Martin Rauch: Refined Earth: Construction & Design with Rammed Earth 9783955532741

Citation preview

Martin Rauch refined earth construction & design with rammed earth Otto Kapfinger, Marko Sauer (eds.)

Use the Earth! – Otto Kapfinger

6

Photo Series – Projects

14

Rammed Earth Flooring

51

The Rammed Earth Wall

65

An Aperture in the Wall

85

Slab and Roof

103

Material

116

Prefabrication

118

Knowledge Transfer

122

Building Regulations

124

Photo Series – Team

128

List of Works

152

Glossary

156

Biography

158

Colophon

160

Use the Earth! The Life and Work of Martin Rauch Otto Kapfinger This publication tells the success story of an unorthodox thinker whose – quite literally – down-to-earth approach led him to develop an eco-social stance shaped by genuine personal experience. Initially positioning himself as an “interesting” local outsider, he has gradually become a globally respected authority on ecologically advanced architecture whose ideas are much in demand. Martin Rauch presents three decades’ worth of regional – and increasingly international – achievements in this book. His approach to basic research has been conducted bottom-up, in every sense of the word. Employing continually enhanced applications tested across varied scales, this approach has led to the creation of a fund of knowledge that has now been made available to a broad audience, along with detailed plans and explanations. This publication is not merely a platform for Rauch to present a body of work that he was able to achieve in collaboration with such well-known designers as Roger Boltshauser, Olafur Eliasson, Herzog & de Meuron, Miller & Maranta, Hermann Kaufmann, Marte.Marte, Snøhetta, Matteo Thun, and Günther Vogt. “Refined Earth” is nothing less than a globally relevant educational compendium for contemporary planning and building with earthen materials.

Rauch did not discover earth building through architecture but rather

through his training and work in the late 1970s as a ceramicist, kiln builder, and sculptor. His penchant for applied craftsmanship, as well as for artistic autonomy in designing environments and ways of living characterized by an extreme economy of resources, was determined by his upbringing in the unpretentious, rural setting of Austria’s Vorarlberg region. He was also greatly affected by foreign influences: like some of his older siblings, he volunteered for a development organization in Africa for several months in 1980. This encounter with “primitive” cultural and building technologies, whose efficacy was evident in close-knit life cycles making optimal use of resources, was accompanied by an awareness of their brutal substitution with imported technologies from industrialized economies that were climatically and ecologically inferior, non-recyclable, and difficult to repair. In Africa, his artistic intuition took on a global perspective: his subjective urge to work with these “poor” artistic ur-materials found an objective, comprehensive context within which to operate. Rauch’s artisanal interest in working with clay grew into a desire to architecturally design with earth, with all its challenges and requirements. The moulding of tiles and kilns turned into a process of shaping and constructing on a large scale: transforming the earth into useful and habitable spaces. He submitted his thesis project in 1983 to Matteo Thun, director of the ceramics programme at the University of Applied Arts Vienna. Entitled “Lehm Ton Erde” (Loam Clay Earth), it described the modernization of rammed earth techniques as a form of autochthonous cultural technology, be it in Africa or Europe.

6  

Since that time, Rauch has followed a vision with universal significance that can be expressed in just a few sentences: _Building in such a way that a house can return to “nature” after a hundred years – without leaving behind any residues or contamination – and break down into its original material constituents _Building in harmony with natural life cycles and using the absolute minimum of grey energy in constructing, maintaining and dismantling architectures _Building with locally available and no-cost materials – using earth taken from the construction site that is as pure and pristine as possible _Advancing the idea of building with earth so that it is technically and logistically up to date, in the process empowering the majority of the world’s population to turn to this technique and use it to significantly improve their living conditions He has always had a particular interest in rammed earth techniques, a process by which the material is not clad with further materials or surface finishes. Once fabricated, non-plastered pisé façades express their character directly, a phenomenon that Rauch encountered in the vernacular, well-preserved outbuildings dating from the nineteenth century that he came across in France and Germany. The layered construction of the wall simultaneously weaves the ornament of its own appearance. The pure structure, colour, and haptic qualities of the material are preserved and heightened during the process of moulding and compacting. With a ceramicist’s sensitivity to the composition and physical-chemical conditions and effects of his material, Rauch set about rearticulating the language of pisé, adapting it to meet contemporary standards and once again exposing the full sensory potential of earthen building material, with technical advances and enhancements going hand in hand with formal complexity. He was thus able to avoid, for example, the need to compensate for certain deficiencies in traditional pisé techniques by adding cement, as this would diminish some of the essential qualities of earth building, such as its ease of recyclability, its breathability, or its minimal entropy. Instead, he sought to improve natural material mixtures, optimized the compaction process and the shape of the formwork, and introduced layers of reinforcement to systematically develop traditional techniques without abandoning their basic structural principles. Tools, procedures, and types of formwork were developed from scratch and then evaluated and refined; test walls were constructed and the practical experience gathered in the process was immediately fed into the next series of experiments.

Rauch made his first forays into building in 1982, in the form of small

projects for family members and friends who were open to experimentation, collaborating with local architects such as Robert Felber and Rudolf Wäger. The house in Schlins constructed for his elder brother Johannes – a farmer, master locksmith, and graduate of the Academy of Fine Arts Vienna, who had been involved for many years in development projects in Zambia, Uganda, and Tanzania – was the very first modern timber-and-earth construction in the Vorarlberg region. The Chapel of Reconciliation in Berlin-Mitte represents a clear turning point in his practice. In accordance with plans drawn up by the

7  

Berlin-based team of Peter Sassenroth and Rudolf Reitermann, a public space for reflection was gradually erected from 1999 to 2000 on the foundations of a church located in the former “death strip” that had been dynamited to make way for the Berlin Wall. The 7 m high oval of the chapel, with a floor and altar of rammed earth and capped with a timber roof, was the first new construction in Germany to utilize pisé techniques in hundreds of years and required its own building permit procedure. As there are no norms or building regulations for load-bearing rammed earth walls, permit offices and engineers found themselves in unexplored territory – one of several requirements was a sevenfold increase in the normal static safety factor! The external monitoring and scientific supervision that had also been stipulated was assumed by the Technical University of Berlin. After countless test procedures, test specimens, and a plethora of expert reports had been enlisted in a process lasting several years, this age-old, global building technique could finally be integrated into – and approved for – our technological age.

Martin Rauch may make fundamental demands when it comes to eco-

logical standards, but the constructional and artistic flair evident in all his built works does not evoke a sense of fundamentalism. After completing the high-profile chapel in Berlin and a large building for Basel Zoo, the threestorey house and atelier he designed for himself in Schlins, in collaboration with Roger Boltshauser, represented a new synthesis of all the experience he had accumulated up to that point. It was here that modern earth building was finally able to separate itself from naïve-ecological clichés and move towards a technical maturity and formal clarity that, even a few years previously, would have seemed unimaginable. From the foundations that extend up into the walls to the floors, slabs, staircase, and window and door openings, Rauch had control over every element – even down to the manifold use of tiles, the water basins, the form of the hearth, and the wall and floor finishes. Every detail of the three-storey building – a product of the teamwork with the congenial Roger Boltshauser – is uncompromisingly a part of his vision, emphasizing the full breadth of physical and aesthetic qualities, from the coarseness of the earth to the porcelain-like delicacy.

This building has garnered national and international awards, been

published worldwide, and opened the doors to further projects of greater dimensions. When I was able to step inside the building shortly before its completion in 2008, it was quite a shock – a positive kind of shock! I had been familiar with Martin’s work since 1996/97, when I began my research for the architecture guide for the Vorarlberg region. In 2001, we collaborated on the trilingual publication “Rammed Earth” for a leading specialist publishing house – this represented an initial large-scale summary of his agenda. But when I first witnessed this quantum leap in quality manifested by the house and atelier he had built for his family, I could only gape with amazement. From the exterior and on the ground floor, everything seemed familiar and as I would have anticipated. But on ascending to the main floor, a sensational shift occurred. Coming up from the coarse-grained, raw-earth atmosphere below, I emerged into ivory-coloured, gleaming rooms, alternating between the light-coloured, vibrant grey of the waxed rammed earth floors, the bright

8  

casein finish of the window apertures and sliding door panels, treated with linseed oil and wax, and the velvety, tactile earth plaster of the walls (which act as hypocausts) and ceilings. On the third floor, comprising the bedrooms, office, and bathrooms, this process of refinement was further elaborated to produce an alabaster-like effect in the earth. This is achieved in no small part by the raku technique applied to the fired floor and wall tiles, with their satin-sheened, light-and-dark ornament – developed by Martin’s wife, the ceramic artist Marta Rauch-Debevec, and his son Sebastian Rauch, who trained as a graphic designer. Rauch describes a central plank of his technical ethos as follows: “The envelope that surrounds us should be able to breathe and diffuse in the same way as our bodies. My buildings are therefore deliberately not encapsulated, sealed, or made smooth with synthetic or high-density, energy-intensive materials; rather, they are assembled and finished in raw form, like sushi – left uncooked! The entire building substance remains permeable, meaning that it is sufficiently resistant to the demands of usage and maintenance and minimally resistant to long-term degradation and the recycling process.” Roger Boltshauser adds, “The archaic, direct workmanship and clear architectural language resulted in a house that melds extremely well with the landscape. In many aspects, it represents a true broadening of the horizon. These principles ought to be the basis of a universal strategy for future architectural design.” This project is a concrete expression of an almost inconceivable possibility: the chance not only to offset the division of labour, knowledge, and material fortuity in architecture, a compartmentalization that dominates our hightech, specialized world, but also to do so using the lowest level of entropy imaginable to satisfy our requirements for building, dwelling, and living appropriately – providing a globally relevant paradigm in the process.

For more recent international projects with Herzog & de Meuron,

Snøhetta, and others, a new wave of innovation was both necessary and of vital importance – including the adaptation of manual rammed earth techniques to suit the demands of industrial-scale production, prefabrication, and the logistical requirements and cost calculations of complex, large-scale construction projects. Rauch developed his own machine to address this challenge – a robot that automatically feeds material into the formwork and compacts it mechanically. This system can be used to produce formwork lengths of 50–80 m in variable thicknesses. After removing this mould, the rammed course – one full length of the formwork – can be cut into elements of any size. This is primarily dependent on how the pieces can be transported and, in particular, on the load-bearing capacity of the crane, which is usually a maximum of five tons. This technique has proved its worth in the recent construction of the Ricola Kräuterzentrum in Laufen as well as the visitor centre at the Swiss Ornithological Institute.

Rauch has long served as a lecturer and has led workshops in Europe,

Asia, and Africa. Perhaps the most far-reaching fruits of his range of small and increasingly larger-scale built works are not so much the many beautiful single-family homes in the architecturally rich Vorarlberg region or the

9  

spectacular collaborations with internationally renowned architectural visionaries in various locations, but rather his consulting work for academic and prototype projects in South Africa – in the townships of Johannesburg – or in Bangladesh. Here his expertise has supported, and continues to support, people who are truly in need, helping them to construct their own simple, low-cost, climatically appropriate buildings by teaching effective techniques, thus promoting a sustainable alternative to exported methods of building, one that is not dependent on large-scale technologies and industry-compatible visions of “foreign aid”. In Bangladesh, a land undergoing enormous population expansion and with disastrous housing and living conditions, Rauch received the 2007 Aga Khan Award for Architecture and the 2008 World Architecture Community Award for technical consulting and support on school and housing projects developed together with architect Anna Heringer: “The big step forward was being able to show people how they can use the earth from the construction site to build low-cost twostorey structures themselves – without any additional technology – and create spaces that are of the highest quality climatically. We managed this via public workshops and using the structures that we built together as an example. As timber is rare in the region, we were forced to use concrete for the slabs in the end. But this is just a fraction of the amount that is utilized for new residential projects there. I have frequently attended conferences in the southern hemisphere, where the idea gets pushed that earth building can be improved with cement in order to better integrate it into established construction industry practices. The only problem is that, to earn a sack of cement, a labourer now has to work three times longer than he did ten years ago, because demand is so high. The really political aspect of pure earth building is that it can be implemented anywhere fully independently of lobbies, share prices, and industrial price controls, with simple craftsmanship being used to construct high-quality, ecologically appropriate buildings. In our part of the world, where labour is particularly expensive, manually crafted earth building is practically a luxury product. In countries where labour is readily available, for example, in Egypt, my house in Schlins would have been approximately 60 per cent cheaper and could even be a kind of standard dwelling! If we were to keep building all around the world in the same way we have in the industrialized nations, it would be an ecological catastrophe. Rethinking practices is just as difficult here as it is there, because there is no proper cost transparency in our construction industry. We only see a brief, and therefore distorted, moment in time: the associated environmental impact and the real secondary costs are not taken into consideration in the calculations.”

Since 2014, Rauch has communicated his knowledge and expertise at

one of the world’s leading technical universities. His guest professorship at the ETH Zurich, run in collaboration with Anna Heringer, lasts for two years. Furthermore, they both serve as honorary professors at the UNESCO Chair of Earthen Architecture. The chapters of “Refined Earth” loosely follow the classifications in Semper’s seminal text “The Four Elements of Architecture”: Floor – corresponds to

10  

Mound, Terrace; Wall – corresponds to Enclosure, Weaving; Slab – corresponds to Roof, supplemented by the category Opening.

However, Semper identified the Hearth, or tamed fire, as the first and

original “moral element of architecture” in order to categorize the other elements as “protecting negations”, or “defenders of the hearth’s flame against the three hostile elements of nature”.

It was precisely this sort of hearth element from Martin Rauch’s work-

shop that prompted my initiation into his philosophy of living and building. In 1997/98, I was working on the editing and layout of my architectural guide to Vorarlberg with Reinhard and Ruth Gassner out of their studio house in Schlins. The house designed by Rudolf Wäger was executed in timber framing, infilled with both bricks and rammed earth components; at its centre was a cubic heating-cooking-washing element of reddish-brown earth, which Rauch had constructed with a smoothed wax finish. In this, the first of many collaborations with Gassner – our book and exhibition projects spanned many years – we stood at the hearth several times a day drinking tea and coffee, sharing snacks, leafing through newspapers, drawing water, and since I was often allowed to spend the night in the lofted roof space above the studio, laying out my clothes in the evening. In short, it was the haven and social heart of the atelier, even more so because we would subconsciously touch the mottled red, earthen surfaces and the smooth, yet not rigidly sealed edges of this element countless times; pushed glasses across its surface; touched it with our hips and knees as we leaned against it; sensed its subtle warmth in winter when the oven was in use and noticed that, in summer, touching this material felt slightly cool, yet never extracted warmth from the hands, as a concrete, terrazzo, or stainless-steel surface, or even a sintered tile floor, certainly would. Many years previously, Gassner had himself described the experience of his tactile “aha” moment with rammed earth walls. In his atelier, through the exposure to the hearth, table, and bar elements that looked like marble but did not have its cold quality, I too gradually transformed from an initial sceptic into an advocate for Martin’s contemporary rammed earth artistry. Rauch always argues that a rammed earth wall retains a large portion of “living” water inside it and therefore corresponds, like no other material, not even wood, to the physiological qualities and needs of our physical beings – expressed in its regulation of room humidity, in its breathability, and in its haptic quality when touched or walked on. Earth floors, walls, and buildings have the most ideal, active resonance with the physiological systems of our physical (and psychological) senses. He also frequently discusses the term Erosion in the debate on earth building, turning it from a commonly accepted negative into an emphatic positive. On the one hand, open-pored materials are a prerequisite for recyclability and also provide the optimal correlation to human physiology; on the other, the surface erosion that exterior walls exposed to wind and rain are particularly prone to can indeed be well controlled by the tried and tested details he developed – and then, instead of the overtechnologized hermetic sealing pursued by current construction practices, a natural “calculated erosion” can be achieved.

11  

This leads us, in conclusion, towards another aspect, one which, in comparison to the energy-intensive artificiality of industrialized technologies, integrates this kind of contemporary earth building much more thoroughly into physical and chemical cycles of organic and inorganic nature. The quality of calculated erosion that is inherent to building with earth and represents one of its special qualities could also be termed “patinophilia”. Without going into further detail here, it is clear that earth buildings do not just age well and with dignity. In each and every condition, they can easily be repaired, so that “aging” does not actually describe an aesthetic category or any other stage of their life cycle – and all of this is diametrically opposed to the tendency of contemporary architecture to emulate the model of mechanized and high-tech production, with its high levels of energy expenditure and complex transformations of natural substances. Allegedly low-maintenance, their extrinsic brilliancy and “patinophobic” glamour means that these modern buildings cannot age but only fade into obsolescence. Building and designing with earth is – to put it succinctly – “low-tech + hightouch + high-performance.” The ethos and Eros of using and shaping are in perfect balance, in resonance with our nature, in particular, as well as with the larger Eros nature of the cosmos in general, whose influence actuates constant transformation. The reality of economic globalization, characterized by the ever-increasing monopolies controlled by the industrialized nations, perhaps argues against a concept that cultivates resources which are readily available at practically no cost (!). However, the technical, ecological, and aesthetic qualities of building with earth – presented in this volume and offered as a basis for emulation and universal advancement – speak for themselves. They substantiate the fact that there is an alternative, if we choose, as we must, to follow the call of an ancient dictum in more determined fashion: Civilization is the sustainable shaping of the earth into a figure that serves mankind.

Gottfried Semper · The Four Elements of Architecture and Other Writings, Cambridge, 1989. Udo Scheidemandel · Typologie des Patinophilen, unpublished dissertation for the Institute of History of Art, Building Archaeology and Restoration, TU Vienna, 1996 Otto Kapfinger · Martin Rauch: Rammed Earth | Lehm und Architektur | Terra Cruda, Basel, 2001

12  

Projects from 1998 to 2014 Photographed by Benedikt Redmann Spring/Summer 2015

13  

2013 – 2014_ Swiss Ornithological Institute, Sempach

2013 – 2014_ Swiss Ornithological Institute, Sempach

2012 – 2013_ Ricola Kräuterzentrum, Laufen

2012 – 2013_ Ricola Kräuterzentrum, Laufen

2011_ Single-Family House B.-S., Flims

2011_ Single-Family House B.-S., Flims

2010 – 2012_ Mezzana Agricultural College, Coldrerio

2010 – 2012_ Mezzana Agricultural College, Coldrerio

2009 – 2010_ Sil Plaz Cinema, Ilanz/Glion

2009 – 2010_ Sil Plaz Cinema, Ilanz/Glion

2005 – 2008_ House Rauch, Schlins

2005 – 2008_ House Rauch, Schlins

2005 – 2008_ House Rauch, Schlins

2001 _ Chapel of Rest at the Batschuns Cemetery, Zwischenwasser

2001 – 2002_ Sihlhölzli Sports Complex, Zurich

2001 – 2002_ Sihlhölzli Sports Complex, Zurich

1998 – 1999_ Etosha House at Basel Zoo

1998 – 1999_ Etosha House at Basel Zoo

Civilization is the sustainable shaping of the earth into a figure that serves mankind. Otto Kapfinger

50  

Rammed Earth Flooring Earthen floors have existed for as long as humans have been building. No other material bears such a direct relationship to the ground on which we walk and stand. A floor composed of rammed earth is natural, simple, and, as such, commonly found in cultures all around the world. With the most elementary means, a space can be created from a clod of earth: a place to live in, set apart from nature. The floor of one’s home carries the living traces of its history. Smooth and responsive to the senses, rammed earth has a distinctly tactile quality. Its irregular surface is not only visually appealing but also acts as a sensual stimulus to the feet. Such floors, which require daily maintenance, can still be found in certain rural areas. Each evening, they are mopped with water to regenerate their sensitive surface. While this type of floor is too rustic for contemporary tastes, the proximity to the earth retains its appeal – it is simply too inconvenient for people used to higher levels of comfort.

To bring the earthen floor into the twenty-first century, it was neces-

sary to refine its conception. Its surface, in particular, has become easy to care for and extremely durable in modern implementations: a layer of customdesigned carnauba hard wax stabilizes the loam and infuses the floor with the necessary level of resilience. The process of construction has also been further developed. In traditional rammed earth flooring systems, only the lowest layers contain coarse gravel, with a finer-grained composite at the top. This creates a homogeneous finished surface, but it is susceptible to mechanical stresses and strains. By contrast, modern earthen floors are filled with the same gravel mixture until just below the surface, and the quality of the earth mixture is the same as would be used for rammed earth walls (see Material, p. 116). This increases the floor’s ability to withstand the tests of time and wear. However, these advances do not change the fact that constructing a rammed earth floor requires both mastery and experience of the techniques involved, since every step in the design process must take into account the unique conditions of the particular situation. One must know the material and have the skill to use it effectively to be capable of cultivating the full beauty and longevity of an earthen floor. Earth-based flooring is labour intensive. It will occupy a craftsman for three to four weeks, because the construction work progresses in a series of staggered steps that are individually tailored to the job. Compared to standard flooring systems, this means higher costs; small floor areas tend to be more expensive, since they still involve the same complex preparation and the work requires the same sequence of steps. However, the effort is reflected in the result: each rammed earth floor is one of a kind – with an outstanding degree of warmth and comfort.

51  

1999 – 2000_ Chapel of Reconciliation, Berlin

52  

53  

The Chapel of Reconciliation in Berlin was built over the foundations of the former Protestant Church of Reconciliation, which was demolished by the German Democratic Republic government in 1985. An oval, in situ rammed earth wall surrounds the interior space of the church. The rammed earth floor was constructed in two layers directly on top of a 1 m thick base of compacted sand, preserving the remains of the former church below. The chapel is part of the Berlin Wall Memorial and hundreds of thousands of visitors have already walked across this floor.

54  

55  

Putting together the material is the first step in creating a rammed earth floor. As the primary ingredient is often soil extracted from local excavation sites, its specific constituents determine the overall framework and construction process of the floor. An earth building expert will examine locally available resources and then generate a material mixture of mineral granulate comprising approximately 30 to 40 per cent loam. This is the same ratio present in a rammed earth wall suitable for exterior conditions. The knowledge required to produce a rammed earth floor must be grounded in experience with the variations and characteristics of individual projects: the real challenge here is a contextual handling of the material, and the proportion, form, and size of the gravel aggregates all play an important role. In traditional ramming practices, the lowest layers are executed with a higher ratio of larger stones. A layer of fine-grained earth is laid above this; then, a final level with a uniform structure and minimal gravel content creates a homogeneous surface finish. In the ramming process, tools and tamping plates are used to stabilize the earth and make the floor able to withstand high static loads. The fine loam layer that forms the surface seals the gaps between the granules.

In traditional earth building, the floors are composed of three layers of differing densities: a fine-grained surface layer, covering a rougher-grained intermediate layer, with the coarsest layer at the bottom.

Since this top layer is not stabilized, it can only withstand a given amount of mechanical stress – but, nevertheless, the material has evident advantages. Moisture levels can be balanced and direct contact with the earth established. However, the wear and tear of everyday life leaves its mark on a traditional earthen floor: scratches show on the soft surface, as do scuffs and general abrasions. The sensitive material composition of these traditional floors means that daily care is a necessary part of maintaining them: a wet cloth will continue to evenly redistribute the smallest particles, smooth out damage, and regenerate the uppermost layer of the floor. A traditional rammed earth floor is durable and easy to make but relatively high-maintenance since it requires daily upkeep.

However, the special properties of a seamless earthen floor have re-

tained their appeal: its surfaces are pleasant to the touch and it can improve the performance of lightweight constructions, as it has the capacity to function as a heat-storing thermal mass. Its smooth finish – which can be achieved even over large floor areas – coupled with the artisanal and sensory qualities of the material, has an aesthetic expressiveness to which no other kind of flooring system can compare. It is the optimal complement to any timberframe or concrete building.

56  

However, the daily cycles of care are not part of what we expect of the floor of a modern living space. First and foremost, this means that changes have had to be made to the sensitive top layer of traditional earthen flooring; it also means that the floor’s archaic construction methods have needed to be adapted to meet the standards of a modern-day construction site. It can be laid floating, as part of a multilayered flooring system, and include footfall sound insulation and in-floor heating. Even the material mixture has had to evolve: to improve the durability of the floor, the structure is no longer graded from rough to fine but rather utilizes a uniform material mixture offering a consistent level of underlying stability up until the surface finish.

A contemporary rammed earth floor is constructed with a homogeneous material mixture. As a result of the vibrating compaction process, the stone content is aligned in relation to the surface.

Compression now occurs with a vibrating plate compactor: as a result, the upper layer of the floor gets more compressed and therefore smoother than the lower one, although the composition of the mixture remains the same throughout the whole section. The larger stone content left on the top layer in turn increases the overall strength of this homogeneous surface.

The surface of the floor has generally gained in significance, but the in-

crease in the number of steps required in this new process primarily affects earth building specialists (see overview on the following page). The small cavities manifesting on the top layer due to the use of rougher material, have to be evened out with slurry and buffed. The floor is then refined and given a custom finish. As with terrazzo, the polishing process unveils the stone content of the top layer: this possible treatment exhibits increased resistance and is therefore frequently employed in places exposed to high level of moisture. In the process of refining the surface, the number of shrinkage cracks can be regulated, which also allows the appearance of the floor to be modulated. In a final step, the floor is treated with a wax emulsion, then laminated with a layer of carnauba hard wax, and finally polished.

The increasing number of factors involved in the construction process

goes hand in hand with an increase in the demands on earth building craftsmen. The archaic floor of the rural era has evolved into a product that requires intricate knowledge and technical experience. Each floor is a custom construction that incorporates the particular constraints of material, function, and design. In it, earth building experts can express their proficiency and mastery of the process. No two earthen surfaces are the same – each rammed earth floor is a singular product whose character is determined by the material mixture, the degree of craftsmanship, and unique surface finishes.

57  

With rammed earth flooring, all the different factors play a crucial role: the substrate composition, the mixture of materials and their

Surface finish

moisture content, and the way the surface layer is completed. Each of these parameters contributes to a successful product; as a result, rammed earth floors are particularly challenging to make.

Rammed earth floor Footfall sound insulation

A modern and durable rammed earth floor is constructed according to the following steps: 1_ The substrate is slurried to create a stronger bond between the loam and the substrate. 2_ The naturally crumbly, earth-moist mixture is put in place and carefully distributed to form a layer whose depth is a third to a half greater than the finished floor will be. The end result should not be less than 10–12 cm. The harder the substrate, the thinner this layer can be, and the more uniformly and carefully this step of the process is executed, the more level the floor will be. 3_ The distributed, loose loam layer is pre-compacted with tamp shoes and then carefully rammed with a vibrating plate compactor. 4_ The surface is then slurried. To do this, the same material is vigorously stirred and then left to sit for several hours. The denser pieces sink and the slurry can be washed off. At this stage, the mixture should be allowed to settle overnight, after which the water that has risen to the top can be drained off. At the end of this process, the slurry is mixed with fine-grained sand before being distributed with a squeegee and scrubbed from the surface. 5_ After one day, the leathery surface is polished with the soft pad of a buffing machine and smoothed with quartz sand. In the process, the slurry is removed from the raised areas but remains in the recesses and holes, giving added solidity to the surface. This can be repeated as necessary. If a handoperated diamond surface grinder with a dust extractor is used instead of a soft-pad buffer, the stones at the surface get polished and are therefore much more visible in the finished product (a terrazzo effect). Individual blemishes can be retouched 6_ Depending on the thickness of the floor and weather conditions, it should be left to dry for two to three weeks. The floor can be traversed if it is covered with protective plates. At this point, the substructure has been installed, has dried, and is now ready for a surface treatment.

58  

Working with heavy equipment on the building site requires extreme care. Since the material has the same moisture content as natural earth, it can be installed in a timber-frame construction without any additional precautions. A rammed earth floor can be outfitted with in-floor heating – conduits are encased with a mixture of loam and sand to achieve the optimal degree of thermal transmission.

7_ The floor is cleaned, vacuumed, and soaked in casein primer. This should be allowed to dry for several hours. 8_A wax emulsion is then thinly and evenly distributed. It should also dry for several hours. 9_ The surface is polished and unsatisfactory spots retouched by hand. 10_ A second layer of wax is applied and polished. 11_ It is then coated with melted carnauba hard wax and immediately buffed by hand or with a machine. After a few hours drying time, it can be polished to a high gloss. The surface of a rammed earth floor can be finished differently depending on the client’s specifications. If a homogenous pattern is desired, the floor can be treated with fine-grained loam slurry and then squeegeed. The material fills any dips and gaps between the gravel stones, and the wax emulsion protects the surface and provides the finishing touch to the floor. A rammed earth floor’s aesthetic appeal is generated by the seamless, homogeneous surface formed by this process of craftsmanship. As such, the challenge lies in the creation of a uniform structure and colour across the entire surface area.

Since the gravel stones contained in the rammed earth are visible, its

homogeneity is enriched by a pattern. This can extend across the entire floor, if the entire surface is abraded and sanded back using a hand-operated buffing machine until the stones are revealed. However, the transition can also be smooth and only partially visible: individual groups of stones then appear seamlessly on the surface as part of the homogeneous mass. For this purpose, the floor is deliberately constructed with additional depth in these areas, before being rammed and then ground down to the same height as the adjacent floor. The smoothed stones stabilize the floor in places susceptible to moisture, such as terrace doors, entrances, and in the kitchen.

59  

Substrate Structure To construct a rammed earth floor, the substrate layer must be stable, pressure-resistant, and, most importantly, immovable, since it cannot cave in under the force of the vibrating plate compactor (see image on the previous page). With lightweight floor plate constructions and large spans, the vibration frequency and weight of the compactor must be taken into consideration. When in doubt, a structural engineer should be consulted regarding questionable spans – if necessary, the slab may need to be braced during the compacting process. Rammed earth floors can usually be installed directly on top of suitable footfall sound insulation, without an additional membrane or lining, since the crumbly, semi-dry loam material does not contribute to any significant extra moisture. In comparison, naturally moist rammed earth and wood both possess a relative humidity of approximately 18 per cent. The wax emulsion acts as a damp-proof membrane, slowing the process of water vapour exchange, and the carnauba wax brings this process almost to a halt.

If in-floor heating is incorporated into the construction, the heating con-

duits are typically embedded in a soft layer of mortar, made of half sand and half loam, immediately prior to installing the rammed earth floor. Through the compacting process, the pipes are pressed into the loam in order to improve heat transmission.

The floor can be insulated with a mixture of loam and crushed cork

material bonded with trass lime. This enhances the environmentally friendly properties of the loam, and the lime increases the compressive strength of the cork. As an alternative, a rammed earth floor can also be installed directly on The surface of a slurried floor is slightly

pressure-resistant fibreboard, cellular glass, or extruded polystyrene (XPS)

irregular and requires a higher tolerance

foam. The boards cannot have any cavities and should preferably be cemented

in terms of its overall flatness – however, the irregularities of the floor reflect its inherent haptic qualities. The ratio of

directly to the substrate layer, such that they are immovable, as described above.

visible stones to loam is approximately 1:4 (see illustration at top). A floor treated with the polishing process is more similar to terrazzo: the proportion of visible stones to loam is closer to 1:1 (see illustration at bottom).

60  

Surface finish 0.1 cm

Standard installation without in-floor heating

Rammed earth floor 10 cm Footfall sound insulation 2 cm Wooden or concrete subfloor

Installation with in-floor heating Surface finish 0.1 cm Rammed earth floor 10 cm Clay mortar Heating pipe Foil 0.1 cm Footfall sound insulation 2 cm Wooden or concrete subfloor

Surface finish 0.1 cm Rammed earth floor 10 cm XPS insulation 12 cm Wooden or concrete subfloor

Installation on insulation boards

61  

Loam-casein-straw mixture 1 cm Mesh 0.2 cm Loam-straw-sand-trass-lime mixture 3 cm Mesh 0.2 cm Heating pipe Loam-cork-trass-lime mixture 6 cm Wooden or concrete subfloor

Lightweight earth floor with casein surface coating

Casein-Stabilized Lightweight Floors If the weight of the floor is constrained by static concerns, a more lightweight construction ending with a layer of casein presents an alternative to the type of rammed earth floor previously described. The construction process is more complex here: various mixtures (cork–loam–trass lime, loam–straw– sand, loam–straw–casein) are used in alternation and these then interact with one another.

The topmost stabilizing layer consists of loam and casein, which is ex-

tremely hard and creates a high level of surface tension. Casein is extracted from milk proteins and is one of the strongest natural forms of glue; it has been in use for thousands of years. The construction is pervious to vapour diffusion and its haptic properties are comparable to those of a rammed earth floor, retaining the fundamental characteristics of loam. Wall Connections One of the distinctive features of a rammed earth floor is how it connects to the adjacent walls. Once the material has dried, the loam contracts and shrinks away from the wall. As a result, it is necessary to keep the floor from touching the wall during the construction process. It is enough to separate the elements with a strip of cardboard along the edge of the wall. Once the structure of the floor is completed, the cardboard can be removed or trimmed off and the floor will be permanently disconnected from the wall. There is no need to finish the connection with skirting boards, unless extra protection for the bottom of the wall is required or has been specified by the client.

62  

Seamless and Easy to Repair As noted with wall connections, shrinkage is part of the drying process in the floor, which causes thousands of micro-cracks to appear on the surface. Because of this, rammed earth floors do not require any further dilatation joints: they can be constructed in any size without any joints. Compared to a floor bonded with cement-based grout, loam is also relatively soft and elastic. Because of this, thermally contingent tensions in the material can be absorbed and reduced.

As with a timber construction, the greatest risk for a rammed earth

floor is standing water; however, this usually only damages the uppermost layer and the loam can easily be repaired. Spot damage can be tamped with a wooden block during the drying process. Afterwards, it must be recoated with the wax emulsion and the final wax layer and then repolished. For this reason, it is important to keep several sacks of the original mixture. This stock of material can be used to repair the floor even decades later without any visible colour differences. Stairs It also possible to fabricate small staircases or individual steps for indoor spaces with rammed earth. The flooring can run seamlessly across multiple levels without any joints. The construction of a staircase is similar to that of a wall: the stairs are compacted on top of a rough-grained gravel fill layer in two rammed courses per step. Particular attention is required for the edge of the stair, because it is subject to increased stress. An edge made of rammed earth would tend to suffer wear and tear over time and break off. To improve stability, the edges are instead fabricated with a trass-lime wedge; its flat edge is stamped into the earth during the compaction process. This material, which is also used to slow down erosion in the walls, has a stronger edge stability than rammed earth (see The Rammed Earth Wall, p. 65). The colour and structure of trass lime is similar to that of earth. As it is built simultaneously, interlocking into the loam, the edge does not stand out compared to the rest of the staircase. The surface can be finished using the same process as for the flooring.

Trass-lime mortar Staircase construction with rammed earth Section at 1:10 scale

Rammed earth

Filling

63  

The quality of calculated erosion that is inherent to building with earth and represents one of its special qualities could also be termed “patinophilia”. Otto Kapfinger

64  

The Rammed Earth Wall The characteristics of rammed earth are expressed most clearly in walls. Through the ramming and compacting of the material, an element is constructed that is capable of withstanding the influences of both time and weather. At the same time, this earth remains part of the natural cycle: if the wall is exposed to the elements, over the years rain will gradually wear away at the façade. Rammed earth will ultimately return without a trace to the soil from whence it came. Even an appropriately protected wall will eventually change: rain softens the surface, as the water washes away the finer clay granules. The colour of the wall will also alter with time, as loam is rinsed away and the stones begin to emerge. The integration of erosion checks made of trasslime or fired clay helps to control the loss of material.

The challenge in building an earthen wall lies in precisely foreseeing

this balance between ephemerality and permanence, and envisaging all the possible ramifications. And this also constitutes the special allure of earth construction. All these aspects are interrelated; for example, if the rammed earth were stabilized and not water soluble, it would be incapable of absorbing water vapour, which is the source of the pleasant indoor climate it can create. Without the rain eroding fine-grained material from the surface, the resulting patina, which gives the material its vibrant, tactile structure, would not exist. Over time, a balance between durability and transformation occurs naturally. While erosion never completely comes to a halt, the loam becomes harder and the stones in the eroded wall serve to stabilize it – as such, it is unnecessary to further weatherproof the façade with cement or other artificial aggregates. On the contrary, additives can significantly impede the positive natural qualities of earth – for example, its ability to be completely recycled (see section on Calculated Erosion, p. 70).

Nevertheless, there are several basic rules to follow with regard to

weatherproofing. The wall must be capped to protect it from standing water and seepage. Traditional buildings made of rammed earth cover the walls with a projecting roof. For constructions with a flat roof or with free-standing walls, coverings made of sheet metal or similar waterproof materials are appropriate. Since splash and rising damp also affect the wall, the plinths should be water resistant.

Constructing an in situ rammed earth wall requires a significant amount

of time, as the compaction process is labour intensive. In order to coordinate with the strict schedules of modern-day building sites – or if no other method is possible – large-scale earth construction projects are carried out with prefabricated elements. Construction cranes are used to install these rammed earth blocks; afterwards, the faces are grouted and the joints retouched. The horizontal striation of the earth and bands of trass-lime are meticulously finished off by hand until the visual appearance is homogeneous. Even if individual joints are still visible at first, the erosive effects of driving rain will soon create a uniform surface.

65  

2001_ Chapel of Rest at the Batschuns Cemetery , Zwischenwasser

66  

67  

The Chapel of Rest at the Batschuns cemetery. The walls of the chapel arise out of the perimeter walls, providing a space to lay out the deceased before their interment. This small building, whose earth structure was created in situ, brings together the main elements of a rammed earth construction in a confined and precisely determined space.

69  

Calculated Erosion and Erosion Checks Photos (facing page): The façade of the

Due to its water solubility, the surface of a rammed earth wall must be pro-

Rauch House exposed to the weather,

tected from erosion. This form of abrasion occurs whenever water flows

just after completion in 2008 (above) and again in 2010 (below), after two years of erosion.

down the wall. If water on the façade runs off too quickly, it will sweep away particles of the material; if it runs off more slowly, then that much more loam will remain. Rammed earth walls should thus include erosion checks in order to slow the velocity of water flow across their surfaces. These horizontal layers can consist of stones and fired clay elements that protrude from the façade, or else of trass-lime mortar courses that run flush with the wall plane. They have the same effect in any form of construction: the water flow decelerates and, with it, erosion.

The material itself naturally inhibits erosion: after the first few years,

the outermost loam layer will have been washed away and more stone will be exposed, making the wall surface rougher. As such, it contains its own mechanism protecting it from erosion, since the uncovered gravel stabilizes the wall. The earthen seams in between the stones are now recessed deeper into the façade and expand when exposed to rain. This swelling process ensures that water does not penetrate further into the wall, the cumulative effect of which is to halt erosion. Since it can be predicted and controlled by checks, this process is referred to as calculated erosion. It must be integrated into the design and technical planning. This also means that a rammed earth wall requires several years before it reveals its finished surface: the windward side of a building will be far more eroded by driving rain than will the leeward aspects.

A rammed earth wall changes its appearance with the course of time: its texture becomes rougher. The illustration to the left shows a wall just after completion; on the right is the same wall revealing the stones that have emerged after the fine-grained loam has been washed off.

70  

71  

Multiple variations of horizontal patterning characterize a rammed earth wall. On the one hand, there are the vestiges of handcrafted production, expressed in individual layers, some 10 cm thick. This delineation is extremely subtle: loose material is deposited into the formwork and compressed to approximately half of the original depth with air rammers, vibrating plate compactors, or the rollers commonly used in civil engineering. The upper portion of each layer is more strongly compacted than its lower counterpart; this means that the lower segment of each course has a more porous appearance, while the upper segment has a more homogeneous and solid surface. This is the inherent rhythm of a rammed earth wall: an alternating pattern of layers of different thicknesses. It is the structure – as well as the ornamentation – that emerges from the process of production and this is the distinguishing feature of an earth wall. The sensory appearance of rammed earth is closely related to this effect.

Another beat in this rhythm comes in the form of the erosion checks,

which slow the flow of water across the surface of the wall. They are integrated at staggered heights approximately every 40 to 60 cm. If they consist of bands of tiles made from fired clay elements, they will protrude from the plane of the façade, their presence accentuated by the shadow they cast. These are influential in defining the final appearance of the wall, dividing it into separate horizontal stripes. There are a multitude of design possibilities for erosion checks: they can be composed of stones, of precisely formed bricks or tiles, or of fragmented materials. To create a lively pattern on the underside of the bricks, they can be scored longitudinally and broken in two. Alternatively, they can be completely handmade, as was the case for the Rauch House in Schlins (see images on p. 71). This creates a soft line that undulates along with the surface of the wall. Erosion checks made of trass-lime mortar have a far more subtle appearance, as they are integrated flush to the wall. Every four to six layers, a wedgeshaped strip on the exterior surface is included in the ramming course. The trass-lime is usually greyer than the earth and appears as a fine line that is Erosion check created by protruding ceramic tiles. An additional form board compensates for the overhang. Section of the formwork at 1:10 scale.

72  

0.5

1

2

In order to control erosion, barriers are integrated to decrease the flow of water. The illustrations above show an erosion check made of trass-lime mortar in a progressive state of erosion. Section at 1:10 scale.

initially flush with the wall after the form boards have been removed. As the outermost layer of earth is gradually eroded by the rain, these bands begin to protrude somewhat from the wall. The earth directly below them is preserved, while the fine-grained loam above is washed off. A wall with erosion checks made from trass-lime mortar will change differently from one with protruding elements. Rammed trass-lime-based checks are more appropriate for prefabricated elements, because they are both easier to produce and less complicated to transport. Protruding erosion checks possess significant design and functional poten-

2

40

tial. These courses stand approximately 2 cm proud of the surface and must be compensated for by means of an insert of the same width fitted into the formwork.

The wall is first rammed up to the bottom edge of the erosion check.

Then the brick or stone layer is inserted and covered with clay mortar; this ensures the durability of the joint and helps distribute the load it must withstand during the ramming process. Afterwards, an additional board is screwed on to the inner edge of the formwork to compensate for the increased width, and the next layers of earth are rammed. There is still space to insert the erosion checks between the boards, sticking out from the actual width of the rammed earth wall. This technique involves simple, though slightly more elaborate, formwork, which is better suited for walls produced on-site. Selecting the type of erosion check has a strong influence on the character of the wall. This is not only true for its initial appearance; the technique used for this layer has a lasting influence on how the wall evolves over a period of years. Both approaches are possible with in situ construction as well as prefabrication – only limited by the fact that protruding erosion brakes present an increased challenge in prefabricated elements (see Prefabrication, p. 118).

73  

If rammed earth walls are built in situ, complex formwork systems are required. In contrast to concrete constructions, the form boards are not set storey by storey; the earth must be compacted with a pneumatic jackhammer – and this can only happen up to a certain formwork height. Each course is completed in large segments, layer by layer, as the building gradually grows higher.

74  

Ramming Walls On-Site Walls constructed in situ with rammed earth are made with formwork. Similar to concrete constructions, the negative form of the wall is created with steel or wooden moulds and then filled with earth. However, there is a fundamental difference between the two: with concrete, these segments are prepared at the full height of one storey of the building, filled, and then reattached to the sides to execute a new storey. With rammed earth, the process can also be segmented, but it is important to retain as much continuous horizontal striation as possible. This is because the earthen mixture is poured into the form in an earth-moist state and then stamped. The building increases in height layer by layer. As a result, the overall height of the formwork is limited; at a width of only 35 or 45 cm, a full-storey structure would allow no space for ramming technicians and equipment. On each storey, the wall terminates in a reinforced ring beam designed to distribute horizontal loads into the walls and to improve vertical load distribution. This is poured into a groove recessed into the top of the wall. Continuous reinforcement is laid throughout the wall construction and then sealed with trass-lime mortar or concrete.

The quality of the wall is verified with test specimens, which are used

to determine basic structural values in a standardized process (see Building Regulations, p. 124). These properties are not just a direct consequence of the material mixture but are also a result of the construction process as well as the manner in which the mixture is rammed. This is yet another instance where the expertise of a trained professional cannot be supplanted by a standard formula or process.

If the technique of continuous horizontal layering mentioned above

has been adhered to during the construction of the segments, the wall will typically require very little retouching when the formwork is removed, and the appearance will coincide seamlessly with the method of construction. This is the archaic essence of in situ earth walls: the result is identical with the means of fabrication. On the other hand, successfully creating walls on-site is associated with high levels of experience and skill: thus, in principle, it is possible to determine many of the construction details on the site itself. This is because the gradual completion of the building allows for enough time to react to problems – which only become apparent once construction has commenced – with individual customized solutions. Earth building experts apply their experience and judgement to facilitate the construction process and must ensure that these skills are aligned with the most recent technological advances and up-to-date knowledge. Of course, collaboration with other planners involved in construction, such as architects, civil engineers, and structural engineers, is also essential (see Building Regulations, p. 124).

In any case, the earth-ramming process, in coordination with the other

technical work, determines the pace of construction. Work on the building proceeds according to its rhythms. Since ramming involves a high degree of manual labour, a rammed earth house requires a corresponding input of time and manpower.

75  

The stages of the construction process can be readily observed in the Sihlhölzli judges’ building. This sports complex in Zurich contains two small, uninsulated structures completed in a combination of rammed earth and concrete. In the first phase, the ground floor is built with notches included for the treads of the staircase. The rammed earth lintels contain vertically aligned iron rebar. The reinforced concrete slab above thus bears the weight of the window lintels (see section on Suspended Earthen Lintels, p. 92). This process is repeated for the upper storey. The rammed earth is constructed layer by layer in continuous horizontal strata. The roof slab is also made of reinforced concrete, and the building is finished with a roof lantern to provide daylighting for the stair. The corner windows offer a good view of the track.

76  

77  

Indoor production is the basis of prefabrication: this allows earth construction to proceed independently of the weather and expedites the building process. However, construction detailing becomes correspondingly more complex, as the walls must be split into elements.

Prefabrication Another method of producing rammed earth walls is to manufacture them in a workshop. The first projects containing prefabricated wall elements were completed in the 1990s. This came about as a result of problems with production, which are still the main reason for prefabrication: firstly, earth cannot be rammed throughout the year during times of potential frost, and, secondly, construction schedules are frequently so tight that ramming a wall in situ would be impossible.

The solution to these problems was to produce elements that could be

joined on-site to create entire walls (see Prefabrication, p. 118). Of course, this alters the mode of production, because formwork no longer needs to be installed on the building site. The challenge lies in connecting these elements to form a wall without losing homogeneity – and with as few visible joints as possible. The segments are typically custom-sized in workshops and prepared for installation. Most of the time, large sections are rammed and are then cut into individually sized pieces. This ensures a uniform optical layering and reduces the amount of retouching that needs to be done on-site. In the process, the vertical seams, which are a few centimetres in width, are filled in according to the natural compaction rhythm.

This is not only important for the visual appearance but is also a techni-

cal requirement for the erosion checks, as any break in this band – as with a crack in a dam – can lead to increased erosion.

78  

Rammed earth has a distinctive horizontal structure. In order to preserve this continuous striation, elements created during a single ramming process are installed in the same order.

2 4

1

2

3

4

5

6

7

8

1

3

The joints are filled with the rammed earth material and retouched by hand. After they have dried, the seams are nearly invisible. The erosion process eventually results in a thoroughly monolithic appearance.

79  

Roof Edge and Plinth An old saying states that “a rammed earth wall needs a good hat and good boots”. The hat must be formed such that no rainwater can collect, permeate the construction, or drain from the coping across the rammed surface in significant quantities. The roof overhang is not nearly as important as the impermeability and functionality of the technical solutions found for the detailing.

During project work, countless ways of covering the top of rammed

earth walls have been developed and reams of experience gained. The following assembly has been thoroughly tried and tested: a thin layer of trass-lime mortar is prepared directly on the edge of the roof – ideally in combination with a ring beam – and bituminous waterproofing is affixed to it. In general, this represents the point of interface between an earth building expert and a roofer. On top of this construction, a conventional roofing system can be installed – for example, sheet metal with a drip cap. As such, the edge of the roof must conform to standard building regulations. The roofing edge can also be anchored into the ring beam (see Ricola Kräuterzentrum edge detail, p. 83).

In plinth detailing, the main job is to prevent capillary action from

causing rising damp through the use of a damp-proof membrane. Another concern is exposure to water splash at the intersection of the horizontal and vertical planes – this applies not only to the point where the wall comes into contact with the ground but also to balconies and terraces on the upper storeys. Earth alone is therefore not a suitable material for foundations or plinths, an alternative being a lean concrete mixture or reinforced concrete. In order not to differentiate too strongly between plinth and wall, the concrete is often coloured with an earth-like pigment or constructed as rammed concrete. The rammed earth walls of the Sihlhölzli buildings are subject to increased erosion, due to the higher velocity of wind-driven rain flowing down the smooth faces of the concrete that lies directly above. To reduce this phenomenon, a porous, coarse layer of trass-lime mortar was integrated in between the rammed earth and concrete as an erosion check. This creates a step-like transition between the extremely hard concrete roof and the nonstabilized rammed earth wall. Nevertheless, practical experience indicates that this joint is subject to intensified erosion. To avoid this entirely, a small overhang with a drip cap should be integrated into the design.

80  

Slope 10%

Slope 1% In the small, uninsulated structures of

Reinforced concrete 25 cm

the Sihlhölzli sports complex in Zurich, the concrete roof was cast directly onto

Trass-lime mortar

the rammed earth wall (see section on Reinforced Concrete Slabs, p. 110).

Bituminous waterproofing 0.5 cm

To avoid water damage from above,

Rammed earth wall 40 cm

the rammed earth is protected with

Trass-lime check

bituminous water-proofing. Roof edge at 1:20 scale.

Corten steel covering 0.3 cm Slope 10% Wooden substructure Bituminous waterproofing 0.5 cm

Slope 7%

Trass-lime coating 2 cm Reinforced trass-lime ring beam 15 x 10 cm

Trass-lime check Rammed earth façade 45 cm

Friction-fit bracket fixed to load-bearing structure

The roof edging of the Swiss Ornithological Institute in Sempach incorporates a conventional detail with sheet-metal capping. The rammed earth wall can be treated in the same way as any other form of massive construction. Roof edge at 1:20 scale.

81  

Rauch House In the Rauch House, the structural system

Slope 3% Low-fired mud tile covering 4 cm

of rammed earth also serves as the façade.

Crushed volcanic rock filling 17 cm

The bituminous roof cladding continues

OSB board with bituminous waterproofing 2.5 cm

right up to the edge of the wall; the parapet is covered with an additional metal sheet and finished with fired clay tiles, which extend seamlessly into the roof cladding. The tiles are set but not grouted. As a result, rainwater seeps into the coarse-grained foam glass fill below and is drained off down a slight gradient. The rammed earth walls that come into contact with the ground have 10 cm thick exterior foam-glass insulation and are

Reed insulation 20 cm Granulated cork-loam-trass-lime slope 0 - 10 cm Solid wood slab (“Dippelbaum”) 18 cm Wooden frame to level ceiling joists 3 cm Clay board and finish clay plaster 3 + 1 cm Rammed earth wall 45 cm Reed insulation 2 x 5 cm Clay undercoat and finish clay plaster 3 + 1 cm

protected from moisture with multilayered bituminous waterproofing. The bitumen layer also extends to the upper edge of the plinth, where the junction is clad with clay tiles. As an additional permanent form of protection, the plinths and surfaces touching the ground are coated with a rich clay slurry. Façade cross section at 1:20 scale.

Low-fired mud tiles Rammed earth floor 8 cm Cork-clay-trass-lime mixture 8 cm Reed insulation 2 x 5 cm Reinfored trass-lime mortar 25 cm Bituminous waterproofing Foam-glass insulation Rich loam

Low-fired mud brick Clay mortar T-beam 60/60

Rammed earth floor 8 cm Cork-clay-trass-lime mixture 20 cm Foam-glass filling 20 cm

82  

Ricola Kräuterzentrum

Slope 3%

Corrugated sheet covering

The walls of the Kräuterzentrum in Laufen do not carry any additional

Concrete wall coping

loads. The prefabricated façade acts as cladding for a post-and-beam

Covering mounting parts

reinforced concrete structure and is

Reinforced trass-lime ring beam

attached with anchoring channels. The edge of the roof consists of

Emergency overflow

corrugated sheet metal attached to concrete coping. The roof is composed of in situ concrete slabs, which are supported by a concrete frame. The plinth is also constructed as a pigmented strip of lightweight concrete. It protects the wall from

Trass-lime check

rain splash while simultaneously

Rammed earth façade 45 cm

providing a base for the various

XPS insulation 7 cm

elements. Façade cross section at

Reinforced concrete pillar 55 cm

1:20 scale.

Friction-fit bracket fixed to façade

Stainless steel profile

Rammed earth façade 45 cm Trass-lime check Bitumen coating and clay mortar 1.2 cm Plinth made of pigmented insulating concrete Gravel drainage XPS insulation

Gravel lawn



Subsoil drain



Blinding concrete

83  

The envelope that surrounds us should be able to breathe and diffuse in the same way as our bodies. Martin Rauch

84  

An Aperture in the Wall A rammed earth building functions best when its surfaces are closed. Massive walls with a minimal number of openings that are as small as possible are best suited to both the nature of the material and the compressive forces that act upon it. The traditional language of earth buildings has therefore developed to take account of these properties: the walls are thick, openings are inserted sparingly – in this, rammed earth is similar to other forms of massive construction. In place of a single large window, there are multiple narrow windows, because the sections of wall in between the openings are better able to transfer the loads exerted on them. Each opening weakens the load-bearing capacity of rammed earth walls and is associated with extra planning and work and increased levels of unpredictability. Rammed earth buildings, with their simple details, have been following these principles for centuries.

The lintels in traditional earth buildings consist of timber beams

rammed into the wall itself. Loam, with an equilibrium moisture content of 6–7 per cent, is drier than wood (9 per cent). As such, wood is well preserved in earth constructions (see Materials, p. 116). Since most historical rammed earth buildings in Europe are covered in plaster, this structure is not visible. However, when rammed earth is exposed as a surface finish – which is typically the case nowadays due to its elegance and haptic appeal – the lintel detail becomes much more sophisticated. Such construction details require considerable experience in dealing with the behaviour of the material.

For smaller openings, it is the responsibility of the earth building expert

to implement the construction according to a recognized set of norms. An experienced technician can also assess the degree of reinforcement required. Here, the dimensioning of the reinforcement is based on the technician’s visual judgement; there are no building regulations or calculation criteria (see Building Regulations, p. 124). However, structural planning based on empirical data will not suffice for larger openings and the load-bearing behaviour of the lintel must be calculated. Horizontal supports made of reinforced trasslime mortar are then integrated into the construction.

The openings require a particularly high degree of planning and struc-

tural design work. Designing with rammed earth involves positioning the apertures intelligently and getting to grips with the material in the construction process. If the walls are closed, calculated erosion completes their surface finish (see Material, p. 116 and section on Calculated Erosion, p. 70). Each opening interrupts this process and creates disruption, while the earth is more liable to erosion on the drip edges on the underside of the lintels. This unintended and – if the building work is carried out incorrectly – potentially uncontrolled form of weathering can be prevented with the proper construction detailing.

Rammed earth buildings have altered their appearance: rather than

closed façades, today these buildings are also characterized by open floor plans with large, horizontal windows. But how can we design and build such openings with rammed earth? How can one do justice to this archaic, massive building material notwithstanding this modified architectural language? Or, to put it another way, how can rammed earth shed its traditional skin?

85  

2012  –  2013_ Ricola Kräuterzentrum, Laufen

86  

87  

88  

The Ricola Kräuterzentrum in Laufen showcases a radical means by which openings can be incorporated into rammed earth. The concise shape of the round window with its 5.8 m diameter is both a part of the architecture and a constructional feature: an arch distributes forces optimally around the opening – reinforcement of the lintel is not necessary – and the circular form consists of two horizontally reflected semicircles. The window surfaces protrude by approximately 20 cm. Water that collects on the window runs off a drip cap rather than draining away across the rammed earth wall below. The façades, made from elements that are 110 m and 30 m long respectively, are constructed as a continuous rammed earth wall, which suits the material, while simultaneously creating superb conditions for calculated erosion (see section on Calculated Erosion, p. 70).

89  

Constructing the Lintel Creating an aperture involves time and effort: the lintel above a window or door must be fitted with a construction detail that is able to fulfil both technical and design requirements.When building with rammed earth, this is possible in six different ways: Eliminating the Lintel Omitting lintels completely is an elegant way to get around the problem posed by their construction. The walls consist of individual panels, which stand between the openings. The role of the lintel is conferred either to the ceiling or the roof, neither of which are made out of earth. This facilitates the use of prefabricated elements but results in a discontinuous, fragmentary appearance. Suspended Lintels Another solution for lintel construction is to suspend a rammed earth element from a concrete slab or ring beam above the opening. Both the earthen lintel and the stirrups holding the element in place and connecting it with the load-bearing component are rammed together with the wall. This method of construction is extremely efficient, as a structural element that would in any case be required is used to span the opening. The edge trim on the underside of the lintel is cunningly made with a metal sheet, onto which the structural reinforcements that project into the slab or ring beam can be directly welded. Exposed Lintels in Another Material This is the traditional solution for a lintel in rammed earth construction. Typically, a timber beam is integrated into the wall and left exposed. Its effect is rustic but also correlates with the tectonics and construction principles of both the rammed earth and the material from which the lintel is fabricated. However, if it was affordable, this construction was typically concealed behind plastering, which was made to imitate a more noble form of construction by adding paintings and ornamentation. Lintels with Integrated Reinforcement If the opening is small and the lintel is to be constructed with earth and visibly exposed, reinforcement can be directly rammed into the wall. This is the most simple and affordable form of opening, since the reinforcement can be continuously integrated into a wall as it increases in height. Moreover, there is no need for a structural engineer to help dimension the lintel.

In order to transfer the load above the openings into the walls, a rein-

forced mixture of earth and trass-lime – which is better able to withstand both compressive and tensile forces – is incorporated over the lintels in the form of an arch. The amount and placement of trass-lime are also determined by the earth-building expert based on their experience. The larger the aperture, the higher the invisible arch must be. The lower edge of the lintel is also stabilized with additional trass-lime mortar. No further measures are required to protect its edge.

90  

Concealed Lintels For larger openings, the structural loading capacity of iron rebar rammed into the walls is no longer sufficient. Moreover, the forces can no longer be precisely calculated, since the relevant data has not yet been researched and verified. The solution is a steel girder or a reinforced concrete element dimensioned by a structural engineer. However, unlike the exposed lintel of a traditional earth construction, this structural system allows rammed earth to appear continuously throughout the façade, even though the construction beneath the surface changes. The earth layer is, in fact, suspended from a concealed loadbearing element.

If a horizontal window is to be incorporated into a rammed earth build-

ing, then an integrated, concealed lintel is the construction of choice. Even if it makes the fabrication process more complex as a result, the element can be rammed along with the wall. Stacking Prefabricated Elements Building with rammed earth is a slow process: the earth-moist mixture is rammed layer by layer in formwork during in situ construction, gradually increasing the structure’s height. Thanks to prefabrication, rammed earth can now keep pace with an industrial building site. Joining together pieces prepared in a workshop is also a positive advantage in designing the lintel. As with the stone architraves of Grecian temples, horizontal lintels span the openings. They bear onto the wall elements and reserve space for windows and doors. These pieces, subject to tensile loads, are reinforced during prefabrication with iron rebar, although this can actually be dispensed with in smaller openings. The bottom lip of the opening is protected from erosion with steel edging, which is recessed where the lintel comes into contact with the underlying rammed earth element.

91  

Neither of the two single-storey toolsheds of the sports complex requires a beam. The slab lies on the rammed earth walls.

Suspended Earthen Lintels The suspended lintel of the judges’ building at the Sihlhölzli sports complex in Zurich demonstrates how this element can be executed in rammed earth (see section on Ramming Walls On-Site, p. 76). In the area above the opening, a steel sheet with welded-on reinforcement is rammed into the layer and is later attached to the iron rebar of the armed concrete slab. The flanges welded to the steel sheet prevent deformation but cannot carry the weight of the rammed earth without being suspended. During the ramming and concrete-pouring processes, the opening is braced with window frame formwork, and once the concrete has dried, the slab supports the lintel. This method of construction is particularly useful if the height of the lintel is limited and it is not possible to insert a lintel made of another material.

If there is no concrete slab included in the design, the ring beam can also

be used to carry the load of the lintel. Both methods improve the efficiency of the construction, since the component used is already on hand. Visible Lintels in Another Material The lintel above the doors of the wellness area in the Waldhaus Hotel in Flims was constructed according to traditional methods: in addition to the lintel, a stone slab was laid atop the walls to span the finished opening. This means of construction is so straightforward and simple that its load-bearing behaviour is immediately evident. To protect the slab from breakage during the ramming process, sand is strewn across the form boards of the door.

92  

A rammed earth lintel suspended from a reinforced concrete slab can be an elegant solution for a large opening. This is also possible when the ring beam is positioned on top of the wall (see section on Calculated Erosion, p. 73). Section of the judges’ building at the Sihlhölzli sports complex in Zurich at 1:10 scale.

Reinforced concrete slab 27/40 cm with upstand beam

Trass-lime check Rammed earth wall 40 cm Suspended lintel

Metal sheet

One traditional solution for a lintel is to span the opening with a stone slab. Lintel in the interior of the Waldhaus Hotel in Flims at 1:10 scale.

Rammed earth wall 45 cm

Stone lintel 45 x 8 cm

93  

Lintels with Integrated Reinforcement If the reinforcement can be rammed into the wall along with the earth mixture, then this is the simplest and most efficient way to create a lintel. This fabrication process is commonly used for smaller apertures: several wedgelike layers of trass lime are inserted above the opening in the wall. This reinforced trass lime can withstand more stress than earth alone and can transfer loads more effectively. The exterior edge is finished in earth.

A number of iron rebars are inserted and then rammed into the trass-

lime courses based on the appraisal of the earth-building expert, who applies his or her judgement to determine the dimensioning of this reinforcement – there are no building regulations and formulas to follow here. Once the lime has hardened, it will hold the iron in place. In order to transfer the forces above the opening, the layers of trass-lime are inserted into the wall on top of the lintel in the form of an arch. The method of choice for spanning small openings is to use iron bar reinforcement rammed directly into

Rammed earth wall 45 cm

the wall and embedded in trass-lime. Lintel at 1:10 scale Reinforced trass-lime mortar

As an alternative to iron reinforcement, a flat timber block, bearing onto the abutting walls, can be rammed into the lintel. The adjacent construction detail shows the window of the Rauch studio in

Brick check Clay mortar

Schlins. The earthen layer below the timber blocking must be held in place with webbing, which is attached to the wood with cords. The bottom layer of the exterior erosion check (tiles) is fortified with trass-lime. Section at 1:10 scale. Reinforced trass-lime mortar

Chopped wood lintel

94  

Concealed Elements Large openings tend to have lintels made of reinforced concrete, reinforced trass-lime mortar, or steel profiles and need to be dimensioned by structural engineers. This allows a high level of structural control and makes it possible to incorporate openings that are larger than those typical of traditional rammed earth construction methods.

The details are executed differently according to the material used: if a

concrete element bears the load of the lintel, the formwork for the rammed earth will be constructed first. If the earth is to remain visible on the bottom face of the lintel, an initial layer of the earth mixture will be filled in and rammed; if this surface is covered with cladding, then the concrete lintel can be prepared directly on the base of the formwork.

Since earth is usually visible on at least one side, a shuttering of the same

volume required for the concrete beam is inserted in the formwork. First, the earth mixture is rammed up to the upper lip of the shuttering. Then the board is removed and a number of rustproof screws are inserted into the soft earth layer – these should protrude approximately 3 cm and ensure that the concrete and the earth are tied to one another (see image, p. 97). The edges of the uppermost layer of the rammed earth are knocked off, so that the forces of the wall segment it supports are channelled into the lintel. The reinforcement is then inserted and the concrete lintel is poured.

Above the altar niche of the Chapel of Reconciliation in Berlin is an (in plan) arch-like lintel, composed of reinforced concrete. Its inclusion is concealed between two layers of rammed earth. On the ceiling face, the concrete beam is covered with loam slurry, in order to match the earthen material of the rammed walls. Since these walls are located in the interior, the corners can have sharp edges without further reinforcement, since there is no danger of them breaking off. Elevation, floor plan, and section of the opening in the Chapel of Reconciliation at 1:50 scale.

95  

With concealed lintels, the suspended rammed earth is tied to the loadbearing beam of reinforced concrete or trass-lime with the bolts. If the construction is to have cladding on the interior, the support beam can be set on the inner edge of the rammed earth wall, as is the case with the large studio window in the Rauch House. As a result, the outward-facing layer of earth is thicker.

The lintel for the openings situated above the wide gates of the Kräuter-

zentrum in Laufen was fabricated with two thermally insulated steel girders. Since the façade here is composed of prefabricated elements, the beam was integrated during the ramming process rather than being installed on the building site. This type of construction can also be readily used for in situ wall construction. In either case, the steel lintel must be inserted in a slightly raised position. The load of the earth positioned on top of it will then press it down into its final position. In order to protect the edge of the rammed earth wall, the lower flange of the girder is fitted with an angled profile, which provides a precise edge for the lintel and precludes excessive erosion of the earth on this edge.

Integrating lintels directly into rammed-earth elements opens the way

Diagram left: Detail section of the

for earth building to explore new paths of formal development. The windows

lintel in the Chapel of Reconciliation.

and doors of traditional rammed earth structures are tall and narrow. For a

The rammed earth wall is visible on both sides and the underside of this beam is covered with earth. Lintel construction detail at 1:10 scale.

long time, wider openings were technically impossible to create – horizontal fenestration and broad lintels have only become feasible in combination with other materials.

Diagram right: The gates of the Kräuterzentrum in Laufen with a steel girder rammed into the wall element. Section at 1:10 scale. Trass-lime check Rammed earth façade 45 cm

Rammed earth wall 60 cm

L-profile 200 x 20 with thermal separation Thermal separation

Reinforced trass-lime mortar

Edge trim

30 x 32 cm

Rectangular hollow structural section frame

96  

Screws ensure that earth layer and trass-lime or reinforced concrete beam hold together. They are screwed into rammed earth before casting.

Diagram left: The lintel above the doors of the Batschuns Chapel, executed in rammed earth on both sides. Section at 1:10 scale.

Diagram right: Standard section of the Rauch House. Façade of rammed earth, interior wall finished with clay plastering. Section at 1:10 scale.

Rammed earth wall 45 cm

Finish clay plaster 1 cm Clay undercoat 3 cm Reed insulation 2 x 5 cm Clay mortar

Reinforced conrete lintel 20 x 32 cm

Brick check Rammed earth wall 45 cm Reinforced trass-lime mortar

Screws

30 x 20 cm

97  

Stacking Prefabricated Elements Prefabrication has been the most significant development in rammed earth construction (see Prefabrication, p. 118). Major innovations have been introduced in this area with regard to technology, building processes, and fabrication. This also pertains to openings, which can be seamlessly integrated into planning and implementation during production through the use of segmentation. In this way, the complex construction details of the lintel can be completely worked out and implemented in the production hall. This facilitates the construction process and ensures a high degree of quality.

The three-storey façade of the visitor centre for the Swiss Ornithological Institute in Sempach was put together from prefabricated elements. The lintels of the openings were created without reinforcement; trapezoidal elements support the sloping roof edge. Plan showing arrangement of elements at 1:100 scale.

Thanks to retouching and careful planning, the surface of a wall composed of prefabricated elements is barely distinguishable from in situ rammed earth. With openings, however, prefabrication is more likely to leave visible traces: the tectonic qualities of the façade appear in their essence.

While the volume of in situ earth buildings appears dense and has a

distinctive sculptural quality, façades made of prefabricated elements follow a logic of joining and stacking. Accordingly, openings are also an extension of this methodology. In this respect, rammed earth is similar to other building methods – it is freed from the restrictions that are imposed on it in traditional construction processes. Prefabrication creates the possibility of finding a new expression for the material.

98  

When using prefabricated elements, completely different geometries can be integrated into the façades. This includes both the round aperture of the Kräuterzentrum windows as well its wide-set gates. Façade details of the Kräuterzentrum in Laufen showing the arrangement of the different elements at 1:100 scale.

99  

The agricultural college in Mezzana was also constructed with prefabricated elements. In contrast to the Swiss Ornithological Institute in Sempach, this structure contains larger openings that must be spanned with an integrated lintel made of reinforced concrete. Façade showing the arrangement of the different elements at 1:100 scale.

The agricultural college in Mezzana provides a good example of the visual appearance of modular earth construction. Its wide openings are not optimal for rammed earth and could not be constructed with traditional building methods. Integrating a reinforced concrete lintel into the ramming of the horizontally positioned elements means that the beam can be very thin. The large number of openings allow the façade to achieve an unprecedented degree of transparency, which creates a dynamic contrast with the visually

Load-bearing brick wall 18 cm Trass-lime check Rammed earth façade 30 cm Mineral wool insulation 14 cm Reinforced concrete slab 25 cm

Reinforced conrete lintel 14 x 16 cm

The section reveals the interplay between rammed earth, steel, and reinforced concrete within the element. The design of the school was executed as a double-leaf construction (see section on Roof Construction, p. 112). Section through the lintel at 1:10 scale.

100  

Axonometric drawing of the lintel construction detail. Although homogeneous in appearance, the lintel element is composed of rammed earth, steel, and reinforced concrete. The steel sheet above the lintel is recessed above the vertical elements and thus remains concealed.

Rammed earth façade

Axonometric drawing at 1:10 scale.

Trass-lime check

Reinforced concrete lintel

Metal sheet

Friction-fit bracket



Reinforced trass-lime



mortrar support

heavy appearance of the material. Viewed from below, the steel sheet at the lower end of the horizontal element is visible. This sheet must bear on the vertical elements in order to correctly transfer the loads, although it should not be visible next to the window opening; the solution is to slightly recess the sheet above the elements and cover it with earth. Even if these modules are implemented with a hybrid form of construction, they will be perceived as a homogeneous rammed earth wall.

This kind of solution is, in principle, also possible with walls constructed

on site. However, their planning and fabrication is considerable more efficient in a workshop – and the architecture that results from this process is a great deal more coherent in its details and expression.

101  

And it’s important, you see, that you honour the material you use. Louis Kahn

102  

Slab and Roof The forces operating in a slab do not suit the properties of rammed earth: the material cannot cope with the tensions acting on the lower surface of the plane, as it only functions in compression. This makes unreinforced rammed earth ill-suited for the construction of a slab – except when in vault form . The same applies to roof systems. To overcome this problem, the rammed earth house must employ another construction material. Timber and concrete are both ideal complements to earth. With an equilibrium moisture content of between 6 and 7 per cent, it naturally preserves wood, which has a higher relative humidity; concrete has a similar mass to rammed earth and can also withstand pressure more effectively than tensile forces. For this reason, in older publications, rammed earth is often referred to as “soil cement”.

These slabs can thus be implemented in timber or concrete, or conceived

as hybrid constructions incorporating earthen elements. The ceiling face of a concrete slab can be finished with clay plaster, and clay boards can be set on a steel or wooden construction with trussed beams. While there are numerous historical precedents of walls in earth building, there are relatively few examples of earth slabs that meet contemporary building standards: there is a great deal that needs to be reconceived and developed anew.

Another possibility is to separate the earthen façade from the rest of the

construction completely and develop an autonomous structural system; earth is then taken out of the equation in questions relating to the slab and the roof. The structure can consist of a conventional concrete or wood-frame system that functions independently and is enveloped by the earth façade. This approach was utilized in projects like the Ricola Kräuterzentrum and the Swiss Ornithological Institute’s Visitor Centre, and is generally applied for interior walls prefixed to the load-bearing system or so-called curtain walls.

On the other end of the spectrum are small-scale projects such as the

unheated and uninsulated judges’ building and storage space at the Sihlhölzli sports complex in Zurich. Here, the concrete slab bears on the rammed earth walls: the two materials touch directly and elegantly, forming a perfect unit.

If a project requires insulation, in contrast with the Sihlhölzli project,

several rules must be taken into consideration. This is particularly important when the exterior façade is made of earth, with the insulation located on the inside. In case of a timber slab, water vapour transfer must be considered. A ring beam plays an important role in this instance. If executed correctly, earth also reveals its hygroscopic properties where it is connected to the slab: it sheathes and protects the wood by regulating its vapour content and transferring moisture to the exterior if it becomes oversaturated. In slab construction, detail planning and technical execution are closely interrelated.

103  

2005 – 2008_House Rauch, Schlins

104  

105  

Axonometric section through the Rauch House, where multiple slab construction systems were applied. Above an open entry hall, fired clay bricks are placed into the profile of a steel beam and covered with a trass-lime mixture. The upper-floor slabs are made of beams that have been machine-cut on three sides (“Dippelbäume”). Rammed earth floors were stamped on top of this system.

The roof also employs the “Dippelbaum” system. As the “fifth façade”, visible from the slope above, the roof and roof edge trim are finished with fired tiles.

106  

107  

Timber Slabs Wooden structural systems are an ideal complement to earth construction. The equilibrium moisture content of rammed earth is 6–7 per cent, while construction-grade timber is installed with a relative humidity of approximately 18 per cent, which eventually balances out at around 9 per cent. The earth thus protects the wood, while simultaneously creating a favourable microclimate, preserving organic building materials over the long term.

Any of the typical methods of timber-frame construction can be imple-

mented: edge-glued timber slabs, hollow-core slabs, joist slabs, or the “Dippelbaum” slab. The heavy mass of this last type of slab is particularly appropriate for a massive earth construction – which is also characterized by a low amount of material waste, since the beams are only hewn on three sides. An earthen floor can be rammed onto the timber slab on top of cork fill bonded with lime and loam (see section on Substrate Structure, p. 60).

Roof structure applying the “Dippelbaum” system in the Rauch House (see The Rammed Earth Wall, p. 82, for a detail section). The beams are tensioned in the longitudinal direction and bear onto the ring beam. Section perspective at 1:50 scale.

In timber slabs, the position of the ring beam significantly affects vapour diffusion. Section at 1:20 scale.

In timber construction, the load-bearing points require particular attention – vapour pressure causes moisture to collect at the heads of the beams, which can rot if the vapour condenses. Damp diffusion is a critical concern. However, if the space between the wall and the slab is adequately filled with earth, humidity cannot condense and the moisture is absorbed and transferred within the wall without harming the wood. Furthermore, in an insulated or plastered construction, the ring beam can usually be located inwards, which mitigates the problem, since the beam is located further inside.

108  

Compressed clay boards are placed in

Custom-shaped timber beams provide the opportunity to create an exposed

between the wooden beams. A gravel

beam slab (“Füllungsdecke”) filled with clay boards. The mezzanine level of

fill layer made of crushed cork, loam, and trass lime provides the necessary mass and reinforces the structural properties of earth buildings. Section at 1:10 scale.

the Rauch atelier exploits this structural possibility. The wooden girders are shaped into T-profiles and inverted, and a continuous groove allows the clay boards to be laid between the beams. The cavity above the boards is filled with a mixture of crushed cork, loam, and trass lime. On top of this lies a floating floor made of wood.

Wooden floating floor Loam-cork-trass-lime filling Clay board Wooden T-profile

Load-Bearing Steel Slabs Steel constructions are also possible, although they are significantly less common than wood. The slab located over the unheated storage room in the Rauch House is a combination of steel and earth. It interprets the principles of a rib-and-block slab in which hollow bricks are inserted between two steel beams.

A series of inverted steel T-beams span the room. Additional armouring

irons are welded onto their base, creating a connection with the adjacent trass-lime layer above (see illustrations, p. 82) . In between the supports, earth bricks fired at a low temperature serve as permanent formwork and are grouted with soft, clay-based mortar. A layer of trass-lime mixture is poured on top of this. Once the lime has hardened, the temporary clay mortar can simply be sprayed off with a hose.

In the Rauch House, a folded slab is formed from fired bricks stacked into inverted steel T-beams. The layer of trass-lime mortar above stiffens the construction and stabilizes the layered bricks. Section perspective at 1:50 scale.

109  

Reinforced Concrete Slabs A reinforced concrete slab is an extremely effective means of spanning a space. The reciprocal relationship between the compression-resistant artificial stone and the iron rebar creates a stiff, slender construction that can be readily combined with rammed earth due to the similarity in their expansion behaviour. The details are correspondingly simple and direct. Moreover, lintels made of rammed earth can be hung from the concrete slab (see section on Suspended Earthen Lintels,p. 92), further simplifying the construction.

To stop erosion occurring directly underneath the concrete slab, it is

installed on top of a layer of bitumen and trass-lime. This waterproof coating prevents rain from travelling along the bottom edge of the slab and penetrating the rammed earth wall. The axonometric drawing shows the uninsulated construction of the judges’ building in the Sihlhölzli sports complex.

In insulated structures, using exposed concrete slabs significantly in-

creases the amount of work required. In this case, the concrete slab should bear on and be connected to the ring beam. The rammed earth wall remains visible and conceals the concrete.

Concrete and earth complement one another well as a hybrid construction. In uninsulated buildings such as the small Sihlhölzli structure, both materials can be visible in the construction. The in situ concrete and rammed earth share the tasks of bearing loads and traversing spans. Section perspective at 1:50 scale.

110  

If the architectural concept requires that a slab be made of rammed earth, then the earth must be incorporated into the slab construction. It is always possible to finish the visible face of the ceiling with clay plastering; however, this underside can also be made with rammed earth. To do so, the earth is laid into the formwork of the floor slab before the concrete is poured: as a first step, a three-layer slab is set into the form boards for the concrete slab in order to preserve a homogeneous surface. The rough edges of a formwork system would also leave a mark in the rammed earth and increase the amount of work required during retouching.

Above this, 2 cm of earth-moist earth is poured in and rammed. A mesh

of iron rebars is placed on top of this first layer with stirrups that penetrate the slab every 40 cm. Then a second course of earth mixture is laid in and rammed. After it has dried sufficiently, the surface is roughened to provide a stronger connection between the earth and the concrete. Then the rebar typically used for concrete slabs is laid out and concrete is poured directly onto the earth. These layers interlock on the contact plane and remain permanently connected through the iron stirrups. With this construction method, the bottom face of the ceiling can be fabricated with earth – even if it seems impossible to use the material for this purpose at first glance. In a more reduced form, this construction system was used for the lintel of the basement window in the Rauch House.

40

The layer of rammed earth is connected

Concrete slab

to the concrete slab with iron rebar.

Reinforcement

Section showing formwork and integrated

Rammed earth ceiling 4 cm

three-layer slab at 1:10 scale.

Formwork plywood Formwork beam

The slab after removing the form boards with a visible rammed earth finish. Section at 1:10 scale

40

Concrete slab Reinforcement Rammed earth ceiling 4 cm

111  

Roof Construction Since the roof cannot be made of earth in a massive construction, its design is The roof edge trim on the agricultural

very similar to the roofing methods used in houses built with other materials.

school in Mezzana is firmly grounded

As most earthen façades are non-load-bearing, they are generally constructed

in the principles of a double-leaf wall: the inner wall consists of conventional honeycomb bricks and the exterior wall is

as double-leaf walls: a structural system of timber, masonry, or reinforced concrete carries the load and the rammed earth cladding carries only its own

made of prefabricated rammed earth

weight. This affects the roof, as its load-bearing segments also bear on this

elements. The envelope of the insulation

inner construction and not the rammed earth. The masonry capstone can be

extends from the wall into the roof; the roof construction did not need to be

installed in several different ways depending on the architectonic concept.

specifically tailored to the earth building.



The anchoring of the elements into the

ground floor than on the upper floors. A timber-frame construction is placed

masonry is also visible in the section:

on top of the resulting corbel, which defines the rooms and the roof. The thin-

the bracket connecting the exterior earthen wall to its interior counterpart

On the opposite page, the section through the Mathies House shows

a reinterpretation of a centuries-old tradition: the walls are thicker on the

ner rammed earth wall only goes as far as the parapet of the uppermost floor.

is embedded into a groove continuing along the top edge of every element. Section at 1:10 scale.

Corten steel covering 0.3 cm

Mineral wool insulation 16 cm Friction-fit bracket fixed to slab Reinforced concrete slab 25 cm

Trass-lime check

Rammed earth façade 30 cm

Friction-fit bracket fixed to load-bearing brick wall Load-bearing brick wall 18 cm

112  

Crushed cork insulation 18 cm

Clay board with clay plaster 4 cm

The Mathies House relies on an

Ceramic tile

ancient earth construction principle:

Clay undercoat 2 cm

the wall is recessed in between floors. Timber framing bears on these ledges, integrating the slab and the roof systems. The projecting roof line protects the

Reed insulation 3 cm Wooden substructure 4 cm

rammed earth wall from rain. This combination allows both materials to exhibit their strengths – earth as a façade and wood as a structural system. Façade cross section at 1:10 scale.

Woodchip-straw-loam insulation 22 cm Rammed earth façade 25/55 cm

Trass-lime check

Stone check Ring beam 30 x 15 cm

113  

114  

Excursus Material Prefabrication Knowledge Transfer Building Regulations

115  

Material

construction purposes. At least 50 per cent, and sometimes as much as 100 per cent, of rammed earth mixtures

Rammed earth cannot be purchased at a building sup-

are made up of this kind of excavated soil. The next step

plies store. If you want to use this material for construc-

is defining the aggregates. Depending on the compo-

tion purposes, you must be able to prepare your own

sition of the excavated earth, either loamy or gravelly

earth mixture. The advantage to this is that the compo-

material must be added, including both round and

nents can be found anywhere in the world. Loam and

rough-edged gravel. Round gravel integrates well into

gravel are readily available and other aggregates, such

the material mass, while the interlocking sharped-

as igneous rocks, marble chips, or marl, can be added

edged rubble (broken stones) helps strengthen the mix.

depending not only on their availability but also on the

The optimal stability therefore requires the presence

purpose and requirements of the job. The result is that

of both round gravel and sharp-edged crushed gravel. A

every rammed earth structure is unique, as the materials

historical example is the Tuscan ceramics village of Mon-

for it are specifically mixed for the purpose. The challenge

telupo: as early as the fourteenth century, the inhabitants

lies in developing an appropriate combination. In con-

of the village shattered round stones to create crushed

trast to other building materials, like concrete, there are

gravel for the construction of their rammed earth town

no standardized formulas. Accordingly, the properties

hall. The expert craftsmen knew that the rough-edged

of each rammed earth mixture vary. Ensuring the suit-

stones would increase the stability of the walls. For their

ability of the mixture and finding the correct formula to

own smaller houses, round gravel sufficed. This is an-

meet the design requirements depend on the expertise

other by-product of the long-term experience gained from

of an earth building specialist.

daily contact with the earth.



Thus the first task is to find the correct raw ma-

terials. This requires on-site research, in which the locally

Rebalancing Parameters

available material is examined and the potential use of

The mixture plays a crucial role in the properties of the

regional resources assessed. This is always the first step

material. The type and amount of the excavated earth as

in earth construction. Brickyards are a useful indicator

well as the supplementary aggregates determine these

here as they also require loam in their production pro-

qualities: rich loam, with a higher concentration of clay,

cess and are well informed about local resources. How-

improves the cohesiveness of the material – but it weath-

ever, pure brick earth is not suitable for rammed earth

ers much more rapidly and is more difficult to process

construction; it can only be used to supplement mix-

than lean loam. Rounded and sharped-edged gravel sta-

tures of excavation material that are too lean – i.e., silty or

bilize the rammed earth, as previously described, in com-

sandy loams with insufficient clay content.

pletely different ways. In creating the mixture, a happy



As indicated above, the primary element of the

medium needs to be found between these different

mixture consists of excavated earth. The most suitable

properties. Each aspect needs to be balanced; tests must

material is a loamy, gravelly material that can either be

be conducted until a unique, optimized material formu-

broken down to the correct size grain with a crushing

la can be developed to meet the requirements of design

mill or sifted to achieve the proper consistency. Builders

and site. The differences are often extremely subtle; a

and civil engineering and construction companies often

slight shift in one direction can significantly improve the

have large quantities of such mixtures available but con-

quality of the mixture. Moreover, the result is dependent

sider it as waste because it cannot be used by brickworks

on a number of additional factors: how the mixture is

or by the gravel industry. Its stone content is too high for

stored and aged, the relative humidity at the time of con-

brick manufacturers, and its clay and loam content is too

struction, the type of formwork and the ramming tech-

high for gravel manufacturers. Leaching, or separating

nique. Satisfactory results are only achieved when the

the raw material, would be uneconomic in either case.

material balance suits the production process. Therefore,

If the building firm or highway engineer were to under-

years of experience with the material and its technical

stand the usefulness of this sort of excavation material

requirements are necessary to enable one to respond

and its inherent value for rammed earth structures, they

to each new set of building conditions (see Knowledge

would be able to prepare and sell this local material for

Transfer, p. 122).

116  

The material is usually tested in three different ways. It is

Overall Experience

first checked by hand: an earth building expert can tell by

Each of these aspects is highly dependent on experience:

touching the material if it sticks together properly, if it is

technical and artistic concerns play a key role here, as do

sufficiently damp, and if the grain is appropriate for the

economic considerations and questions of quality. It is

building task. In general, three to four different mixtures

inherent to the nature of the material that it should

are prepared and the optimal quality is obtained through

maximize its regional content. Nevertheless, financial

a balanced combination of the components.

constraints can necessitate imports from other regions:



The next step is to prepare rammed test specimens.

the costs of transport – visible and hidden – must be

If the composition has passed the initial hand test, a small

weighed against the efforts required to prepare the ma-

amount of earth is compacted under realistic conditions

terial in a decentralized manner. It is for this reason that

(with the proper filling height and degree of compaction).

the elements for the Swiss Ornithological Institute in

The resistance of the material and its resonance during

Sempach, for example, were prefabricated 90 km away in

the stamping process reveal many of its characteristics,

Zwingen rather than constructed in situ. The production

as does the visual appearance of the earth after removing

hall had already been equipped to produce the Ricola

the formwork.

Kräuterzentrum in Laufen. Modifying and transporting



The third, quantifiable step in assessing the quality

the facilities would not have been economically feasible

of the material is measuring the compressive strength of

and would have likewise incurred transportation costs.

test specimens in a laboratory.

All things considered, 90 km remains relatively short



compared to the distances required to transport conven-

The process of creating a rammed earth blend is the

reverse of mixing concrete: whereas the latter is prepared

tional building materials.

according to a prescribed formula, with rammed earth the formula is only derived at the end of the process, once the

Life-Cycle Advantages

right mix has been found.

The advantages of rammed earth construction, as described in the process of material mixing, are associated

The Impact of the Mixture

with increased outlay in terms of time and effort. Al-

The quality of the earth mixture regulates the durabil-

though creating its outstanding qualities is often labour

ity of the construction and its susceptibility to erosion.

intensive, it requires almost no grey energy to produce

These properties are also influenced by the leanness or

and transport it. Accordingly, in an ideal case, rammed

richness of the loam: a rich loam can better weather rain

earth can have an extremely localized life cycle: formed

than one which is lean, but a lean mixture is more readily

from regional materials, processed on site, and poten-

processed and displays less cracking from shrinkage. The

tially reused without loss of quality or returned directly

loam component, in turn, helps regulate the amount of

to the earth at the end of a building’s life cycle. Due to its

internal moisture. All of these parameters must be cal-

water solubility, it can also easily be separated from other

culated relative to one another.

building materials – without any residual at all.





In addition to this, aggregates have an effect on the

As such, we strongly believe it is a mistake to stabi-

mixture’s appearance. The degree of erosion determines

lize earth construction with cement or silicon-based

whether gravel is visible in the structure of a wall subject

chemical additives. These additives are not required

to weathering, or if the loam layer remains intact. This

to resist weathering (see section on Calculated Erosion,

has a direct impact on the structure and aesthetic of the

p. 70) and, if altered, the earth loses both its natural ex-

wall. A higher gravel content also influences its specific

pression and many of the beneficial properties men-

gravity (ranging from 1,850 to 2,300 kg/m3) and there-

tioned above.

fore its physical and structural properties – for example,



its capacity as a thermal mass.

vidual mixtures may be perceived as too labour inten-

Although the necessary process of creating indi-

Particle size and porosity also play a role here. The mate-

sive or as an anachronistic constraint, it leads to precisely

rial’s density, and thus its thermal conductivity ( -value),

customized and well-balanced solutions made of local

can also be regulated by using a lighter aggregate such as

materials and uniquely suited to the specific design re-

crushed volcanic rock, pumice, or brick chippings.

quirements.

117  

Prefabrication

tion schedule, even details such as the location of the crane and the maximum load capacity relative to its out-

Prefabrication represents a new paradigm in rammed

reach are considered: elements nearer to the crane can be

earth construction, as it is a quantum leap both in a quan-

proportionally heavier and therefore longer in design. In

titative and in a qualitative sense. It takes the practice

constructing the Swiss Ornithological Institute in Sem-

to a new level and gives more options for finding pro-

pach, strict attention was paid to each of these aspects.

jects that can be executed with rammed earth. Economic



considerations support the argument for separating the

much simpler: prefabricated details are standardized and

processes of production and installation, primarily due

can even be put in place by unskilled labour. The task can

to on-site logistics: rather than employing a team of

be dispensed to multiple actors, which is of overall ben-

labourers to ram the earth in situ, gradually putting up

efit to the earth building trade (see Knowledge Transfer,

the building over time, cranes can quickly mount the

p. 122).

In contrast, technical implementation has become

finished elements in accordance with the demands of a tight schedule. As the elements are already dry when they are erected, integrating the remaining building

Production Advantages

trades of other subcontractors is seamless, which signif-

The first prefabricated element completed by Lehm Ton

icantly shortens the duration of the construction work.

Erde was a living room wall in 1997. It was to be installed

Fabricating the walls is still just as time intensive a pro-

in a timber-frame construction, which at first appeared

cess, but the production and mounting phases can be

to be logistically impossible: the schedule of the framing

more easily planned and coordinated.

was extremely tight in a fixed window of time, and, more-



As there are virtually no historical precedents for

over, planned for January, when the earth could not be

earth being rammed off-site rather than in situ, prefabri-

stamped on site due to frost. A solution was thus sought

cation in earth construction is largely unexplored terri-

that would allow the wall to be installed with a crane si-

tory, although experience is now beginning to emerge in

multaneously with the timber construction process.This

this field. Its technical and structural requirements are

was the catalyst for prefabrication.

becoming more refined – as are the solutions in matters



The first larger-scale project from this period was a

of design. While the rudimentary joints of the first pre-

office building for Gugler Printers in Pielach. The stand-

fabricated buildings were roughly finished, retouching

ardized elements, which were also interior walls, were

has become considerably more advanced, such that walls

stacked on top of one another and the joints then sealed.

made up of compound elements are as homogeneous

The modules contain flues for ventilation powered by a

in appearance as walls rammed on site. Improvements

geothermal heat collector: the earth walls function like

needed to be made in the planning process, as defining

hypocausts, capitalizing on their haptic properties while

the earth elements requires hard and fast decisions to be

creating a comfortable indoor climate.

made at an early stage. This involves a close collaboration



between construction documentation and production,

for the Gugler project – these were then put in place over

as often factors only tangentially related to the manu-

the course of a mere two weeks. The most recent projects

facturing and ramming process can be crucial to their fab-

completed with prefabricated elements are the Kräuter-

rication. For example, once the wall thickness has been

zentrum in Laufen and the Swiss Ornithological Insti-

decided, the next step is to adjust the size of the elements

tute’s Visitor Centre in Sempach. Due to improved work-

It took three months to finish the 160 pieces required

to match the room height. The length is dependent on the load limitation of the crane that lifts the elements into place. Thus, the length is a product of the maximum permissible weight, the height, and the wall width. These interdependencies, at the interface between planning and production, must be carefully evaluated. In order to limit the number of elements as much as possible, which in the end results in a lower price and a shorter construc-

118  

flow and increased production speed compared to the

Mechanical Prefabrication

1990s, the current ratio of production to installation in

Since, as we mentioned above, this is largely virgin terri-

prefabricated parts is approximately 3:1.

tory, in order to develop prefabrication and further im-



The number of projects constructed with prefabri-

prove its efficiency, several new inventions have been

cated materials has grown significantly: walls can be pro-

required. Progress has primarily targeted a reduction in

duced efficiently regardless of weather conditions and

the amount of physical labour required. The most stren-

schedules are simpler to coordinate. In addition, trans-

uous task is filling the formwork with the material and

portation of commodities has become much easier –

compacting the mixture.

which also favours the indoor fabrication process. Even



the demand for building with local materials can be ful-

this particular challenge by automatically distributing

filled; for example, the elements of the Ricola Kräuter-

the earth within the formwork and mechanically com-

zentrum were made of earth from an area in the vicinity

pacting it with a moving rammer (see the axonometric

of the building site. The distance from the production

drawing above). There is still a good deal of manual labour

A machine was therefore developed to address

hall to the construction site was less than 3 km. For large projects, it is often expedient to set up the production facilities locally, in order to utilize regional materials while decreasing transportation distances.

Mechanical prefabrication alleviates physically strenuous labour and expedites the production process. The machine was developed by Lehm Ton Erde.

119  

As the elements cannot be subjected to tensile loading, a suspension system had to be developed. This also allows the elements to be set in place vertically.

Fig. 1

Fig. 2

Fig. 3

involved but a major part of it can be accomplished by

with wooden wedges, which could be stamped into the

this feeder mechanism. The machine also allows for the

walls and driven through them after removing the form-

production of thinner walls, since the process no longer

work. As a result, the suspension straps can be attached

requires a person to be able to stand inside the form

directly through these gaps.

boards to ram the material. Long formworks enable the



production of entire walls in a single segment with con-

every 60 cm. The load is distributed through a system of

tinuous horizontal layering. Afterwards, the elements

cables between the block and the beams. The element is

can be cut to the appropriate size and installed in the

then aligned vertically on site using two chain hoists (see

same order on the building site.

fig. 3).

Suspension and Transportation

Installation Process

Since the elements have very low tensile strength, forces

The element is placed on a bed of clay mortar approxi-

must be evenly distributed along the lowest edge of the

mately 1 cm thick, composed of the same materials. The

element during the installation process – blocks of unre-

friction-fit joining of the elements is actuated by their

inforced earth cannot be suspended from two points.

own weight, as the block embeds itself into the mortar.

With thinner and therefore lighter pieces, a wooden beam

Clay must well out of the gap on all sides – this is the only

and several lifting straps suffice to distribute the weight

way to ensure that the entire cavity has been filled. Once

(see fig. 1). However, with larger and heavier elements, a

the block has been correctly placed on the mortar, its

specialized and custom-developed transport mechanism

position is fixed with wooden wedges. After the mortar

The straps attach the element to the lifting beam

must be employed to allow adjustments on all three axes

has dried, the entire load will bear down flat onto the ele-

while setting the piece. To support the blocks from be-

ment below. This is particularly important with rammed

low, the first round of stamping includes a ladder-like

earth as compared with reinforced concrete, because it

structure made of round piping and iron rebar at the bot-

cannot withstand tensile forces.

tom. Anchor rods are then laid into these pipes and at-



tached directly to the lifting gear with two steel plates

ual elements are sealed during or just after the mounting

(see fig. 2). The disadvantage of utilizing such an aux-

process. However, preparation for this begins during

iliary construction is that it remains a part of the wall

production: a groove is notched into the vertical edges of

after placement. To reduce the complexity and avoid

the sides as well as the upward-facing horizontal aspect.

material waste, these steel constructions were replaced

After the elements have been set, with a minimum gap of

All the connections and joints between the individ-

120  

1 cm, the vertical grooves are filled with trass-lime mor-

creep deformation exhibited by earth, it should be exe-

tar. Since these columns of trass-lime are stiffer than the

cuted as a movable connection. Due to the use of iron

earth and have different movement characteristics, the

spacers, the structural system and the façade retain their

bottom of the groove is pitched with a trowel of soft clay.

separate thermal envelopes.

When the columns harden and then deform, they can ex-



pand into the softer clay.

the seams are meticulously sealed and integrated into

Finally, after positioning and joining the elements,



The elements are horizontally connected by plac-

the rhythm of the striation. The breakthrough in prefab-

ing two contiguous iron rebar pieces in the horizontal

rication has only truly occurred since perfecting this

grooves and embedding them with trass-lime mortar.

retouching method, as this meant that the optical and ar-

This functions similarly to the use of a ring beam for in

chaic qualities of rammed earth could then be combined

situ rammed walls. Since there must be approximately 15

with an efficient fabrication process.

cm covering the groove on both sides of the wall, it can be 15 cm wide in a 45 cm thick wall, whereas a 35 cm wall

Insulated Elements

leaves only 5 cm to play with. The groove is milled to a

So far, only single-leaf walls have been prefabricated. Pre-

depth of about 6 cm.

liminary tests for the production of cavity-wall modules



If the earth wall is not load bearing, it must be at-

have been conducted, in which a lightweight earth insu-

tached to the structural system on its inner façade. Rein-

lation layer is sandwiched between two rammed earth

forcing the horizontal grouting in between the elements

wythes. They can thus retain their aesthetic appearance

is well suited to this purpose. A Z-bracket enclosing the

and technical properties on both sides. As an additional

rebar can be used to friction-fit the element to the build-

benefit, the middle segment can be outfitted with heat-

ing’s load-bearing structure. Due to the relatively strong

ing and cooling conduits.

Friction-fit Trass-lime check Rammed earth Insulation Heating pipes

The elements are joined with trass-lime mortar. Rebar is laid into

The most recent development: insulated prefabricated

the structure horizontally. Horizontal section (above) and

elements. These make it possible to create an earth façade

vertical section (below) at 1:20 scale.

where the ramming pattern is visible on both sides.

121  

Knowledge Transfer

The old procedures are still surprisingly efficient: understanding is best gained from concrete experience with

Globally speaking, the long tradition of earth construc-

real projects. After ramming earth by hand, one instinc-

tion is endangered – one might go so far as to say that in

tively knows the correct material mixture without need-

certain parts of the world it had almost ceased to exist.

ing measuring gauges or formulas. This knowledge goes

There were almost no skilled labourers still capable of

together with sensory experience; one can feel with one’s

producing rammed earth structures and technical know-

fingers if the mix has been correctly formulated. How-

ledge was in constant decline. As there was no one left to

ever, the work brings with it an understanding not only

teach this method of construction, the number of practi-

of the material but also of the technical minutiae and

tioners dwindled. The tradition of knowledge transfer

auxiliary structures. One learns by doing.

that had previously passed from generation to gener-



ation was interrupted and was in danger of vanishing

men to impart and disseminate this knowledge. Every

completely.

job must produce new specialists; there is simply no other



It is therefore the responsibility of skilled trades-

This process was mainly due to earth construction

way that this empirical knowledge can be acquired. As

falling victim to industrialization: building materials

such, it is important not only to have a trained workforce

and their transportation over long distances became in-

on the building site but also artisans and designers who

creasingly affordable, while labour costs have risen in-

can start to gain experience through a process of practi-

exorably right up to the present day. All that matters is

cal training. In Martin Rauch’s office, this kind of intern-

the time required to complete the work. As such, a labour-

ship lasts a minimum of three months and involves both

intensive building system is less economically viable

research and a period spent working on a building site:

than a method involving more mechanized processes.

learning by doing. Many interns extend their training

Timber construction, for example, established itself as

and are eventually hired as regular employees or get in-

an efficient and rational practice.

volved in planning if they have the necessary ability.





In emerging and developing nations, earth con-

The survival, advancement and future of earth

struction is still a popular method of construction. More

building are thus dependent on knowledge transfer be-

than a third of the world’s population lives in earth hous-

tween trained professionals. For example, more than half

es, even if it dreams of a life replete with Western status

of the twenty-five people involved in the construction of

symbols – a vision that certainly does not include earth

the Ricola Kräuterzentrum, joined the project to learn

building. Even in countries where earth building still

about the building material. This is how the requisite

plays a role, the material is often used as a last resort, be-

knowledge is shared, allowing the people involved to

cause such simple buildings are associated with poverty.

pursue their own projects in the future and carry the

Naturally, neither the dwindling traditions of European

earth building tradition forward.

techniques nor the predominant construction methods of developing countries comply with the levels of ther-

Projects and Workshops

mal comfort, or indeed durability, that we now expect. It

Well-executed projects are the best advertisement for

is that much more important then that this building

rammed earth. In the Western world, they revive the for-

method is further developed on the technical level and

gotten material; in emerging and developing countries,

adapted to our current body of knowledge and needs. To

carefully designed and executed buildings increase the

achieve this, we need to look both backwards and for-

prestige of the material, giving it a new status. A renais-

wards, examining the historical precedents that still ex-

sance of rammed earth would benefit global energy use.

ist today in order to break new ground. Contemporary

This renaissance can be promoted through quality pro-

earth construction finds itself doing a balancing act

jects – as was the case with energy-efficient building. A

between tradition and experimentation.

new start will most likely not originate with construction industries and their organizations. There is simply

Reviving Learning by Doing

too little to be earned from a material that can be readily

Culture and construction of rammed earth building are

found everywhere in the world and utilized with very

rarely taught. How can one then approach the material?

little effort. In other words, earth will never have a lobby.

122  

However, a number of different universities have begun

unique opportunity to explore the properties of rammed

showing an interest in the material: students often first

earth both conceptually and in practice.

come into contact with earth building through workshops. Each of these seminars acts as a source of inspira-

Research Fundamentals

tion, sparking the interest of individual participants,

However, one thing that is still missing is systematic

who then stick with the material – sometimes for dec-

investigation of the technical aspects of the material,

ades. One workshop at Harvard University in 2012 had

such as its structural behaviour, material properties, and

over 150 students attending for nine days. At the Earth

systematization in production. This also reflects the fact

Works international summer school at the University of

that earth building has no lobby to back it; the impulse

Art and Design Linz, students and young architectural

for such research generally comes from industry, often

professionals from four continents met in Upper Aus-

accompanied by the necessary funding. In the case of

tria. In Dhaka, the capital of Bangladesh, more than one

rammed earth, these elaborate studies fall to earth build-

hundred participants crowded into a workshop origi-

ing companies and are frequently driven by individual

nally planned for thirty people. Such events have enor-

actors. It is essential to delve into the fundamentals of

mous ramifications. Thanks to the dedicated work being

earth construction: How can production make do with

done at universities, a network of earth building enthu-

less labour? How do construction and mixing processes

siasts is emerging and stretching across the globe. Its

affect the earth’s physical parameters? How much ener-

members became acquainted with rammed earth through

gy is required to build and operate a house out of earth?

project work or participating in workshops. And so the

There are a whole range of topics to be examined. In pur-

enthusiasm continues to grow.

suing these questions, it is essential that not just one university is involved but that an entire network of re-

Researching by Doing

searchers is created.

In addition, universities also provide the opportunity to research the fundamentals of rammed earth building.

Developing Knowledge

There was a lively process of exchange with the Chair of

Although awareness raising, research and further devel-

Prof. Annette Spiro at the ETH Zurich. An elective course

opment, and the generation of enthusiasm amongst the

entitled “Materials Workshop”, led by research and

architectural practitioners of tomorrow all have an im-

teaching assistant Gian Salis, investigated the possibility

portant part to play, the shortage of qualified earth build-

of erecting a pavilion in the form of a rammed earth

ing specialists cannot be overemphasized. In contrast to

dome on the university’s Hönggerberg campus. Stu-

other building techniques, rammed earth requires em-

dents were able to conduct material tests in Lehm Ton

pirical experience to develop a feeling for how to handle

Erde’s workshops to find out whether their ideas were

the material. Subtle qualitative differences can only be

feasible and construct the dome themselves under the

discerned by touch; in the first instance, this always

guidance of trained professionals. This represents an ini-

involves going out on a limb, because no conclusive de-

tial step in conducting pure research into rammed earth.

scriptions can be formulated. However, confidence grows



Martin Rauch took up a guest professorship with

as one comes to understand the material. In a nutshell,

architect Anna Heringer at the ETH in 2014, officially giv-

this knowledge cannot simply be acquired and learnt.

ing the Grenoble-based UNESCO Chair for Earthen Ar-

One also has to work for it.

chitecture a home in Zurich. There, they research how a high level of architectural quality can be achieved with the simple medium of rammed earth. However, these questions are not confined to the airless realms of academia’s ivory towers: the task for the spring semester 2015 was to design a home for orphans and a assembly hall in Tanzania. The best projects were selected and these designs were then built by the students themselves in a three-month summer school. This gave them a

123  

Building Regulations

tions – because the people concerned will have to assume responsibility for a material they do not have experience

Construction-grade earth can be found nearly anywhere

with.

in the world; ideally any rammed earth building is



made with a mixture produced from local material – this

surrounding the material and how to work with it, there

fact alone precludes standardization. Moreover, for hun-

must be collaboration between earth building experts,

dreds of years knowledge was transmitted primarily in

structural engineers, building physics engineers, and ar-

oral form. Written resources on the topic are therefore

chitects. In larger and more complex jobs, in particular,

rare: the building method was too vernacular, too firm-

this has led to a huge increase in both innovative and via-

ly anchored in the everyday lives of ordinary people. It

ble solutions over the last few decades. Interdisciplinary

seemed as though earth construction was not worthy

developments have created a range of new options for

of being preserved and passed on as a cultural achieve-

using rammed earth, most notably in the case of large-

ment. However, this probably comes not so much from a

scale buildings. This collaboration has significant poten-

sense of disdain as from the simple fact that it was once

tial: with the support of universities and research insti-

the primary method of building in Europe. It did not

tutes, new insights into earth building techniques can be

seem necessary to delineate a phenomenon that was at

achieved (see Knowledge Transfer, p. 122).

once so prevalent and so inherently modest. In the past,



building with this simple material was self-evident; as

search is to disseminate knowledge – formulating a set of

recently as two hundred years ago, most houses belonged

building standards for earth coxnstruction is a secondary

to the same typology, were constructed with the same

goal. Building regulations should guarantee quality as-

materials, and even executed in the same colour. Once

surance when design calculations and implementation

such a tradition had become established, it was repli-

are carried out in compliance with the standards they

cated without requiring explicit instruction.

stipulate; these specifications are intended to simplify



As a result, local traditions of earth building have

the work of planners in producing calculations and make

arisen, their techniques just as individual as the different

life easier for the technicians implementing the work.

regionally specific materials. This has remained a distinc-

While this is a logical approach in and of itself, ever-esca-

tive feature of earth building to this day, since it is a con-

lating demands have taken it to the point of absurdity,

struction method characterized by craftsmanship.

whereby the conflation of multiple building regulations



In order to establish a broad base for the knowledge

The purpose of collaborative endeavours and re-

This tradition of skilled labour is one of the great

and increased safety standards have made the act of

strengths of earth construction, because the work on each

building more and more complex and exacting. This has

building increases and deepens our knowledge of the

tended to impede innovation, because skilled tradesmen,

material’s properties, and this further develops the tech-

who were once one of the driving forces behind innova-

niques applied. Thus, each building can and should push

tion in the construction business, cannot afford to build

designers and earth building specialists to test the limits

outside the accepted regulations, which acts as an obsta-

of the material and the structures; this is the only way to

cle to new and often simpler solutions. In short, building

develop a feeling for rammed earth and, just as impor-

regulations must walk a tightrope between the conflict-

tantly, to stimulate innovation.

ing needs of guaranteeing safety and promoting innova-



tion.

In contrast to other building materials, skilled

workers cannot rely on product liability. They must ap-



The fact that earth – as typically local in origin – is

ply their own expertise to ensure that the material mix-

not covered by a set of building regulations, has very posi-

ture and technical execution comply with the latest sci-

tive aspects: it can appear as an exotic species on a build-

entific knowledge and methods. The competence they

ing site – the last DIN regulations on rammed earth were

have developed themselves allows them to predict how

discarded in 1956 and never replaced – while the legal

the material will behave and determine the proper pro-

limbo it occupies permits further exploration and devel-

portions that are required for the job. Technical planners

opment.

and institutions are often required to perform structural



analyses and, in some cases, provide elaborate certifica-

tion. The German Association for Building with Earth

Nevertheless, there have been efforts at codifica-

124  

(Dachverband Lehm e.V.) began publishing norms for earth building at the end of the 1990s. A norm seems more appropriate than a building regulation, per se, since even the word itself allows more space for innovation and personal expertise. On the other hand, the Association has successfully developed rules for certain industrially produced building elements and materials, such as non-stabilized earth blocks, clay mortar, and clay plaster. Such progress will enable these products to have a much broader application and is therefore welcome.

Most building regulations, however, tend to favour

industrialized manufacturers over smaller producers, since creating them is a costly business; an industry like earth construction, oriented towards craftsmanship, does not possess the necessary financial resources. So, in accordance with rich local traditions, earth building specialists should be allowed to continue making their own earth bricks, clay mortar, and clay plaster. Specific Values and Calculation Criteria To allow builders to work according to a set of technical norms, verifiable minimum specific values can be stipulated for rammed earth. Most of this data – such as compressive strength – can be proven simply and straightforwardly for each new mixture and building task and used by structural engineers for both design and implementation. The process also occurs in other building sectors and has stood the test of time: both prior to and during the construction phase, mixtures of local materials are worked out. They are based on the specifications of technical experts and tested in a laboratory to determine their compressive strength using test specimens conforming to established building regulations.

These are the minimum specific values that can be used as a basis for calculating an earthen mixture in line with professional standards: Compressive strength: 2.4 N/mm2 Flexural strength: 0.52 N/mm2 Shear strength: 0.62 N/mm2 Material shrinkage: depending on the material, 0.25 % – 1 % Creep deformation: 0.2 % Thermal expansion: 0.005 mm/mK Thermal conductivity: depending on the material, 0.64 – 0.93 W/mK

125  

Team Dominik Abbrederis, Michael Abbrederis, Daniel Aebischer, Mahmadu Ba, Uwe Bär, Lukas Baumann, Elias Binggeli, Hanno Burtscher, Lydia De Martin, Gertrude Filzmaier, Roland Frick, Lukas Fritz, Tobias Fritz, Dominique Fulterer, Candotti Giacomino, Nikolaus Gohm, Dominik Grafl, Viviane Greuter, Annina Gubser, Michael Haider, Joachim Haug, Anna Heringer, Reiner Hettenbach, Thomas Honermann, Sascha Horni, René Kindler, Manuela Kiss, Eveline Koch, Markus Lerch, Elmar Losch, Daniel Lüthi, Adnan Mahmudi, Laura Marcheggiano, Aaron Merdinger, Richard Mitchell, Johannes Moll, Claudia Müller, Stefan Neumann, Samuel Nesensohn, Christoph Obernosterer, Stefan Peball, Clemens Quirin, Elke Radlspäck, Assunta Rauch, Benno Reber, Ute Salzgeber, Philipp Schoder, Markus Schröcker, Egon Schwarzhans, Pauline Sémon, Martin Stenflo, Hubert Stephan, Leonar Stieger, Wayne Switzer, Brigitta Tomaselli, Emanuel Tomaselli, Lukas Tomaselli, Christoph Trojok, Tanja Ursella, Sabrina Vonbrül, Ariane Wilson, Uwe Wirthwein, Monika Wolfinger, Jomo Zeil, Paul Zeller Partners Studio Anna Heringer, ETH Zürich, BASEhabitat – Kunstuniversität Linz, KARAK – Marta and Sebastian Rauch, Lehmo – Müller Ofenbau, Johannes Rauch, Malerwerkstatt Gerold Ulrich

I would like to take this opportunity to sincerely thank all of my former and current colleagues, as well as the many people not named in this publication who have, over the years, supported my work with earth building. I am also indebted to my clients, whose courage and considerable trust allowed many innovative projects to come to fruition.Earth building unites and a shared interest in this healthy building technique encourages good teamwork – a guarantee for optimal results! Martin Rauch Lehm Ton Erde Studio and Production Hall Zwingen/Laufen 2013, Schlins 2015 Photographed by Markus Bühler-Rasom

Lehm Ton Erde Studio, Schlins

Lehm Ton Erde Studio, Schlins_mixing and ramming

Lehm Ton Erde Studio, Schlins_filling the formwork

Lehm Ton Erde production hall, Zwingen_premixing

Lehm Ton Erde production hall, Zwingen_ramming

Lehm Ton Erde production hall, Zwingen_routing vertical groove

Lehm Ton Erde production hall, Zwingen_warehouse

Ricola Kräuterzentrum construction site, Laufen_installing prefabricated elements

Ricola Kräuterzentrum construction site, Laufen_sealing round window

Lehm Ton Erde production hall, Zwingen_test drilling

Ricola Kräuterzentrum construction site, Laufen_retouching

Ricola Kräuterzentrum construction site, Laufen_after installation of final element

List of Works

Omicron Crossing Border – Art installation



Klaus, Austria, 2014, Design: Anna Heringer &



Martin Rauch , load-bearing, in situ, 80 m², 33 t



Single-Family House B.-S. – Rammed earth wall



Almens, Switzerland, 2014, Architecture: Norbert Mathis



Architekt, non-load-bearing, prefabricated, 42 m², 44 t



Single-Family House Ö.-E. – Rammed earth wall



Ruggell, Liechtenstein, 2014, Architecture: Architektur



Atelier, non-load-bearing, prefabricated, 37 m², 26 t



Novartis Campus – Trass-lime wall



Basel, Switzerland, 2015, Landscape architecture:



Vogt Landschaftsarchitekten, free-standing, in situ, 1,050 t

Swiss Ornithological Institute – Rammed earth façade Sempach, Switzerland 2013 − 2014, Architecture: mlzd Architekten, non-load-bearing, prefabricated; 1,240 m²; 1,130 t

ETH Materials Workshop – Rammed earth cupola –



Zurich, Switzerland, 2013 − 2014, Organization & Design:



D-ARCH, Chair of Prof. Annette Spiro, research



assistant Gian Salis, elective course Materials Workshop



load-bearing, prefabricated, 39 t



Kindergarten Muntlix – Rammed earth floor Muntlix



Austria, 2013, Architecture: Hein Architekten, 492 m², 93t

Ricola Kräuterzentrum – Rammed earth façade Laufen, Switzerland 2012 − 2013, Architecture: Herzog & De Meuron, non-load-bearing, prefabricated; 2,780 m²; 2,935 t

Harvard University Workshop – MudWorks



Cambridge , USA, 2012, Design: Anna Heringer &



Martin Rauch, free-standing, in situ, 30 m², 45 t



Single-Family House F. – Rammed earth wall & Lehmo



Schwarzach, Austria, 2012, Architecture: Heim & Müller



non-load-bearing, in situ, 55 m², 46 t

School Pavilion Allenmoos II – Rammed earth façade Zurich, Switzerland 2011 − 2012, Architecture: Boltshauser Architekten, load-bearing, in situ, 130 m², 119 t

Bad Schinznach Sauna – Rammed earth wall



Bad Schinznach, Switzerland, 2011, Architecture: Hans Peter



Fontana & Partner, non-load-bearing, in situ, 73 m², 61 t

Gaissau Cemetery – Rammed earth wall

Gaissau, Austria, 2011 − 2012, Architecture: Georg Rauch



free-standing, in situ, 31 m², 31 t



Earth Building, Merian Gardens – Rammed earth façade



Basel, Switzerland, 2011 − 2012, Architecture: Barcelo Baumann



Architekten, non-load-bearing, prefabricated, 281 m², 169 t

Single-Family House B.-S. – Rammed earth wall Flims, Switzerland 2011, Architecture: Fehlmann Brunner Architekten, load-bearing, prefabricated, 230 m², 195 t

152  



Eschen Cemetery – Rammed earth wall



Eschen, Liechtenstein, 2010 − 2012, Architecture: Hans-Jörg



Hilti, free-standing, prefabricated, 125 m², 112 t



Earth Works Summer School – Workshop



Gmunden, Austria, 2010, Organization & Design:



Linz University of Art and Design – BASEhabitat; Anna



Heringer & Martin Rauch, free-standing, prefabricated, 15 t

Mezzana Agricultural College – Rammed earth façade Coldrerio, Switzerland, 2010 − 2012 Architecture: Conte Pianetti Zanetta Architetti, non-load-bearing, prefabricated, 930 m², 760 t

King Abdulaziz Centre for World Culture – Rammed earth

wall , Dhahran, Saudi Arabia, 2010 − 2014, Architecture:

Snøhetta, non-load-bearing, prefabricated; 2,823 m²; 3,009 t



Haus der Architektur Graz – Exhibition Graz, Austria



2010, Exhibition design: Martin Rauch & Eva Guttmann

Single-Family House Stall Plazza Pintgia – Rammed earth wall Almens, Switzerland, 2010, Architecture: Gujan + Pally, load-bearing, prefabricated, 59 m², 70 t

Gönhard School Complex – Trass-lime façade



Aarau, Switzerland, 2009 − 2010, Architecture: Boltshauser



Architekten, non-load-bearing, prefabricated, 243 m², 200 t



Lohbach Home for the Elderly – Rammed earth wall



Lohbach, Austria, 2009, Architecture: marte.marte



architekten, non-load-bearing, prefabricated, 16 m², 2 t



Jung Funeral Parlour – Rammed earth sculpture



Salzburg, Austria, 2009, Design: Martin Rauch



non-load-bearing, prefabricated, 47 m², 12 t



Single-Family House G. – Trass-lime floor



Rapperswil, Switzerland, 2009, Architecture: Miller &



Maranta Architekten, 660 m², 144 t



Embach Spiritual Centre – Rammed earth wall



Embach, Austria, 2009 − 2010, Architecture:



LP Architektur, load-bearing, in situ, 85 m², 39 t



Sil Plaz Cinema – Rammed earth wall and floor



Ilanz/Glion, Switzerland, 2009 − 2010, Architecture: Capaul &



Blumenthal Architects, non-load-bearing, in situ, 182 m², 67 t

Letzi Apartment Complex – Rammed earth wall Küsnacht, Switzerland 2009, Architecture: Peter Kunz Architektur, free-standing, prefabricated, 287 m², 238 t

“Plant Room”, Kunstraum Dornbirn – Art installation



Dornbirn, Austria, 2008, Artist: Simon Starling



load-bearing, in situ



Single-Family House H. – Rammed earth floor Basel, Switzer-



land, 2007, Architecture: Luca Selva Architekten, 113 m², 21 t



Confignon Community Center – Rammed earth wall



Confignon, Switzerland, 2007, Architecture: atelier b & m



architecture & territoire, free-standing, in situ, 54 m², 57 t

153  



Wil Cemetery, Phase 2 – Rammed earth wall Wil



Switzerland, 2007, Landscape architecture: Engeler Freiraum-



planung & Martin Rauch, free-standing, in situ, 85 m², 104 t



Novartis Campus – Trass-lime wall



Basel, Switzerland, 2007, Landscape architecture:



Vogt Landschaftsarchitekten, free-standing, in situ, 800 t



Fluntern Cemetery – Rammed earth wall Zurich,



Switzerland, 2007, Landscape architecture: Berchtold.Lenzin



Landschaftsarchitekten, free-standing, in situ, 25 m², 29 t

Single-Family House Rauch – Rammed earth façade and floor Schlins, Austria, 2005 − 2008, Architecture: Roger Boltshauser & Martin Rauch, load-bearing, in situ

Verwaltungsgebäude UVEK – Art Installation



Bern, Switzerland, 2005 − 2006, Design: raderschallpartner



landschaftsarchitekten, Martin Rauch, 6 m², 27 t



Hergiswil Cemetery – Rammed earth wall Hergiswil



Switzerland, 2005, Architecture: Richard Kretz, Renato



Lampugnani & Martin Rauch, free-standing, in situ, 41 m², 70 t



Riem Church – Rammed earth floor and altar



Munich, Germany, 2005, Design: Florian Nagler



Architekten & Martin Rauch, 28 m², 9 t



Warehouse Grounds – Trass-lime wall



St. Gallen, Switzerland, 2005, Architecture: Vogt Land-



schaftsarchitekten, free-standing, in situ, 47 m², 81 t



Kardinal-Schwarzenberg-Haus – Rammed earth wall



Salzburg, Austria, 2005, Architecture: Flavio Thonet



non-load-bearing, in situ, 77 m², 31 t

La Raia Vineyard – Rammed earth façade Novi Ligure, Italy, 2005, Architecture: Ivana Porfiri, non-load-bearing, in situ, 223 m², 239 t

Wellness Area at Waldhaus Mountain Resort – Rammed



earth wall Flims, Switzerland, 2004, Architecture: Hans Peter



Fontana & Partner, non-load-bearing, in situ, 130 m², 99 t



Quasi Brick, la Biennale di Venezia – Exhibition



Venice, Italy, 2003, Artist: Olafur Eliasson



Vigilius Mountain Resort Hotel – Rammed earth wall



Lana, Italy, 2003, Architecture: Matteo Thun, free-standing



prefabricated, 230 m², 98 t



Chesa Valisa Hotel – Rammed earth wall



Hirschegg, Austria, 2002, Architecture: Architekten



Hermann Kaufmann, load-bearing, prefabricated, 69 m², 65 t



Schlins Cemetery – Rammed earth wall



Schlins, Austria, 2001, Design: Martin Rauch



free-standing, in situ, 68 m², 79 t

Chapel of Rest at the Batschuns Cemetery – Rammed earth façade Batschuns Austria, 2001, Architecture: marte.marte architekten, load-bearing, prefabricated, 176 m², 153 t

154  



Thüringen Bus Station – Rammed earth wall



Thüringen, Austria, 2001, Architecture: Bruno Spagola



non-load-bearing, prefabricated, 17 m², 6 t



Sihlhölzli Sports Complex – Rammed earth façade



Zurich, Switzerland, 2001 − 2002, Architecture: Boltshauser



Architekten, load-bearing, in situ, 250 m², 247 t



“The Mediated Motion”, Kunsthaus Bregenz – Exhibition



Bregenz, Austria, 2001, Artist: Olafur Eliasson &



Günther Vogt, 470 m², 50 t



“Earthwall”, Hamburg Bahnhof – Exhibition



Berlin, Germany, 2000, Artist: Olafur Eliasson



free-standing, in situ, 96 m², 100 t

Etosha House at Basel Zoo – Rammed earth façade Basel, Switzerland, 1998 − 1999, Architecture: Peter Stiner, load bearing, in situ, 420 m², 400 t Gugler Printers Office Building – Rammed earth wall Pielach, Austria 1998 − 1999, Architecture: Ablinger, Vedral & Partner, non-load-bearing, prefabricated, 350 m², 210 t

Alpbach Congress Centre – Rammed earth wall



Albpach, Austria, 1998, Architecture: DINA4 Architektur



non-load-bearing, in situ, 270 m², 110 t



Wil Cemetery, Phase 1 – Rammed earth wall Wil, Switzer-



land, 1997 − 1998, Landscape architecture: Engeler Freiraum-



planung & Martin Rauch, free-standing, in situ, 200 m², 380 t



Single-Family House R. – Rammed earth wall



Hard, Austria 1997, Architecture: Architekten Hermann



Kaufmann, non-load-bearing, in situ, 14 m², 9 t



St. Gerold’s Priory Cemetery – Rammed earth wall



St. Gerold, Austria, 1994, Design: Martin Rauch



free-standing, in situ, 145 m², 40 t



Single-Family House M. – Rammed earth façade



Rankweil, Austria, 1993 − 1996, Architecture: Robert



Felber & Martin Rauch, load-bearing, in situ, 150 m², 160 t

Feldkirch State Hospital – Rammed earth wall Feldkirch, Austria, 1992 − 1993, Design: Martin Rauch, non-load-bearing, in situ, 550 m², 250 t

Chapel of Reconciliation – Rammed earth façade



Berlin, Germany, 1999 − 2000, Architecture: Rudolf Reiter-



mann & Peter Sassenroth, load-bearing, in situ, 180 m², 250 t

Lehm Ton Erde Studio – Rammed earth façade Schlins, Austria, 1990 − 1994, Architecture: Robert Felber & Martin Rauch, non-load-bearing, in situ, 132 m², 144 t

Atelier Gassner – Rammed earth wall



Schlins, Austria, 1984, Architecture: Rudolf Wäger



non-load-bearing, in situ, 8 m², 8 t



Single-Family House R. – Rammed earth wall



Schlins, Austria, 1982 − 1986, Architecture: Johannes Rauch



non-load-bearing, in situ, 70 m², 40 t

155  

Glossary Air rammer

Druckluftstampfer

Air pressure rammers are pneumatic compaction devices that are usually operated by hand.

Carnauba hard wax

Carnauba-Hartwachs

Wax that is derived from the leaves of the carnauba palm. It is the hardest known form of natural wax.

Casein

Kasein

The main protein present in milk – a traditional, natural, and powerful binding agent.

Clay

Ton

Clay is composed of natural, fine-grained minerals. With the addition of water, it becomes malleable. After it dries, the clay hardens but the process remains reversible; after firing, the bond becomes non-water-soluble.

Construction

Werksplanung

documentation

Construction documentation refers to the preparation of drawings for elements to be produced in the factory or the in situ formwork plan for the building site.

Drum compactor

Walzen

Compaction rollers are commonly used in civil engineering and were originally used to compact the earth for trenches. The same process is also possible in solid formwork.

Earth building

Lehmbau

General term for building with loam using a variety of techniques.

Earth-moist

erdfeucht

Describes the natural moisture content of earthen material. During construction process rammed earth mixture should be earth moist.

Earth mortar

Lehmmörtel

Used to join together different earthen elements – composed of a simple mixture of slightly fluid loam, sand, and water. Earth mortar is reversible and can be reinforced with plant fibres.

Equilibrium

Gleichgewichtsfeuchte

moisture content

The water content of a material that has stabilized after being stored under stable conditions over a period of time. The equilibrium moisture content of earth is 6–7 per cent, which is less than that of wood (ca. 9 per cent).

Erosion

Erosion

The natural weathering and abrasion of stone and soil. In rammed earth building, calculated erosion refers to a predictable form of erosion whose development is determined by structural features (erosion checks) and the quality of both the material and the compaction process.

Excavation

Aushub

The material that is removed from a construction pit (through the digging out of cellars and foundations). With rammed earth, this cannot contain any topsoil.

Gravel additives

Gesteinszuschläge

Mineral additives made of different kinds of stone; in rammed earth they can range in size by up to 32 mm.

In situ construction

Vor-Ort-Herstellung

On-site processes of fabrication refer to the production of rammed earth walls and floors directly on the job site.

Loam, lean

Lehm, mager

Loam with a low clay content is described as lean.

Loam, rich

Lehm, fett

Loam with a high proportion of cohesive clay is described as rich.

Loam, soil, earth, mud

Lehm

Loam is a mixture of sand, silt, and clay. It is created by the processes of weathering and erosion.

156  

Marl

Mergel

A sedimentary stone composed of clay, silt, and lime.

Micro-crack

Mikroriss

A very fine crack invisible to the naked eye. During the drying process, loam is subject to shrinkage. In the case of rich loam, the visible cracks will always be accompanied by countless micro-cracks.

Moisture

Feuchtigkeit

Dampness – both in the form of water (moisture that is rising, standing, running off, or used as part of the mix) and as water vapour – plays an important role in earth building (moisture control).

Moisture expansion

quellen

If water is added to loam, its volume increases and it swells.

Prefabrication

Vorfertigung

The production of rammed earth components in a workshop. The finished elements are then transported to the building site for installation.

Rammed earth

Stampflehm

Massive earth building technique. Rammed earth is made from a mixture of loam and granulated stone, that can be frequently be found in nature.

Rammed earth facade

Stampflehmfassade

A rammed earth wall that is usually self-supporting and is exposed to the weather.

Rammed earth floor

Stampflehmboden

A massive floor made of rammed earth that has been compacted to ca. 10 cm.

Rammed earth prefebricated

Stampflehmfertigteil

component

An indoor-prefabricated segment, which is then installed on-site with other prefabricated elements to form a wall.

Rammed earth wall

Stampflehmwand

Massive, vertically oriented building component made of rammed earth.

Ramming

stampfen

A method of compaction to bind earth-moist loam. In the process, the loose earthen material is turned into a solid mass.

Retouching

Retusche

The process of making additional improvements to a surface or joint.

Self-supporting

selbsttragend

Building element able to carry its own weight but not that of others.

Shrinking

schwinden

As moisture evaporates, the volume of loam decreases, causing it to shrink.

Slaking

mauken

The conscious storage of readily mixed earth. The process of resting and aging increases the cohesiveness of clay as a binding material.

Slurry

Lehmschlämme

A mixture of loam and a large amount of water. As such, loam-based slurry is more fluid than earth mortar.

Trass lime

Trasskalk

Trass is a natural volcanic stone with a high level of silicic acid, which reacts with lime to become an almost completely non-water-soluble substitute for mortar or cement.

Water vapor

Dampfdiffusion

diffusion

The transmission of water vapour through a building component. If this transmission is unrestricted – i.e., it is not retarded by a damp-proof membrane – it is referred to as vapour permeability.

Wax emulsion

Wachsemulsion

Water-soluble emulsion with a wax component.

157  

Martin Rauch · A graduate of the Technical College of Ceramics and Kiln Construction, Stoob, he studied ceramics under Prof. Matteo Thun and Prof. Maria Bilger-Perz at the University of Applied Arts Vienna; in 1983, his diploma thesis “Lehm Ton Erde” (Loam Clay Earth) was awarded an honorary prize by the Austrian Federal Ministry for Science and Research. Since 1990, he has conceived, planned, and implemented numerous earth building projects both in Austria and abroad; he founded the firm Lehm Ton Erde Baukunst GmbH in 1999. He has taken part in solo and group exhibitions and has won countless prizes and awards, including the Ernst A. Plischke Award (in 2014), the Holcim Award (in 2011), the Fassa Bortolo International Prize for Sustainable Architecture, and the Client Award of the Austrian Association of Architects (both in 2008). From 2003 to 2010, he was a lecturer at the Linz University of Arts and hosted international workshops and summer schools in a number of countries, including Bangladesh, South Africa, Tanzania, and Austria; since 2010, he has been honorary professor of the UNESCO Chair of “Earthen Architecture” and a visiting lecturer at the ETH Zurich since 2013. Otto Kapfinger · Studied architecture at the Vienna University of Technology; in 1970, he cofounded Missing Link (with Angela Hareiter and Adolf Krischanitz); from 1979 to 1990, he was editor of UMBAU magazine and, from 1981 to 1990, architectural critic for the newspaper “Die Presse”. He has produced a range of publications and exhibition concepts on modern and contemporary architecture in Austria and headed the curator team for the exhibitions “Visionäre und Vertriebene”(Visionaries and Exiles) at the Kunsthalle Wien and “Architektur im 20. Jahrhundert: Österreich” (Architecture in the Twentieth Century: Austria) at the German Architecture Museum. He is a long-standing jury member for vaious architecture prize committees, including the Client Award of the Austrian Association of Architects and the Austrian National Prize for Architecture and Sustainability. Marko Sauer · Studied educational science and architecture in St. Gallen, Vaduz, and Tokyo. He was project architect at Staufer & Hasler, Frauenfeld (CH) for three years and subsequently head of communications for the St. Gallen Building Department in Switzerland. He is also trained as an architectural journalist. He has published articles in specialist journals and newspapers and has authored a number of different books; he has been an editor for the “TEC21” periodical since 2013 and helped conceive and implement “unit architektur: Baukultur im Unterricht”. Since 2015, he has been director of the “Spacespot” association, which sets out to introduce and mediate architecture to schoolchildren. From 2011 to 2014, he was on the board of the East Switzerland regional chapter of the Swiss Werkbund; since 2011, he has been director of the Architektur Forum Ostschweiz and headed the project “Gutes Bauen Ostschweiz” (Quality Building in East Switzerland), which saw him running a series of articles in the news dailies.

Editors: Otto Kapfinger, Marko Sauer Author: Marko Sauer (except where otherwise indicated) Production management/subeditor: Clemens Quirin Translation from German to English: Lindsay Blair Howe Technical copy-editing: Laura Marcheggiano Copy-editing: Simon Cowper Publishing coordination: Cornelia Hellstern Graphic concept and design: Gassner Redolfi KG Andrea Redolfi Photographs: Reinold Amann: p. 74, Beat Bühler: pp. 71, 104 – 105, 152 Markus Bühler-Rasom: pp. 79, 114, 128 – 151, 155, Ralph Feiner: p. 153 Michael Freisager: p. 92, Bruno Klomfar: pp. 52 – 53, 155 Benedikt Redmann: pp. 14 – 49, 66 – 67, 86 – 87, Dominique Wehrli: p. 153 Lehm Ton Erde: pp. 59, 74, 97, 154 Illustrations based on plans/details by: Boltshauser Architekten: Haus Rauch, pp. 82, 97, 106 – 107, 108, 109, 154 Sportanlage Sihlhölzli, pp. 76 – 77, 81, 93, 110 Conte Pianetti Zanetta Architetti: Mezzana Agricultural College, pp. 100, 101, 112, 153 Fehlmann und Brunner Architekten (FeBruAr), p. 152 Robert Felber: Lehm Ton Erde Studio, pp. 94, 109, Mathies House, p. 113 Hans Peter Fontana und Partner: Waldhaus Mountain Resort, p. 93 Herzog & de Meuron: Ricola Kräterzentrum, pp. 79, 83, 88 – 89, 96, 99, 152 marte.marte architekten: Batschuns Chapel of Rest, pp. 68 – 69, 97, 154 :mlzd: Swiss Ornithological Institute Visitor Centre, pp. 81, 98, 152 Rudolf Reitermann & Peter Sassenroth: Chapel of Reconciliation, pp. 54 – 55, 95, 96 Peter Stiner: Etosha House at Basel Zoo, p. 155 Plan graphics: Pauline Sémon and Laura Marcheggiano Printing: Eberl Print GmbH, Immenstadt © 2015 DETAIL – Institut für internationale Architektur-Dokumentation GmbH & Co. KG, Munich All rights reserved. No part of this publication may be reproduced, distributed, or transmitted without the prior written consent of the publisher, except in non-commercial uses permitted by copyright law. Bibliographic information published by the German National Library. This publication is catalogued in the Deutsche Nationalbibliografie by the German National Library; bibliographic details can be found online at http://dnb.d-nb.de. ISBN 978-3-95553-273-4 (Print) ISBN 978-3-95553-274-1 (E-Book) ISBN 978-3-95553-275-8 (Bundle)

160