should also be protected, as handling adhesive materials may damage other surfaces. Adhesive tape may be used to protect isolated accessories, like window frames and other singularities. Materials should be stored in a shelter if they are transported to the site before their application day. Materials should be stored at temperatures higher than 4 °C, preferably away from sunlight and in a dry place. Insulation boards should be stored on a flat surface.

2.6.3.1

Substrate Preparation

Before applying ETICS, it is essential to check the substrate’s conditions and, if necessary, take a set of cleaning and preparation measures. In new buildings, masonry or concrete substrates should be flat, free of flatness defects above 0.5 cm when controlled with a 2 m batten. Substrates should be normally absorbing, consistent and should not have dust or demoulding oil residue. In the case of degraded concrete substrates, they should be treated. Any open crack

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Table 2.15 Treatment measures for substrates (adapted from Sto Corp. [2009]) Substrate condition

Treatment

Dirty

Cleaning with a brush or pressurised water

With efflorescence

Eliminating the causes. Cleaning with a brush or pressurised water

With algae and fungi

Removal and cleaning

With rigid adhesive claddings

Removal

Loose wall render

Mechanical removal and application of a screed.

Cracked wall render

Repair of cracks

Synthetic resins wall render

Cleaning

Porous painted façade

Cleaning and primer application

Non-permeable painted façade

Removal

Absorbing

Cleaning and primer application.

Irregular

Cleaning and primer application. Use lime and cement-based filling plasters with a minimum curing period of 14 days

Bituminous membrane

Removal

With fat or demoulding oil

Jet cleaning, using detergents

Peeled paint

Stripping and jet removal

Damp

Eliminate the origin of damp and let dry

larger than 0.5 mm should also be repaired, as cracking may limit the performance of the system in the future (Fernandes et al. 2016). In rehabilitation, substrates should be assessed in terms of consistency, degradation and cracking, removing any areas without adequate conditions and repairing damaged areas. The existing cladding should be assessed to decide whether it should be kept or not. Adhesion tests should be performed to determine the substrate’s adequacy to receive the system. ETICS may be used in substrates with cracking up to 0.5 mm wide, stable, with watertightness loss, that require light adhesive corrective claddings or requiring the improvement of hygrothermal properties. Table 2.15 suggests some treatment measures in various cases of anomalous substrates. Various types of primer may be used taking each case into account (Table 2.16). The use of primer should consider the substrate’s condition. After preparing the substrate, a month should pass before the application of the system, as a drying period is required to avoid transferring construction moisture to the insulation material (Lucas 2011).

2.6.3.2

Installation of Starting Profiles

To be protected from any kind of water entrance, the system should be adequately topped off, namely at plinth level, tail-ends with the ground and connections with

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Table 2.16 Primer examples for substrate preparation Primer type

Specifications

Adhesion and colour uniformity

Regularises colour and adhesion to the substrate. Applied with paint brush or roller

Hardening the surface

Primer for hardening the surface of friable and absorbing substrates

Adhesion for smooth concrete

Regularises the concrete’s porosity. Applied with paint brush or roller

Adhesion for old and non-absorbing substrates

Applied over ceramic tiling, substrates in cement with epoxy or bituminous adhesive residue, wood boards and acrylic paint. Applied with paint brush or roller

Adhesion and porosity regulation

For new substrates’ preparation before applying adhesive mortar. Regularises the substrate’s porosity and improves adhesion

other buildings, the roof or wall openings. The starting profile helps to begin the execution of the system (ensuring horizontality and bearing the boards before bonding) and protect the bottom of the system against dampness and external aggressions. When starting profiles are applied, the dimension and type of profile should be determined according to the thickness of the thermal insulation material and type of system. Preferably, the substrate area that bears the starting profile should be flat, so that it fits the substrate perfectly, without voids. If the substrate is not perfectly flat, spacers between the profile and the wall may be used, using different thicknesses to adjust to the substrate’s irregularities. Joints with 2–3 mm between each starting profile should be created, using PVC connectors so that any future material deformations are absorbed. These joints should then be sealed with a polyurethane mastic cord. Applying reinforcement mesh over the profiles’ joints is also suggested (Fig. 2.19). Profiles are mechanically fastened with fasteners placed every 30–50 cm, with a fastener less than 5 cm from each end. Corners should be executed with adequate corner profiles. Starting profiles should be placed at least 10 cm above the higher elevation point of the surrounding ground, to avoid the system’s degradation due to direct contact with the ground. If the bottom face of the profile is coated with reinforced render, the reinforcement mesh should be directly bonded over the substrate, before applying the profile, and then folded over the insulation material (back-wrapping) (The Minnesota Lath & Plaster Bureau 2001) (Fig. 2.20). In below ground systems, the buried bearing surface should be waterproofed up to a level above the starting profile location (using a bitumen-based product), stopping groundwater from entering the wall by capillary action, behind insulation boards. In the case of below-ground walls’ insulation, and continuing that insulation, the above-ground EPS board should be placed over the substrate as a continuation of the below-ground insulation from a level of at least 20 cm above the final ground

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d

detail A detail A reinforcement with regular mesh 0.3 m x 0.3 m t t

0.1 m

2 mm

d

3 mm

detail A

Fig. 2.19 Reinforcement of joints between starting and lateral profiles

a

b

Fig. 2.20 Bonding of the reinforcement mesh directly on the substrate before placing the starting profile (a) and reinforcement mesh folded and bonded over the thermal insulation boards using mortar (back-wrapping) (b)

level. If the above-ground EPS board is thicker, a starting profile should be applied, creating a separation joint with at least 5 mm that should be sealed with mastic.

2.6.3.3

Application of the Adhesive Material

Bonded systems are easier to apply than those mechanically fastened, but they require a more careful preparation of the substrate, mainly in cases of rehabilitation, where

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40 °-

thermal insulation board

50 ° Fig. 2.21 Illustration of the execution of the peripheral cord at 45°

stripping of the paint and other organic products is necessary and, if needed, the friable or poorly adhesive renders must be removed. The specified minimal adhesion tension should be checked, and the adequate bonding of the board edges should be ensured to prevent excessive deformations. The preparation of the adhesive material must comply with contents defined by the manufacturer, mixing components with mechanical equipment for a homogeneous mixture. The application of adhesive may be done 5–10 min after preparation, over the insulation boards. Adhesive material should not be used to fill joints between thermal insulation boards.

Points and Peripheral Cord Method This application method consists of applying a peripheral cord and points of adhesive material on the back face of the board (European Associaton for External thermal insulation composite systems 2011; Fassa Bartolo 2013; Sulakatko et al. 2017). The execution of the peripheral cord should be done with a metallic trowel at 45° (Fig. 2.21) so that, during the installation of the board, no adhesive material residue is visible in the joints. This method is the most common as it allows bonding on less flat substrates, considering the minimal area of product that should be applied on the board’s surface, which should not be below 60% of the board’s total area, varying according to the manufacturers’ specifications.

Total Bonding Method Using this method requires a smooth and flat substrate. The adhesive material is applied over the whole back face of the insulation board with a metallic trowel, using a notched trowel with 6–10 mm notches (European Associaton for External thermal insulation composite systems 2011; Fassa Bartolo 2013; Sulakatko et al.

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2017). A strip of about 2 cm should be left in the board’s contour to avoid adhesive material from filling the joints between boards.

Mechanical Application of Adhesive Material This method refers to the use of mechanical means to apply the adhesive material (Fassa Bartolo 2013). A continuous cord should be applied over the periphery and in some internal areas of the board’s back face. Once again, precautions should be taken to stop adhesive material residue from spreading to the lateral faces of the board, ensuring a minimal percentage of adhesive material on the board’s surface, established by the supplier, but always guaranteeing a minimal bonding area of 60%.

Mechanical Projection of Adhesive Material In this case, the adhesive material is mechanically projected on the whole area of the substrate, if it is completely flat. The adhesive material should be pressed with a notched trowel (notches of 10 mm × 10 mm, minimum).

2.6.3.4

Installation of the Mechanical Fastening

As mentioned, the use of mechanical fastening should be limited to cases of absolute necessity, as the fastener is a thermal bridge point. Mechanical fasteners should be specified by the system’s supplier, according to the requirements of the European Organisation for Technical Assessment (2017), carefully assessing each situation to define the type and number of fasteners, as well as their placement pattern. The volume of the building, the type of system, the finish, the substrate and the dominant weather conditions should be taken into account to choose the type of fasteners. When the substrate is unstable, mechanical fastening is conditioned and should go deeper into the wall. Figure 2.22 represents wind loads in a building façade, which increase from the centre to the periphery and from bottom to top of the façade. Wall plugs are installed by drilling holes of adequate diameter and depth in the substrate. After placing the plug in the hole, it should be tightened using an expansion nail (Fig. 2.23). If the finishing coat is composed of ceramic tiles or stone plates, mechanical fastening is always needed. If necessary, some tests may be performed at the construction site to determine the type of fasteners to be used.

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Most affected area by wind loads

Least affected area by wind loads

h

Fig. 2.22 Simplified effect of wind loads in a building façade

Fig. 2.23 Mechanical fastening of wall plugs

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Installing the Insulation Material

After choosing the type of fastening, the thermal insulation boards are applied. The insulation material should be set from bottom to top, bearing each row of boards over the previous one. The boards may be bonded using only adhesive material, if the substrate allows it, or using additional mechanical fastening. Alternatively, additional metallic rails may be used (Malanho and Veiga 2011). Boards are placed in its final position, pressed against the substrate, squashing the adhesive mortar. Boards should be placed with unaligned joints, both in the current surface and in the corners (Fig. 2.24, part a), and they should not coincide with discontinuities in the substrate, except for expansion joints (Fernandes et al. 2016). Around doors and windows, the boards should be cut in an L-shape, avoiding aligned joints (Fig. 2.24, part b). On the other hand, the joints between thermal insulation boards should not coincide with the expansion joints of starting profiles, differing at least 10 cm. After fixing the boards to the substrate, necessary adjustments are made. Boards should be aligned and adjusted so that a levelled surface is formed, eliminating gaps, joints and misalignments. This implies pressuring the boards against the substrate using a spirit level and a wooden or metallic batten, trying to simultaneously level as many boards as possible. Constant diagonal movements should be made for this purpose. If any gap between boards is detected (over 2 mm), it should be filled with small chips of EPS or with polyurethane injections. This type of gap should never be filled with base coat or adhesive materials. In connections of the system with door or window frames, sills or other singularities in the façade, there should be a gap of about 5 mm for further placement of mastic. If any imperfection is detected, it should be sanded using an abrasive trowel in circular movements. The sanding process should only occur 20 h after placing the

incorrect correct

a

b

Fig. 2.24 Arrangement of insulation boards with unaligned joints (a) and L-shaped boards around a window (b)

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boards to ensure that the adhesive material has dried. No finishing mortar should be used to correct flatness defects, as the finishing coat should not be thick; otherwise, it may result in further defects, such as cracking or other flatness defects. After fastening to the substrate, EPS boards should not stay exposed for a long period.

2.6.3.6

Fire Safety Protection

If systems with EPS, XPS or ICB are used, it is recommended that a strip of mineral wool is used over lintels of wall openings (e.g. horizontal strips at each floor level), ensuring better fire resistance in those areas.

2.6.3.7

Treatment of Edges and Singularities in the System

Singularities are those areas needing special care and treatment, as they may condition the system’s performance. Windowsills, copings, joints between the system and other building elements are some examples of the system’s singularities.

Treatment of Windowsills An adequate design of windowsills is important to stop water from running off directly over the finishing coat, dragging residue. On the other hand, in rehabilitation works, the need to increase the width of the windowsill is common, as the wall thickness increases with the installation of ETICS. In these cases, there are several solutions for windowsills, such as replacement, extending the existing stone windowsill, applying a thin layer of material on the top, or applying a new metallic windowsill over the existing sill, with a proper tail-end with the window frame. Considering the larger thickness of the wall after applying ETICS, it is also necessary to assess the need for revising tail-ends and top protection of façade panes. In the case of eaves and cornices, the need to revise their design should be assessed.

Corner Profile with Mesh The edges of the system, whether wall edges or edges of wall openings, should be reinforced with a metallic or PVC corner profile with mesh. Before executing the reinforced base coat, reinforced profiles should be placed directly over the insulation boards, so that they are completely embedded in the base coat thickness. The bonding of profiles should be made with the same mortar used for bonding the boards. The reinforcement mesh of profiles should be overlaid at least 10 cm over the system’s reinforcement mesh. Joints between corner profiles should not match the joints between boards, and they should be sealed as starting profiles were.

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Reinforcement of Angles This type of reinforcement aims at substantially increasing the mechanical resistance of edges. These corner profiles without mesh are applied over the corner profiles with mesh, at the level of the reinforced base coat, placed after executing that layer, before finishes. They are advised for areas with high impact risk but should only be applied if the finish has enough thickness to embed them.

Expansion Joints Expansion joints are fundamental in the execution of ETICS and they should be respected, as they absorb structural movements, thus preventing defects (e.g. cracking). The positioning of joints should be studied considering the position of the façade surfaces, as the type of joint to be used in coplanar façades is not identical to that used in non-coplanar façades. Expansion joints are created through the application of joint profiles with mesh. The mortar used in the reinforcement layer may be used to bond these profiles. As the profile’s flaps should be executed simultaneously, both façade panes, on each side of the joint, should also be executed simultaneously. Joints should be placed before executing the reinforced base coat, ensuring at least 10 cm of reinforcement mesh overlay. So that both faces of the joint profile are centred along the joint, it is recommended to use an EPS cord with the thickness of the joint, which is removed after executing the finishing coat. The inner space of the joint profile should be sealed with polyurethane mastic over a cord of polyethylene foam. Where the system meets rigid surfaces (door or window frames, protruding surfaces and balconies, for instance), an open joint of about 5 mm should be executed and filled with elastic and waterproof material, like polyurethane mastic. The treatment of lintels of wall openings should be done applying a drip profile with mesh, wrapping the edge. This type of profile allows reinforcing the edge and avoiding recessing water running off the façade.

Aesthetical Joint An aesthetical joint creates a visual break in the system’s surface. It should not be placed over expansion joints, as it may result in cracking. This type of joint does not have any role on the structural movement of the building. Overlaying reinforcement meshes should be avoided where aesthetical joints are defined by the design of the façade, as the execution of the joints would be hindered and a homogeneous surface would be harder to create. Areas where the aesthetical joints intercept singularities of the system should be adequately treated, as the joint may become the preferable path for water runoff and accumulation of dirt. The supplier should be consulted to determine the minimal insulation thickness below the joints (around 20 mm) (Sto Corp. 2009).

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Execution of the Reinforced Base Coat/Reinforcement

The reinforced base coat is a component of the system that reinforces and mechanically protects it. It is a layer that not only includes reinforcement mesh but also any other reinforcement and joint accessories, as it is essential to overlay meshes (of the system and of accessories). According to the exposure of the facing to external agents, one or two meshes may be applied or, in more sensitive cases, a regular mesh and a reinforced mesh. Before executing this layer, façade elements should be protected, such as aluminium window frames, to prevent any possible contamination or damage. Additionally, the reinforced base coat should not be considered a filling layer but rather a reinforcement.

Application with Regular Reinforcement The reinforced base coat should never be executed before the adhesive material has dried, i.e. never before 24 h after its application. The mortar may be applied using a metallic notched trowel or mechanical equipment, ensuring a uniform thickness. After applying the base coat mortar, and before starting to dry, the reinforcement mesh should be placed using the flat edge of the trowel. The mesh should be completely embedded after the application of the last layer of mortar, always ensuring 10 cm overlays between meshes. For a higher reinforcement level, two layers may be used. The first reinforced coat is applied and, after drying, a new layer of mortar is applied followed by the second reinforcement mesh, preferably with unaligned joints. After a drying period, the last mortar layer is applied, completely embedding the second reinforcement mesh.

Applying Diagonal Reinforcement Mesh in Wall Openings Next to corners of façade openings, reinforcement mesh in a diagonal direction should be applied as these areas are very sensitive to cracking. The reinforcement mesh should be embedded in the base coat. This reinforcement should be done with pieces of mesh around 50 cm long and 35 cm wide, positioned at 45° in the corners of façade openings.

2.6.3.9

Finishing Coat

Applying the finish should take weather conditions and drying of the base and key coats into account. Additional precautions should be taken in case of high temperatures and intense sunlight exposure, as they can cause shrinkage and mortars to dry too fast.

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The choice of colour of the finish is fundamental as it compromises the specificity of the whole system. To avoid unexpected joints in the finishing coat, application teams should correctly dimension the materials needed, as complete façade panes should be executed, considering singularities and edges of the façade. Before executing the finish, adhesive tape should be applied in areas not meant to be coated to avoid contamination.

Executing the Key Coat The key coat should only be applied one to seven days after applying the base coat so that it is completely dry. The execution is made using a paint brush or roller, with a coat of primer product diluted in water according with the instructions of the manufacturer. The whole surface should be previously brushed, and it should be sound, dry, and free from dust, fat, oils or any other substances.

Applying the Finishing Coat The finishing coat may be applied mechanically or with a metallic or plastic trowel. To choose the trowel, the intended texture of the finish should be taken into account. Finishes may have different appearances according to the tools used and movements during application. The coat should be as thick as the particles of the finishing product. The flat edge of the trowel should be used to spread any excessive material. After a small pause, the trowel should be used again to make the coating more compact and uniform. A more textured finishing coat will tend to accumulate more dirt and debris than a smooth finish. For a smoother finish, a wet sponge may be used. For a scratched texture, a metallic brush may be used, but the base coat should not be damaged. This type of finish is only possible with pigmented rigid renders that may be executed in a thicker layer. Acrylic paint may be applied with a paint brush or roller in consecutive coats. The dilution of this type of paint should follow the suppliers’ recommendations. If the system is correctly applied, no irregularities or significant deformations should be detected at 30° lighting. Hence, the maximum admissible deformation is 7 mm using a 2 m batten.

Applying Stone Plates or Ceramic Tiling Finishing Coat Ceramic tiling may give the system greater strength. Either stone plates or ceramic tiles may be applied in ETICS, considering the following limitations and important details:

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• In new buildings, the substrate of the system should be completely flat (render or concrete); • The adhesive mortar of the insulation boards should be applied using the complete buttering method; • Bright colours’ plates/tiles should be preferred, as they absorb less heat than darker ones; • Insulation boards should be bonded and mechanically fastened, considering the number of fasteners and their pattern according to the type of tiles/plates; • The adhesive ceramic tiles should only be applied over the base coat after 7 days; • The joints between tiles should be 5 mm wide and filled with adequate material (Fernandes et al. 2016), corresponding to a joint area above 6% of the surface; • Elastic joints should be done to help absorb deformations; these joints should be placed horizontally at each floor level and vertically every 4 m; such joints should be filled with mastic; • All good practice rules referring to the adhesion of ceramic tiles in façades should be followed; • If the ceramic tiling is coplanar with another type of finish, the tail-end should be detailed so that it is waterproof, and no defects arise from different deformation behaviours of different materials.

2.7 Architectural Concrete Surfaces The technological knowledge associated with architectural concrete surfaces contributes to better understanding the pathological phenomena that may occur in this type of cladding. In this section, an outline of the materials used in architectural concrete surfaces is presented, as well as design concerns associated with their aesthetical possibilities in terms of shape, texture and colour, and with their functional requirements. Then, the construction process is summarised. The use of concrete exposing all its surfaces requires the detailed knowledge of its composition and understanding the manufacturing and placement techniques to avoid pathological problems and to enable adequate structural integrity and durability, while highlighting architectural concrete strong aesthetical attributes.

2.7.1 Materials Used in Architectural Concrete Surfaces Concrete has highly variable properties and is composed of constituents that are not inert after the building element is constructed, changing properties through time influenced by environmental factors. Being a mixture of aggregates, binder and water, concrete also has the possibility of including pigments, admixtures and additions. It

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is necessary to conveniently choose these constituents at the design stage to allow obtaining a surface with the required characteristics. Additionally, the choice of the formwork’s material is an important decision that depends on the dimensional constraints of the building element and on the desired surface finish. In any way, the intended finish for an architectural concrete surface may itself condition the remaining choices associated with the construction process. In this case, even the reinforcement position is affected, due to exposure to aggressive environmental agents. The minimisation of cracking and crazing should be a concern at design and execution stages in order to increase the protection of concrete, as no cladding is applied, and to improve the final appearance of the surface.

2.7.1.1

Mix Materials

Binder The binder is used to agglutinate aggregates together and influences the resistance of the final material. In Europe, the binder must comply with EN 197 series (CEN 2011c, 2014d) and in the USA, for instance, ASTM International defines four separate standards according to the nature of the binder—natural cement, Portland cement, blended hydraulic cement and hydraulic cement (ASTM International 2014, 2017a, 2019a, b). In a given building, the binder’s provenance should not vary, so that colour variations are minimised. So, manufacturers must provide origin control bulletins indicating the binder’s extraction/production location, as well as associated properties. For colour control purposes, white cement is preferred in architectural concrete surfaces, but, for darker colours, grey cement is more adequate. This choice also depends on the required strength for the building element. Colour variations in a grey cement matrix are higher than those of white cement. Grey cement may result from using a mineral that results in a grey binder, or grey cement may result from using minerals intended for white cement and black pigments (Kenney et al. 2008). The latter allows more homogeneity. When compared with grey cement, white cement shows lower workability, higher shrinkage, and better compressive strength results of the final product. In architectural concrete surfaces, Portland cement types CEM I 42.5R, CEM II/BL 32.5, CEM II/B-L 32.5 (Br) and CEM II/A-L 52.5 N (Br) are the most frequently used. If higher strength is needed, lime fillers may be used in the binder composition, decreasing the water needed in the mix (Schlumpf et al. 2013). Moreover, cement storage should be protected from humidity.

Aggregates According to the EN 206:2016 (CEN 2016f) standard, which refers to the specification, performance, production and conformity of concrete, aggregates are mineral

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granular materials to be used in concrete. They need to have adequate dimensions, mechanical strength, and chemical properties according to the binder and environmental aggressive actions. Aggregates need to have satisfactory thermal properties and be free from harmful substances. In Europe, aggregates for concrete must comply with EN 12620:2008 (CEN 2008c), including storage requirements, while in the USA, for instance, the standard of ASTM International C33/C33M-18 (ASTM International 2018) is to be followed. Aggregates may represent about 70% of the volume of concrete (Schlumpf et al. 2013). Specifically in architectural concrete, the size grading of the aggregates depends on the surface finish, while contributing for porosity and strength properties. The surface colour may also be influenced by the choice of aggregates, mainly in bright surfaces. The selection of coarse aggregates and of their colour is important when the surface is intended to have exposed aggregates. In turn, the choice of fine aggregates is more relevant when a smooth finish is wanted. In a building construction site, all aggregates of the same type should have the same provenance, as mentioned for binders. Additionally, aggregates should not react with the cement alkalis and they should be free from clay particles, contaminant agents and impurities able to change the concrete’s colour (Kenney et al. 2008). In exposed aggregates surfaces, some intermediate sizes in the admitted range of aggregates for the mix should be rejected in view of a more uniform final appearance.

Water In a concrete mix, water should be clean, free from oils and other impurities that may cause stains, as well as free from salts likely to contaminate the mix. Potable water at room temperature should be used, since very cold or hot water risks affecting workability (Kosmatka 2008). The water-cement ratio is important to prevent exudation phenomena (Sawaide and Iketani 1992), hence the water content should not be excessively high, but preferably constant throughout the mixing process and remaining steps of construction to avoid colour variations in architectural concrete surfaces.

Additions and Admixtures Additions (also known as mineral admixtures) and admixtures enable significant improvements in fresh and hardened concrete properties. While the content of additions may be above 5% of the cement’s weight, admixtures are added to the mix in amounts below 5% the weight of cement. Fly ash and silica fume are examples of additions. In architectural concrete surfaces, the amount of fine aggregates and binder is frequently higher, especially when self-compacting concrete is used. To avoid the effect of an excessive amount of binder, additions are used, like lime fillers, which give the mix a higher water absorption capacity (Schlumpf et al. 2013).

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The mix used in the trial wall that is mandatory in architectural concrete construction should include the additions used in the remaining building to test and assess colour results, as additions may also influence the expected colour. Superplasticisers and set retarders are examples of admixtures. In concrete, admixtures are used to improve its properties, such as workability, strength, water-cement ratio and setting time. They may also result in different surface colour, especially in bright concrete, due to their mineral or organic nature. Hence, admixtures should be of bright colours and resistant to UV radiation. Admixtures need to be tested in a trial wall (ACI Committee 303 2012). Superplasticisers are particularly important to decrease vibration needs, avoiding bug holes and other defects associated with the execution.

Pigments Pigments are the cheapest and most effective means to colour architectural concrete. The most common pigments are based on metallic oxides, simultaneously being the most stable under UV radiation. They are available in powder, grains or liquid format, and are added at a later manufacturing stage of the mix (CCAA T57 2006). ASTM International (2016) uses standard ASTM C979/C979M-16 as reference for pigments used in integrally coloured concrete. The manufacturing process influences the cost of some pigments. Samples should be used to choose pigments according to the final result, and the chosen pigments should be included in the mix used in the trial. Still, an amount of pigment above 10% of the cement’s weight may damage the concrete’s quality (ACI Committee 303 2012).

2.7.1.2

Reinforcement

Although not visible, reinforcement has a direct contribution to the aesthetical quality of architectural concrete surfaces. That is the case when metallic oxides occur in fresh concrete, as they quickly migrate to the surface and cause nasty visual defects. Therefore, storage and cleaning procedures are paramount to ensure that reinforcement steel is free from oils, clays, oxidation and substances that hinder the adhesion of concrete. Moreover, the quality of the final surface is better when reinforcement follows design and execution rules, specifically treatment and adequate placement. Due to the possibility of oxidation run-offs while a building is under construction, reinforcement already placed on-site should be protected with epoxy paint or based on polyurethane. In this way, an orange stain on the surface before the first year of the service life of the building element is avoided. On the one hand, reinforcement may need additional cover in architectural concrete surfaces. To ensure the designed cover, polymeric or concrete spacers should be used in a similar colour to that of the finished surface. On the other hand, while

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designing reinforcement, highly dense areas need to be avoided, to stop coarse aggregates from getting stuck, consequently hindering the vibration process. In densely reinforced structures, the use of self-compacting concrete is preferable. In terms of mix, the aggregate’s size and vibration process, in Europe, Eurocode 2 (CEN 2014e) should be complied with, ensuring that the volume of concrete fits the formwork volume. Particularly ties in stainless or galvanised steel are advised, and their ends must face the inner volume of concrete (Kenney et al. 2008). Whenever possible, the concrete placement should be performed immediately after the reinforcement is done, to avoid oxidation and subsequent oxidation stains.

2.7.1.3

Formwork

Formwork may not be considered so much as a material, but more as a tool or equipment to build reinforced concrete elements, and specifically architectural concrete surfaces. Still, considering the limited amount of times formwork can be reused, and its importance for the appearance of surfaces, it is included in this section. In Europe, standard EN 13670:2009 (CEN 2009b) should be complied with, while in the United States of America, for instance, a guide by ACI Committee 347 (2014) is available. Nevertheless, essential knowledge about formwork properties and materials is important at the design and construction stages. More porous formwork materials are likely to result in darker architectural concrete surfaces. In this context, steel, aluminium, plastic and sealed wood are considered non-porous materials, also resulting in smoother surfaces, while non-treated wood and engineered wood are porous formwork materials. In addition, the strength of formwork needs to resist fresh concrete’s impulses. Thus, metallic formwork has better behaviour in this sense but requires inner cladding with stainless steel plates or marine-grade plywood to prevent contamination with oxidation stains. A system of controlled permeability formwork allows to significantly increase the durability of an architectural concrete surface and improve its appearance. The system consists of coupling a textile to regular formwork in order to drain and filter excessive air and water. At the same time, fine materials of the mix are kept in the surface (smoother results) and enough moisture is ensured for the curing process of concrete. Surfaces created with controlled permeability formwork are less porous, have fewer bug holes and higher strength. Thus, results for architectural concrete surfaces are proven to be better (Chen et al. 2012; Lin et al. 2014). The location and finish of formwork fastenings, as well as the stereotomy of the concrete surface originated by formwork joints, have to be planned at the design stage. The architect has to include formwork designs and specifications to detail fastening and joints, as well as formwork panels dimensions (PERI Portugal; PERI Group 2018). Like formwork panels, which exist in standard and custom sizes, formwork fastenings may be designed according to predefined positions in standard size formwork

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panels, or custom positions in customised panels. The desired design pattern should rule these options, considering execution and financial constraints. Pathology wise, fastening points are a critical area of architectural concrete surfaces, as they may cause loss of fine constituents of concrete during construction, if not properly fit and sealed (Kenney et al. 2008). Fastenings should be placed inside PVC anchor cones (PERI Group 2018) and tubes to create adequate negative imprints for fastening placement and removal. Then, visible fastening marks on the finished surface may remain visible or be disguised. When they are intended to be visible, several options are available. Usually, holes are left on the surface of concrete, but an additional set of holes, with the same diameter, may be designed, generating a harmonious pattern (Fig. 2.25). Alternatively, fastening voids may be tamponed with specific accessories or filled with adequate mortar or polyurethane sealant. These mortar and sealant must fulfil visual demands in terms of colour, ageing and durability, compatible with the appearance of concrete. Fastening marks may, in fact, be disguised but are very hard to become unnoticeable without using an opaque coating over the surface, after filling the voids. As for joining formwork panels, the efficacy of the task prevents the loss of fine constituents of concrete and subsequent surface defects. Joint sealing materials, like mastic and rubber joints, must be used to connect panels and silicone may also be applied on the outer surface of the joint to increase joint sealing. Whenever possible, concrete placement joints should coincide with joints between panels. Expansion joints should coincide with both. At the execution stage, the alignment of panels must be checked to avoid flatness defects on the architectural concrete surface.

Fig. 2.25 Pattern of fastening marks in an architectural concrete surface

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Release Agents

Release agents are materials applied on formwork that, by creating a barrier between the latter and concrete, avoid the adhesion of fresh concrete to the form, favouring the form removal process and the appearance quality of the concrete surface. Some factors should be taken into account while choosing release agents, namely (adapted from Kenney et al. 2008): • Compatibility of the agent with the formwork, formwork-sealer and mixture; • Possible interference with subsequent application of products on the concrete surface; • Possibility of occurrence of colour changes and surface stains; • Time elapsed between the application of the agent on formwork and the placement of concrete; • Weather and curing conditions. Although release agents are indispensable products for the construction process of architectural concrete surfaces with high-quality visual properties, they are simultaneously the main cause of colour variations in this type of surfaces (Kenney et al. 2008). To avoid colour stains, the use of oil-based products is not advised and antistaining release agents should be used, which are based on colourless paraffin and are sprayed to form a very thin layer (Schlumpf et al. 2013). As both inadequate and excessive applications of release agents are prone to cause anomalous architectural concrete surfaces, the trial wall should be built using the intended release agent, and smaller samples may also be tested, including their behaviour towards environmental aggressive agents. Application procedures used in the trial should be followed in the whole building for more homogeneous surface results (Kenney et al. 2008; ACI Committee 303 2012).

2.7.2 Design of Architectural Concrete Surfaces Besides concerns associated with materials, the design of architectural concrete surfaces from a non-structural point of view should cover the choice of surface finish, colour and standardisation. At this stage, the design team must prepare a set of documents to be included in a separate section of the building project. Ideally, those documents should consider budgeting, drawings, specifications and quality control criteria, in view of quality control and assurance, bids and trial wall construction (Kenney et al. 2008), not to mention the necessary discussions between the whole design team, owner and contractors.

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Types of Surface Finish

Smooth An architectural concrete surface with a smooth surface (Fig. 2.26, part a) is obtained by the removal of forms without further texturing work. For this reason, appearance variations occur according to the type of form, as its texture (different levels of smoothness) or any imperfection is engraved in the concrete surface.

Polished After form removal and curing, a polished concrete surface is obtained through a mechanical process. It consists of the controlled abrasion of the surface with sequential erosive steps, resulting in a new surface at the end. The depth of wear caused by grinding depends on the desired aggregates exposure degree. The final polishing step should be repeated as many times as necessary to reach the intended glow.

Formed Relief Bas- to mid-relief (Fig. 2.26, part b) and sunk relief (Fig. 2.26, part c) give the concrete surface any pattern, figurative or non-figurative shape, only constrained by form removal and the minimal thickness of reinforcement cover. Such finishes are obtained using polyurethane, elastomer or silicone formwork. Relief forms are bonded or nailed to the forms, taking advantage of the plasticity of fresh concrete to obtain the designed shape.

a

b

c

Fig. 2.26 Architectural concrete surface with: a smooth finish (a); mid-relief (b); and sunk relief (c)

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Tooled An architectural concrete surface with a tooled finish is obtained through a mechanical process, after form removal and cure, using a jackhammer and a bush hammer. This type of finish is of a destructive nature, so the adequate resistance and reinforcement cover of concrete need to be ensured prior to tooling procedures.

Scaling Although some authors (Kenney et al. 2008) consider scaling a type of tooled finish, it is treated separately in this book. For a scaling texture, the surface is chipped using chisel tips in pneumatic tools. Macroscopically, the surface shows a rough appearance, similar to a rock, depending on the irregularity of the chiselling pattern. Like a tooled finish, scaling decreases the thickness of the reinforcement cover, thus it should be increased at the design stage, accounting for the variability of the cover thickness of the finished concrete surface.

Blasting Blasting techniques for concrete surfaces finish are used to expose the aggregates of concrete. This set of finishes allows choosing the aggregate exposure degree, whose depth/depth range must be specified, up to a maximum of a third of the size of coarse aggregates (CCAA T57 2006). Exposure depth may surpass this limit if blasting is combined with set retarders. Blasting techniques include sand or abrasive blast, high-pressure water jet, and the combination of these techniques (Kenney et al. 2008). While using blasting techniques, if possible, the same team and equipment should be used in the whole building, since distance, speed and pressure changes using the equipment result in finishing differences (Kenney et al. 2008).

Flame-Cleaning Flame-cleaning is a type of finish with a slightly rough and ridged texture, also softening the original colour of the unfished architectural concrete surface. The technique consists of applying a flame over the surface of concrete. This texture is anti-slip; hence, it is frequently used in architectural concrete floorings. When flame-cleaning is to be used, concrete must have granite aggregates in its composition, due to their melting capacity, fundamental for flame-cleaning.

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Reactive The reactive properties of concrete enable the creation of any pattern or image over a concrete surface with the presence of water. The technique consists of: (i) sealing the whole surface of concrete; (ii) using a waterproof mask (stencil-like) over the concrete; and (iii) applying a reagent over the negative imprints of the mask. The mentioned mask is the shape of the intended pattern or image. After this finish technique is complete, the reagent interacts with water poured over the concrete surface and acquires a darker colour, showing the image otherwise invisible (when the concrete is dry).

2.7.2.2

Colour

The constant exposure of architectural concrete surfaces determines that special attention has to be given to their appearance, particularly to uniformity, surface details, colour and texture standards (Kenney et al. 2008). The colour of architectural concrete surfaces depends on the binder, aggregates, pigments, fillers and formwork used (CCAA T57 2006; Precast/Prestressed Concrete Institute [PCI] 2007). While grey concrete is composed of Portland cement, white concrete is composed of white cement, and coloured concrete results from adding inorganic pigments to the concrete mix. Grey architectural concrete surfaces are more vulnerable to degradation agents that affect their colour, namely environmental factors, curing cycle and amount of water (PCI 2007). Hence, even in grey surfaces, it is frequent to resort to pigmentation processes, which enable a great variety of shades. The adequate selection of fine and coarse aggregates is relevant for the colour of concrete surfaces, especially when the intended finish consists of exposing the aggregates (CCAA T57 2006; Kenney et al. 2008). Plasticisers may also be included in the concrete mix to promote an easier dispersion of pigments, maximise their intensity and the colour’s uniformity (Peurifoy and Oberlender 2011). Still, it is found that every pigment has a saturation point beyond which the colour intensity will not increase (CCAA T57 2006). The water-cement content also needs to be analysed, as it may lead to colour variations (Kenney et al. 2008). The use of fillers for colouring purposes is also possible but may decrease concrete’s strength. For economy and colour uniformity purposes, grey and white cement can be blended, but colour uniformity is expected to increase as the percentage of white cement increases. Grey cement is associated with architectural concrete surfaces with less intense colours (PCI 2007), as brighter surfaces result from the use of white cement.

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Standards

Considering the European case, out of the standard series EN 1504, titled “Products and systems for the protection and repair of concrete structures—Definitions, requirements, quality control and evaluation of conformity”, some parts should be highlighted: part 1, referring to terms and their description (CEN 2005b); part 2, referring to the specification of products and systems for the surface protection of concrete (CEN 2004h); part 3, providing specifications for structural and non-structural repair (CEN 2005c); part 5, with specifications for the injection of concrete (CEN 2013d); part 9, defining the general principles for using products and systems (CEN 2008d); and part 10, that refers to site application of products and systems and quality control of the works (CEN 2017f). Any issues associated with placement, compaction and cure of concrete are ruled by EN 13670:2019 (CEN 2009b), for general rules in the execution of concrete structures. Standard EN 206:2016 (CEN 2009f) applies to the specification, performance, production and conformity of concrete and may refer to other relevant standards in the specification and design of architectural concrete surfaces, namely about constituents: EN 197-1:2011 on cement (CEN 2011c); EN 450-1:2012 on fly ash (CEN 2012f); EN 13263-1:2009 on silica fume (CEN 2009c); EN 934-2:2012 on admixtures (CEN 2012g); EN 12620:2008 on aggregates (CEN 2008c); EN 13055:2016 on light aggregates (CEN 2016g); EN 1008:2002 on water (CEN 2002c); and EN 12878:2014 on pigments (CEN 2014f). There are other standards on testing: EN 12350 series on fresh concrete (CEN 2009d, e, f, g, h, i, 2010b, c, d, e, f,); EN 12390 series on hardened concrete (CEN 2009j, k, l, m, 2012h); and EN 12504 series on concrete in structures (CEN 2004i, 2005d, 2009n, 2012i). Durability standards are defined locally (in each country), as does Laboratório Nacional de Engenharia Civil (LNEC) (2006, 2007a, b, c) in Portugal, with specifications E 461 (on the prevention of expansive internal reactions), E 464 (on the prescription methodology for a design service life of 50 and 100 years towards environmental actions), and E 465 (on the methodology for estimating the performance properties of concrete that allow compliance with the design service life of reinforced and pre-stressed concrete under more aggressive conditions). In the USA, for instance, a list of the set of cement and concrete standards developed by ASTM International is available online (ASTM International 2019c), considering, among others: abrasion testing, additions, aggregate reactions in concrete, aggregates, air entrainment, chemical admixtures, compositional analysis, concrete’s resistance to fluid penetration, fibre-reinforced concrete, hydraulic cements for general concrete construction, lightweight aggregates and concrete, materials applied to new concrete surfaces, non-destructive and in-place testing, organic materials for bonding, petrography, self-consolidating concrete, strength, testing, volume changes and workability. However, as in Europe, no specific standards for architectural concrete are available. So, the work developed in this field by the American Concrete Institute (ACI) should be a reference for good-practice implementation in design and

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execution. The guide on cast-in-place architectural concrete developed by ACI Committee 303 (2012) presents a broad approach of the production of architectural concrete, with recommended rules for specifying materials, formwork, concrete placement, curing, additional treatment, inspection and their effect on the finished product. In the same institute, another committee developed a guide regarding formwork for as-cast concrete surfaces (ACI Committee 347 2014), considering recommendations to meet the expected appearance of this type of surfaces, including a section for architectural concrete surfaces. Additionally, Standards Australia (2018) developed a standard on formwork for concrete, whose first edition was published in 1990, setting the requirements for the design, fabrication, erection and stripping of formwork, including the evaluation of the cast concrete surface.

2.7.3 Execution of Architectural Concrete Surfaces 2.7.3.1

Placement

The placement process of an architectural concrete surface must be carefully planned so that the final result is successful, thus avoiding surface defects associated with this execution stage. From the moment concrete leaves the plant until placement is complete, operations must follow a schedule. For instance, the travel time between the concrete plant and the construction site is important as it influences the state of the mix when it is cast. Adequate planning should consider that trucks ought to leave plants in order to arrive at the site little before they are needed, to avoid excessive waiting times, prone to cause colour variations in architectural concrete surfaces (ACI Committee 303 2012). While beginning placement procedures, it is advised (Kenney et al. 2008) not to use the first 0.2 m3 of pumped concrete, as the equipment retains some material that originates water-cement ratio variations and subsequent colour variations on the surface of concrete. Furthermore, the placement of concrete should be done from heights below 1.5 m using different pumps, conveyors or steep-sided buckets with easy to move chutes (Kenney et al. 2008). In columns and walls, concrete should be placed in layers of no more than 50 cm to ease its compaction. Thus, during continuous vibration procedures, 10–15 cm from the previous layer should be transposed for uniformization purposes. The contact between the vibrating equipment, formwork and reinforcement should be avoided, as it can cause irreversible damage, namely on the surface of concrete. When self-compacting concrete is used, it must be pumped using adequate and constant velocity through the whole process, while avoiding sudden movements. Moreover, interruptions during the placement process are prone to cause placement joints and the incorrect homogenisation between layers, due to the irreversibility of the gravity compaction process.

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Demoulding

The success of demoulding procedures is also very important for the appearance of architectural concrete surfaces. And, once again, planning is key. Demoulding should be done with care, preventing damages on surfaces associated with impact or pressure for the removal of forms. Adjacent surfaces should be demoulded after the same curing time, otherwise, colour differences are likely to occur. The demoulding schedule should be thoroughly stipulated, hence avoiding pulling off pieces of concrete, mainly next to edges and corners, resulting from premature demoulding. The accurate timing of demoulding procedures also tends to avoid colouring issues associated with changes in the properties of release agents, in this case, due to late demoulding. Once moulds are removed, the surface should be protected to avoid any harm, including from normal construction operations (ACI Committee 303 2012). Sharp edges and protruding corners require specific protection, as they are more vulnerable.

2.7.3.3

Curing

Correctly curing architectural concrete surfaces stops some types of staining, discolouration and cracking on the surface. The curing process involves keeping acceptable moisture content and temperatures to obtain the designed surface colour, texture and durability. Thus, all the architectural concrete areas need to go through the same process and curing time to prevent colour variations on the surface (CCAA T57 2006; Kenney et al. 2008). Products for concrete curing are not advised in architectural concrete surfaces, especially if white, because they can cause staining. The most significant curing period corresponds to the first stages of strength development (Kenney et al. 2008), i.e. from the initial set until strength required for stripping is reached. Adequate care and procedures should be followed according to curing needs, considering: curing in the moulds, moist curing, membrane curing and hot-weather or cold-weather curing. More information on specific curing types should be consulted in the literature (CCAA T57 2006; Kenney et al. 2008; ACI Committee 303 2012).

2.7.3.4

Surface Finish

At this stage, if applicable, anchor points of formwork are treated, with adequate accessories and products, according to the intended appearance (Sect. 2.7.1.3). Also at this stage, the designed surface finish is executed, considering the options mentioned in Sect. 2.7.2.1, or others more innovative. At the end of the surface finish works, general cleaning is advised using plain water or water with a neutral detergent. These cleaning procedures will remove dirt accumulated during execution and prepare the surface for prescribed water-repellent or anti-graffiti treatments. Superficial water-repellent products may be colourless or cause a glowing surface, and are usually silane, siloxane or acrylic resins-based.

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Quality Control at the Execution Stage

As a general rule for assessing procedures and products used in architectural concrete surfaces, they should be applied in the trial and, after approval, they should be the standard for the whole building. In any case, it should be ensured that: reinforcement and formwork are free from oil and dirt; release agents are applied as thin uniform films; and formwork joints are adequately sealed and watertight. Quality control mechanisms should be put in place on-site to enforce compliance with rules and good practices advised by professional associations, standardisation agencies, manufacturers and suppliers. Those rules and good practices have been approached throughout Sect. 2.7.

2.8 Door and Window Frames Throughout the history of architecture, and accompanying the evolution of building technology, the opaque area of building façades progressively decreased, giving place to increasingly larger wall openings. This tendency allowed increasing natural lighting of indoor areas, as well as ventilation. However, the susceptibility of the building envelope to aggressive agents also increased. The mentioned openings, whether windows or doors, need to answer multiple performance requirements. They need to work as a barrier, protecting the building from weather conditions and noise, but also as an intermediary, as they provide access, ventilation and visual contact. To positively reply to such functional requirements, the industry of door and window frames is very dynamic, constantly presenting innovative solutions, techniques and materials (Steven Winter Associates Inc. 1999). The central innovation point in door and window frames manufacturing is associated with the transition from handcrafted manufacturing (for instance, in wood frames) to industrialised/standardised manufacturing (for instance, wood milling and aluminium extrusion). This approach to the technology of door and window frames is expected to familiarise the reader with the main materials, design and execution issues within this type of building element so that the diagnosis process of defects and the recommendation of repair techniques are more contextualised.

2.8.1 Materials Used in Door and Window Frames Door and window frames may be built using several materials. Still, this book focuses only on four framing materials: wood, iron/steel, aluminium, and PVC. These materials started to be used in door and window frames approximately in the presented order, always trying to improve the comfort and inhabitability conditions offered by

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previous solutions. Such improvement process is still in progress, as new materials and adaptations are constantly being offered by the industry. For instance, hybrid frames (combining two or more materials) are becoming common and the use of wood composites, fibreglass, glass fibre reinforced polymers, polyurethane, among others, is also rising. Additionally, the set of accessories used in door and window frames is also addressed in this section, comprising ironmongery, glazing shims, joints and sealants, mastics, and sealing rubber and tape.

2.8.1.1

Wood Door and Window Frames

Wood is an organic material. When compared with other building materials, it may be considered more complex, according to its use, as it requires specific technical and scientific knowledge. For instance, for each wood species, the variability degree and the species’ properties need to be taken into account, as they limit the type of application. Those properties may be colour, texture, odour, gloss, but also density, hardness, mechanical resistance, permeability and workability (Sousa 2002). Table 2.17 lists the most common wood species used in door and window frames. In its natural state, wood may present some negative characteristics concerning the good performance of frames. However, the effect of those characteristics has been progressively reversed as a result of technological advances (Stamm 1977; Hoadley 2000; Henriques and Azevedo 2018): • The degradation of wood properties and the occurrence of internal stresses resulting from changes in the moisture content were reversed by controlled drying processes; • In an environment favouring the development of biological agents, deterioration was circumvented with preservative treatments and protecting finishes; • The high heterogeneity and anisotropy, due to the structure of oriented fibres, were solved by processing wood into laminates, plywood and wood agglomerates. Table 2.17 Wood species commonly used in door and window frames (Sousa 2002)

Commercial nomenclature

Scientific nomenclature

Scots pine

Pinus sylvestris

Sweet chestnut

Castanea sativa

Northern red oak

Quercus rubra

European black pine

Pinus nigra

Afzelia africana/African mahogany

Afzelia bipindensis

Iroko

Chlorophora excelsa

Cherry tree

Amburana cearensis

Utile

Entandrophragma utile

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Most of the improved durability properties of wood door and window frames result from treatments and finishes applied to natural wood. Most preventive treatments are meant to ensure good resistance of wood towards living beings, namely fungi, insects and marine xylophagous. As for the finishing coats, they may be applied for decorative purposes, but also as a means of protecting the wood substrate. Additionally, finishing coats may also be applied to improve the resistance to microorganisms and mechanical and chemical resistance (Grüll et al. 2011). There are various treatments for wood, but only the most common ones are mentioned, namely: preventive treatments for wood, applied by brushing, spraying, dipping, immersion, autoclave and heat treatment; and finishing coats, which are paints, varnishes and wood stains.

2.8.1.2

Iron and Steel Door and Window Frames

The first metallic window frames were made of wrought iron. In a subsequent stage, cast iron started to be used and the production of iron window frames became industrialised. In a third stage, considering technological developments in the production of metals, steel started to be used, taking its improved properties into account when compared with iron. In fact, during the twentieth century, steel door and window frames became popular, due to their slenderness and fire safety (Steven Winter Associates Inc. 1999). Still, the high susceptibility of steel to corrosion, its weak thermal performance and the rise of new materials, more economical and with improved efficacy, led to the less frequent use of steel door and window frames. Even though technological advances allowed improving the behaviour of steel, like galvanisation and the use of stainless steel, in door and window frames, it is a type of material whose value for money cannot compete with that of aluminium and PVC. However, galvanised and stainless steel are frequently used in fire doors, which is a niche market within the door frames industry.

2.8.1.3

Aluminium Door and Window Frames

Aluminium is a very abundant metal in the Earth’s crust. Still, its extraction requires complex tasks with high environmental impact (Norgate et al. 2007). Nevertheless, aluminium is also a metal with high recycling potential (Duflou et al. 2015). In the construction industry, aluminium has assumed a progressively important role as a result of the inherent quality of the material combined with improvements in the transformation industry, as well as in the finishes applied in aluminium building elements (Steven Winter Associates Inc. 1999). The use of aluminium in door and window frames has become one of the main applications of this type of metal in construction, due to its aesthetical potential, great variety of colours, finishes and shapes, associated with good resistance and durability. Still, aluminium has two disadvantages: (i) the high amount of energy

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used in the manufacturing stage; and (ii) its high thermal conductivity. Nevertheless, the most recent technological advances have tried to deal with these disadvantages. The extraction of aluminium has been progressively substituted by recycling, which spends 5% of the energy spent during extraction (Duflou et al. 2015). As for thermal conductivity, it was dealt with by the adoption of profiles with an intermediate thermal break (Gustavsen et al. 2011). The main degradation process of aluminium door and window frames is corrosion. Aluminium is chemically active towards alkaline materials. Hence, cement, gypsum and lime attack aluminium in their hardening process, as well as afterwards, if these materials are kept constantly damp. So, it is convenient to protect aluminium surfaces according to the claddings surrounding them (a coat of bitumen compound between wet cement and aluminium, for instance) (Lane 2018). Two main processes are used to treat the surface of aluminium door and window frames (Lane 2018): (i) anodising, which creates a superficial layer of aluminium oxide through an electrochemical process; and (ii) thermo-lacquering, which protects aluminium with a pellicle of a thermosetting polymer. Both these treatments grant aluminium high durability properties, low maintenance and enable the use of various colours in the latter (Asif et al. 2005).

2.8.1.4

PVC Door and Window Frames

PVC is a synthetic material that, with great value for money and good properties, is abundantly used by modern societies in a various range of products, from construction products to consumer goods, despite the most recent trends against the use of plastic materials. It is also used in door and window frames. The first PVC door and window frames were known to degrade easily, due to a high coefficient of thermal expansion, resulting in great dimensional changes when subjected to high thermal amplitudes (Steven Winter Associates Inc. 1999). However, nowadays, due to manufacturing advances, PVC door and window frames can perform adequately in terms of dimensional stability and degradation resistance, which is mainly caused by solar radiation, but also by extreme temperatures, with relatively low maintenance. PVC frames are also very resistant to moisture (Hinks and Cook 1997). PVC door and window frames are manufactured through an extrusion process. After extrusion, the material is cut in linear pieces, which, after assembling, result in a door or window frame. To give PVC framing good structural stability, the sections are generally less slender than those of aluminium framing. The dimensions of PVC sections for door and window frames are similar to those of wood frames. In PVC door and window frames, it is frequent to add metallic or wooden reinforcement (Hinks and Cook 1997; Gustavsen et al. 2007). Several colours and finishes are available for PVC door and window frames, namely through lacquering and the application of pellicles. In addition, this type of door and window frames has good thermal and acoustic insulation properties (Gustavsen et al. 2007).

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Accessories Used in Door and Window Frames

Accessories represent about 20–30% of the final cost of a door or window frame system. Very frequently, they are also the source of various defects, mainly due to faulty assembling (Preiser and Schramm 2005). Additionally, accessories are fundamental for the door or window frame’s adequate performance considering its functional requirements.

Ironmongery In the production of ironmongery, extruded aluminium, cast aluminium, brass, stainless steel, zamak (a zinc, aluminium, magnesium and copper alloy), carbon steel, nylon, polyacetal and 1020 steel may be used. The choice of material depends on the material used in the door or window frame, its type and intensity of use. In sliding doors and windows, four main types of ironmongery are available (Gorse et al. 2012): • Flush mount latch: latch with a recess for locking the door or window using a finger, with or without a key; it is installed levelled with the frame surface; • Crescent sash lock: compact lock, usually in aluminium or zamak and nylon; it may be adjusted to several situations; • Multipoint locks: normally used in double sash sliding doors or windows, consisting in a lock for each sash with the option of including a handle; usually made in aluminium or steel; • Rollers: meant to allow the sliding of movable sashes through the guides in the bottom or top rail (or both); rollers are normally made of nylon or steel and use aluminium or zamak housing. The main types of ironmongery used in hopper and awning windows are (Gorse et al. 2012): • Tie bars: used in awning window frames with a window sill higher than 1.60 m; the tie bar needs a guide; it is usually made of aluminium or nylon, and normally has multiple notches allowing multiple opening angles; • Locking handles: composed of a lock and a handle, it is an effective and sturdy system for intensive use windows; • Keepers: they are used to limit the opening angle of awning windows up to a point agreeable with the hinges’ properties and the intended use. In casement windows, three main types of ironmongery are used (Gorse et al. 2012): • Cremone bolt: used when the locking mechanism needs to be hidden inside the frame profiles; it is made of aluminium, steel or brass and consists of a box with a lever or handle that activates a rod that locks within holes in the outer frame; a version working outside the profiles of the frame also exists;

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• Bolts: they are usually made of aluminium, stainless, zinc plated or chrome steel, brass or nylon; bolts are also an option when doing repair works in more complex locking systems; • Hinges: made of steel, aluminium or brass, they allow the opening of movable sashes.

Glazing Shims Shims have bearing and positioning functions for the door or window glazing within the frame. They transmit existing stresses in the glass to specific areas of the frame. Simultaneously, shims keep the glass away from direct contact with the door or window frame profiles. According to their function, there are four types of shims (Snider 1977): • Bearing (or ribbed) shims: used to bear the weight of the glazing, they are placed between the edge of the glazing unit and the bottom rail (Kubal 2008); normally made in plastic materials, their length depends on their material and on the glazing dimensions; • Peripheral and safety shims: with a smaller size when compared with bearing shims, this type of shim stops the glass from getting into direct contact with the profile of moveable sashes; peripheral and safety shims are installed loose so that they act only in case of additional stresses resulting from the movement of the sash; • Side shims (spacers): meant to transmit horizontal stresses, side shims also allow keeping a uniform distance between the glazing unit and the frame profile; they also help to limit lateral deformations of the joint and maintaining a uniform thickness of the watertightness mastic; • Wedges: the use of wedges allows to avoid that opening and closing movements of moveable sashes displace the glazing unit from its original positioning. The distance between the axis of glazing shims and the edge of the glazing unit should be 1/10 of the length of the opening, as the distance between the external edge of the shim and the edge of the glazing unit should be 1/20 of the glazing unit length (Snider 1977). Shims should be placed as shown in Fig. 2.27.

Joints and Sealants As sealants are one of the most degradable elements in a door or window frame system, their choice and correct application associated with adequate maintenance are essential for the watertightness of the system. Leakages through door or window frames essentially occur in four instances: • • • •

In the joints between the frame and the opening in the wall; In the joints between the frame and moveable sashes; Between glass panes/glazing units and mullions or rails; In the gaps between profiles.

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C3

C3

C1 C1

C1

C1 C1

C2

C2

C2

C2

C2

C2

C2 C2

C2 C1

C2 C3

C2 C1 C2

C2

C2 C2 C1

C1

C2

C2

C2 C1

C1

C2

C2

C1 C2

C2 C2

C2 C2

C2

C2

C2 C2

C2 C2

C2

C1

C1

C1

C1

C1

C1

Fig. 2.27 Location of the different types of shims in different types of door and window frames (from left to right, top to bottom: fixed window, casement window, hopper window, awning window, European tilt and turn window, pivot window, sliding window, vertical sliding window). C1— bearing shims; C2—side shims; C3—safety shims

Hence, it is essential to adopt systems ensuring that these areas are watertight for the longest possible period with little maintenance. Joints between glazing units and rails may be treated as follows (Snider 1977): • Open joints: for small thickness glazing or with small dimensions (4 mm thick, semi-perimeter of 2.5 m or maximum length of 2 m) joints may be open; the glass is mechanically fastened with the aid of nails, pegs or bolts and the mastic will then ensure watertightness and stop the glass from vibrating (Fig. 2.28); • Closed joints: this type of joint is characterised for completely wrapping the glass unit, totally filling any voids; closed joints may be made with glass stops or glazing beads (Fig. 2.28); • Joints for sliding frames: the joint in sliding frames is made of U-profiles without a glass stop, docked at the edges of the glazing unit;

Fig. 2.28 Different types of joints between the glazing units and rails (from left to right: open joint, closed joint, joint with exterior glass stop fastened with nails or screws and self-draining joint)

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• Self-draining joints: when double glazing is used, joints need draining holes, so that water leakage and condensation phenomena are avoided; drainage is ensured by 8 mm diameter holes, connecting the bottom of the bottom rail profile to an exfiltration chamber or directly to the exterior; for door and window frames less than 1 m long, two holes should be done, one at each corner of the bottom rail; for door and window frames more than 1 m long, a hole should be added for each supplemental 0.5 m (Fig. 2.28).

Mastics Mastics are the bonding element and watertightness barrier in many joints in door and window frames, complementing the shape of the joints and the sealants. They may be distinguished according to their properties, namely movement capacity, adhesion, durability, ease of application, chemical compatibilities and types of curing. From the great variety of existing products in the market, the most common are: • Putty: it is still found in most of iron and wood door and window frames needing repair works; putty is made with raw linseed oil and ground chalk; it is usually used for heritage preservation purposes, as it does not have good durability, adhesion and elongation properties; still, it is a low-cost solution; • Butyl bitumen: made with poly-isobutylene and isoprene filled with talc or calcium carbonate, additives and solvents, butyl bitumen is usually used in inner sealing of frames and for filling slits; it has the advantage of being relatively cheap, with good water resistance and adhesion; however, the service life of butyl bitumen depends on its low elasticity, low memory when tensioned and a tendency for staining the substrate with exuded oils (Kubal 2008); • Acrylic bitumen: made with acrylic polymers mixed with adhesion enhancers, plasticisers and additives, the classification of acrylic bitumen depends on the solvent used; if the solvent is water, acrylic bitumen have properties similar to those of butyl bitumen, not tolerating temperature changes; this type of bitumen is normally used in indoor environments; if any other solvent is used, curing is not complete, thus accomplishing 10% elongation; this type of bitumen has good adhesion properties and a service life of about 10 years, when exposed to aggressive weather conditions, although having an unpleasant odour while curing and limited elastic memory (Kubal 2008) (Fig. 2.29, part a); • Polysulfide: due to its high adhesion capacity and low permeability to damp, polysulfide is normally used in double glazing manufacturing; it is made with polymers, curing agents, stabilisers and adhesion enhancers, having elongation up to 25%, rapid curing and good adhesion; however, polysulfide shows low resistance to ultraviolet radiation (Kubal 2008); • Polyurethane: it is not recommended for intense solar exposure, but it has high resistance to friction and ageing; it may be painted and has an elongation of about 25%; it may be bi-component or mono-component and it is made with a polymer, usually polyester, which reacts with a di-isocyanate, calcium carbonate and catalysers.

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b

c

Fig. 2.29 Mastics and sealing accessories used in door and window frames: a acrylic bitumen; b sealing rubbers; and c sealing tape

Sealing Rubber and Tape Sealing rubber and tape usually ensure watertightness between the fixed frame and the moveable sash of door and window frames. Sealing rubber (Fig. 2.29, part b) should have mechanical strength properties (permanent deformation), chemical resistance (towards detergents, ozone and ultraviolet radiation, among others) and dimensional stability (for temperatures between −20 °C and 170 °C) compatible with its function (Bolte and Boettger 1997). The properties of sealing rubber are determined by their material (PVC, ethylene propylene diene monomer (EPDM), natural or thermoplastic rubber, silicon or styrene-butadiene (SBR), among others) and dimensional adequacy to the design and materials of the door or window frame. Sealing tape (Fig. 2.29, part c) is essentially used in sliding doors. It is composed of polypropylene fibres, which have a rigid base, usually with an adhesive surface on the back. Hence, these tapes adhere to the intended surface, ensuring a good level of insulation. Sealing tape should always be applied considering the manufacturers’ recommendations. The polypropylene fibres may be improved with silicon, allowing to improve watertightness as well as sliding properties. Products as chlorine, turpentine, acids and combustible oil are aggressive for this type of tape, altering its characteristics.

2.8.2 Design of Door and Window Frames Windows and doors are placed in wall openings. Windows are composed of glazing and framing profiles, meaning that not all of its surface is transparent or translucent, as the frame represents the fraction of the window that is opaque (Gorse et al. 2012). The wall opening is composed of jambs (or door jambs), on each side, a lintel, on the top, and a door or windowsill, on the bottom (Fig. 2.30, part a). Sills are very important to protect façades against rainwater action. Wall openings are filled with doors or windows, allowing ventilation and lighting of indoor rooms, as well as a visual relationship between indoors and outdoors. The framing is a transition element between the wall (opaque) and the glazing, allowing fastening the glass to other building elements and bearing the glass itself. Although

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moveable sashes jamb hinge

lock and handle

windowsill sealant and glass stop glazing

a

bottom rail of the fixed frame

b

Fig. 2.30 Elements of a wall opening (a) and basic components of a door or window frame (b)

door and window frames are a relatively small part of the building envelope, they are extremely important to the performance of the building. Frames bear glass panes, ensure watertightness of indoor areas, absorb various requests (for instance, from wind loads), and give an important contribution to the optimisation of the building’s energy efficiency. A door or window frame is composed of various elements, which vary according to the type of frame material and type of window. The base elements of a door or window frame are (Fig. 2.30, part b): a (fixed) frame; sashes (fixed or moveable); glazing, opaque sheets or grating; glass stops; ironmongery (hinges, locks, etc.) and sealants. In Europe, the vocabulary associated with door and window frames is standardised by EN 12519:2018 (CEN 2018d).

2.8.2.1

Functional Requirements of Door and Window Frames

The set of door and window frames of a building is considered a subsystem of the building and should comply with various requirements that influence their performance, e.g. control of lighting, thermal and acoustic insulation, ease of use, maintenance, aesthetical demands, safety and watertightness (Steven Winter Associates Inc. 1999). External pedestrian doors and windows are comprised in Regulation (EU) No. 305/2011 (The European Parliament and The Council of the European Union 2011), which lays down harmonised conditions for the marketing of construction products. Within the European Union, this document determines the minimal expected performance levels for construction products establishing rules for those products to be adequate for their use conditions, hence presenting properties that allow the building to comply with safety, health, comfort, durability and environmental protection requirements (Pinto and Fernandes 2011). According to the mentioned regulation, construction products, as door and window frames, should have CE marking and the

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respective declaration of performance. Particularly door and window frames, in order to have CE marking, should comply with the requirements defined by standard EN 14351-1:200+A2:2016 (CEN 2016h). According to this standard, the requirements door and window frames must comply with, as well as their performance assessment, depend on their expected use. Still, generally, the performance assessment requires (Pinto and Fernandes 2011): • Making initial type tests to the product in a certified laboratory; • That the manufacturer implements a system of internal control of production, referring to the main properties of the product that are declared in CE marking. The initial type tests are meant to demonstrate that the product complies with the harmonised standard requirements (Table 2.18) and that the declared performance Table 2.18 Initial type test for external windows and pedestrian doors (adapted from Pinto and Fernandes [2011]) Essential characteristics

Calculation or test standard

Field of application

Resistance to wind load

EN 12211:2016 (CEN 2016i)

All types of doors and windows

Watertightness

EN 1027:2016 (CEN 2016i)

All types of doors and windows

Mechanical resistance of safety mechanisms

EN 14609:2004 (CEN 2004j)

Applies to doors and windows with safety mechanisms

Acoustic performance

EN ISO 10140-3:2010 (test) (CEN 2010g); and EN 14351-1:2006+A2:2016 (calculation) (CEN 2016h)

All types of doors and windows and specific types

Heat transmission rate

EN ISO 12567-1:2010 (test) (CEN 2010h); EN ISO 12567-2:2005 (test) (CEN 2005e); EN ISO 10077-1:2017 (calculation) (CEN 2017g); and EN ISO 10077-2:2017 (calculation) (CEN 2017h)

All types of doors and windows

Air permeability

EN 1026:2016 (CEN 2016k); and EN 14351-1:2006+A2:2016 (CEN 2016h)

All types of doors and windows

Impact resistance

EN 13049:2003 (CEN 2003)

Applies to doors with glass

Door height

EN 12519:2018 (CEN 2018d)

Applies to doors with glass

Unlocking capability

EN ISO 179-1:2010 (CEN 2010i); and EN 13637:2015 (CEN 2015e)

Applies to doors with emergency/panic mechanisms

Acting force

EN 12046-2:2000 (CEN 2000)

Applies only to automatic doors

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characteristics translate the behaviour of the product. Besides the harmonised properties comprised by CE marking, other characteristics highlighted by EN 14351 1:2006+A2:2016 (CEN 2016h) are also relevant, namely (Pinto and Fernandes 2011): • • • • •

Impact resistance in bay windows (windows that extend down to the ground); Durability; Acting forces; Mechanical resistance; Resistance to repeated opening and closing actions.

Additionally, some other less common characteristics may be considered (Pinto and Fernandes 2011): • • • • •

The behaviour between different environments; Ventilation, when ventilation grids are included in the door or window frames; Bullet resistance (bulletproof glazing); Explosion resistance; Burglary resistance.

2.8.2.2

Types of Windows

The use of a specific type of window implies having good knowledge on its characteristics and influence on the users’ daily life, due to the interaction of the user with the window and the importance of windows as a defining element of the building envelope. Windows are used to allow the entrance of light in indoor rooms and for ventilation. They are composed of a (fixed) frame and sashes; the former is fastened to the wall opening and the latter may be moveable. As for types of windows, an ample range is available, whether in the market or in existing buildings. Fixed (or picture) windows (Fig. 2.31) do not have moveable sashes. Thus, their function is limited to lighting indoor rooms and visual contact between indoors and outdoors. They are frequently complemented by windows with moveable sashes. Fixed windows are very common in storefronts and office buildings. As for maintenance, their exterior surface must be cleaned from the outside. Casement windows (Fig. 2.31) are very common in buildings. This type of window allows moving vertically hinged sashes, normally with the axes on the sides of the fixed frame. In this type of windows, the locking mechanism is usually placed on the opposite side of the hinges, in the moveable sashes. Casement windows may have one or two moveable sashes. The single moveable sash is connected to the fixed frame through the hinges and the locking mechanism. The two moveable sashes are connected at the centre through the locking mechanism, and each one is connected to the fixed frame through their hinges. Casement windows may be completely opened, as such favouring maintenance/cleaning operations. When completely opened, casement windows do not control ventilation well. If moveable sashes rotate towards indoors, casement windows are said to be French-style, otherwise, they are English-style.

2.8 Door and Window Frames

a

109

b

d

g

c

e

h

f

i

j

Fig. 2.31 Different types of windows. a—fixed window; b—casement windows; c—hopper window; d—awning window; e—European tilt and turn window; f—vertical pivot window; g—horizontal pivot window; h—sliding window; i—double-hung window; j—jalousie window

Hopper and awning windows (Fig. 2.31) work similarly to casement windows, but instead of a vertical axis, they rotate around a horizontal axis. They can open towards the outdoors (awning) or indoors (hopper), having the axis at the upper and bottom rail, respectively. These types of windows have the advantage of providing good ventilation, even when it is raining. However, their external surface is difficult to clean, needing to be cleaned from the outside. The combination of casement and hopper windows results in the so-called European tilt and turn windows (Fig. 2.31). This type of window allows the opening of sashes through their rotation both around a vertical (at the side of the frame) and a horizontal axis (at the bottom of the frame). Pivot windows (Fig. 2.31) are generally composed of a single sash that opens through the rotation around a central vertical or horizontal axis. Since, when the sash opens, a part of the window is projected outside, no grating or outside blinds or shutters may be used. Sliding windows (Fig. 2.31) are composed of one or more sliding sashes that move on rollers in the horizontal direction. If necessary, this type of windows may be encased in the wall in such a way that the moveable sash moves inside the wall. In terms of air permeability, sliding windows normally present a worse performance, requiring some accessories to improve their performance. In terms of ventilation, except in the case of sliding sashes encased in walls, only a percentage of the window may be completely open, depending on the number of rails and sashes.

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A vertical sliding window (single or double hung window) (Fig. 2.31) has one or more sashes that slide vertically. This type of window is usually manually opened and the sashes stop on bearing lateral accessories (butterfly fasteners or pivot bars with lock shoes). If the size of vertical sliding windows does not allow easy opening, they have a counterbalance system. It is usually hidden laterally and consists of two weights, whose sum is equal to the weight of the sash. This system allows opening the window in various positions, hence allowing to control ventilation. Jalousie windows (Fig. 2.31) are composed of many adjustable slats of metal or glass, generally horizontal. Opening jalousie windows allow good control over ventilation and easy cleaning. As they project externally, the slats may compromise the use of external blinds or shutters.

2.8.2.3

Types of Doors

In the building envelope, doors control the access between indoors and outdoors. They have a more limited set of types, compared to windows. Still, the most common are highlighted. A side-hung door (Fig. 2.32) is the most common type of pedestrian door. It works similarly to a casement window and when it has two moveable sashes it is called a casement door, or French door.

a

b

d.1

c

d.2

Fig. 2.32 Different types of doors. a—side-hung door; b—folding door; c—revolving door; d.1— encased sliding door; d.2—surface hung sliding door

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111

Doors may also function as folding doors, sliding doors and revolving doors. Additionally, doors are commonly divided into manually and automatically opened doors. Folding doors (Fig. 2.32) are made of several articulated leaves that bend over each other around vertical axes that slide horizontally. Sliding doors (Fig. 2.32) have one or more moveable leaves that slide horizontally over the surface of the wall (surface hung sliding door) or encased in the wall (like windows can be). Revolving doors (Fig. 2.32) generally have three or four leaves that rotate around a concentric vertical axis.

2.8.3 Execution of Door and Window Frames Considering the complexity and the most recent and innovative systems of doors and window frames, the execution process requires specialised labour. Most of the work is done in a workshop, and only the installation is done on-site. The good performance of doors and windows relies on their adequate installation in order to comply with functional requirements.

2.8.3.1

Execution of Wood Door and Window Frames

In simple terms, the process of execution of a wood door or window frame (Fig. 2.33) is described next. First, the dimensions should be checked, considering a ±1 mm tolerance. Then, glass stops and sealants are cut to their size and installed. Next, the glazing unit is installed and the profiles are assessed in terms of torsion or any fault. Lastly, all the ironmongery is installed. Then, the doors or windows are transported to the construction site and installed in the respective opening with the adequate materials recommended by the manufacturer.

a

b

c

Fig. 2.33 Steps in the execution of wood door and window frames: a gluing wood profiles; b installing sealants; and c ironmongery

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2.8.3.2

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Execution of Iron/Steel Door and Window Frames

After the production process of the iron or steel profiles, they are mounted to form a door or window frame. Next, they receive the desired finish, for instance, electrostatic painting. Then, sealants and accessories are installed in the door or window frame. After transportation, the frames are installed on-site with the adequate materials recommended by the manufacturer, taking into account the correct treatment for the joint between the fixed frame and the wall opening.

2.8.3.3

Execution of Aluminium Door and Window Frames

After extruding the profiles, there is a dimensional and fault checking process. Then, the profiles are cut and holes are drilled so that they can be mounted into a frame. Joints are sealed and connectors are fastened (Fig. 2.34, parts a and b). Next, a new dimensional checking process is carried out (±1 mm tolerance). Then, glass stops and sealants are cut to their size and installed with the glazing unit. The frame is assessed in terms of torsion or any faults and, lastly, ironmongery is installed (Fig. 2.34c). After transportation to the construction site, the door and window frames are applied in the wall opening using the materials recommended by the manufacturer.

2.8.3.4

Execution of PVC Door and Window Frames

After extrusion, the profiles are cut into the required size, as well as any reinforcement. Then, holes are drilled where necessary and the reinforcement is applied and fastened. Afterwards, the profiles are welded together and cleaned. Then, joint sealants are applied and ironmongery is installed. Sashes are mounted in fixed frames and, next, the glazing unit is installed. After transportation, the door or window frame is installed on-site using adequate materials recommended by the manufacturers.

a

b

c

Fig. 2.34 Steps in the execution of aluminium door and window frames: a sealing profiles; b fastening profiles; and c ironmongery

2.9 External Claddings of Pitched Roofs Table 2.19 Types of external claddings of pitched roofs

113

Type of cladding

Examples

Natural stone

Clay-slate

Artificial stone

Ceramic tile Micro-concrete tile Fibre-cement

Metallic

Steel Aluminium Copper Zinc

Plastic

Acrylic (polymethacrylate) Polycarbonate Glass fibre reinforced polyester PVC

Mixed

Composed plates Sandwich panels Asphalt shingles Metallic tiles

2.9 External Claddings of Pitched Roofs External claddings of pitched roofs have evolved as Mankind developed its knowledge about materials. Ceramic tiles are a traditional roof cladding in Mediterranean countries, but, in other countries, micro-concrete tiles and asphalt shingles, for instance, are commonly used. The development of fibre-cement, metallic and plastic claddings resulted in a great variety of solutions and applications mainly for industrial buildings and other roofs with a great span. The need for improving the characteristics of metallic claddings led to the appearance of mixed solutions (composed plates, sandwich panels and composed metallic tiles). External claddings of pitched roofs may be grouped as shown in Table 2.19.

2.9.1 Materials Used in External Claddings of Pitched Roofs Most of the materials used nowadays in external claddings of pitched roofs emerged in the nineteenth century, associated with technological innovations, the industrialisation of processes and significant advances in various scientific fields. Still, external claddings of pitched roofs have progressed in terms of functional performance, durability and optimisation of manufacturing processes (Schunck et al. 2003). External claddings of pitched roofs should be waterproof, resistant to fire and weather agents, and should ensure thermal insulation. In Europe, external claddings of pitched roofs should comply with CR 833:1992 (CEN 1992).

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2.9.1.1

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Clay-Slate Tiles

The use of clay-slate tiles goes back to the seventeenth century. It is common in housing and historical buildings (Fig. 2.35). Clay-slate is a sedimentary rock with variable composition and microstructure. The combination of minerals dictates its physical, chemical and mechanical characteristics. Clay-slate tiles may show different shapes and colours, allowing the designer to play with those characteristics. These tiles show high dimensional stability towards significant temperature variations. If adequately maintained, this material may last over 100 years. Roofs with clay-slate tiles should have a minimum slope of 15° (Association Française de Normalisation [AFNOR] 1993a; Levine 1993). Clay-slate is extracted from mines and transported and stored off-site. While being transported to the construction site, elements should be stacked up in rows separated with wooden slats, protecting the corners and avoiding any contact with the ground. The main characteristics of clay-slate tiles are shown in Table 2.20. This material should comply with ASTM C406/C406M-15 (ASTM International 2015a), EN 12326-1:2014 (CEN 2014a) and EN 12326-2:2011 (CEN 2011a).

a

b

Fig. 2.35 Heritage building with the pitched roof cladded with clay-slate tiles (a) and building with the external cladding of the pitched roof in clay-slate tiles (b)

Table 2.20 Main characteristics of clay-slate tiles (Levine 1993)

Parameter

Clay-slate tiles characteristics

Unit weight [kg]

0.5–5.8

Length [cm]

15–35

Thickness [cm]

0.5–1

Width [cm]

25–61

Fire behaviour

Incombustible

Width between bearing points [cm]

Depends on the dimensions and arrangement of the slates

Number of elements [unit/m2 ]

5–27

Weight [kg/m2 ]

15–54

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115

Singularities in clay-slate roofs are executed with metallic elements, generally in copper or lead. The malleability of these metals allows their quick and simple adjustment to the singularity. The execution of the ridge, hip and abutment may be done with lead or copper sheet, moulded as required, or with slates. The valley is executed with clay-slate tiles arranged along this line. Ventilation is provided by grids.

2.9.1.2

Ceramic Tiles

The origins of ceramic tiles go back to the Roman Empire. The massive application of roof tiles, in various types of buildings, mainly in southern Europe, results from the availability of raw materials and low cost, as well as from a simple manufacturing process. Ceramic tiles are probably the first artificial material with standard dimensions applied in buildings (LNEC 2018). The growing needs of the market led to a large range of ceramic tiles, whose appearance, with various colours, tones and finishes, allows answering a large range of wishes of homeowners. Ceramic tiles are also available with factory-applied water-repellents. Moreover, the search for higher efficiency at the construction site, allied with the intent of decreasing the number of joints, made ceramic tiles larger (Avellaneda 1998). The field of application of ceramic tiles comprises most traditional buildings, current housing, commercial, office, school and other services buildings, older industrial buildings, churches, pavilions, among others. Ceramic tiles show good performance towards the main weather agents (rain, hail, frost, freeze-thaw cycles, wind, thermal variations, sunlight), high durability, high dimensional precision, simple manufacturing process, low cost of raw materials, high variety of shapes and styles, and are non-toxic, inert and recyclable products. Still, ceramic tiles are associated with high waste (during the manufacturing process, transportation and application), a long application process (making it more expensive) very susceptible to human error, requiring qualified labour, and performance being highly dependent on the correct execution of singularities. Ceramic tiles are manufactured from clay. It has hygroscopic properties, acquiring plasticity with water. This property allows moulding the intended element. The clay used in tiles manufacturing should be homogeneous, of regular size grading and free of impurities. These properties will influence the quality of the final product. Ceramic tiles for roofs should comply with TR 13548:2004 (CEN 2004k), EN 538:1994 (CEN 1994a), EN 539-1:2005 (CEN 2005f), EN 539-2:2013 (CEN 2013e), EN 1024:2012 (CEN 2012j) and EN 1304:2013 (CEN 2013f). Ceramic tiles may have multiple shapes, like flat tiles, Roman tiles, Monk and Nun tiles and interlocking roof tiles (Fig. 2.36).

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a

d

b

e

c

f

Fig. 2.36 Different types of ceramic roof tiles. a—interlocking roof tile; b—Marseille roof tile; c—interlocking flat roof tile; d—Monk and Nun roof tiles; e—Roman roof tiles; f—flat roof tile

Roof Tiles with Interlock Interlocking roof tiles (known as Lusa tiles in Portugal) and Marseille roof tiles are the most common types of roof tiles with interlock. Compared with flat tiles, roof tiles with interlock allow considerably improving water and airtightness due to the longitudinal and transverse lock between elements, creating a barrier to several external agents, simultaneously avoiding slippage. The interlocking of elements eases the application on-site and improves application efficiency. Marseille tiles (Fig. 2.36), originally from France, provide good watertightness to the roof due to intertwining joints, ease of interlocking and fastening of elements. Compared with interlocking roof tiles, Marseille tiles are lighter per square metre, thus they are adequate for larger roofs, as the structure may be more economic. Table 2.21 shows the main characteristics of Marseille roof tiles. The most common accessories for Marseilles tiles are ventilation tiles, pathway tiles, ventilation-pathway tiles, chimney accessories, ridge and hip tiles and eaves’ tiles. Interlocking roof tiles (Fig. 2.36) provide an effect similar to that of Monk and Nun tiles, but with interlock. These tiles provide high watertightness, given by the interlock. Interlocking roof tiles should be carefully transported and handled, as breaking between the flat and the curved areas is common (LNEC 2018). Table 2.22 shows the main characteristics of interlocking roof tiles. The most common accessories for interlocking roof tiles are used in chimneys, for ventilation and pathways, ridges, hips and eaves.

2.9 External Claddings of Pitched Roofs Table 2.21 Main characteristics of Marseille roof tiles (CTCV 1998; LNEC 2018)

Table 2.22 Main characteristics of interlocking roof tiles (CTCV 1998; LNEC 2018)

117

Parameter

Marseille roof tiles’ characteristics

Unit weight [kg]

2.8–4.5

Length [cm]

39–48

Height [cm]

5–9

Width [cm]

23–30

Longitudinal overlay [cm]

4–8

Transverse overlay [cm]

4–8

Width between bearing points [cm]

33–45

Number of elements [unit/m2 ]

10–15

Weight [kg/m2 ]

36.4–44.8

Parameter

Interlocking roof tiles’ characteristics

Unit weight [kg]

2.9–4.5

Length [cm]

38–48

Height [cm]

5–9

Width [cm]

23–30

Longitudinal overlay [cm]

4–8

Transverse overlay [cm]

4–8

Width between bearing points [cm]

33–45

Number of elements [unit/m2 ]

10–16

Weight [kg/m2 ]

36.7–42.6

Cover and Channel Tiles Monk and Nun tiles and Roman tiles are included in this set of tiles. Roman tiles are composed of an element working as a cover and another working as a channel, while in Monk and Nun tiles (Fig. 2.37) these elements are not differentiated. When cover and channel tiles started to be used, they showed locking problems when applied in roofs with a considerable slope, leading to watertightness problems. With the progress in the industry of building materials, fasteners started to be used, providing more stability to the roofing. Nowadays, this type of tiles is mainly applied in traditional or historical buildings. Monk and Nun tiles (Fig. 2.36) satisfyingly adapt to different types of pitched roofs. They can be red, beige or brown. Their main characteristics are presented in Table 2.23.

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Fig. 2.37 Example of a pitched roof with Monk and Nun tiles

Table 2.23 Main characteristics of Monk and Nun roof tiles (LNEC 2018)

Parameter

Monk and Nun roof tiles’ characteristics

Unit weight [kg]

1.3–2.5

Length [cm]

40–58

Height [cm]

5–7

Width [cm]

12–20

Longitudinal overlay [cm]

9–15

Transverse overlay [cm]

5–9

Width between bearing points [cm]

20–50

Number of elements [unit/m2 ]

14–36

Weight [kg/m2 ]

35.0–46.8

Monk and Nun tiles need accessories for ridges, ventilation and eaves. Roman tiles (Fig. 2.36) are traditionally composed of two elements, the cover and the channel, which can be semi-circular or trapezoidal. The main characteristics of Roman roof tiles are shown in Table 2.24. Roman tiles need ridge and eaves accessories.

Flat Tiles Flat tiles (Fig. 2.36) need very careful application due to watertightness requirements. The main characteristics of flat tiles are shown in Table 2.25.

2.9 External Claddings of Pitched Roofs Table 2.24 Main characteristics of Roman roof tiles (CTCV 1998; LNEC 2018)

Table 2.25 Main characteristics of flat roof tiles (CTCV 1998)

119

Parameter

Roman roof tiles’ characteristics

Unit weight [kg]

1.8–4.0

Length [cm]

40–57

Height [cm]

5–6

Width [cm]

12–23

Longitudinal overlay [cm]

10–15

Transverse overlay [cm]

5–8

Width between bearing points [cm]

25–48

Number of elements [unit/m2 ]

7–35

Weight [kg/m2 ]

28.0–63.0

Parameter

Flat roof tiles’ characteristics

Unit weight [kg]

1.2

Length [cm]

25–27

Height [cm]

2

Width [cm]

15–17

Longitudinal overlay [cm]

7–9

Transverse overlay [cm]

–

Width between bearing points [cm]

15–18

Number of elements [unit/m2 ]

30–35

Weight [kg/m2 ]

36.0–42.0

This type of tile does not require many accessories, except for the ridge and hip.

Interlocking Flat Tiles Interlocking flat tiles (Fig. 2.36) allow taking advantage of the appearance given by flat tiles with the fastening and watertightness properties of roof tiles with interlock. The most relevant characteristics of interlocking flat tiles are shown in Table 2.26. Interlocking flat tiles use a large range of accessories, including for the ridge, abutments, ventilation, eaves and chimneys.

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Table 2.26 Main characteristics of interlocking flat roof tiles (CS Coelho da Silva SA 2016)

2.9.1.3

Parameter

Interlocking flat roof tiles’ characteristics

Unit weight [kg]

4

Length [cm]

49.1

Height [cm]

3.6

Width [cm]

25.3

Width between bearing points [cm]

38.5

Number of elements [unit/m2 ]

12.5

Weight [kg/m2 ]

50

Micro-concrete Tiles

Micro-concrete tiles were first developed in northern Europe countries, where clay does not have the best properties, resulting in tiles with a low resistance to freezing. The most common micro-concrete tiles’ profiles are a double “S” and double Roman tiles. Micro-concrete tiles show good dimensional stability, homogeneous characteristics, good watertightness, high mechanical strength, low susceptibility to thermal variations and good behaviour in coastal areas and areas affected by freeze-thaw cycles. Micro-concrete tiles have a large range of colours and finishes, adapting to the visual needs of each roof. Still, the weight of micro-concrete tiles is a disadvantage, implying greater loads in the bearing structure. Additionally, this type of tiles implies high energy consumption in the manufacturing process. In terms of physical properties and application, micro-concrete tiles are similar to ceramic tiles. The size of micro-concrete tiles has progressively increased, showing better application efficiency and better watertightness, as the number of joints decreases (Avellaneda 1998). Roofs with micro-concrete tiles should have a minimum slope of, approximately, 15°. Lower slope values imply complementary measures to ensure watertightness (sublayer or waterproofing membrane) (Schunck et al. 2003). Micro-concrete tiles should comply with EN 491:2011 (CEN 2011d) and EN 490:2011+A1:2017 (CEN 2017i). Micro-concrete tiles are manufactured with cement, sand and water. Colours may be obtained using pigments, obtaining blue, green, red, orange, beige, white, brown and black tiles. Coarse aggregates may be added to the mix so that tiles have a rougher texture. The main characteristics of micro-concrete roof tiles are shown in Table 2.27. The singularities of the roof should be executed using special pieces produced by manufacturers of micro-concrete tiles. These special pieces are used in the ridge, eaves, for pathways and ventilation.

2.9 External Claddings of Pitched Roofs Table 2.27 Main characteristics of micro-concrete roof tiles (Argibetão 2009; LNEC 2018)

2.9.1.4

121

Parameter

Micro-concrete roof tiles’ characteristics

Unit weight [kg]

4.5–4.6

Length [cm]

42.0

Height [cm]

5–7 (Roman profile) or 4–6 (double “S” profile)

Width [cm]

30.0–33.3

Width between bearing points [cm]

29.5–35

Number of elements [unit/m2 ]

9.5–11.3

Weight [kg/m2 ]

42.0–48.0

Fibre-Cement Roof Claddings

Fibre-cement is one of the oldest composite materials used in the construction industry. Fibre-cement is an incombustible, stainless, waterproof, not putrescible, chemically stable material, with low susceptibility to impact deformations and thermal gradients, with a reasonable capacity to absorb noise and good mechanical behaviour. As fibre-cement is light and has good mechanical capabilities, it may be used in large spans. As it is also highly resistant to chemical agents, it is recommended for farms, factories and buildings in the shoreline. The application of fibre-cement is highly efficient and low cost. Still, it is not a solution with a pleasant appearance, it becomes brittle with long exposure to ultraviolet radiation and the replacement of elements (large elements) is more difficult than that of tiles or slates. Fibre-cement sheets are applied in schools, factories, farms, sports arenas, storage facilities and housing with lower aesthetical requirements. Fibre-cement may be manufactured as sheets (medium size elements) or large size corrugated elements. Fibre-cement tiles are also available. Fibre-cement large-size corrugated elements are self-bearing. Since the production of fibre-cement elements with asbestos was banned (due to its health hazard), fibre-cement has been produced with synthetic (polyvinyl alcohol [PVA]) and natural (cellulose) fibres. This change in the manufacturing process led to stopping the production of large-size corrugated elements, as the new synthetic or natural fibres did not have good properties to produce large-size elements. In the current market, fibre-cement sheets may be used as an external cladding of pitched roofs or as a sublayer. Sheets may be rose, green, black or white. The minimal slope for this type of cladding is 6°. Raw materials, the manufacturing process and the final characteristics of fibre-cement products should comply with EN494:2012+A1:2015 (CEN 2015f), EN12467:2012+A2:2018 (CEN 2018e) and EN15057:2006 (CEN 2006i). Fibre-cement is manufactured with a cement matrix (73%), synthetic (PVA) (2%) and natural (cellulose) (3%) fibres, admixtures (12%) and water (10%). Fly ash may be used replacing part of the cement content. Fibre-cement sheets have polypropylene strips in the corrugated profile for better protection of application, inspection and maintenance labour (Fig. 2.38).

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polypropylene reinforcement strips

Fig. 2.38 Inclusion of polypropylene strips in the corrugated profiles of fibre-cement sheets for better resistance Table 2.28 Main characteristics of flat fibre-cement roof tiles (Cembrit 2018; Eternit 2019a) Parameter

Flat fibre-cement roof tiles’ characteristics

Length [mm]

40, 50 or 60

Width [mm]

24, 25, 30 or 40

Thickness [mm]

4

Unit weight [kg]

0.67–1.5

Number of elements [unit/m2 ]

10.1–26.04

Weight [kg/m2 ]

13.43–21.3

Minimum roof pitch

20°–35°

Table 2.29 Main characteristics of corrugated fibre-cement roof sheets (Cembrit 2017, 2019; Eternit 2019b) Characteristics

Pitch of corrugation [mm] 72.3

130

146.5

Length [mm]

1525, 2450 or 3050

1375, 1675, 1825, 1975, 2275, 2600 or 2900

1220, 1375, 1525, 1675, 1825, 1975, 2125, 2275, 2440, 2600, 2750, 2900, 3050 or 3660

Width [mm]

782

1020

1086

Thickness [mm]

5.8

6.0

Depth of profile [mm]

19.8

36

Apparent density [kg/m3 ]

1400

Approximate weight [kg/m2 ]

14.5

13

Minimum pitch

10°

5°

47.6–54 1400–1700 17

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123

Fibre-cement flat tiles and corrugated sheets are available. Flat fibre-cement tiles have the characteristics shown in Table 2.28. Corrugated fibre-cement sheets may show a pitch of corrugation of 72.3 mm, 130 mm or 146.5 mm. If compatible, fibrecement corrugated sheets may be used as a sublayer. Common corrugated fibrecement sheets have the characteristics shown in Table 2.29. Accessories are used in the ridge, hips and abutments.

2.9.1.5

Metallic Roof Claddings

Metallic roof claddings have an important role in the cladding of pitched roofs. They are mostly applied in industrial buildings, sports arenas, aircraft hangars, farm buildings and large commercial buildings, as they allow building large span roofs quickly and low cost due to their light weight. Metallic elements, compared with small size claddings, have the advantage of a lower number of joints, resulting from using large-size elements, and having great versatility. However, fastening points are sensitive and they should be well defined at the design stage. Metallic claddings ensure the correct drainage of rainwater with a relatively low slope, as the material is very smooth, hence giving high velocity to the flow of rainwater and hindering the accumulation of snow. This type of roof cladding may have a large range of colours, selected according to the needs of the designer and building owners. Metallic claddings may also be used in roofs with a curvature (Fig. 2.39, part c). Metallic roof claddings are removed and recycled at the end of their service life. Still, some disadvantages are associated with the use of metallic roof claddings, like low acoustic

a

c

b

d

e

Fig. 2.39 Different types of metallic roof claddings: a copper roof cladding; b zinc roof cladding; c curved metallic roof cladding; d trapezoidal metallic sheet roof cladding; and e moulded metallic sheet roof cladding mimicking ceramic roof tiles

124 Table 2.30 Metallic materials used in the external cladding of pitched roofs and their minimal thickness

2 Technology Material

Minimal thickness [mm]

Standard

Steel

0.60

EN 505:2013 (CEN 2013g)

Stainless steel

0.40

EN 502:2013 (CEN 2013h)

Aluminium

0.60

EN 507:2019 (CEN 2019f)

Copper

0.50

EN 504:1999 (CEN 1999c)

Zinc

0.60

EN 501:1994 (CEN 1994b)

and thermal insulation, high absorption of solar radiation, high dimensional variations and high susceptibility to the occurrence of condensations. The finish protection of metallic sheets should be selected according to the exposure of the cladding given its sensitiveness to aggressive environments and indoors condensations. Finishes may be polymeric paints (Fig. 2.39, parts d and e), oxides, metallisation and plastic or reflective pellicles. Metallic materials used in roofs should have a minimum thickness that ensures functionality and resistance towards weather agents (Table 2.30). Ferrous materials, like steel and iron, oxidise when exposed to harmful agents, producing iron oxide. This component is indicative of the degradation of the cladding. So, in ferrous materials, corrosion protection is applied. In the case of non-ferrous materials, such as aluminium, copper (Fig. 2.39, part a) and zinc (Fig. 2.39, part b), oxidation is not a degradation process but protection. The production of an adhesive and compact layer of oxide provides high protection towards weather agents. The corrosion of metallic claddings should be considered: at the design stage, selecting and adapting the cladding according to the environment corrosivity; at the installation stage, avoiding assembling errors; and during the service life, using the cladding as it was designed and doing the planned and needed maintenance works. The environment corrosivity may be assessed according to standards EN ISO 9223:2012 (CEN 2012k) and EN ISO 9226:2012 (CEN 2012l). Metallic roof claddings should comply with EN 14782:2006 (CEN 2006j). The slope of roofs with metallic claddings should take the location of the building into account. If the building is in a flat region, away from the shoreline and with normal exposure, the minimum recommended slope is 15°. If the building is in the shoreline, in a mountain or highly exposed, the slope should be above 27°.

2.9 External Claddings of Pitched Roofs

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Steel Steel roof claddings are available as tiles, slates or sheets. Steel for roofing may be galvanised, lacquered, stainless or with plastic or reflective pellicles. Galvanised steel is a cheaper material that allows taking advantage of the mechanical properties of steel with improved behaviour towards corrosion. Lacquered steel is obtained through the application of an organic coating over galvanised steel. However, when compared with stainless steel, galvanised or lacquered steel show lower durability, due to the faster degradation of the finish treatment if the environment is aggressive. Stainless steel shows good behaviour in industrial, maritime and farm environments. Still, its cost is significantly higher than other metallic roof claddings, only surpassed by copper. Thus, stainless steel is not very commonly used in roofs. Materials that come in contact with steel should comply with EN 508-1:2014 (CEN 2014g) and EN 508-3:2008 (CEN 2008e), so that early deterioration does not occur. The main characteristics of steel elements are shown in Table 2.31. Table 2.31 Main characteristics of steel roof claddings (EDAR 2018; LNEC 2018; Mundiperfil 2019) Tilea

Slateb

Characteristics

Sheet Flat

Corrugated

Trapezoidal

Length [mm]

2000–2500

1000–4000

1000–5000

Width [mm]

1000–1250

836

570–1000

Dependent on the selected shape

Minimal thickness [mm]

0.60–2.8

0.6–1.25

0.4–1.25

0.5–1.25

0.5–0.6

0.5–0.8

0.5–0.8

Steel Stainless steel

Pitch of corrugation [mm]

–

76

76–310

–

Depth of profile [mm]

–

18

18–150

–

Apparent density [kg/m3 ]

7870

Thermal conductivity [W/m °C]

57

Coefficient of thermal expansion [°C−1 ]

0.000012

Fire behaviour

Incombustible

Tensile strength [MPa]

3500–5500

a Dimensions follow those defined for ceramic and micro-concrete tiles according to the target profile b Dimensions

follow those defined for clay-slate tiles according to the target profile

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Aluminium Aluminium is a light, soft, non-magnetic, grey metal, with a low fusion point, high thermal and electrical conductivity, good workability and high coefficient of thermal expansion. Aluminium roof claddings are available as tiles, slates or sheets, but sheets are the most common, as they allow taking full advantage of the material’s properties. Aluminium sheets are composed of aluminium alloys with copper, magnesium, silicon and manganese, for instance. These alloys show good mechanical properties and corrosion resistance. Aluminium may be anodised, lacquered, varnished or have a plastic or reflective pellicle. Aluminium has a high chemical affinity with oxygen. This affinity results in the creation of an alumina pellicle, due to oxidation. This is a transparent adhesive pellicle with 0.1 µm that avoids oxidation from spreading inside the cladding. Aluminium sheets should not be in contact with some metals, nor with wood, paint with lead oxide, acids and chlorides, as they result in the corrosion of aluminium. The application of aluminium sheets in roofs is not advised in maritime (10–15 km from the shoreline) or industrial environments. If the bearing structure is made of steel, a strip of bituminous cardboard should be placed between the aluminium cladding and the bearing elements, to avoid bimetallic corrosion. Materials in contact with aluminium should comply with EN 508-2:2019 (CEN 2019g). The main characteristics of aluminium roofing elements are shown in Table 2.32. Table 2.32 Main characteristics of aluminium roof claddings (Zappone 2000; EDAR 2018; LNEC 2018) Characteristics

Tilea

Sheet

Slateb

Corrugated

Trapezoidal

Length [mm]

1000–3000

1000–3000

Width [mm]

660–1120

660–1120

Dependent on the selected shape

Thickness [mm]

0.6–1.2

Pitch of corrugation [mm]

68–98

127–310

–

Depth of profile [mm]

19

35–150

–

Apparent density

[kg/m3 ]

2700

Thermal conductivity [W/m °C]

200–230

Coefficient of thermal expansion [°C−1 ]

0.0024

Flexural strength [MPa]

0.7–1.5

Young’s modulus [MPa]

6700

a Dimensions follow those defined for ceramic and micro-concrete tiles according to the target profile b Dimensions

follow those defined for clay-slate tiles according to the target profile

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Copper Copper is a highly ductile material, with high thermal and electrical conductivity, easy to weld, recyclable and that does not require any protection pellicle. It shows a long service life, as it may be seen in roofs with about 120 years. However, it is very expensive. The durability of copper is effective even in highly aggressive environments, namely in coastal, industrial and farm areas and highly polluted urban centres. Copper is available as veneer, slates, tiles, rolls or sheets. Copper roof claddings should comply with EN 1172:2011 (CEN 2011e). Copper alloys may include zinc (brass), tin (bronze) or nickel, but zinc and tin alloys are the most common. Still, in a maritime environment, the nickel alloy shows excellent performance. Materials in contact with copper roof claddings should comply with EN 506:2008 (CEN 2008f). In contact with environmental agents, copper produces a patina of copper oxide that provides a protection layer, which is easily rebuilt after any damages. This pellicle is initially brown, then grey and, at the end, green. The main characteristics of copper roof claddings are shown in Table 2.33. Table 2.33 Main characteristics of copper roof claddings (Bragança et al. 2003; EDAR 2018) Roll

Veneer

Tilea

1000–1250

–

1000–1250

800–1000

500–800

800–1000

Dependent on the selected shape

76

160–200

–

Depth of profile [mm]

18

35–55

–

Apparent density [kg/m3 ]

8930

Thermal conductivity [W/m K]

293–400

Coefficient of thermal expansion [°C−1 ]

0.0000168–0.000017

Tensile strength [MPa]

2200–3000

Young’s modulus [MPa]

1.32

Characteristics

Sheet Corrugated

Trapezoidal

Length [mm]

1000

Width [mm]

836

Thickness [mm]

0.50–1.0

Pitch of corrugation [mm]

Slateb

a Dimensions follow those defined for ceramic and micro-concrete tiles according to the target profile b Dimensions

follow those defined for clay-slate tiles according to the target profile

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Table 2.34 Main characteristics of zinc roof claddings (VMZINC 2016; Rheinzink 2017; EDAR 2018; LNEC 2018) Characteristics

Tilea

Sheet

Slateb

Flat

Corrugated

Trapezoidal

Length [mm]

1250–3000

1000–2500

1000–2500

Width [mm]

432–1000

750–836

800

Dependent on the selected shape

Thickness [mm]

0.6–1.0

Pitch of corrugation [mm]

–

63–103

200

–

Depth of profile [mm]

–

18–37

25–35

–

Apparent density

[kg/m3 ]

7500

Thermal conductivity [W/m K]

95–119

Coefficient of thermal expansion [°C−1 ]

0.000022–0.000029

Tensile strength [MPa]

1900–2500

Compressive strength [MPa]

2.0

Flexural strength [MPa]

1.5

a Dimensions follow those defined for ceramic and micro-concrete tiles according to the target profile b Dimensions

follow those defined for clay-slate tiles according to the target profile

Zinc The use of zinc in roof claddings goes back to the nineteenth century and is very common. It is available as sheets, tiles or slates. Zinc shows good performance in urban environments. Zinc and tin alloys are especially advised for roofs in chemically aggressive environments, such as industrial areas or the shoreline. Zinc may deteriorate in the presence of wood, lime, gypsum, cement, bituminous cardboard or acids. When exposed to environmental agents, a pellicle of zinc oxide and zinc salts is formed, becoming a barrier towards the attack of environmental agents. When in contact with a steel bearing structure, a non-acid material should be applied between the zinc element and the bearing structure to avoid bimetallic corrosion. Materials in contact with zinc roof claddings should comply with EN 506:2008 (CEN 2008f). The main characteristics of zinc roof claddings are outlined in Table 2.34.

2.9.1.6

Plastic Roof Claddings

Plastic roof claddings are recommended for industrial, commercial and farm buildings when natural lighting needs are a relevant factor. Plastic claddings may be divided in thermoplastics (polymethacrylate, PVC and polycarbonate) and thermosets (glass fibre reinforced polyester).

2.9 External Claddings of Pitched Roofs Table 2.35 Distance between bearing points for polymethacrylate sheets’ roofs (INDAC 2015)

Thickness [mm]

129 Distance between bearing points [mm]

3.0

600

4.0

800

5.0

950

6.0

1100

8.0

1300

10.0

1500

12.0

1700

Plastic roof claddings easily adapt to different types of pitched roofs. However, the use of this type of material implies a shorter service life than most of the remaining roof claddings. Ultraviolet radiation is the main source of degradation of plastic roof claddings, as the energy from solar radiation starts a set of oxidation reactions in plastic. This oxidation process implies losing the ability to transmit light and makes plastic claddings very brittle and progressively opaque. The prolonged contact of plastic claddings with damp accelerates the degradation process associated with ultraviolet radiation. In rural and coastal areas, the degradation risks increase. To decrease the material’s susceptibility to ultraviolet radiation, a protective membrane is applied over the plastic cladding to provide increased stability and durability towards solar radiation. Plastic sheets are very susceptible to thermal differentials (day-night), as they cause considerable volumetric variations. The mechanical resistance is very low, as well as fire resistance. Plastic claddings should comply with the requirements defined in EN 1013:2012+A1:2014 (CEN 2014h). The minimal slope of roofs with plastic claddings is 5°. The distance between bearing points should be as defined in Table 2.35 (Instituto Nacional para o Desenvolvimento do Acrílico [INDAC] 2015). Plastic tiles may also be applied in roofs cladded with ceramic tiles to allow the entrance of natural light. These plastic elements should have the size of the corresponding ceramic tiles and should comply with EN 1873:2014+A1:2016 (CEN 2016l).

Polymethacrylate Sheets Polymethacrylate sheets, more commonly known as acrylic sheets, are similar to glass in terms of transparency and are used to make domes, skylights and other small surfaces. Their shape may be flat, circular or corrugated. The dimensions and profiles of acrylic sheets vary according to the manufacturer. The main characteristics of this type of roof cladding are shown in Table 2.36.

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Table 2.36 Main characteristics of polymethacrylate roof sheets (INDAC 2015; LNEC 2018) Parameter

Polymethacrylate roof sheets’ characteristics

Length [mm]

1000–3050

Width [mm]

1000–2030

Thickness [mm]

0.8–24.0 −30–240

Service temperature [°C] Apparent density

[kg/m3 ]

1200–1500

Thermal conductivity [W/m °C]

0.16

Coefficient of thermal expansion [°C−1 ]

0.000028–0.000073

[kg/m2 ]

4,900,000–8,400,000

Tensile strength

Flexural strength [kg/m2 ]

14,000,000

Young’s modulus [kg/m2 ]

330,000,000–500,000,000

Polycarbonate Sheets Polycarbonate sheets are presented with flat, corrugated or trapezoidal profiles, adjusting to the designer’s needs. Polycarbonate sheets may be compact, with higher impact resistance and transmittance, or alveolar, with better thermal and acoustic behaviour. This material may be applied in stadiums, subway stations, swimming pools and greenhouses, for instance. The main characteristics of polycarbonate sheets are shown in Table 2.37. Table 2.37 Main characteristics of polycarbonate roof sheets (Sabic 2013; Dagol 2016a, b; Onduline 2019) Parameter

Compact polycarbonate sheets

Alveolar polycarbonate sheets

Length [mm]

2050–3050

3000–8000

Width [mm]

1250–2050

1230–2100

Thickness [mm]

0.8–10.0

4.5–32.0

Service temperature [°C]

−40–135

Apparent density [kg/m3 ]

1200

Thermal conductivity [W/m °C]

0.16–0.21

1.4–3.9

Coefficient of thermal expansion [°C−1 ]

0.000073

0.000067

Tensile strength [kg/m2 ]

4,900,000–8,400,000

–

Flexural strength [kg/m2 ]

1500

650

Young’s modulus

[kg/m2 ]

220,000,000–230,000,000

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Table 2.38 Main characteristics of glass fibre reinforced polyester roof sheets (LNEC 2018; Onduline 2019) Parameter

Translucent sheets

Opaque sheets

Length [mm]

2000–3000

2000–3000

Width [mm]

800–1000

1058

Thickness [mm]

0.8–1.7

1.45

Pitch of corrugation [mm]

31.7–76.2

250

Depth of profile [mm]

15

35

Service temperature [°C]

−30–130

−30–140

Apparent density [kg/m3 ]

1200–1500

1700

Thermal conductivity [W/m °C]

0.16–0.21

Coefficient of thermal expansion [°C−1 ]

0.000012–0.000028

Glass fibres mass

[kg/m2 ]

0.000067

0.270 (class 1 profile); 0.350 (class 2 profile); 0.450 (class 3 profile); above 0.580 (class 4 profile)

Tensile strength [kg/m2 ]

8,800,000–11,200,000

–

Flexural strength [kg/m2 ]

9,500,000–17,000,000

10,000,000

500,000,000–1,200,000,000

–

Young’s modulus

[kg/m2 ]

Glass Fibre Reinforced Polyester Sheets Translucent glass fibre reinforced polyester sheets may have flat, corrugated or trapezoidal profiles. The dimensions and profiles vary according to the manufacturer. The main characteristics of this type of sheets are highlighted in Table 2.38. Opaque glass fibre reinforced polyester sheets are also available in a wide range of colours. This type of cladding is mainly applied in industrial buildings, due to the good resistance to chemical agents. These sheets show better fire and chemical behaviour than translucent sheets.

PVC Sheets PVC sheets are opaque and may be flat or corrugated. The dimensions and profiles vary according to the manufacturer. The main characteristics of PVC sheets are highlighted in Table 2.39.

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Table 2.39 Main characteristics of PVC roof sheets (Palram 2013; H&F Manufacturing Corporation 2018; LNEC 2018) Parameter

PVC roof sheets’ characteristics

Length [mm]

1820–3640

Width [mm]

660–1080

Thickness [mm]

0.8–3

Pitch of corrugation [mm]

32–177

Depth of profile [mm]

14–51

Resistance limit temperature [°C]

70

Apparent density [kg/m3 ]

1400

Thermal conductivity [W/m °C]

0.107–0.130

Coefficient of thermal expansion [°C−1 ]

0.000038–0.000063

[kg/m2 ]

4,600,000–6,300,000

Tensile strength

Flexural strength [kg/m2 ]

9,500,000

Young’s modulus [kg/m2 ]

329,000,000

2.9.1.7

Mixed Roof Claddings

Mixed roof claddings combine the properties of different materials to overcome the limitations of individual materials.

Bitumen and Aluminium Sheet Coated Steel Plates Bitumen and aluminium sheet coated steel plates are also known as isothermal plates. They are composed of a resistant core in galvanised steel 0.45 mm or 0.63 mm thick, protected on both sides by bituminous coats with mineral fillers, which are then coated with embossed aluminium sheets. The upper side of the plate may be grey, yellow, red, blue, white, black or green, and the back face of the plate is white or grey (Fig. 2.40) (LNEC 1982, 2000). This type of plates is commonly used on roofs with a great span. The use of bitumen decreases the noise associated with rainfall and improves the thermal behaviour. These plates should be used in low corrosive environments and with a slope higher than 5%. Compared with galvanised steel plates, bitumen and aluminium sheet coated steel plates allow reducing about 90% of the noise caused by rainfall.

Sandwich Panels’ Roof Claddings Sandwich panels are composed of two metallic sheets, in aluminium or steel, or by a metallic sheet and a fibre-cement sheet, and a core of rigid foam or mineral wool. Metallic sheets may have different finishes: pre-patinated, aluminium, zinc, an alloy

2.9 External Claddings of Pitched Roofs

133 ribbed aluminium sheet

bituminous coat with mineral fillers

galvanised steel plate

bituminous primer

ribbed aluminium sheet

Fig. 2.40 Composition of bitumen and aluminium sheet coated steel plates

of aluminium and zinc, anodised, organic or plastic or reflective pellicle, according to the type of metal and the environment. Sheets may be flat, corrugated or trapezoidal. Sandwich panels should comply with EN 14509:2013 (CEN 2013i). The use of prefabricated sandwich panels allows taking advantage of the use of metallic roof claddings with some disadvantages mitigated. The use of polyurethane foam between two metallic sheets significantly improves the acoustic and thermal behaviours, compared with a simple metallic roof cladding. The application efficiency of sandwich panels is slightly better, according to its dimensions, and it does not need an extra thermal insulation layer. However, at the end of its service life, this type of roof cladding is hard to recycle, due to the difficult separation between metallic elements and thermal insulation (Zamora 1998). Natural lighting is possible using translucent plastic sandwich panels. These panels are composed of two connected plastic plates with an air gap between them. These panels allow natural lighting without significantly compromising thermal insulation. Translucent plastic sandwich panels are composed of glass fibre reinforced polyester plates or polycarbonate plates with thicknesses ranging from 30 to 80 mm and length and width according to the design needs. This type of panels is only used to complement the application of metallic sandwich panels. The main characteristics of sandwich panels are shown in Table 2.40.

Asphalt Shingles Asphalt shingles are composed of ceramic granulate, oxidised bitumen, fibreglass and silica sand. Asphalt shingles are waterproof, flexible, recyclable and easy to apply. However, their application is not efficient, they show high expansion and capture high levels of solar radiation, which may result in the loss of volatile components, causing cracking. Asphalt shingles are not advised for warm weather regions. As

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Table 2.40 Main characteristics of sandwich panels for roof claddings (Irmalex 2015; Painel 2000; Alaço 2019a, b) Parameters

Sandwich panels for roof claddings Flat

Corrugated

Trapezoidal

Length [mm]

2000–20,000

20,000

2000–24,000

Width [mm]

1000

1000

1000

Thickness [mm]

30–200

64–104

30–115

Pitch of corrugation [mm]

–

125

250–500

Depth of profile [mm]

–

37

35–40

Width between bearing points [mm]

4000–6000

Density [kg/m3 ]

–

–

42

Weight [kg/m2 ]

11.3–28.9

14.5–16.1

9.9–11.5

Thermal conductivity [W/m K]

0.20

0.25

0.26

Compressive strength [kg/m2 ]

14,276

a protection measure, a reflective product may be applied over the shingles, but it usually has a short service life (Richardson 1980). Asphalt shingles have different shapes and colours. Asphalt shingles require a minimum slope of 11° (AFNOR 1993b; Schunck et al. 2003). This type of roof cladding should comply with EN 544:2011 (CEN 2011f), ASTM D7158/D7158M-19 (ASTM International 2019d), ASTM D6381/D6381-15 (ASTM International 2015b), ASTM D3018/D3018M-11(2017) (ASTM International 2017b), ASTM D3161/D3161M-19 (ASTM International 2019e) and ASTM D3462/D3462M-19 (ASTM International 2019f). Asphalt shingles do not use accessories in singularities. The most relevant characteristics of asphalt shingles are shown in Table 2.41. Table 2.41 Main characteristics of asphalt shingles for roof claddings (GAF 2019; Onduline 2019) Parameters [mm]

Asphalt shingles for roof claddings Rectangular

Oval

Variable shape

Length

305–432

334

Variable

Width

876–1016

1000

Thickness

0.8–3.0

Spacing between slots

333

200

Exposed length

114–191

140

Variable

2.9 External Claddings of Pitched Roofs

135

Table 2.42 Main characteristics of metallic tiles and slates coated with mineral granules for roof claddings (Decra Metal Roofing 2015; Boral Steel 2018, 2019) Parameters

Metallic tiles and slates coated with mineral granules’ characteristics

Length [mm]

1113–1330

Width [mm]

348–368

Thickness [mm]

20–40

Metallic Tiles and Slates Coated with Mineral Granules This type of cladding is used in new housing buildings with a slope above 27%. The mineral granulates allow absorbing noise, namely that from rainfall. The main characteristics of metallic tiles and slates coated with mineral granules are shown in Table 2.42.

2.9.2 Design of External Claddings of Pitched Roofs 2.9.2.1

Functional Requirements

The functional requirements of a pitched roof refer to a set of minimal properties that should be complied with so that the roof fulfils its purpose. The functional requirements of pitched roofs have been progressively becoming stricter. Functional requirements may be grouped in structural safety, inhabitability, durability and economy and environmental protection.

Structural Safety The structural safety of a pitched roof is given by the adequate design in terms of permanent (dead), variable (live) and accidental loads. Permanent loads refer to the weight of the external cladding, bearing structure, singularities, equipment and accessories. Variable loads refer to wind, rain, snow, thermal changes and earthquakes. Accidental loads are associated with exceptional phenomena, like fire, explosions or impacts. These loads should be taken into account while considering the codes in place for structural dimensioning, which are out of the scope of this book. Still, it may be mentioned that the bearing structure of a pitched roof may be continuous or discontinuous. Continuous bearing structures refer to reinforced concrete slabs with a specific slope that allows creating living spaces below the roof surface. Discontinuous bearing structures may be executed using wood, reinforced concrete, steel or masonry. This type of structure is composed of trusses, bearing purlins, rafters and battens that bear the external cladding of the pitched roof.

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Inhabitability Inhabitability requirements for a pitched roof include air and watertightness, thermal insulation, ventilation and acoustic insulation. A pitched roof should be built so that it is water and airtight. The waterproofing of a pitched roof is provided by its external cladding and complementary elements. The choice of an adequate roof cladding is important, as well as the adequate execution of singularities (ridges, hips, valleys, among others), joints, fastening, overlays and the selection of an adequate slope. The slope is a very important property of a pitched roof, as it increases water and airtightness when the quality of the cladding elements or of the design is insufficient. Increasing the slope of the roof, the velocity of the rainwater flow increases, hence decreasing the risk of leakage. However, increasing the slope of the roof may have an adverse result if fastening is not adequately designed, as the roof becomes more unstable due to wind and rain loads. The selection of the roof’s slope requires assessing the type of external cladding, exposure of the building and the length of spans. Opting for a steeper slope allows taking advantage of the area below the roof surface, but significantly increases the cost of the roof, as more cladding elements are needed and the bearing structure must be designed for more demanding requirements. The slope of a roof also influences the maximum length of the roof side. This limitation is associated with the velocity of the rainwater flow and adequate drainage. The overlay between cladding elements ensures the protection of the roof towards weather agents. The minimum overlay should be determined according to the exposure of the building, weather conditions and distance to the shoreline. The roof plays an important role in the building’s thermal performance, as a significant amount of thermal exchanges occur through the roof. As the most recent directives point towards decreasing energy needs of buildings, and the roof is a highly exposed building element, its behaviour is decisive to reach low energy objectives. So, in terms of thermal behaviour, the roof is important for the thermal comfort of indoor areas and, simultaneously, for the energy performance of the building. Additionally, the lower surface of roofs is very susceptible to condensations, which have a negative impact on the durability of claddings. Hence, the design of the roof should prevent the occurrence of condensations. The ventilation of roofs is also important. It may occur next to the lower surface of the external cladding, in the ridge and in ventilation tiles, if the attic is not ventilated, or in the attic. The ventilation of a roof is essential to decrease its maintenance costs and prolong its service life (Oxley 2001). On the other hand, it allows removing the excess moisture on the lower surface of the roof cladding, avoiding a long period of occurrence of moisture (Lstiburek and Carmody 1991). Still, the roof should not be excessively ventilated, as it implies higher energy needs in the winter, although better thermal comfort may occur in the summer. Thus, a balanced solution is required according to the comfort needs of the building. Acoustic comfort requirements are associated with the need to improve the performance of the roof towards the discomfort caused by outdoors’ noise. The acoustic insulation characteristics should be adequate to the type of use of the building and the surrounding conditions. Acoustic comfort is more frequently considered in buildings

2.9 External Claddings of Pitched Roofs

137

next to industrial areas, air traffic areas, railways and high traffic roads. At the design stage, it is essential to determine the type of acoustic insulation, defining a set of protection measures for the inhabitants. The acoustic insulation of a roof consists of applying materials with elastic properties and low inertia and density. Durability Durability is an essential requirement of all building materials. It refers to the ability of a given building element keeping its performance levels during a predefined service life, considering the action of aggressive agents and regular maintenance. The service life of the elements that compose a pitched roof depends on the characteristics of each material, design, local environmental conditions, weather, chemical and physical limitations, and on how and when maintenance actions are carried out. The main durability requirements of pitched roofs refer to the mechanical behaviour, dimensional stability, resistance to chemical agents, resistance to freeze-thaw cycles and appearance homogeneity. Economy and Environmental Protection Economy in the context of building pitched roofs aims at optimising the use of resources during the various stages of the life cycle of a roof, including construction, maintenance, replacement and waste treatment. External claddings of pitched roofs should be easy to apply on-site. Variable application conditions will influence construction costs and the complexity of works, which should be as low as possible. At the construction stage, the initial costs of acquiring cladding materials and transporting them to the construction site should be taken into account. Next, application costs, including labour, equipment and accessories, should be considered to determine the total construction costs. Replacing materials implies the removal of existing materials and taking that waste to recycling or treatment plants. Removed materials, if in adequate conditions, may also be reused. A sustainable roof is one that emphasises the selection of efficient and environmentally friendly materials (Hutchinson and Roberts 1999).

2.9.2.2

Design of Pitched Roofs Cladded with Ceramic Tiles

Given the importance that ceramic tiles have in some regions (for instance, southern Europe), the main good practice rules for designing pitched roofs cladded with ceramic tiles are presented. Slope The slope to be used for different types of ceramic tiles is shown in Table 2.43.

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Table 2.43 Minimum slope of pitched roofs with ceramic tiles in Portugal (slope in centimetres per metre of horizontal projection) (CTCV 1998) Type of tile Interlocking roof tiles

Exposure of the roof

Size of the roof side

Locationa Zone I [%]

Zone II [%]

Zone III [%]

Protected

Up to 6.0 m

32

40

45

39

44

50

Normal Exposed Protected

6.0–10.0 m

Normal Exposed Marseille tiles

Protected

Up to 6.0 m

Normal Exposed Protected

6.0–10.0 m

Normal Exposed Monk and Nun tiles

Protected

Up to 6.0 m

Normal Exposed Protected

6.0–10.0 m

Normal Exposed Roman tiles

57 50

43

48

55

48

56

63

61

65

70

67

73

78

77

84

90

66

72

77

74

80

86

85

91

99

50

55

59

55

61

66

64

69

76

55

59

65

61

67

73

69

77

84

45

49

Normal

44

49

55

Exposed

51

57

64

44

50

55

Normal

48

55

61

Exposed

56

63

69

58

64

68

Normal

64

70

76

Exposed

75

81

87

64

69

75

Normal

71

77

84

Exposed

83

89

96

10–22b or >22

10–22b or >22

10–22b or >22

Protected

Protected

Interlocking flat tiles

51 44

40

Protected

Protected

Flat tiles

44 39

Protected Normal

Up to 6.0 m

6.0–10.0 m

Up to 6.0 m

6.0–10.0 m

–

Exposed a Zoning in continental Portugal combining wind loads and rainwater levels. Higher or lower climate

severity was attributed according to the average annual rainfall, altitude of the region and distance to the sea b When underlayment or a waterproofing membrane exists

2.9 External Claddings of Pitched Roofs

139

Table 2.44 Overlay according to exposure of the roof for ceramic tiles without interlock (CTCV 1998) Type of roof tiles

Exposure

Location Zone I [m]

Zones II and III [m]

Monk and Nun tiles and Roman tiles

Protected

0.14

0.15

Normal

0.15

0.16

Exposed

0.16

0.17

Flat tiles

Protected, normal and exposed

0.07

0.08

F F

F

F

F

F

F F

F F

F

F

F

F

F

F

F

F

F

F F

F

F

F

F

F

F

F F

F

F

F

F

F

F

F

F

F

F

F

F F

F

F

F

F F

F

a

F

F

F

1 m²

F

b

F F

F F

F

F F

F- roof tiles that should be fastened

Fig. 2.41 Application of fastening criteria for ceramic roof tiles with interlock in a roof with a slope higher than 150% (a), and for flat ceramic roof tiles in a roof with a slope higher than 175% (b)

Overlay The overlay of ceramic tiles with interlock is defined by their design and is not adjustable. On the other hand, flat tiles, Roman tiles and Monk and Nun tiles should have the recommended overlay shown in Table 2.44.

Fastening Fastening of ceramic tiles is influenced by the slope of the roof. As a general rule, the use of slopes higher than 65° implies fastening the tiles (Schunck et al. 2003). Ceramic tiles with interlock should be fastened to the substrate when the slope is higher than 150% or wind loads are significant. One in every five tiles should be fastened, as shown in Fig. 2.41 (part a) (CTCV 1998), or one tile per metre should be fastened (Zamora 1998). Flat ceramic tiles should be fastened when the slope is higher than 175% or exposure conditions demand it. Ten flat tiles should be fastened per square metre (Fig. 2.41, part b). In slopes higher than 300%, or in extremely

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Table 2.45 Fastening of cover and channel tiles according to wind loads and the slope of the roof (adapted from CTCV [1998]) Slope [%]

Location and wind exposure

Eaves and sides

Current area

s ≤ 30

Zones I and II, protected and normal places

Fastened tiles

Tiles without fastening

Zones I and II, exposed places

Fastened tiles

Fastened tiles

30 < s ≤ 60

Zone III, every place

Fastened tiles

Zones I and II, protected and normal places

Fastened tiles

Tiles without fastening

Zones I and II, exposed places

Fastened tiles

Fastened tiles

Zone III, every place

Fastened tiles

aggressive exposure conditions, all tiles should be fastened. Cover and channel tiles should follow instructions in Table 2.45. Tiles may be fastened with clamps, nails, metallic wire, synthetic products or mortar. Galvanised steel should not be used to fasten tiles in a maritime or industrial environment. The application of synthetic products (mastic or polyurethane foam) or mortar provides more stability and watertightness to roofs cladded with cover and channel tiles (Appleton 2011). When mortar is used, it should not be excessive to avoid overweighting and restricting the adequate ventilation of the roof. Hence, joints between tiles should never be completely filled. Mortars should be of hydraulic lime, with a content of 250–350 kg of hydraulic lime per cubic metre of dry sand, or 150 kg of cement and 175–225 kg of hydraulic lime per cubic metre of dry sand. The use of simple cement mortars is not advised due to their excessive hardness, which may lead to cracking (of the mortar and roof tiles), considering the high thermal variations in a roof (CTCV 1998; Zamora 1998). Sand should be free from impurities and the application of admixtures should not cause the degradation of other materials. If colouring agents are needed, the content should be around 5–7%. After applying the mortar, all residues should be removed (CTCV 1998). The application of mastic or polyurethane foam is meant for increasing cohesion between roofing elements, limiting their movement and absorbing any dimensional changes without cracking. Materials should be clean and free from fat to promote better adhesion. Next, the mastic or polyurethane foam is applied followed by the tiles. These products show advantages comparing to mortar, as they are not putrescible, are less porous, easier to apply, lighter and present better labour efficiency.

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141

2.9.3 Execution of External Claddings of Pitched Roofs 2.9.3.1

Clay-Slate Tiles

The application of clay-slate tiles is generally done over a wood deck (Fig. 2.42, part a), but they may also be applied over wood battens with a flexible underlayment (Fig. 2.42, part b). A roof with clay-slate tiles may have three different displays: regular, textured and gradual. The regular appearance is given by the application of tiles with very similar colour, smooth texture, dimension and thickness. The tiles have the shape of a rectangle, allowing to provide a regular appearance. The textured display uses tiles with different thicknesses and a rougher texture, and their colour is not as homogeneous as in the regular display. In the gradual display, tiles are graded according to their thickness, size and exposure. Thicker and larger tiles are placed next to the eaves, while smaller and thinner tiles stay close to the ridge. This way, from the ridge to the eaves, tiles increase their thickness and dimension. Clay-slate tiles for slopes over 30° should be overlaid about 7.5 cm or 5 cm in mansards and roofs with a slope above 60°. For pitched roofs with a slope lower than 30°, tiles should overlay about 10 cm (Levine 1993). Tiles are mechanically fastened to the substrate with nails or clamps, properly sealed with washers, cement or synthetic mortar, increasing the watertightness of the roof (Stahl 1984; AFNOR 1993a).

a

b

Fig. 2.42 Application of clay-slate tiles over a wood deck using nails and clamps (a) and over wood battens using nails (b)

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4th

3rd rows of roof tiles 2nd

1st

4th

3rd

2nd

1st

columns of 4 roof tiles

Fig. 2.43 Alignment and beginning of application of interlocking ceramic tiles

2.9.3.2

Ceramic Tiles

Roof Tiles with Interlock Interlocking roof tiles start to be applied from the bottom right of the roof, with rows perpendicular to the slope of the roof, aligned by the centre of the tile’s channel (Fig. 2.43). Interlocking tiles are placed over wood battens, supported by protruding bolts in the back face of tiles.

Cover and Channel Tiles The application of cover and channel tiles follows the same procedures as roof tiles with interlock, namely in terms of the order of application of tiles and alignment. Channel tiles are placed with the larger edge on top and the cover tiles fit over channel tiles with the larger edge on the bottom. These tiles should be fastened with clamps, nails, mastic or mortar.

Flat Tiles The application of flat tiles follows the same procedures as tiles with interlock, in terms of the order of application and alignment. Flat tiles require that battens are spaced according to the size of tiles and overlay, considering exposure conditions. As for the adjustment of elements, tiles may have aligned or misaligned joints, according to the desired visual effect (Fig. 2.44).

2.9 External Claddings of Pitched Roofs

a

143

b

Fig. 2.44 Flat tiles with aligned (a) and misaligned joints (b)

Interlocking Flat Tiles Interlocking flat tiles follow the same application methodology of roof tiles with interlock. As for the alignment, the same adjustments used for flat tiles are followed.

2.9.3.3

Micro-concrete Tiles

The application of micro-concrete tiles follows the procedures used for ceramic tiles with interlock in terms of the order of application and alignment of the different elements. Micro-concrete tiles require battens with high-quality geometric characteristics so that interlocking elements are well adjusted, making the application process easier. The slope of the roof defines the overlay between elements and, in turn, the spacing between battens. As for the overlay, minimal values should follow recommendations in Fig. 2.45, between 7 cm and 12.5 cm (LNEC 2018; Argibetão 2019). The application of micro-concrete tiles requires fastening to the substrate so that the roof shows adequate stability and watertightness (Appleton 2011). Fastening may use metallic clamps, mortar (cement) or synthetic products (mastic or polyurethane foam). Metallic fasteners should be in stainless steel, copper, zinc or galvanised steel (except in maritime or industrial environments). The use of mortar or synthetic products should follow the procedures recommended for ceramic tiles.

2.9.3.4

Fibre-Cement Claddings

Fibre-cement sheets should be applied in the opposed direction of prevailing winds. Each element is placed overlaying the previous one (Fig. 2.46). To avoid overlaying

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slope [%]

373% 275% 214% 180%

overlay 7 cm

143% 120% 100%

slope [deg]

75°

70°

65° 61°

overlay 8 cm

81% 70%

55°

60%

50° 45° 39° 35° 31° 27° 24° 20° 16° 11°

rlay

51% 45%

ove

m

10 c

36% 29% 20%

m

2.5 c

lay 1

over

supplementary waterproofing systems

11%

6°

Fig. 2.45 Minimal overlay of micro-concrete tiles according to the roof slope

four adjacent sheets, the corners of sheets should be cut diagonally with an electric disk saw complemented with the use of a dust vacuum cleaner. Fibre-cement sheets should overlay according to the slope of the roof. The longitudinal and transverse overlay should follow recommendations in Table 2.46. A watertightness complement may be required. It is applied in the overlay area to avoid rainwater blown by the wind from leaking in the joints (LNEC 2018). Fastening fibre-cement sheets provides an adequate response to external loads. To place fastening elements in fibre-cement sheets, holes have to be drilled on the top of the corrugated profile using an electrical drill with a diameter 3 mm higher than the fastening element diameter. Adequate screws or self-drilling screws should be used, considering the material of the purlins (timber or steel, for instance), and washers should also be used.

2.9.3.5

Metallic Roof Claddings

Metallic sheets should be applied in the direction opposite to dominant winds. Each element is placed over the previous one. As metallic sheets are light, they are very susceptible to wind loads. The lateral overlay between metallic roof sheets should be of 1½ corrugations, in the case of a corrugated profile, and 1 corrugation, in the case of trapezoidal profile (LNEC 2018). As for the top overlay, it should not be below 0.15 m. If the roof slope is below 10%, overlays should be sealed, to improve watertightness. The sealant should be flexible and follow the dimensional movements of the cladding and substrate (Richardson 1980), like mastic or a bituminous strip (Fig. 2.47) (Metal

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145

direction of prevailing winds ridge

direction of lay

eaves direction of lay

Fig. 2.46 Direction for applying fibre-cement sheets Table 2.46 Overlay of fibre-cement sheets according to the roof slope (LNEC 2018) Slope of the roof [°]

Minimal overlay of fibre-cement sheets Transverse

Longitudinal [cm]

Watertightness complement

Roof side up to 10 m

Roof side over 10 m

6–10

1½ corrugations

1½ corrugations

20

Needed

11–14

1½ corrugations

1½ corrugations

20

Needed

15–17

½ corrugation

1½ corrugations

18

Needed

Exposed areas: 1½ corrugations 18–20

½ corrugation

½ corrugation

16

Unnecessary

21–45

½ corrugation

½ corrugation

14

Unnecessary

≥45

½ corrugation

½ corrugation

10

Unnecessary

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a

b

Fig. 2.47 Applying bituminous strips as a watertightness complement in the transverse (a) and longitudinal (b) overlays of metallic roof claddings

Table 2.47 Different fastening systems for metallic roof claddings

Fastening system

Metal

Screwed

Aluminium, steel, copper and zinc

Clamped

Steel, copper and zinc

Interlocked

Aluminium, steel and zinc

Riveted

Aluminium, steel, copper and zinc

Welded

Aluminium, steel, copper and zinc

Construction Association 2014). Movements are caused by thermal loads, dry-wet cycles, freeze-thaw cycles, dynamic loads and structural movements (Stahl 1984). Metallic roof claddings have different fastening methods, shown in Table 2.47. Fastening should be done with washer faced screws (wooden bearing structure), clamps (steel or reinforced or prestressed reinforced concrete bearing structure), screws (wooden and steel bearing structure) or steel cables (domed bearing structure). Fastening elements may be in copper or stainless. Fastening holes should be drilled on the top of the corrugated profile or rib with a diameter 2 mm or 3 mm larger than the fastening element. Washers may be bituminous, plastic or metallic, stopping rain from leaking in fastening holes. The fastening element should be adequately tightened, not too rigid or loose. Fastening elements should then be protected with a plastic cap to provide better protection from environmental agents. Cladding sheets should be fastened to each other every 50 cm. Fastening to the bearing structure should be guaranteed every 1 m, placed alternately (Fig. 2.48). Fastening elements should be compatible with the metallic roof cladding to avoid the occurrence of bimetallic corrosion. The number and spacing of screwed or riveted fasteners should be adjusted according to the size of the sheet, weight, aggressiveness of the location and loads.

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147

b

b a

a

a

a

a

a

b

b

b

b

a

a

a

a

a

a

b

b b

b a

a

a

a

a

a

Fig. 2.48 Arrangement of fastening elements of metallic and plastic roof claddings. a—Fastening to structure elements; b—fastening to underlaying cladding sheets

The clamping process consists of profiling the sheet on-site, laterally overlaying the sheets in homogeneous strips with a coil that clamps the joint. The minimum height of the joint should be 3 cm. The connection to the substrate is done in the lateral rim of the element using structural fasteners. The height of the joint and spacing between elements should be adjusted according to the roof’s exposure. Interlocking elements consists in applying the elements using lateral fittings between sheets, resulting in a faster application process. Capping may be applied to the joint, if necessary. The connection to the bearing structure is done in the lateral rim of the element. This on-site application methodology requires high labour efficiency. Elements may also be fastened to each other using welding. The connection to the bearing structure is welded, if it is a metallic bearing structure, otherwise another type of fastening should be applied (LNEC 2018).

2.9.3.6

Plastic Roof Claddings

The execution of plastic roof claddings should start at the lower right corner and end on the upper left corner, in the opposite direction of dominant winds. Plastic roof claddings may be prepared using tools normally used in metal and wood. Tools manufactured with hard metal are recommended. Cutting may be done using manual or automatic saws. To drill holes, a regular drill for metallic sheets may be used, and the drill should be about 5% larger than the fastening element, to allow dimensional variations of the roof cladding. When local heating is detected, the plastic cladding should be cooled with water or compressed air.

148 Table 2.48 Top overlay according to the roof’s slope for plastic roof claddings (LNEC 2018)

2 Technology Roof slope [°]

Minimal top overlay [cm]

Watertightness complement

5–15

25

Recommended

15–30

20

Unnecessary

>30

15

Unnecessary

The minimal lateral overlay should correspond to two corrugations (corrugated sheets). The top overlay is associated with the slope of the roof (Table 2.48). As plastic sheets are very light, their fastening needs special attention, as the light weight makes plastic sheets very susceptible to wind loads. The number of fastening elements should take the element size into account, as well as weight and environmental exposure. Fastening is only recommended at the top edge of the sheet, below overlay joints. Fastening of plastic sheets (between sheets and to the substrate) should follow the criteria for metallic roof claddings using screws. The tightness of fastening should be adequate to avoid breaking the plastic element. The use of shims under the sheets is recommended during the fastening process, to prevent fractures. Polycarbonate sheets may also be interlocked. Fastening may also use adhesive material or adhesive tape. Adhesive materials should be judiciously selected to avoid unwanted reactions with the plastic roof cladding. The adhesion process starts with cleaning the surface, removing any foreign elements with a cloth with isopropanol. Next, a fine coat of adhesive material is applied below one of the pieces placing both surfaces together and pressing them slightly. If the adhesion between elements needs to be increased, the surfaces may be slightly pricked. After a few minutes, the adhered pieces may be moved, although maximum resistance of the adhesive connection is only achieved after a few days. Adhesive unions are exemplified in Fig. 2.49. Sealants applied in plastic roof claddings should follow recommendations for metallic roof claddings.

Fig. 2.49 Examples of ways of adhering plastic roof claddings elements together

2.9 External Claddings of Pitched Roofs

2.9.3.7

149

Mixed Roof Claddings

Sandwich Panels Roof Claddings Sandwich panels are applied with highly specialised joints between panels, which allow increasing the watertightness level of the roof. The overlay of elements is done according to the pre-fabricated interlock. Fastening between elements and to the substrate is done using metallic screws, according to recommendations for metallic roof claddings.

Asphalt Shingles The application of asphalt shingles requires a continuous roof deck substrate, which is usually made of wood, over which a flexible membrane may be applied to increase watertightness. A cord of cementitious mastic is applied along the eaves, followed by the first row of asphalt shingles, about 10 cm high along the eaves, fastened with nails. This first row is meant to increase the roof’s watertightness. Over this row, the application of the exposed cladding starts. The application starts in the steepest side of the roof and follows the order mentioned for ceramic tiles. The arrangement of elements is done so that joints are misaligned. Fastening may be applied manually or automatically, provided that at least 4 nails per tile are applied, or 8 nails if the slope is higher than 80°. To obtain a homogeneous overlay, each row should be marked. Asphalt shingles should be overlaid, at least, 15 cm to ensure the roof’s watertightness.

Metallic Tiles and Slates Coated with Mineral Granules The application of this type of cladding starts in the lower right corner and the elements are fastened to the bearing structure with metallic fastening elements (nails or clamps). The elements are interlocked in each other and, in the end, singularities are executed, namely in the ridge and hips.

2.10 Flat Roofs In this section, the main technologies available for building flat roofs are concisely presented, considering that the technology itself is not the central focus of this book, but understanding it potentially allows a better diagnosis of detected defects, as well as more adequate proposals of repair techniques. A flat roof is composed of horizontal layers (or with a pitch below 10°, as defined by BS 6229:2018) (Gorse et al. 2012; British Standards Institution 2018). In a flat

150 Table 2.49 Basic requirements (The European Parliament and The Council of the European Union 2011) and components of a flat roof

2 Technology Basic requirements

Flat roof component

Mechanical resistance and stability

Bearing structure

Safety in case of fire

Bearing structure

Hygiene, health and the environment

Waterproofing

Thermal insulation Thermal insulation In-service safety and accessibility

Protection layer

Protection against noise

Bearing structure

Energy economy and heat retention

Thermal insulation Shaping layera

Sustainable use of natural resources

All components

a If

the shaping layer is made of concrete with lightweight aggregates, it will complement the action of the thermal insulation layer (Cohendet et al. 1988)

roof system, those overlapping layers are responsible for the satisfaction of functional requirements (Table 2.49). In general terms, a flat roof is composed of: (i) bearing structure; (ii) shaping layer; (iii) thermal insulation; (iv) waterproofing; and (v) protection layer. A flat roof may also include a screed layer, a vapour-barrier and a separation layer. The drainage system is a very important part of a flat roof. It may be composed of gutters, downpipes, and secondary scuppers/overflow pipes, with the objective of draining rainwater. The drainage system needs adequate care, as any faulty drainage element may compromise the roof’s watertightness, or, if clogged, the lack of drainage may affect the mechanical strength of the flat roof. Flat roofs may be classified according to accessibility, protection layer, type of waterproofing, positioning of the thermal insulation layer in relation to the waterproofing layer, slope and bearing structure (Lopes 2010). Even considering regular inspections and maintenance of flat roofs, rehabilitation may be needed after some time in service. Rehabilitation may increase performance levels or provide a response to updated functional requirements, such as improved energy efficiency, improved noise reduction and prevention of damages in the bearing structure.

2.10.1 Materials Used in Flat Roofs Nowadays, a vast diversity of materials may be used in waterproofing systems in the building sector. According to Lopes (2010), considering the types of materials used, a waterproofing system may be classified as traditional or non-traditional. Additionally, auxiliary materials for waterproofing need to be used and the flat roof cladding system requires the use of thermal insulation.

2.10 Flat Roofs Table 2.50 Classification of traditional waterproofing materials (adapted from Lopes [2010])

151 Application

Class of materials

Type of materials

On-site

Bituminous materials

Direct distillation bitumen Oxidised or blown bitumen

Engineered materials

Bituminous emulsions Bituminous paints Modified bituminous products Pozzolanic cement

Prefabricated

Saturated or impregnated meshes

Bituminous canvas

Bituminous membranes

Reinforced with felt

Bituminous felt Reinforced with canvas Reinforced with sheet

2.10.1.1

Traditional Waterproofing Materials

Traditional waterproofing materials may be liquid/viscous, being applied on-site, or prefabricated, the latter also known as waterproofing membranes (Table 2.50). The application of liquid or viscous traditional materials decreased a lot, and, nowadays, they are mainly used as preliminary surface treatment or as protection of other waterproofing materials (Lopes 2010).

Bituminous Materials Bitumen is a black liquid mixture with high viscosity, non-volatile, mostly nonsoluble in water, with adhesive and waterproofing properties. The bitumen viscosity decreases at temperatures between 150 and 200 °C. It is composed of various organic raw materials, mainly carbon and hydrogen. Bitumen may be produced artificially (refinery processes from petroleum) or naturally extracted (asphalt) (EOTA 2004a). Artificial bitumen is commonly known as oxidised bitumen (or blown) and is usually part of multilayer systems applied on-site, used as an adhesive for bituminous membranes or to execute tail-ends (Lopes 2010). Most waterproofing bituminous materials are applied hot and in a liquid or viscous state. The ageing of bituminous materials is affected by sunlight, namely the ultraviolet range, low and high temperatures and sudden temperature changes.

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Engineered Materials Engineered traditional waterproofing materials are applied on-site in a hot state, either liquid or viscous. In flat roofs, bituminous emulsions are used as an impregnation product for porous substrates or as part of a multilayer waterproofing system applied on site, guided by part 7 of ETAG 005 (EOTA 2004b). Bituminous paints may be used as a primer, to treat the adhesion surface (substrate) of waterproofing bituminous systems, as well as a protection for those systems, when applied as the upper layer. Modified bituminous products are those with a bituminous base to which small amounts of additives are added, generally resins, with the objective of improving the products’ characteristics (Lopes 2010).

Prefabricated Materials Traditional prefabricated materials are bituminous meshes and membranes, with one or more layers of canvas, felt or sheet reinforcement involved in bituminous mixtures and with a lower and upper finish (Lopes 2010). Standard EN 13707:2013 (CEN 2013j) is focused on reinforced bitumen sheets for roof waterproofing.

2.10.1.2

Non-traditional Waterproofing Materials

Non-traditional waterproofing materials (Table 2.51) are those modified bituminous materials with a percentage of modifying elements equal to or above 7%, as well as non-bituminous materials used in the building sector. Bitumen-polymers, thermoplastic and elastomeric membranes are currently among the most used in flat roofs’ waterproofing systems. Polymeric resins are also commonly used, not only as waterproofing but also in the repair of these systems. The most used non-traditional waterproofing materials are highlighted next.

Emulsions and Solutions of Polymer-Modified Bitumen Emulsions of modified bitumen do not work as a waterproofing material by themselves, but rather as a primer to treat surfaces for the application of waterproofing membranes. This type of bituminous mixtures contains a considerable amount of dispersed-bitumen in an aqueous medium with one or more emulsifying agents and polymers. The emulsion may contain fine aggregates, fillers or fibres and it may be applied using a paint roller, paint brush or spray gun. Catalytic elements may also be added to the emulsion’s mixture if there is a need to speed up the curing process. In general, the type of elements used to modify the bituminous mixtures varies according to the required properties of the end-product, in order to improve the mixture’s characteristics (McNally 2011). Polymer-modified bitumen emulsions and solutions should comply with part 2 of ETAG 005 (EOTA 2004a).

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Table 2.51 Classification of non-traditional waterproofing materials (adapted from Lopes [2010]) Application

Class of materials

Classification

Type of materials

On-site

Liquid or viscous material

Emulsions and solutions

Emulsions and solutions of polymer-modified bitumen Water-dispersible polymers

Polymer-modified bitumen applied hot Polymeric resins

Unsaturated resilient polyester resins reinforced with fibreglass Unsaturated flexible polyester Polyurethane

Prefabricated

Membranes

Cementitious products

Mixture of polymeric resins and cement

Bitumen-polymers

APP bitumen-polymers

Thermoplastic

PVC incompatible with bitumen

SBS bitumen-polymers

PVC compatible with bitumen CPE (chlorinated polyethylene) FTO or TPO (flexible thermoplastic polyolefins) Elastomeric

Butyl rubber (isoprene-isobutylene) EPDM (ethylene-propylene-diene monomer) Chlorosulfonated polyethylene PIB (poly-isobutylene)

Polymeric Resins and Cementitious Products Polymeric resins are applied in a liquid or viscous state and are framed by the stipulations of part 8 of ETAG 005 (EOTA 2004c). They are composed of resin with fillers, solvents and pigments. The resins are usually applied in two consecutive layers to create the waterproofing system (Lopes 2010). If used, the polychloroprene resin is applied first to ensure watertightness. Next, if that is the case, a layer of chlorosulfonated polyethylene resin is applied. This second layer main purpose is

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to resist heat, solar radiation (ultraviolet range) and ensure colour stability. Another popular option is to use acrylic and polyester resins. In the case of unsaturated resilient polyester resins reinforced with fibreglass, part 3 of ETAG 005 (EOTA 2004d) should be followed while, in the case of unsaturated flexible polyester resins, part 4 of ETAG 005 (EOTA 2004e) should be followed. Acrylic and polyester resins products may also be used to repair waterproofing systems, besides being used in new flat roofs, with various accessibility options (vehicle circulation, for instance). The thickness of a polymeric resins’ waterproofing system is between 2 and 4 mm, usually corresponding to three layers, consuming around 1–1.5 kg/m2 . Cementitious products also include a mixture of polymeric resins with fillers and additives. They may be applied using a paint brush or a float trowel. Cementitious products, as well as polymeric resins, require great care at the execution stage to ensure a uniform thickness of the whole layer after drying. The curing time is also important, and application in regions with more frequent rainfall patterns should be planned ahead. It is good practice to use reinforcement within these systems. It is applied over the first layer of the waterproofing system while it is still fluid so that the reinforcement gets impregnated into the layer. The most commonly used reinforcement is non-woven polyester felt if the system uses polyester resins or modified bitumen. Reinforcement of woven polyamide, polyester or fibreglass may also be used in systems using polyurethane resins or acrylic emulsions (Lopes 2010). The use of polyurethane resins should follow the guidelines of Part 6 of ETAG 005 (EOTA 2004f). Cementitious products are generally reinforced with fibreglass mesh, but polyester felt may also be used. Polymeric resins have the advantage of being easily applied in singular points of the flat roof, as well as of being easily repaired. They may also be applied using bright colours, which reflect the sunlight better when compared with asphaltic membranes. It is also a product with good chemical resistance, which can be in permanent contact with seawater (Lopes 2010).

Membranes of Bitumen-Polymers Membranes of bitumen-polymers are made of a modified bituminous mixture, with direct distillation bitumen, polymers, mineral fillers and various additives. These membranes are obtained by covering one or two reinforcement meshes with a modified bituminous mixture incorporating plastomeric resin (atactic polypropylene polymers [APP] membranes) or elastomeric resin (styrene-butadiene-styrene [SBS] membranes) (European Union of Agrement 2001). Reinforcement meshes may be in polyester or fibreglass (Lopes 2010). According to Rodriguez et al. (1993), SBS membranes show better mechanical behaviour when submitted to low temperatures, while APP membranes show better mechanical behaviour when submitted to high temperatures.

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155

Both APP and SBS membranes are supplied in the form of rolls, usually 4 mm thick (±1 mm) with 3.0–5.0 kg/m2 . Rolls should be stored and transported vertically to avoid deformations. Generally, the waterproofing system using this type of membranes is composed of two membranes, and at least one of them is reinforced with a polyester felt. If the flat roof has limited access, the system may use only one membrane in the waterproofing layer. In fact, the prescription of any waterproofing system using membranes of bitumen-polymers is conditioned by the flat roof’s accessibility, as loads acting on the flat roof may affect the connection of the waterproofing system with the substrate (Lopes 2010). Membranes of bitumen-polymers are usually applied over a first coat of primer (bituminous emulsion) and then they are welded using a blowtorch or hot air. Membranes should be overlaid longitudinally with lap joints of about 10 cm and 15 cm in the transversal direction (Gonçalves et al. 2008; Lopes 2010). As for the environmental impact of this type of membranes, it should be highlighted that they do not contain tar, hence constituting common industrial residues.

Plasticised PVC Membranes Synthetic membranes of polyvinyl chloride (PVC), are among the most commonly used thermoplastic membranes. They are composed of monomeric plasticised PVC (PVC-P), plasticisers, pigments and fillers. Plasticisers provide the membrane with enough flexibility to be applied in roofing, or it would be too rigid (Griffin 1982). Still, the loss of plasticiser (due to volatility, solvents or water action) is one of the factors contributing to the membranes’ ageing (Foley et al. 2002), as well as the contact with bitumen or mineral oils. To decrease the loss of plasticisers, it is recommended to add polymers with high molecular weight to the PVC membranes (Gonçalves et al. 2005). PVC membranes may contain reinforcement meshes, usually in fibreglass or polyester. The reinforcement may decrease shrinkage due to the loss of plasticisers and help to stabilise dimensional variations due to temperature changes (Gonçalves et al. 2005). The PVC membranes’ flexibility and elasticity allow easy adaptation to various shapes of the substrate and ensure better durability, as they are associated with fewer defects resulting from expansion. Additionally, this type of membranes is very light; five times lighter than asphaltic solutions, for instance. The thickness of plasticised PVC membranes varies between 1.2 mm and 1.5 mm, with 1.6–2.0 kg/m2 (Lopes 2010). Waterproofing systems using plasticised PVC membranes only require a single layer. As rolls (1–2.1 m wide and 15–20 m long) are larger than those of bituminous membranes, for instance, the amount of lap joints is lower. Lap joints (about 40 mm wide) are welded with hot air equipment, working at about 620 °C, which is a faster and more efficient welding solution (Oba and Björk 1993). Furthermore, adhering membranes using solvents is also applicable (30 mm lap joints, approximately), as

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well as mechanical fastening (Foley et al. 2002), although the latter is more common over metallic bearing structures. Still, using mechanical fastening is limited to inaccessible flat roofs, or to those only accessible for maintenance purposes. Mechanical fastening must connect the waterproofing system to the substrate. Additionally, to mechanically fasten membranes, wind loads must be previously considered at the design stage (Miyauchi et al. 2011).

EPDM Membranes Elastomeric ethylene-propylene-diene monomer (EPDM) membranes result from mixing the EPDM with additives, like fillers, vulcanised agents and oils. This type of membranes may also be manufactured with reinforcement, most commonly in polyester and polyamide (Gonçalves et al. 2005; Lopes 2010). EPDM membranes are generally applied through full bonding (liquid adhesive), partial bonding (mechanical fastening), or loose laid. These membranes are stored in the format of rolls (15–40 m long, 1.35–1.5 m wide) and typically are 1.5 mm thick with 1.2–2.3 kg/m2 (Lopes 2010).

2.10.1.3

Auxiliary Materials for Waterproofing

As mentioned in Sect. 2.10.1.2, waterproofing materials may benefit from the incorporation of reinforcement meshes to improve their mechanical behaviour. Reinforcement may be classified, according to fibre orientation, in two categories: felt or canvas. In felts, fibres are interlaced without a preferential direction, while canvases are obtained through intertwining threads creating an orthogonal mesh. The most commonly used reinforcement of membranes is made of fibreglass or polyethylene. The former does not deteriorate, does not absorb water and has great dimensional stability, while the latter has high mechanical and high-temperature resistance (Beer et al. 2005; Lopes et al. 2011).

2.10.1.4

Thermal Insulation Layer

In a flat roof cladding system, the thermal insulation layer is characterised by its low thermal conductivity. The relative position of this layer to the waterproofing layer in a flat roof determines the type of thermal insulation material that may be used, as each one has different properties when in contact with water. The thermal insulation materials most commonly used in the building sector are (i) mineral (rock or glass) wool, (ii) expanded perlite (both of mineral origin), (iii) XPS or EPS (both synthetic), and (iv) poly-isocyanurate foam (also synthetic). A fifth option may be added to this list, particularly with a growing market in Mediterranean countries, namely ICB (of natural origin).

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Particularly in Europe, if an inverted flat roof solution (insulation layer over the waterproofing layer) is to be used, the thermal insulation material requires specific proprieties, such as (Schaefer 1977; Zirkelbach et al. 2013): • Not absorbing water in such a way that all thermal and mechanical characteristics are ensured (according to standard EN 12087:2013 (CEN 2013k)]); • Good resistance to freeze-thaw cycles (according to standard EN 12091:2013 [CEN 2013l]); • Good mechanical resistance to handling and to every load the material must withstand during its application; • Good resistance to high water vapour diffusion and very low water absorption through vapour diffusion; • Being non-putrescible. Thermal insulation made with mineral fibres, namely rock or glass wool, is very common in flat roofs. Rock wool is manufactured from volcanic rock and glass wool from sand fibres. Both products are sold as rolls or slabs, whose thickness varies between 20 and 120 mm. The slabs’ dimensions vary between 1.0–2.4 m long and 0.6–1.2 m wide (Lopes 2010). Slabs may be sold without any coating or with a bituminous membrane coating protected by a thermo-fused plastic film. Mineral thermal insulation materials are incombustible and have high resistance to chemical and biological agents, also showing good soundproofing performance. A vapour barrier may be used below this type of insulation, to avoid condensations inside the roof cladding system. The main technical characteristics of rock wool are shown in Table 2.52. Expanded perlite insulation is composed of about 60–70% perlite and cellulosic and glass fibres agglomerated by a bituminous binder. This type of insulation is sold as rigid plates that may be applied over bearing structures of concrete, wood or corrugated metal sheets, with dimensions similar to those of mineral insulation slabs. Expanded perlite insulation shows satisfactory compressive strength. However, dimensional variations due to thermal variations are higher than those of mineral insulation slabs (Lopes 2010). The main technical characteristics of expanded perlite are shown in Table 2.52. XPS and EPS are manufactured using thermoplastic resins and then sold as boards. These materials are adequate to be used in inverted flat roofs solutions (EPS only with high density), for their high mechanical and biological resistance, as well as high dimensional stability, null capillary absorption, good resistance to water absorption and to putrefaction. All these characteristics are important in inverted solutions due to the constant contact of the insulation material with water. Still, applying XPS or EPS in inverted solutions requires the additional application of heavy protection over the thermal insulation layer, as the insulation material is loose-laid. The heavy protection layer acts not only to ensure the positioning of the insulation boards but also to protect the system against solar radiation (Schaefer 1977). Alternatively, some paving slabs solutions already combine the thermal insulation material (XPS) with a layer of fibre reinforced mortar, integrating heavy protection and insulation in a single product. On the other hand, polystyrene thermal insulation materials may

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Table 2.52 Technical specifications of the most commonly used insulation materials in the building sector (adapted from Lopes [2010], ImperMachado [2014], DuPont [2019a], Fibrosom [2019], and Viero [2019]) Thermal insulation material Rock wool

Expanded perlite

XPS

EPS

Poly-isocyanurate foam

ICB

Thickness [mm]

Thermal resistance [m2 K/W]

Density [kg/m3 ]

Thermal conductivity [W/m K]

Fire reaction [EN 13501-1:2018 (2018a)]

60

1.55

25–300

0.038

Euroclass A1

80

2.10

100

2.60

60

1.20

15–180

0.041–0.050

Euroclass A2

80

1.60

100

2.00

30

0.85

30–55

0.034–0.036

Euroclass E

40

1.15

60

1.70 15–25

0.034–0.037

Euroclass E

30–38

0.023

Euroclass B

100–120

0.037–0.040

Euroclass E

30

0.80

140

3.9

240

6.7

30

1.30

40

1.70

60

2.60

40

1.00

60

1.50

80

2.00

also be applied in traditional flat roofs systems, although preferably in combination with an independent waterproofing system. In other words, the waterproofing system should not be applied with the use of heat, as, in those cases, polystyrene may fuse (Lopes 2010; British Board of Agrément 2013). The low density of XPS and EPS, associated with easy cutting, allows an easier and faster application when compared with mineral insulation materials. The boards generally are 1.2 m long by 0.6 m wide, with thicknesses ranging from 30 to 120 mm for XPS boards, and 30–300 mm for EPS boards. The main technical characteristics of XPS and EPS are shown in Table 2.52. Poly-isocyanurate foam boards have dimensional and mechanical characteristics similar to those of polystyrene boards. Still, poly-isocyanurate foam has great dimensional stability at high temperatures and excellent behaviour towards fire. These properties allow the application of a layer of synthetic or bituminous membranes using heat over the insulation layer (Lopes 2010; Polyisocyanurate Insulation Manufacturers Association 2018). The main technical characteristics of poly-isocyanurate foam are shown in Table 2.52.

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ICB result from cork, a natural and renewable raw material, whose extraction from trees is compatible with their life cycle. Besides good thermal insulation properties (Table 2.52), it is also frequently used as an acoustic insulation material. As ICB have high permeability to water vapour, when applied in flat roofs, it requires the additional application of a vapour barrier layer below the boards. Moreover, the behaviour of this material in the presence of water shows average values of capillary absorption, after 24 h, 3.5–7 times higher than those of rock wool or expanded polystyrene. In the case of absorption by immersion, values are even higher, namely 4.5–17 times higher (Lopes 2010; Gil 2015).

2.10.1.5

Design of Flat Roofs

Flat roofs are susceptible to the action of atmospheric agents (Potter 1991; CarreteroAyuso et al. 2019). So, the design of flat roofs must consider the satisfaction of strict functional requirements in view of adequate performance levels. These requirements are typically grouped in three fundamental classes, namely: safety, inhabitability and durability. Economic requirements may be added to the fundamental classes of requirements. Table 2.53 presents the main functional requirements a flat roof should comply with. During the design of flat roofs, and considering the mentioned economic and functional requirements, various options should be taken into account, namely bearing in mind: accessibility; the existence of a protection layer; type of waterproofing; the relative position of the thermal insulation and waterproofing layers; slope; and type of bearing structure. The available options in each of these scopes are listed in Table 2.54. As for accessibility concerns, an option is to make the flat roof non-accessible. This means there is limited access only for maintenance and repair personnel. If this is the case, special circulation areas, although temporary, should be considered, creating some pathways. The other options (accessible to people or vehicles) mean that the design should consider the actions that result from the access to the flat roof, paying special attention if it should be accessible to heavy vehicles. Special access refers to green roofs and roofs with industrial or other types of equipment. The protection layer of flat roofs is meant to protect the waterproofing or thermal insulation layer from mechanical, weather and chemical aggressive actions. If the flat roof does not have a protection layer, the upper layer, typically waterproofing, is exposed. Light protection refers to prefabricated or applied on-site protection. Many times, prefabricated light protection refers to self-protected membranes, using: fine sand, fine gravel, and shale lamellae, of mineral origin; aluminium sheet or copper sheet, of metallic origin; or plastic sheet, of organic origin. Light protection applied on site refers to fine gravel, aluminium and lime paints. As for heavy protection, which allows creating pathways, it is always applied on site. Still, it may be a rigid layer or a layer of loose material. That rigid layer may be a screed, tiles over a screed, or prefabricated plates of concrete, ceramic materials or wood. Typically, the layer of loose material results from the use of cobble or coarse gravel.

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Table 2.53 Functional and economic requirements of flat roofs (adapted from Lopes [2010]) Functional requirement class

Requirement category

Description

Safety requirements

Structural safety

Adequate dimensioning considering the combination of actions

Safety in case of fire

Choice of products with an adequate fire safety classification

Safety against regular use hazards

Taking into account: puncturing and accidental impacts actions, according to the accessibility conditions of the flat roof

Resistance of non-structural layers towards various actions

Taking into account: the aggressive actions of atmospheric agents and the variability of the indoor environmental conditions

Water and airtightness

Towards water, snow, dust and air

Thermal comfort

Comfort in the winter (thermal insulation and risk of condensations) and comfort in the summer (thermal insulation and sun protection)

Acoustic comfort

Protection against air and percussion sounds

Visual comfort

Natural lighting and adequate reflectiveness of the protection layer

Equipment and accessories positioning

Adequate position of various equipment and accessories that need to be placed on the roof

Appearance

Adequate indoors and outdoors’ appearance

Preservation of characteristics

Preservation of mechanical resistance properties, materials, and resistance towards regular use actions

Cleaning, maintenance and repair

Aequate cleaning, maintenance and repair conditions

Global costs limitations

Complying with the overall limit of costs of the building

Energy efficiency

Improving the building’s energy efficiency, hence reducing future energetic costs

Inhabitability requirements

Durability requirements

Economic requirements

2.10 Flat Roofs Table 2.54 Available options to consider at the design stage of a flat roof (adapted from Lopes [2010])

161 Scope

Options

Accessibility

Non-accessible Accessible to people Accessible to vehicles Special access

Protection layer

Without a protection layer With a light protection layer With a heavy protection layer

Type of waterproofing material

Traditional

Relative position of the thermal insulation layer

Thermal insulation below the waterproofing layer

Non-traditional

Thermal insulation above the waterproofing layer Slope

Class I Class II Class III Class IV

Type of bearing structure

Rigid Flexible

As for the type of waterproofing material, at the design stage, two main possibilities must be chosen: traditional or non-traditional materials. Both options may be applied on-site or prefabricated, and the details on these choices have already been discussed in Sects. 2.10.1.1 and 2.10.1.2. The thermal insulation layer may be placed, according to the position of the waterproofing layer, in two different areas. According to the thermal insulation position, the effect of thermal, mechanical and other types of actions affects the remaining layers of the flat roof system differently. The most common solution consists in applying the thermal insulation as an intermediate layer, as the substrate of the waterproofing layer. However, another solution is becoming more frequently used, which consists of applying the thermal insulation layer over the waterproofing. This solution is called an inverted flat roof (Schaefer 1977). The inverted solution has the advantage of protecting the waterproofing layer from the extreme temperatures that may affect a flat roof (Fig. 2.50). Still, a wise choice of materials, whether the type of waterproofing or thermal insulation, is paramount for the success of the traditional or inverted solutions. Flat roofs’ main characteristic is having a very low slope, close to horizontal. Still, the slope below which roofs may be considered flat varies from country to country, although with small differences. As for the minimal slope, some countries admit a null slope and others do not. In Portugal, for instance, the General Regulation for Urban Buildings (Government of Portugal 1951) establishes a minimum 1% slope

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b

Fig. 2.50 Comparison of the temperature profile (warm weather case) in (a) a traditional flat roof and in (b) an inverted flat roof (data from DuPont [2019b]). 1—protection layer; 2—waterproofing layer; 3—thermal insulation layer; 4—bearing structure

for flat roofs (even though 2% is often recommended). Still, categorising flat roofs according to slope values cannot be separated from the constituting layers of the roofing solution and its accessibility. For instance, the slope of accessible flat roofs should not go over a limit that would hinder the easy circulation of people. Additionally, roofs may be indirectly classified according to their slope, considering the ease of rainwater drainage and the possibility of applying specific types of protection. These are the UEAtc criteria, which defines the four roofing classes referred in Table 2.54 (European Union of Agrement 2001): • • • •

Class I: allows free standing water and possible use of heavy protection; Class II: allows free drainage of water and the possible use of heavy protection; Class III: allows free drainage of water, but not the use of heavy protection; Class IV: special laying techniques are required because of the slope.

As for the bearing structure, it may be rigid or flexible. These designations are attributed according to the relative deformations perpendicular to the roof surface (Chudley and Greeno 2005; Lopes 2010). Rigid structures may be further categorised in continuous and discontinuous structures. Rigid continuous structures include solid reinforced and prestressed concrete slabs and rigid discontinuous structures include precast reinforced or prestressed concrete boards and joists. The most usual types of flexible structures are corrugated metal sheets and wooden planks (Centre Scientifique et Technique du Bâtiment 2007).

2.10.2 Execution of Flat Roofs Considering all the specifics about flat roofs that have been mentioned in Sects. 2.10.1 and 2.10.2, some information may be added in the perspective of the execution of a flat roof. Starting with the bearing structure, and considering that the details of its execution are out of the scope of this book, it still should be highlighted that, during its

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service life, it is necessary to regularly assess the existence of deformations in the bearing structure. If they exist, they may originate the failure of overlaying layers and subsequent leakages (Potter 1991). The shaping layer is usually executed directly over the bearing structure, and it attributes a slope to the roof surface. This layer may be left out if the bearing structure already incorporates the desired slope. If executed with materials with insulating properties, the shaping layer may (totally or partially) replace the thermal insulation layer. If that is the case, the vapour-barrier should be placed between the bearing structure and the shaping layer, instead of being applied over the shaping layer (Glover 2009). The shaping layer is considered a significant overload of the flat roof, while not attributing additional resistance to the bearing structure. Hence, it should preferably be made with lightweight materials (cellular concrete or lightweight concrete with expanded clay, insulation cork or expanded polystyrene granules) (Schlumpf et al. 2013), allowing the correct performance of the whole flat roof system. The screed layer is used to smooth surfaces when the shaping layer or the bearing structure is too rough or uneven to receive the next layer (usually, the vapour-barrier). The vapour-barrier is placed below the thermal insulation layer and over the shaping or screed layer (depending on the case). It works as a way of avoiding vapour coming from indoors to condense on the (cold) surface of thermal insulation, which could decrease its performance. As mentioned, the thermal insulation layer may be applied between the shaping layer and the waterproofing layer (traditional solution) or over the waterproofing (inverted solution). In both cases, execution varies according to the chosen materials. The water vapour diffusion layer has the purpose of matching the pressure of the water vapour trapped between the waterproofing layer and its substrate (HoughtonEvans 2005). This water vapour should be released through adequate construction solutions like venting chimneys or adequate detailing towards emerging elements (Lopes 2011). Ultimately, the water vapour diffusion layer has the same purpose as the vapour barrier, which is preventing water vapour from getting to thermal insulation. However, if combined with construction details, it also allows the evaporation of water vapour without the occurrence of condensation (Richardson 2001). The waterproofing layer is responsible for the watertightness of the flat roof system. It may be laid over the thermal insulation layer or over the shaping layer, depending on the adopted solution (traditional or inverted, respectively). There are several techniques to apply the waterproofing layer, depending on the adopted solution and on the chosen material. Those techniques were approached in Sects. 2.10.1.1 and 2.10.1.2. The protection layer’s purpose is to preserve underlying layers protecting them from mechanical and environmental actions, ensuring the durability and performance of the waterproofing or thermal insulation layers. In some cases, namely when underlying elements are laid loose, the protection layer may also serve as ballast, avoiding the lifting of elements (like insulation boards) (Schaefer 1977; Dow 2019). Choosing the type of protection needs to take the accessibility of the roof and the type of waterproofing into account. Executing the protection layer requires special care

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to ensure the correct performance of the whole system (Potter 1991; Harrison et al. 2009). Additionally, in a flat roof system, a separation layer may be used, especially when a heavy protection layer is applied. In these cases, the separation layer intends to decrease interactions between the heavy protection layer and the underlying layer (usually waterproofing). Equally important for the performance of flat roofs, singular points of flat roofs require complementary waterproofing works, namely in expansion joints, tail-ends in emerging elements, parapet walls, rainwater hoppers, downpipes, doorsills, among others. The execution of construction detailing in singular points of flat roofs is decisive for the performance of the roof (Chudley and Greeno 2005). Additionally, the adequate dimensioning of the drainage system, including the slope value, is paramount to avoid defects through the service life of the flat roof (Lawson 2012). Ensuring watertightness in singular points essentially depends on applying waterproofing with great care, considering some specific preventative measures, such as (Kubal 2008): • Starting to apply waterproofing from singular points, then continuing to the current surface, beginning from areas with lower height; • All tail-ends should be completely adhesive, regardless of the type of connection used in the current surface; • Tail-ends should also be reinforced, ensuring a better resistance to pull out, slipping and cracking; • When using accessories and auxiliary products, it must be ensured that they are adequate and advised by the waterproofing manufacturer, thus contributing to the complete compatibility between used products. In the case of emerging elements (parapet walls, chimneys or doorsills), where the current surface meets the emerging element, it is important to design a detail that simultaneously ensures the watertightness of the waterproofing system and its durability, considering all potential aggressive agents. In parapet walls, the tail-end should be executed around the perimeter of the flat roof, considering a height of 10– 30 cm above the final level of the flat roof (Kubal 2008), although the tail-end may go up to 1 m high (or up to the coping level). Two types of tail-ends may be generally considered: a protected tail-end and an unprotected tail-end (Fig. 2.51). Unprotected tail-ends typically end sealed below metal flashings. Typically, protected tail-ends penetrate the parapet wall, below a layer of reinforced wall render. As for the tail-end detail below doorsills, special attention should be paid not only to the extent of waterproofing below the doorsill but also to the height of the doorsill. A minimum height of 15 cm (from the waterproofing level) is recommended for this type of tail-end. If such height is not possible to execute, then it is advised to prolong the waterproofing under the doorsill, protected with mortar, over which the doorsill element is applied (Centre Scientifique et Technique de la Construction 2016a). Figure 2.52 illustrates the adequate design of the tail-end below a doorsill.

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a

165

b

Fig. 2.51 Design details of tail-ends of waterproofing in parapet walls (general cases): a protected tail-end and b unprotected tail-end. 1—wall render; 2—brick masonry; 3—tail-end strip of APP modified bitumen membrane; 4—heavy protection layer; 5—separation layer; 6—APP modified bitumen waterproofing membrane; 7—primer (bituminous emulsion) or vapour-barrier (if necessary); 8—bearing structure; 9—sealant; 10—aluminium flashing profile; 11—tail-end strip of self-protected APP modified bitumen membrane

Fig. 2.52 Design detail of the adequate tail-end in doorsills (general case). 1—doorsill with a drip edge, laid on a bed of mortar; 2—metal flashing; 3—waterproofing layer; 4—pavers on paver pedestals; 5—thermal insulation (thickness in accordance with thermal regulations); 6—vapourbarrier; 7—shaping layer; 8—bearing structure; 9—thermal break to avoid a thermal bridge

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Fig. 2.53 Design detail of a coping in stone or precast concrete of a parapet wall

In the coping of parapet walls, watertightness should also be ensured. For that purpose, adequate coping elements should be used, namely self-protected waterproofing membranes, sheet metal copings, or prefabricated stone and concrete elements. Besides the material used, every coping should have a slight slope towards the flat roof (inward, not outwards) and a water drip in each edge (Fig. 2.53) (Lopes 2011). As for expansion joints, if they exist, they should have specific design detailing in order to avoid cracking in the waterproofing layer or detachments in areas of overlaid tail-ends. Expansion joints details vary according to the type of flat roof. In accessible flat roofs, the tail-end in expansion joints should not occur at the circulation level. Hence, the bearing structure (the slab) should be slightly lower in the area of the expansion joint. Another option is to create the tail-end elevated from the circulation level. Additionally, if there is a protection layer, and if it has joints, they should coincide with the expansion joints. Another good practice is to separate the waterproofing of the expansion joint’s tail-end from the surrounding surface so that both can move independently. Moreover, expansion joints should not be close to gutters or roof drains, and the shaping layer should be built so that water runs on the opposite direction from the expansion joint (Fig. 2.54). No sharp edges should remain in an expansion joint detail. Both sides of the expansion joint should be connected by a strip of membrane (wider than the joint itself) and neoprene cord, while the membrane from the current surface should be interrupted at both sides of the expansion joints (Fig. 2.54). Over the neoprene cord, a second strip of membrane is applied, adhesive only on each side (30 cm wide, minimum) (Centre Scientifique et Technique de la Construction 2016b; Departamento de Edifícios LNEC 2016). The general case for any singular point in a flat roof consists in applying a flexible cord at the lower edge to separate the waterproofing layer used in the current surface from the emerging element. Then, the top of the tail-end should be made through the strapping of the area, complemented with an appropriate sealant.

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Fig. 2.54 Design detail of an expansion joint in a flat roof (general case). 1—neoprene cord; 2—tailend strip of self-protected APP modified bitumen membrane; 3—tail-end strip of APP modified bitumen membrane; 4—heavy protection layer; 5—separation layer; 6—APP modified bitumen waterproofing membrane; 7—primer (bituminous emulsion) or vapour-barrier (if necessary); 8— shaping layer; 9—bearing structure

Furthermore, in the drainage system, it is important to avoid any kind of obstruction and connection flaws between the current surface and the drainage equipment. A roof drain, including a dome strainer, should always be used at the top of downpipes (Lawson 2012). Also at the top of downpipes, the shaping layer should be lower to face the thickening of the waterproofing layer in the area and connection elements should be used between the waterproofing system and the downpipe. In rainwater drainage areas, it is important to ensure that membranes are applied in an upwards direction, so that the slight step resulting from the overlaid joints of the membranes will not be exposed directly to the rainwater.

2.11 Concluding Remarks This chapter provides a general understanding of the technologies associated with claddings and building elements included in the proposed building inspection system. Reading this chapter does not dismiss reading more detailed references, although, according to the complexity of the analysed building elements, some sections have a reasonable level of detail. It is expected that, after reading this chapter, the subject of building pathology, approached in Chap. 3, is better informed, as well as the application of repair techniques (Chap. 5).

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Chapter 3

Pathology

Abstract The study of building pathology in a systemised way should privilege the development of classification lists. Defects and their probable causes are organised as diagnosis tools in the form of classification lists, providing a sound knowledge base to the surveyor. These lists should be easy to refer to, organising defects and their probable causes in a logical sequence. In the context of a global inspection system for the non-structural building envelope, the classification of defects is organised into four categories: defects of physical, chemical and mechanical nature, and other defects. As for probable causes of defects, five categories are devised: design errors; execution errors; mechanical actions; environmental actions; and use and maintenance errors. Using both lists, the relationship between each defect and each cause is determined according to the probable contribution of the causes to the occurrence of a defect. That relationship is identified in the correlation matrix between defects and probable causes. Furthermore, and considering that often defects occur in a sequence, defects are associated in an inter-defects correlation matrix, which is based on the defects–causes correlation matrix and provides the probability of occurrence of a defect when another occurs.

3.1 Proposed Methodology Considering the scope of building pathology, and any further established context, like a specific building element or material, objective classification lists are a determining tool for an inspection system, or for the organisation of information (CIB W86 1993). The importance of classification lists requires that some time is dedicated to this exercise, as a first step in creating an inspection system. It is essential to review the literature on building pathology in general and in the specific context of the study. This review should not only include previous approaches to defects and causes of defects in buildings, façades or building elements, but also information on building technology, as it provides essential guidelines to issues in construction and design that can be potential causes of failure. The literature review should be directed at identifying the common defects and how they are originated.

© Springer Nature Switzerland AG 2020 J. de Brito et al., Expert Knowledge-based Inspection Systems, https://doi.org/10.1007/978-3-030-42446-6_3

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In this process, two lists should be built, one for defects and one for their probable causes. There should be no confusion about what constitutes a defect or a cause. When the inspection system is to be used in a general inspection of a building, it is advantageous to analyse common defects and causes in specific building elements and materials. This approach results in separate comprehensive lists per element that lead to a complex inspection system, with occasional repetitions and a great level of detail. Such a system may not be ideal when the inspection is not focused on a specific building element, such as a ceramic tiles cladding. Hence, the separate lists should be merged into a single global list, adjusting the level of detail, eliminating repetitions and keeping it concise. This process implies combinations and divisions of defects or causes, so that the global list may be applied to any building element. Shorter lists are easier to read, but detail should not be neglected. It should be clear for a surveyor to which defect a visual observation should correspond to. After the extension of the lists of defects and causes is adjusted, they should be coherently organized. The organization criteria should make sense for the context of the classification and should improve the lists’ readability. It is common, and advisable, to organize causes in a chronological order; i.e. if an error may occur at an earlier stage of a building life cycle, like the design or the construction stages, then the creation of a group of causes named “design errors” may make sense. Finally, it is important to create a coding system for each list. A code may be useful to refer to defects or causes in some contexts. Codes are usually a combination of letters and digits that identify to which list the codes refer to. Additionally, they also usually identify the group to which a defect or a cause belong to (e.g. A-A1, A-B1, A-B2, Df7, Df8).

3.2 Classification of Defects Considering the multiplicity of building elements and materials used in the building envelope, a global inspection system should be focused on a coherent and consistent list of defects that could be applied to any building element. The list of defects for a global inspection system for the non-structural elements of the building envelope is defined in Table 3.1. The list is organised in four categories, namely: defects of physical nature; of chemical nature; of mechanical nature; and other defects. These categories refer to the implicit origin of the defect. Each category corresponds to a code composed of a capital A (for anomaly), a hyphen and a sequential capital letter (A, B, C and D). Within each category, a sequential number is attributed to each defect (A-A1, A-A2, A-B1, A-C1, A-D1, A-D2, and so on). Categories group the defects according to the type of aggressive actions that affect buildings, the latter being identified based on visual criteria easily applicable in fieldwork. Each defect should match a visually identifiable phenomenon. Therefore, the classification of defects cannot include, for instance, the identification of flaws in the thermal insulation or in the ventilation system, but only the visible effects caused by such flaws.

3.2 Classification of Defects

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Table 3.1 Classification of defects in a global inspection system for the building envelope Code

Denomination

A-A

Defects of physical nature

Code

Denomination

A-A1 A-A2

Leakage damp

A-A4

Colour changes

Surface moisture

A-A5

Spalling/peeling/exfoliation and pop-outs

A-A3

Dirt and accumulation of debris

A-A6

Cohesion loss/disaggregation and chalking

A-B

Defects of chemical nature

A-B1

Biodeterioration/biological growth

A-B4

Blistering/bulging

A-B2

Vegetation growth

A-B5

Corrosion on the current surface

A-B3

Efflorescence/cryptoflorescence and carbonation

A-B6

Corrosion in metallic fastening or tail-end elements

A-C

Defects of mechanical nature

A-C1

Mapped cracking

A-C7

Warpage, swelling, deformation and other flatness deficiencies

A-C2

Oriented cracking on the current surface

A-C8

Material gap/puncture

A-C3

Fracture or splintering on the current surface

A-C9

Detachment

A-C4

Cracking and/or splintering adjacent to joints/edges

A-C10

Loss of adhesion

A-C5

Wear or scaling of the finishing coat

A-C11

Bending and rupture of metallic fastening elements

A-C6

Scratches/grooves and deep wear

–

–

A-D

Other defects

A-D1

Flaws in tail-end elements

A-D9

Insufficient or excessive overlap of the claddings elements in roofs

A-D2

Misalignment of cladding elements

A-D10

Clearances/gaps in door and window frames

A-D3

Finishing defects/discontinuities in architectural concrete surfaces

A-D11

Absent or damaged hinges or locks in door and window frames

A-D4

Finishing colour flaws in painted façades

A-D12

Ponding/insufficient or excessive slope in roofs

A-D5

Finishing texture flaws in painted façades

A-D13

Inadequate operation of elements of the rainwater drainage system

A-D6

Degradation of the filling material of current joints

A-D14

Deficient capping adjacent to flat roofs

A-D7

Absence/loss of filling material in connecting elements or current joints

A-D15

Incorrect or deficient interventions in claddings of pitched roofs

A-D8

Inadequate operation of expansion joints in flat roofs

–

–

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3.2.1 Defects of Physical Nature The “defects of physical nature” (A-A) are related to matter, the physical states of substances and energy, without changing the chemical composition and properties of substances (Zumdahl and Zumdahl 2006). Although phenomena of physical nature are, sometimes, hard to dissociate from phenomena of chemical nature, in the buildings context, defects associated with moisture, staining, soiling, colour and disaggregation of claddings are considered defects of physical nature. Starting with humidity defects, leakage damp and surface moisture are considered. “Leakage damp” (AA1) refers to the development of stains (Fig. 3.1, part a), long-term or temporary, associated with the presence of water, rainwater or plumbing water (Hedlin 1979; Künzel and Zirkelbach 2008; Agence Qualité Construction [AQC] 2013a). In door and window frames, it also refers to the admission of water through the glazing. The defect “surface moisture” (A-A2) refers to the development of stains, longterm or temporary, associated with the presence of water on the cladding surface resulting from construction damp, rainwater, soil damp and condensation (i.e. droplets on the cladding surface, as a result of water vapour passing to the liquid state) (Powell and Robinson 1971; Hedlin 1979; Camuffo 2014; Junior and Carasek 2014). In door and window frames, condensation may occur inside multiple glazing (Fig. 3.1, part b), in the air gap (Song et al. 2007; AQC 2015). In a specialised inspection system referring only to door and window frames, defect A-A2 could be divided into two defects: one to identify condensation on the surface of glazing, and another to identify condensation inside multiple glazing (Santos et al. 2017). However, in view of creating a concise list of defects, and avoiding repetition, defect A-A2 includes a set of similar phenomena, varying according to the building’s element and the material in which they occur. “Dirt and accumulation of debris” (A-A3) refer to changes in the appearance of the cladding due to the accretion or deposition of leaves, animal remains, waste, stickers, paint, dirt (Fig. 3.1, part c), dust, soot or other foreign elements on claddings. In roofs, it may lead to the obstruction of the rainwater drainage system. Defect AA3 also corresponds to graffiti, i.e. unauthorised paintings, drawings or tags on the claddings’ surface using various types of paint, usually associated with vandalism,

Fig. 3.1 Examples of defects of physical nature: a A-A1 leakage damp; b A-A2 surface damp; c A-A3 dirt

3.2 Classification of Defects

191

excluding graffiti as an authorised form of artistic expression. Some authors (Amaro et al. 2013; Sá et al. 2014; Pires et al. 2015; Silva et al. 2017), in the context of specialised inspection systems, consider that graffiti is a defect per se, due to a higher level of detail in the identification of defects. However, the classification of defects in the context of a global inspection system does not allow that level of detail, thus combining more specific defects in a broader defect, such as A-A3. The defect “colour changes” (A-A4) refers to a coating with a heterogenous tone or brightness or with an altered original colour (e.g.: loss of pigmentation saturation or yellowing) (Gil et al. 2011). In pitched roofs with plastic claddings and PVC window frames, this defect is characterized by chemical reactions of oxidation (Asif et al. 2005; Berdahl et al. 2008). A-A4 may also refer to stains of orange ferrous colour due to corrosion in adjacent or subjacent metallic elements (Fig. 3.2, part a). “Spalling/peeling/exfoliation and pop-outs” (A-A5) refer to the detachment of small portions or layers of the cladding elements without originating the fracture through their whole thickness. A-A5 also corresponds to little craters on the surface of ceramic tiles, with concentric cracks and a white dot on the back. In painted façades, it refers to the spontaneous separation of limited areas of skin due to lack of adhesion to the substrate (Fig. 3.2, part b). In architectural concrete surfaces, A-A5 refers to the local fragmentation and detachment of the concrete cover layer, possibly exposing the reinforcement, particularly in prominent areas of the surface (CCAA T57 2006). The defect “cohesion loss/disaggregation and chalking” (A-A6) refers to the loss of mass or separation of the cladding constituents in granule, crystal or dust shape, with deposition on the surface, resulting from the degradation of one or more constituents. It may also correspond to the progressive disintegration of superficial layers of the cladding (Fig. 3.2, part c), with gradual loss of the agglutinative role of cement, if applicable, originating the separation of the constituent aggregates. In pitched roofs claddings, it is characterized by the deterioration and disaggregation of fibre-cement claddings (Taylor 1990; Zivica and Bajza 2001; Beddoe and Dorner 2005; Dias et al. 2008).

Fig. 3.2 Examples of defects of physical nature: a A-A4 colour changes; b A-A5 peeling; c AA6 disaggregation

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3.2.2 Defects of Chemical Nature “Defects of chemical nature” (A-B) are those related to interactions between substances that result in transformations of matter. These phenomena are frequently associated with phenomena of physical nature. In the context of building pathology, defects of chemical natural concern the development of living beings (plants, fungi or insects—biological nature), efflorescence and corrosion. “Biodeterioration/biological growth” (A-B1) accounts for the accumulation and development of microorganisms on the surface of claddings or in joints, in the presence of humidity, mild temperatures, adequate pH and lighting (Precast/Prestressed Concrete Institute 2007; Barreira and Freitas 2008). A superficial layer, generally thin, of biological nature and variable colour, usually greenish (Fig. 3.3, part a) or blackened is generated. It normally arises in corners, top areas and areas of water accumulation. In wood frames, A-B1 also corresponds to rotting or attack of xylophages, with changes in the material colour and texture. In the case of fungi, characteristic stains appear; in the case of woodworms or termites, small holes appear in the wood (Dinwoodie 2000; Bravery et al. 2003). A-B1 is a broad defect, which may arise in every building element or material used in the building envelope. The defect “vegetation growth” (A-B2) accounts for the accumulation and proliferation of plants (Fig. 3.3, part b), herbaceous or shrubs, which develop on the surface of claddings or in joints, in the presence of damp, having solar radiation as energy source (Flores-Colen et al. 2008; Sazedj et al. 2016). “Efflorescence/cryptoflorescence and carbonation” (A-B3) refer to usually whitish stains of variable extent and shape, at times with local deformation of mortars or paint coatings. A-B3 corresponds to the crystallization of salts on the surface (efflorescence) or inside the pores (cryptoflorescence) of the cladding or joint filling material. Water-soluble crystalline flakes are developed with a powdery appearance, as well as vitreous-like films hardly soluble in water or runoffs from cracks, as in Fig. 3.3 (part c) (Precast/Prestressed Concrete Institute 2007; Goldberg 2011). Cryptoflorescence may originate the loss of cohesion/disaggregation due to volume increase of crystallised salts. This defect accrues from the migration followed by evaporation of water containing soluble salts. Carbonation corresponds to the appearance of whitish non-soluble calcium carbonate salts incrustations on the cladding surface.

Fig. 3.3 Examples of defects of chemical nature: a A-B1 biological growth; b A-B2 vegetation growth; c A-B3 efflorescence

3.2 Classification of Defects

193

Fig. 3.4 Examples of defects of chemical nature: a A-B4 bulging; b A-B5 corrosion on the current surface; c A-B6 corrosion in metallic fastening

“Blistering/bulging” (A-B4) refers to the separation of a cladding layer from the substrate with small convex deformations on the surface, translating into the appearance of pleats, blisters or bulging (Fig. 3.4, part a). Blisters may be filled with air or water (Paroli and Booth 1997). In severe cases, it may be accompanied by cracks or detachment (Busching et al. 1978; Ransom 1987; Waldum 1993; Warseck 2003). “Corrosion on the current surface” (A-B5) is linked to changes in metallic elements involving the colour, runoffs, blisters, detachments, pricks and perforations (Korb and olson 1992; Porter 1994; Mattsson 2001). It is applicable to the main cladding elements and to frames (Fig. 3.4, part b). In turn, “corrosion in metallic fastening or tail-end elements” (A-B6) is specifically applicable to auxiliary elements of fastening (Fig. 3.4, part c) or tail-ends (Centro Tecnológico da Cerâmica e do Vidro [CTCV] 1998; Gómez and Gilles 2006).

3.2.3 Defects of Mechanical Nature “Defects of mechanical nature” (A-C) are related to the phenomena associated with movement, as well as with energy variations and loads that act on bodies. In the case of “mapped cracking” (A-C1) (Day 2006; ACI Committee 224 2007), a set of cracks without a well-defined orientation is formed on the current surface of the cladding, with a polygonal pattern, resembling a net or mesh (Fig. 3.5, part a). Mapped cracking does not separate cladding elements in pieces through their whole thickness, but it may compromise the cladding’s water tightness and durability. In architectural concrete surfaces, mapped cracking is also known as crazing As for defect “oriented cracking on the current surface” (A-C2) (Douglas and Ransom 2007; Bakri and Mydin 2014; Bonshor et al. 2016; Liisma et al. 2016), it corresponds to isolated cracks with variable dimensions on the cladding’s current surface that, generally, have a precise direction and slope (Fig. 3.5, part b). They may also present a mildly jagged/zigzag appearance, according to their origin. The cracks thickness may be significant and their depth is variable. “Fracture or splintering on the current surface” (A-C3) is the development of crevices in cladding elements with its separation into uneven parts, affecting the

194

3 Pathology

Fig. 3.5 Examples of defects of mechanical nature: a A-C1 mapped cracking; b A-C2 oriented cracking on the current surface; c A-C3 fracture on the current surface

whole thickness of the cladding (Fig. 3.5, part c), causing fragments or shard (CTCV 2018). A-C3 compromises water tightness and may be considered an extreme case of cracking. “Cracking and/or splintering adjacent to joints/edges” (A-C4) is a specific case of cracking. A-C4 refers to cracking, crushing or splintering of the cladding in singularities, as in expansion joints, borders (Fig. 3.6, part a) or fastening points. In these cases, cracks may have a considerable thickness and normally have a welldefined orientation. “Wear or scaling of the finishing coat” (A-C5) refers to irreversible changes on the surface of building elements due to peeling, wear or ageing of the coating (such as glazing, in tiles) (CTCV 2003). Hence, the surface of the cladding below the finishing coat becomes exposed (Fig. 3.6, part b). “Scratches/grooves and deep wear” (A-C6), in turn, refers to superficial lines or grooves, with wider or narrower depth, wear or ageing of the cladding layers, with mass loss, very common in floorings, but also occurring in walls, as in Fig. 3.6 (part c) (Neville 2011). Generally, these changes are caused by mechanical actions. “Warpage, swelling, deformation and other flatness deficiencies” (A-C7) refer to the appearance of convex or concave areas in claddings, with the irregular displacement of elements outside their own plan (Fig. 3.7, part a, illustrating a deformed door). This defect may correspond to the expansion or swelling of elements, dents and shrinkage (Emmons 1994; Douglas and Ransom 2007; Precast/Prestressed Concrete Institute 2007). In external thermal insulation composite systems (ETICS), equally

Fig. 3.6 Examples of defects of mechanical nature: a A-C4 splintering adjacent to edges; b AC5 scaling of the finishing coat; c A-C6 deep wear

3.2 Classification of Defects

195

Fig. 3.7 Examples of defects of mechanical nature: a A-C7 flatness deficiencies; b A-C8 material gap; c A-C9 detachment of the wall render

spaced horizontal lines may be visible as a result of uneven insulation plates. “Material gap/puncture” (A-C8) is the localized absence of cladding material (Fig. 3.7, part b), corresponding to holes due to piercing actions or to the partial separation and loss of pieces of the cladding elements, in current areas or in singularities (Madsen 2004). The defect “detachment” (A-C9) (Douglas and Ransom 2007; Camposinhos 2014; Gaspar et al. 2016) is the complete or partial separation of cladding elements from the substrate, possibly resulting from/in gaps on the current surface (Fig. 3.7, part c) or in singularities. Depending on the application area, detachment may cause the fall of elements. It was considered, in this classification list of defects, that detachment applies to wall renders and non-continuous claddings with an indirect fastening system. on the other hand, “loss of adhesion” (A-C10) is the adhesive rupture in the cladding-substrate interface (Fig. 3.8, part a), which may result from/in new gaps (Paroli and Booth 1997; Edis et al. 2014). In the context of the proposed classification list of defects, “A-C10 Loss of adhesion” only occurs in claddings that were fastened to the substrate using an adhesive system (e.g.: tiles). The defect “bending and rupture of metallic fastening elements” (A-C11) refers to deformations (Fig. 3.8, part b) and breakage of fastening elements, contributing

Fig. 3.8 Examples of defects of mechanical nature: a A-C10 loss of adhesion; b A-C11 bending of metallic fastening element

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3 Pathology

to the loss of water tightness of a roof or wall. It may also be associated with the inadequate distribution of fastening points.

3.2.4 Other Defects The group “other defects” (A-D) includes three types: (i) defects specific to a single type of building element or material; (ii) defects referring to a singularity of the cladding system/building element; and (iii) defects related with design and construction errors, i.e. which already existed at the start of the building’s service life, and that are associated with a poor quality control throughout the construction process. Although the third type may represent, for instance, a mechanical problem, it is distinguished from defects in groups A-A, A-B and A-C because those only occur in-service conditions. Following these classification criteria, “flaws in tail-end elements” (A-D1) refer to the poor design, use of inadequate materials and components, and works incorrectly executed (Fig. 3.9, part a), originating local degradation in tail-ends/singularities of the cladding system, which enable the accumulation or leakage of water in those areas (Madsen 2004; AQC 2013b; CTCV 2018). “Misalignment of cladding elements” (A-D2) refers to incorrect longitudinal and transversal fittings, resulting in rows of elements with clearly irregular alignments in pitched roofs, and translating into variable overlays from area to area. In natural stone claddings (Fig. 3.9, part b), A-D2 refers to the absence of linearity/variable dimensions in the joints of stone elements. As for defect “finishing defects/discontinuities in architectural concrete surfaces” (A-D3), it is a specific anomaly that corresponds to a set of errors resulting from the execution conditions of concrete surfaces (Emmons 1994; ACI Committee 309 1998; CCAA T57 2006; Vikan 2007; Figueroa and Palacio 2008). Bug-holes (Fig. 3.9, part c) are small cavities of irregular shape, similar to pores, which do not go over 15 mm of diameter, and, in more severe cases, can be 20 mm deep. Honeycombing corresponds to large cavities (above 20 mm), not necessarily but often spherical, with variable depth, arising when the space between aggregates is not totally filled with mortar. Fastening marks result from the need of interconnecting the formwork panels, and are considered defects when their shape

Fig. 3.9 Examples of other defects: a A-D1 flaws in tail-end elements; b A-D2 misalignment of cladding elements; c A-D3 finishing defects/discontinuities in architectural concrete surfaces

3.2 Classification of Defects

197

is different from the design or when disaggregation of concrete particles or small voids are detected in the fastening area. Dribbling is a discontinuity visible on the surface of architectural concrete, which manifests itself through slight linear protrusions (reliefs), due to the path taken by the flux of cement grout. Crusts correspond to the setting of mortar layers, frequently with a different colour, on the hardened concrete. Formwork incrustation refers to the adhesion of pieces of the formwork panels to the concrete surface. “Finishing colour flaws in painted façades” (A-D4) corresponds to a set of flaws associated with the application conditions of painting works (Talbert 2008). Lapping is characterized by visible joints between adjacent painted areas, resulting from the division of the surface during application. Bleeding is the diffusion of a coloured substance (pigments) through the coating layer, from the substrate, creating stains or colour changes (Fig. 3.10, part a). “Finishing texture flaws in painted façades” (A-D5) are also associated with the application conditions of painting works. Cratering is the appearance, in the coat, of small circular cavities that persist after the drying period (Schoff 1999). Sagging are local irregularities in the thickness of the paint coat, caused by the vertical or canted runoff of the painting product during the drying period. The heterogeneous texture is characterized by local texture irregularities in the painting coat (Fig. 3.10, part b). In the context of a specialised inspection system for painted façades, defects A-D4 and A-D5 could correspond to five different defects (lapping and bleeding, and cratering, sagging and heterogeneous texture, respectively) (Pires et al. 2015). However, as these defects are only applicable to painting works, and correspond to a low severity level, although visually unappealing, in the context of a global inspection system, they were merged into two defects, one corresponding to colour flaws and the other to texture flaws. “Degradation of the filling material of current joints” (A-D6) refers to flaws in the joints’ appearance, such as colour changes, staining (Fig. 3.10, part c) or powdery consistency of the filling material. In flat roofs, it may also refer to ageing or oxidation in overlay areas (Croce 2013). The “absence/loss of filling material in connecting elements or current joints” (A-D7) is characterized by the absence of mastics in pitched roofs, or joints’ filling material, in situations in which they would be required (Fig. 3.11, part a). For instance, connecting elements in metallic claddings of pitched

Fig. 3.10 Examples of other defects: a A-D4 finishing colour flaws in painted façades; b AD5 finishing texture flaws in painted façades; c A-D6 degradation of the filling material of current joints

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Fig. 3.11 Examples of other defects: a A-D7 loss of filling material in current joints; b A-D8 inadequate operation of expansion joints in flat roofs; c A-D9 insufficient overlap of the claddings elements in roofs

roofs requires the application of mastics. When filling materials are present, they may show cracks, erosion, dissolution, swelling or loss of adhesion. The defect “inadequate operation of expansion joints in flat roofs” (A-D8) refers to the absence of expansion joints, when needed, or to its poor design Fig. 3.11, part b). It may also refer to the wear, ageing or oxidation of the joints’ elements (Cullen 1965). “Insufficient or excessive overlap of the claddings elements in roofs” (A-D9) (CTCV 1998) corresponds to the opening of undesired joints between the cladding elements (Fig. 3.11, part c), compromising the water tightness of roofs. It may also correspond to the absence of overlay joints in flat roofs, or to their poor design and execution. “Clearances/gaps in door and window frames” (A-D10) is the defect that refers to an incorrect clearance between the frame and the span or between the frame and the leaf, i.e. between the finished masonry and the frame or between the fixed frame and the movable leaf, respectively. It may also refer to the opening of connection joints between frame elements (Fig. 3.12, part a) and to unevenness between movable adjacent frames (leaves) (Douglas and Ransom 2007). “Absent or damaged hinges or locks in door and window frames” (A-D11) refer to damaged or malfunctioning hinges or locks (Fig. 3.12, part b), as well as to missing hinges or locks. “Ponding/insufficient or excessive slope in roofs” (A-D12) corresponds to roofing slopes that do not follow the minimum (Fig. 3.12, part c) or maximum established values for each type of external cladding, considering that, when there is an excessive

Fig. 3.12 Examples of other defects: a A-D10 gaps in door and window frames; b A-D11 absent or damaged hinges or locks in door and window frames; c A-D12 ponding/insufficient slope in roofs

3.2 Classification of Defects

199

Fig. 3.13 Examples of other defects: a A-D13 inadequate operation of elements of the rainwater drainage system; b A-D14 deficient capping adjacent to flat roofs; c A-D15 incorrect or deficient interventions in claddings of pitched roofs

slope, there may not be an adequate fastening to the substrate elements (National Roofing Contractors Association 1989; Madsen 2004; Lawson 2012). “Inadequate operation of elements of the rainwater drainage system” (A-D13) includes the inexistence of downspouts or roof drains (in Fig. 3.13, part a, the drain dome strainer is loose), the poor design of downspouts (location, execution) and the absence or inadequate design of scuppers, secondary scuppers/overflow pipes or gutters. “Deficient capping adjacent to flat roofs” (A-D14) refers to the absence of capping (Fig. 3.13, part b) or to its incorrect design or execution, such as a capping with no slope or drip detail. “Incorrect or deficient interventions in claddings of pitched roofs” (A-D15) is the application of cladding elements with shape or dimension incompatible to the pre-existing elements, and the application of mortar (except in specific types of pitched roofs) and/or asphalt membranes, for instance, over the existing cladding in repair works (Fig. 3.13, part c).

3.3 Occurrence of Defects in Building Elements and Materials Pathological phenomena have different manifestations, according to the building element and the building material in which they are detected, even if some defects tend to occur in almost every type of element. Considering the global building inspection system of the building envelope, and the methodology applied in its development, a defects–building elements/materials matrix (Table 3.2) establishes the link between the classification of defects and the types of building elements and buildings materials included in the research. The lack of connections registered in such matrix will then match lines filled with zeros in the defects–causes, defects–diagnosis methods and defects–repair techniques correlation matrices, as well as lines and columns filled with zeros in the inter-defects correlation matrix. In the defects–building elements/materials correlation matrix, if a defect does not match a specific element/material, it may not mean that other defect classification processes would not match that defect with that element/material. It means that,

•

•

•

A-A4

A-A5

A-A6

Defects of Chemical nature

Defects of mechanical nature

A-B

A-C

•

A-C3

• •

•

A-C7

A-C6

•

•

•

•

•

•

•

•

•

Adhesive ceramic tiling

•

•

•

•

•

•

•

•

•

•

•

•

Flat roofs

A-C5

•

•

A-C2

A-C4

•

•

A-B6

A-C1

•

A-B5

A-B4

A-B3

•

•

A-A3

A-B2

•

A-A2

•

•

A-A1

Defects of physical nature

A-A

A-B1

External claddings of pitched roofs

Defects

•

•

•

•

•

•

•

•

•

•

•

•

•

•

Natural stone claddings

•

•

•

•

•

•

•

•

•

Door and window frames

•

•

•

•

•

•

•

•

•

•

•

•

Wall renders

Table 3.2 Defects–building elements/materials matrix in a global inspection system for the building envelope

•

•

•

•

•

•

•

•

•

•

•

ETICS

•

•

•

•

•

•

•

•

Painted façades

•

•

•

•

•

•

•

•

•

•

•

(continued)

Architectural concrete surfaces

200 3 Pathology

other defects

•

•

Wall renders

•

•

•

ETICS

Painted façades

•

•

A-D14

A-D15

•

•

A-D13

•

•

A-D12

A-D11

•

•

•

•

A-D10

•

•

A-D9

•

A-D7

A-D8

•

A-D6

• •

•

Door and window frames

A-D5 •

•

•

•

•

•

Natural stone claddings

•

•

•

Adhesive ceramic tiling

A-D4

•

•

A-D3

A-D2

•

A-C11

•

•

A-C10

A-D1

• •

•

•

A-C9

Flat roofs

A-C8

External claddings of pitched roofs

• Indicates that the defect is considered in the specific building element/material

A-D

Defects

Table 3.2 (continued)

•

Architectural concrete surfaces

3.3 Occurrence of Defects in Building Elements and Materials 201

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in the context of this global building inspection system, that relationship was not considered.

3.4 Classification of Probable Causes After a comprehensive collection of all causes of defects that may affect the several building elements and materials of the building envelope, successive association and dissociation iterations were made with the main goal of reaching a list of causes simultaneously broad and succinct. In the context of a global inspection system for non-structural elements of the building envelope, the list of probable causes is defined in Tables 3.3, 3.4, 3.5, 3.6, 3.7, and 3.8. This list is organised in five categories that follow a chronological order (Branco and de Brito 2004), according to the stages of the building life cycle in which they occur: design errors (design stage), execution errors (execution stage), mechanical actions, environmental actions and use and maintenance errors (use stage of the building). Each category is identified by a code composed of a capital C (for cause), a hyphen and a sequential capital letter (A, B, C, D and E). Within each category, each defect is attributed a sequential number (C-A1, C-A2, C-B1, C-C1, C-D1, C-D2, C-E1, and so on). Table 3.3 Classification of probable causes in the category “design errors” in a global inspection system for the building envelope Code

Denomination

C-A

Design errors

C-A1

Deficient design of the structure/support

C-A2

Deficient design/detailing of the slope

C-A3

Missing/incorrect design/detailing of the ventilation systems

C-A4

Missing/incorrect design/detailing of the thermal insulation system

C-A5

Missing/incorrect design/detailing of constitutive layers

C-A6

Deficient specification of layers’ thickness

C-A7

Missing/incorrect design/detailing of pathway accessories for maintenance access

C-A8

Specification of inadequate or incompatible materials, or missing specification

C-A9

Insufficient functional classification of the elements for the aggressiveness of the environment in window and door frames

C-A10

Deficient application of regulations and/or specifications

C-A11

Deficient design/detailing of tail-end areas

C-A12

Deficient design/detailing of protruding elements in flat roofs

C-A13

Missing/incorrect design/detailing of singularities

C-A14

Missing/incorrect design/detailing of mechanical reinforcement systems

C-A15

Deficient design/detailing of expansion joints (continued)

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Table 3.3 (continued) Code

Denomination

C-A16

Missing/incorrect design/detailing of the water drainage system

C-A17

Deficient design/detailing of overlaps

C-A18

Poorly designed or insufficient cladding joints

C-A19

Missing/incorrect prescription of the fastening system

C-A20

Deficient design/detailing of the area next to the ground

C-A21

Detailing inadequate to the substrate

C-A22

Deficient specification of the clearances between the span and the frame and between the frame and the leaf in window and door frames

C-A23

Insufficient or badly distributed locks in window and door frames

C-A24

Missing/incorrect prescription of the application method/construction process

C-A25

Missing/incorrect prescription of the environmental conditions for application or substrate conditions and preparation in painted surfaces

C-A26

Inadequate prescription of formwork or form-release agent in architectural concrete surfaces

C-A27

Deficient detailing of the reinforcement in architectural concrete surfaces

3.4.1 Design Errors The causes in the category “design errors” (C-A) are defined in Table 3.3. This category includes all the causes that may result in building defects and that could have been avoided at the building design stage, whether if considered in the design and detailing or in the prescription of materials and of their adequate application. “Missing/incorrect design/detailing of constitutive layers” (C-A5) is one of the common design errors. In roofs, it may refer to the absence of the water vapour barrier or thermal insulation, which may result in condensations in the winter (Lstiburek and Carmody 1991). Some authors (Douglas and Ransom 2007) argue that the arrangement of the roof’s building elements determines the probability of occurrence of condensations. The water vapour barrier should be placed below the thermal insulation so that it stops the water vapour from reaching the cold surfaces and forming condensations due to the thermal differences between the interior and exterior. As for the thermal insulation, it should be placed in the exterior layers of the roof, to increase the temperature of the layers that are in direct contact with the indoor water vapour, minimizing the risk of superficial condensations. The use of thermal insulation in roofs meets the need of decreasing the heat flux between the interior and the exterior, contributing to the improvement of the hygrothermal comfort and to a lower energy consumption. C-A5 may also refer to the absence of a separation layer between the protection layer and the waterproofing layer in flat roofs, which may result in cracks (Walter et al. 2005). In adhesive ceramic tiling, C-A5 may refer to the prescription of a single bedding instead of a double bedding, also known as “back-butter” the tiles. A double bedding may be advantageous, for instance, when the tiles area is larger than 50 cm2 . In these

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Table 3.4 Classification of probable causes in the category “execution errors” in a global inspection system for the building envelope (part 1 of 2) Code

Denomination

C-B

Execution errors

C-B1

Deficient compliance with the design project or tender specifications

C-B2

Use of inexperienced or poorly qualified/unspecialised labour

C-B3

Deficient application of the ventilation and thermal insulation elements

C-B4

Deficient application of layers

C-B5

Lack of precision in the execution of the lath or alignment of the external cladding elements in pitched roofs

C-B6

Incorrect handling of materials or use of inadequate tools

C-B7

Use of unprescribed, inadequate, incompatible, low quality, non-certified and/or non-approved materials

C-B8

Use of deficient materials due to the manufacturing process

C-B9

Deficient storage/transportation of materials

C-B10

Incorrect application of sealants

C-B11

Application under unfavourable/extreme weather conditions

C-B12

Missing/incorrect execution of tail-ends and associated protection elements

C-B13

Deficient execution of expansion joints in flat roofs

C-B14

Missing/incorrect execution/dimensioning of cladding joints

C-B15

Cladding laid continuously over substrate joints or over different substrate materials

C-B16

Deficiencies in the filling of joints

C-B17

Disregard for the cladding’s stereotomy

C-B18

Deficient execution of the water drainage system

C-B19

Deficient fastening

C-B20

Missing/incorrect execution of slope

C-B21

Disregard for the pauses between execution stages

C-B22

Application in dirty, chalky, irregular or damp and unprepared substrates

C-B23

Inadequate thickness of the bedding material

C-B24

Use of bedding material with high shrinkage or expansion

C-B25

Deficient application of the span frame, the glass or the window and door frames in general, or deficient levelling of the leaves

C-B26

Deficient finishing coat

C-B27

Disregard for the composition or recommendations of the manufacturer or of the prescription, or in the formulation of the product in general

C-B28

Insufficient supervision/quality control

C-B29

Inadequate thickness of the render

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Table 3.5 Classification of probable causes in the category “execution errors” in a global inspection system for the building envelope (part 2 of 2) Code

Denomination

C-B

Execution errors

C-B30

Deficient execution of joints between strengthening profiles and between insulation boards in ETICS

C-B31

Deficient treatment of singularities in ETICS

C-B32

Deficient overlap of reinforcement mesh in splices or of the finishing coat in ETICS

C-B33

Deficient execution of the finishing coat in ETICS

C-B34

Incorrect application of construction elements in ETICS

C-B35

Deficient casting/compaction/curing in architectural concrete surfaces

C-B36

Badly executed casting joint in architectural concrete surfaces

C-B37

Imprecise reinforcement positioning in architectural concrete surfaces

C-B38

Absent/deficiently applied form-release agent in architectural concrete surfaces

Table 3.6 Classification of probable causes in the category “mechanical actions” in a global inspection system for the building envelope Code

Denomination

C-C

Mechanical actions

C-C1

Deformation of the bearing structure/substrate

C-C2

Movements of structural nature of walls or foundations

C-C3

Movement of people or vehicles over the claddings

C-C4

Excessive loads on roofs and floorings

C-C5

Excessive vertical loads in wall claddings

C-C6

Impacts of heavy objects in result of inclement weather

C-C7

Intentional collisions/vandalism

C-C8

Accidental collisions with the cladding

C-C9

Stress concentration within the substrate

C-C10

Fragmentation of the substrate in expansion, peripheral or stone plate joints

C-C11

Vibrations

C-C12

Abrasion

cases, the adhesive material is spread both on the substrate and on the back of the tile. This method maximizes the contact area between the adhesive material and the back of the tile and allows the absorption of some flatness flaws of the substrate (Ezral et al. 2011). In ETICS, C-A5 may refer to a flawed interface between the system and other elements (corners and claddings transitioning areas) or to the absence of a primer coat, which may affect the adhesion of the finishing coat (Kvande et al. 2018). In painted surfaces, C-A5 may refer to the incorrect prescription of the paint scheme,

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Table 3.7 Classification of probable causes in the category of “environmental actions” in a global inspection system for the building envelope Code

Denomination

C-D

Environmental actions

C-D1

Wind

C-D2

Excessive, insufficient or differentiated solar radiation

C-D3

Chemical action of organic compounds or dirt

C-D4

Action of vegetation growth, fungi or mould

C-D5

Atmospheric contamination/pollution

C-D6

Accumulation of dust dirt or small solid particles

C-D7

Temperature

C-D8

Presence of rainwater or snow

C-D9

Wet-dry cycles

C-D10

Freeze-thaw cycles

C-D11

Action of water vapour or high relative humidity

C-D12

Dampening of the cladding system

C-D13

Natural ageing

C-D14

Thermal shock

C-D15

Action of chemical agents from the soil, cryptoflorescence and leaching

C-D16

Corrosion of fastening metallic elements and reinforcement

C-D17

Rising damp

C-D18

Erosion

C-D19

Alkali-silica reaction, sulphates or chlorides in architectural concrete surfaces

C-D20

Acids in architectural concrete surfaces

according to the intended purpose (e.g.: decoration, protection of the substrate or increasing durability). At the design stage, the paint scheme should be prescribed, including its constituents and formulation, the application method and the treatment of the substrate. The “specification of inadequate or incompatible materials, or missing specification” (C-A8) is also a common design error. In pitched roofs, an incorrect specification may lead to the corrosion of metallic claddings when incompatible metals stay in direct contact; for instance, steel or copper elements in contact with aluminium or zinc, originating bimetallic corrosion phenomena (Douglas and Ransom 2007). In flat roofs, the chemical incompatibility between substrate materials and waterproofing materials may originate the migration of components, like in some plasticised PVC membranes applied over insulation substrates or bituminous products. As a consequence, it may reduce the deformation capacity of waterproofing materials and easily cause cracking (Walter et al. 2005). In adhesive ceramic tiling, C-A8 may result, for instance, in the choice of cement grout or standard tile adhesive, without aggregates, to fill joints larger than 5 mm,

3.4 Classification of Probable Causes

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Table 3.8 Classification of probable causes in the category “use and maintenance errors” in a global inspection system for the building envelope Code

Denomination

C-E

Use and maintenance errors

C-E1

Inexistent or inadequate maintenance

C-E2

Missing/inadequate cleaning of debris

C-E3

Replacement of elements by others of different geometry or tonality in external claddings of pitched roofs

C-E4

Change of the originally planned use conditions

C-E5

Vandalism

C-E6

Insufficient ventilation

C-E7

overly premature use of the flooring in adhesive ceramic tiling

C-E8

Incorrect handling of the movable parts and locking mechanism in door and window frames

C-E9

Accidental actions inherent to the occupation, movement and normal use of users

C-E10

Equipment failure

C-E11

Perforation of the system/inadequate hole through a wall in ETICS

leading to cracking or loss of adhesion due to the high shrinkage and low elasticity of the material. In natural stone claddings, it is insufficient to choose the type of stone merely according to aesthetical criteria, as it may lead to solutions with limited durability due to inadequacy to use. At the design stage, the prescription of a stone cladding should include the size of the plates, their thickness and the stone characteristics, the detailed specification of the fastening system and the characteristics and size of the joints (Camposinhos 2014). An adequate choice of stone for a cladding should consider its future use, wear and the surrounding environment. In door and window frames, the inadequate choice of materials may lead to excessive deformations of the frame, as, for instance, the incorrect choice of a coating may lead to a higher vulnerability to degradation mechanisms. In ETICS, the choice of an insulation material with insufficient dimensional stability may cause the joints between insulation plates to become apparent or even to result in cracks in the coat layer (Mack 2014), if adequate measures are not put in place. It is also agreed that the choice of dark colours for the finishing layer of a façade surface may result in cracking. In ETICS, it is also common to associate C-A8 with the lack of corrosion protection in metallic elements (e.g. unprotected metallic profiles), causing oxidation stains. In painted surfaces, the incorrect prescription of products may indirectly lead to the occurrence of peeling, blistering, cracking, chalking, colour fading, dirt accumulation, microbial colonization, craters, sagging or heterogeneous texture, and may directly lead to the occurrence of lapping or bleeding (Pires et al. 2015). For instance, the choice of texture of a painted surface conditions its future accumulation of dirt, and is also associated with the type of paint and paint scheme. The cause “missing/incorrect design/detailing of singularities” (C-A13) is also frequently detected. In adhesive ceramic tiling, C-A13 may reflect the absence of

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reinforcement solutions of the bedding material (with a fibreglass mesh, for instance) in areas with stress concentration in the substrate, in order to decrease the stress transferred to the tiles. In natural stone claddings with an indirect fastening system, incorrect detailing may cause the rupture of stone plates in the fastening area and the bending or rupture of the fastening elements (Neto and de Brito 2011). In door and window frames, the incorrect detailing of the window sill or the absence of drips may cause leakages, for instance. The lack of capping is also a consequence of missing detailing and may lead to the occurrence of defects on the façade, as it is left unprotected from environmental actions. The absence or incorrect detailing of capping, flashings and drips may lead to the accumulation of dirt on the façade and to damp associated with water runoff (Fig. 3.14). In more severe cases, damp may then be associated with biological growth on the façade. The absence of flashings in ETICS’ parapet walls may also cause blisters. As in the classification of defects, in the classification of probable causes, the level of detail had to be adjusted to be integrated on a global inspection system, frequently merging similar causes that occur in different building elements or materials. However, some causes specific to a building element or material were kept isolated, given the potential severity of their effects. The cause “deficient detailing Fig. 3.14 Incorrect detailing of a window-sill in an ETICS façade

3.4 Classification of Probable Causes

209

of the reinforcement in architectural concrete surfaces” (C-A27) is an example, as it may result in the occurrence of spalling or honeycombs (Silva et al. 2017).

3.4.2 Execution Errors Tables 3.4 and 3.5 list the causes in the category “execution errors” (C-B). It refers to the problems that arise from a poor execution of the design. It includes issues related to a faulty quality control of materials, as well as with the use of inadequate tools. “Deficient compliance with the design project or tender specifications” (C-B1) is a common execution error, as a consequence of lack of communication between designers, contractors and manufacturers. In pitched roofs, it may lead to faulty tailends and to a slope too low or too steep (Garcez et al. 2012b). In door and window frames, C-B1 may cause deformations, open joints, misalignments and damaged or missing hinges and locks (Santos et al. 2017). In wall renders, C-B1 may be an indirect cause to a multitude of defects, including visual, humidity and mechanical defects. In painted surfaces, C-B1 may contribute to the occurrence of any defect. Even when the prescription is correct, if the tender specifications are not fulfilled, the rapid and pronounced appearance of defects is favoured. In architectural concrete surfaces, the non-compliance with the design project may lead to the occurrence of stains, efflorescence, cracking, disaggregation, spalling, flatness defects, honeycombs and fastening marks (Silva et al. 2017). The “use of inexperienced or poorly qualified/unspecialised labour” (C-B2) is also a common cause of defects associated with the execution stage. In roofs, it may result in faulty fastening and tail-ends, loose or detached cladding elements and in an inadequate slope. Additionally, in pitched roofs, C-B2 may cause faulty overlaps, sealants and repairs, condensation, significant deformation, misalignments, corrosion and cracking (Garcez et al. 2012b). In flat roofs, C-B2 may also cause creasing/bulging, inadequate expansion joints and overlapping joints, an inadequate drainage system and faulty capping (Conceição et al. 2017). In door and window frames, the use of inexperienced labour often results in a lack of care in handling materials or tools, causing various damages in frames, like burns due to sloppy welding, dents and distortions. In wall renders, unspecialised labour may be one of the causes of the occurrence of corrosion stains (as it may result indirectly in insufficient protection of metallic elements), dirt, damp, efflorescence/cryptoflorescence, carbonation, adhesion loss, crumbling and cracking (Sá et al. 2014). In painted surfaces, C-B2 is associated with the use of an inadequate application method, which may also cause cracking, as well as peeling, blistering, lapping, sagging, and a heterogeneous texture (Pires et al. 2015). In architectural concrete surfaces, most of the construction defects can be avoided with experienced labour. otherwise, defects such as flatness defects, honeycombs, fastening marks, cement paste runoff, crust and formwork incrustation tend to appear. Stains, bug holes and cracking may also be related to the use of inexperienced labour (Silva et al. 2017).

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Another common execution error is the “incorrect handling of materials or use of inadequate tools” (C-B6). In pitched roofs, this cause particularly affects metallic claddings, as it may result in the early appearance of corrosion associated with damages in the protection layer. The use of inadequate tools may also leave embedded particles of other types of metal or cause damages, which become the preferential points for the occurrence of bimetallic corrosion. In door and window frames, CB6 is often associated with broken glazing. In wall renders, this cause is mainly reflected in the use of unclean tools during construction, which is associated with the occurrence of efflorescence/cryptoflorescence (if the tools are contaminated with salts) and loss of adhesion/detachment (Sá et al. 2014). In painted surfaces, C-B6 may cause cracking, peeling, blistering, lapping, sagging, and a heterogeneous texture (Pires et al. 2015). In architectural concrete surfaces, the use of inadequate tools is mainly associated with the formwork, namely panels not properly clean, free of dust, demoulding agent residue and corrosion. Furthermore, formwork panels should not be deformed or wrapped due to previous use, which would compromise their performance (Kenney et al. 2008). The cause “use of unprescribed, inadequate, incompatible, low quality, noncertified and/or non-approved materials” (C-B7) includes the use of materials with manufacturing defects, which is a reflex of quality control issues at the construction site. In pitched roofs, corroded fasteners are often detected because they are not stainless (inadequate materials). It is also frequent to detect the use of inadequate materials in tail-ends, namely the excessive use of mortar and of asphaltic membranes. In adhesive ceramic tiling, the use of inadequate materials may cause detachments, crushed borders, scratches, efflorescence/cryptoflorescence, pop-outs, the degradation of joints, and the cracking or scaling of the tiles glazing (Silvestre and de Brito 2009). In natural stone claddings, cause C-B7 may be associated with the use of mortars with poorly washed sand (direct fastening system). Stains in stone plates may anticipate and indicate their forthcoming detachment, associated with the application of non-prescribed products which have constituents that may be absorbed by the plate, such as solvents of bituminous mastics that exist in joint filling materials. Cause C-B7 also includes the inadequate acceptance of materials with ruptures, gaps, scratches and burnishing and polishing damages. Additionally, the application of weakened or cracked stone plates increases the likelihood of being affected by environmental agents, such as damp. Those plates may also deteriorate faster, contributing to the rupture or mechanical instability of the cladding. In door and window frames, the use of inadequate or low-quality materials is highly associated with the detachment of sealing. It may also be associated with the degradation of the frame coating, as the material may not be adequate to the aggressive environmental actions to which the frames are subjected. In wall renders, cause C-B7 may refer to various faults. C-B7 may refer to the use of water or materials with soluble salts, causing efflorescence, or to the use of mortars or paint insufficiently permeable to water vapour, hence stopping the evaporation of water to the exterior, and favouring the occurrence of cryptoflorescence. C-B7 may also refer to the inadequate use of dark colours in external claddings, which may amplify the mortar susceptibility to cracking due to differential thermal variations.

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211

In ETICS, cause C-B7 may reflect the use of: an insulation material with insufficient dimensional stability; insulation plates with different thicknesses; metal elements without corrosion protection; and a finishing coat with insufficient water permeability or with a biocide with inadequate protection against micro-organisms. In architectural concrete surfaces, the use of inadequate materials may be associated with the presence of chlorides, namely concrete admixtures composed of chlorides, or with the use of beach sand in the construction process. The use of contaminated water or reactive aggregates is a direct cause of the occurrence of efflorescence (Silva et al. 2017). At first sight, the cause “application under unfavourable/extreme weather conditions” (C-B11) could be associated with environmental actions. However, the group of environmental actions, as well as mechanical actions and use and maintenance errors, refers to causes that occur during the use stage of the building and that are not related with the quality of execution. So, in this case, if the material is applied under unfavourable weather conditions, the issue is rushing the application of the material not waiting for the optimal conditions. Hence, cause C-B11 is an execution error. In flat roofs, blisters may occur in the waterproofing membrane if the moisture content of the substrate is not within specific limits, highlighting the importance of the weather conditions during the application process. While applying adhesive ceramic tiling, the solar radiation and the wind intensity should be taken into account for the drying process of the used materials. Excessive solar radiation and wind, as well as too high (>30 °C) or too low (35 °C) or cold weather (