Loam Cupola rises on Zurich's ETH campus

In autumn 2014 Martin Rauch led a team of twenty six students on a practical research project to make an earthen vaulted structure. ETHZ's Gion Salis records the results.

In this research and teaching project on rammed-earth vaulting, experts and students developed constructions that make it possible to use rammed earth to build previously impracticable load-bearing arches and vaults. The project was the first time that load-bearing rammed-earth vaulting was constructed using pre-fabricated elements. The new load-bearing rammed-earth vaults and arches expand the range of design options for rammed earth and will contribute to the further spread of this sustainable building material.

The aim was to convey the relationship between material, construction, form and architectural appearance. The search was for new architectural images for buildings whose character is defined via material and construction.

Rather than working theoretically, the students experienced a practical opportunity to explore the building materials. The set task was to develop and to built a pavilion consisting of space-spanning constructions made out of rammed earth on the Campus Hönggerberg of the ETH Zurich.

We were looking for a material-specific form of architectural expression for rammed-earth buildings. The materials ability to span arches has not previously been exploited. Its vivid archaic qualities are particularly expressive in the sculptural underside views of the vaulting. Vaulting is widespread in loam constructions, but nevertheless to date has not been executed using rammed-earth techniques, even though this potential was theoretically described by the Frenchman François Cointeraux in as early as 1803. The construction of roofs or arches was previously attainable only through the use of loam bricks and mortar. In the meantime technical innovations have provided new scope to realize such ideas. Rammed-earth vaulting is made possible by prefabrication. During construction, the dry units are fully load-bearing and there is no further shrinkage. The prefabrication technique for rammed-earth elements developed by Martin Rauch and further elaborated for rammed-earth vaulting allows more efficient and weather-independent semi-industrial production, enabling cheaper and faster construction even of larger buildings. New shapes can be built that would not be rammable on site. The vaulting could also be made larger using the same technique.

As opposed to walling, in arches and vaulting the forces no longer run perpendicular to the packed layers. Our experiments showed that the compressive strength is independent of the direction in which the rammed earth layers runs. As a new development, this means that ceiling vaults can be rammed vertically and installed after by 90-degree rotation.

During the seminar, 26 students working in groups of three or four developed seven different designs. Due to the fact that rammed earth can only absorb compressive force the students designed the respective structures together with experts. Mock-up-models were built in the scale 1:1 with local loam from the campus Hönggerberg. After the final review the design of a five-metre-high multi-purpose shelter defined by six wide arches and six domes that open outwards was chosen for further elaboration.

During a two-week workshop the students completed all 19 rammed earth elements of the later cupola in the prefabrication hall. Robust wood formworks were filled with layers of local loam, which was then compressed with pneumatic rammers. The vaulted roofs were rammed resting on their faces and then later rotated during the assembly process.

Last summer after the concrete foundation was built, the dried elements - weighing up to three tonnes - were erected by the students at the Hönggerberg campus, using a pneumatic crane. Afterwards the students plastered the joints and filled the holes for the crane suspension by applying moisture, pressing it down with loam and lightly tapping the area with a hardwood board and hammer. In the end a galvanized metal roof was constructed to protect the loam from the rain.

Cooperative collaboration between students, experts and artisans in planning and implementation lead to a deeper understanding of design, craft and the materials cycle. In addition, the students learned how to plan and actually build with clay. Our rammed-clay mixture from local excavations does not contain any stabilizing material like cement. Hence it could be fully re-used as construction material without any loss of quality.

The open rammed-earth pavilion on the campus is now open to the public and equipped with tables and chairs as a meeting-point for students and should serve as an inspiration for further innovative and sustainable projects.

Project lead
ETH Zürich, Department of Architecture
Prof. Annette Spiro,
Architecture und Construction
Lecturer Gian Salis, Wahlfach Material-Werkstatt

Martin Rauch, Lehm Ton Erde GmbH Schlins, with Dominik Abbrederis, Hanno Burtscher, Clemens Quirin, Thomas Honermann, Laura Marcheggiano, Assunta Rauch
Dr. Andreas Galmarini, Oliver Bruckermann, Walt+Galmarini AG, Structural engineering
Prof. Dr. Philippe Block, Block Research Group ETH Zürich

Master Students, Department of Architecture, ETH Zürich
Andreas Zimmerli, Anil Erkan, Anna Hüveler, Antonia Forster, Audrey Mondoux, Basil Witt, Beat Lüdi, Blanca Rieder, Botian Li, David Brunner, Deborah Suter, Elisabeth Suter, Francesca Wyser, Georg Bachmann, Gnanli Landrou, Jessica Wilcox, Per Johan Alvfors, Julianne Gantner, Leif Linhoff, Lion Haag, Lorraine Haussmann, Lukas Nacht, Manuel Däster, Manuel Lergier, Mathias Lattmann, Nadine Jaberg, Nina Hug, Patrick Suhner, Remo Reichmuth, Ricardo Joss, Simon Burri, Simon Schoch, Tessa Vollmeier, Thomas Meyer, Valentin Surber, Zimu Wang, Ziyue Ding