Together with Martin Steinmann and the artist Josef Felix Müller, Diener & Diener realized the extension of the "Schlössli", a rough medieval tower made of boulders, which is used as Stadtmuseum and has its address at Schlossplatz. The program of the new museum section on the west side are column-free large exhibition rooms, offices in the attic and a workshop space in the basement. The staircase and the elevator open up the new building and the winding path system of the tower. The main entrance has been moved to the new building.
The new figure shifts the weight of the museum to the axis of the Schlossplatz, the public space. The slightly outwardly folded 12 m high, 25 m wide representative wall of the new building facing the square, consists of 134 portrait format concrete slabs based on sketches by the artist. From the wood of the sequoia, which had to give way to the new building, he carved portraits of people he met at airports and railway stations, and had cast a unique series of concrete panels from the woodcuts to make them a monumental mural in the square.
In addition to the respective incised drawing, it was possible to mark the saw marks, seams and grains of the glued shuttering boards of the tree, with matrices, concrete and additives for the pigmentation of the basic material, on the concrete surface. Visually and haptically, the production and the origin of the façade are made comprehensible to the visitor. The other facades were insulated with mineral wool and provided with an outer shell of brick, plastered and planted.
The solid construction, with load-bearing walls made of recycled concrete and large windows, also appears inside the wide-stretched exposed concrete ribbed ceilings. Industrial terrazzo and wooden floorboards form the floors, smooth plaster the surfaces of the walls. The materiality serves the tranquility of the new exhibition rooms, which are twice as high as the rooms of the tower. Alternating between the "Schlössli" and the extension, a variety of spaces and atmospheres arise. The expansive thematic exhibitions contrast with the presentation of the collection, which is rearranged in the rugged architecture of the tower in larger periods.
The Minergie modernization certificate was awarded to the tower and the Minergie ECO certificate for the new building. Flexible uses were taken into account in the planning. For the prefabricated elements of exposed concrete ceilings, the concrete was recovered from recycling. The different shades of the concrete were included in the restrained color play of the rooms.
Diener & Diener, Martin Steinmann