Othmarstrasse extension, Zürich

The project
The static load-bearing capacity of the existing flat roof was not sufficient for the two-story addition. In order to be able to absorb the loads from the addition, a steel girder grid was mounted on the existing flat roof. In this way, the loads could now be selectively diverted into the load-bearing exterior and interior walls.

The construction method
In order to obtain the largest possible free window areas, particularly narrow visible steel columns were installed on the room side of the facade. The stiffening of the extensions was achieved by means of the staircase, which grew with the building, in solid construction. The newly created flat roof areas are designed as accessible terraces and provide a magnificent view over the city and Lake Zurich.