A small south-east german town celebrates its shellfishing heritage with a museum entrance that double-curves like a mussel and glistens under a constant flow of fresh water

 Adorf, a small town close to the Czech border, shares the same problems as many rural areas in the former East Germany: an ageing and shrinking population, unemployment and economic decline. At one time, however, it was a major centre of freshwater pearl mussel fishing. The pearls – found in only one out of every two thousand mussels – were highly prized, while the shells were used to craft a variety of artisanal objects including purses, clocks and jewellery boxes.

In an effort to reverse the town’s fortunes, Adorf recently opened a museum celebrating this cultural heritage. But the shell that has caught the most attention is the building itself: a carapace of boardmarked concrete wedged between two half-timbered buildings on a formerly vacant site in front of the medieval city wall.

“The facade represents a transformation of a seashell,” explains Ansgar Schulz, director of Leipzig-based architect Schulz und Schulz. “Both seashells and concrete shells are created through mineralisation – through a biological process in the case of the shell, and through a chemical-technical process in the case of the building envelope, namely the hydration of cement.”

Schulz has reinterpreted the curved mussel shell as a warping, windowless front wall. A fold in the roofline corresponds to the eaves of the neighbouring buildings. From here, the wall descends three storeys to the first floor level, where it is pulled outwards at one corner.

This creates an overhang to the entrance below and twists the whole wall into a double curve. The concrete wall suggests a mussel shell in other ways too. Anthracite pigments give a dark grey tone, while the narrow horizontal lines of the timber formwork evoke the crustacean’s annual growth rings. Water flows continuously over the rough surface of the wall, “symbolising the basis for life of mussels”, says Schulz.

Individually adjustable nozzles on the roof, usually used in agriculture, ensure the facade is evenly wetted. The water is then collected in a concrete gutter on the edge of the entrance canopy. “Our roofer constructed a small pouring aid, similar to that used when pouring wine from a bottle, which allows the water to drain off precisely.” From here, it is funnelled into a well before being pumped back to the top of the building in a solar-powered loop.

The wall comprises an inner and outer leaf of 250mm-thick in-situ concrete, filled with 200mm of XPS insulation. The inner leaf is a loadbearing part of the structure, tied into the slabs, and has a “very slight” curvature. “For this reason, the formwork elements were as narrow as possible and only clamped at the top and bottom, and at the floor slabs,” says Schulz. Bespoke anchors were embedded into the shell to connect to the outer shell.

The asymmetric outer layer was initially given shape in the workshop of André Schürer, master carpenter at contractor SP Bau Lengenfeld. He created a non-scale model to illustrate the curves, before applying the hyperbolic paraboloid form to the actual dimensions of the roof ridges and eaves. At the same time, the architects and contractor were making mock-ups to explore colouring, board sizes and finishes. To create the crustacean-like texture, they chose thin strips of open-pored timber, “flamed but not charred”.

The boards were laid on large panels, flexible enough to be twisted into shape. These were then placed in the formwork system, which was tied into the structural wall with anchor beams and individually adjusted spacers. Electronic sensors measured the concrete strength as it cured, enabling the formwork to be struck after three days.

Despite the windowless concrete wall, the glazed entrance offers passers-by tantalising glimpses of the museum inside. Here, smooth white surfaces frame a section of the historic city wall, naturally lit from above. Just like the pearl mussel, a rough shell washed by water encloses a precious, shimmering interior. 

Interview by Nick Jones

Photos: Gustav Willeit, Albrecht Voss