In Switzerland, Boltshauser Architekten Brings Upscale Housing Down to Earth

For Roger Boltshauser, founder of Zurich-based Boltshauser Architekten, the 2008 Rauch House in Schlins, Austria, changed the course of his career. Codesigned with Martin Rauch, a European pioneer in the revival of earth construction, it was built almost entirely from soil excavated on-site. Since then, Boltshauser has been progressively pushing client boundaries with respect to low-carbon building techniques, in particular earth construction. At Kilchberg, just outside Zurich, his firm recently turned the dial up a notch when it completed a small apartment building—seven rental units, ranging from a studio to two-bedrooms—that uses both recycled fired bricks and unbaked earth block.

With its hillside views over Lake Zurich and the old city beyond, Kilchberg is at the upper end of the Swiss residential market, attracting the kind of wealthy occupants who drive Ferraris and Porsches. Fearing that those with such a social profile might be put off by anything too radical, the client rejected Boltshauser’s proposal for load-bearing earth and brick walls, instead preferring the standard Swiss solution of a concrete frame. “Faced with this situation, we aimed to minimize the frame and maximize the filling,” explains the architect. Using a post-and-slab system he likens to Le Corbusier’s 1914 Maison Dom-Ino proposal, Boltshauser designed a building that is reminiscent of another celebrated Corbu project, the 1955 Maisons Jaoul in Paris. Both Jaoul and Kilchberg display a similar combination of exposed structural concrete and tactile brickwork infill, but, where Le Corbusier changed bricklayer every few courses to achieve a roughed-up effect, Boltshauser used time-patinated 100-year-old clinker bricks. These were reclaimed from a demolished church in Cologne, Germany, 250 miles away, a distance “that’s about the limit for sustainability,” comments the architect. “We debated whether we should use these bricks, but decided to go ahead, to show that it can be done, because there’s no brick-recycling industry in Switzerland.” Since modern mortars make it impossible to separate bricks without breaking them, Boltshauser specified a weaker mix, so the clinkers can be recycled again when the time comes.