Addition of a floor to Sonnenberg School, Thalwil

The design of the extension building allowed for the addition of a floor in the future, but only two classrooms and a group room were envisaged. In the intervening period the amount of additional space needed had doubled and therefore an entire new storey was added on top of the building. The layout of spaces is the same as on the first floor, in particular the central, cross-shaped foyer between the classrooms, which is not only a circulation space, but also serves as a space for casual meetings and a lounge and, if required, can also be used for exhibitions or workshops.

The new storey is reached from the foyer on the first floor. The main entrance to the building is retained, the lift and staircase remain in their existing position and are extended upwards. A new free-standing external staircase serves as the escape route required by fire safety regulations, while not restricting the flexible use of the corridor area.

The new rooms are to be built using a CO2-low timber construction method that makes economic use of resources and saves time. This will minimize disruption of the ongoing operation of the school. Although the facade of cedar boarding seamlessly continues the existing building, the detailing and the slightly different fenestration make the new storey clearly legible from outside. In the interior the wood surface of the walls in the foyer remains unclad, analogous to the exposed concrete walls of the existing stories. A continuous projecting roof canopy will contribute to the lifespan of the facade and offer protection from the sun in summer.