The town hall of Cannstatt, which was probably first built as a granary in 1490/92, has been reconstructed many times throughout its history. The present facade of the building is characterized by the design of the 19th century. The major remodeling tasks were: foundation relaying, more space, better accessibility (with elevator), fire protection and a better thermal protection for the historical building. In addition, the house should obtain an appropriate facade towards today's "Marktplatz”, which was the most important square in town in history and nowadays.
The wish of building a glazed extension to get more space was soon replaced by the idea of developing the first attic floor. By demolishing a small old addition on the building, the Marktplatz-facade has been revalued and got a new portal in extension of the central corridor. Due to a sinkhole, the staircase area of the building had sunk about 80 cm which meant that a preservation of the strongly deformed timber framing structure was not possible. A concrete tower was built instead which transmits the forces into the new supporting structure above the sinkhole. The floor plan is based on the historical structure of 15 (five times three) squares (about 4.5x4.5 meter each) with a central corridor.
The new staircase, which is built as safety stairway according to fire protection requirements, also fits into the axis of the new concrete tower. The arrangement of the new rooms on the first attic floor follows this fundamental principle of axis with central corridor as well. In order to find a reasonable solution for the sophisticated redevelopment, we had to intensively work on material and details during the planning process.
We tried to use historical material concepts as much as possible, not only that they have proven their constructive worth, they also exude beautiful liveliness. And the new material should achieve the same value. In terms of structure, color effect, proportion and subtlety the new, contemporary elements do not interfere with existing parts. The frames of the new wooden windows were made as slim as possible and the conical glass retainer profiles define the inside while the copper bars define the outside of the windows.
The exterior plaster is pure lime plaster, stained with French ocher and black marble chips, which is painted above a layer of mineral insulating plaster. With these two layers of plaster, the building can reach the EnEV (Energy Saving Regulation)-old-building standard.
The slim steel stair tapers gradually from ground floor to top floor, so that at the end of the staircase there will be enough headroom under the roof slope. The blue color we chose to paint the steel stair brightens the stairwell and creates a special space. The goal of our design was to create livable spaces in this historical building, to improve its function so that it can fulfill today’s needs and to tell its story to the people.
