Historic Villa Extension

Thalwil Switzerland

Historic Villa Extension

Calibrating old and new in a historic village

RAUMEINHEIT has planned and obtained permit for the renovation and extension of this 1925-built house in the city of Thalwil, Switzerland. An open living and dining area extends seamlessly from the old into the new building, playing with the contrasting spaces.

A bright all-glass wintergarden makes the connection between the old and the new volume. A staircase in the new part connects all three levels of the house. In order to separate old and new volume and grant more privacy to the work space in the attic of the old house, a separate stair leads up there from the main floor.

A terrace, accessible from the living room on the main floor, stretches alongside the new volume with a lake view towards the Noth-East direction. Towards the back of the plot, it connects to the sloping terrain and surrounding lawn area.


The floor plan features a studio unit on the first floor, alongside the master bedroom with direct access to the garden. The open living, dining and cooking area takes up all of the second floor. The third floors feature two kids’ bedrooms in the new annex and a study area under the pitched roof of the existing house.

Today, the existing house has a good built substance, but only tiny rooms with surface areas less than 100sf and tiny windows. The renovation plan keeps the existing wood beam ceilings, and replaces most of the interior load-bearing walls with steal joists. 

The load-bearing structure in the ceiling remains visible throughout the house. The formerly existing small windows get replaced by floor-to-ceiling, fully openable window-doors.


The design strives to balance old and new volumes, despite adding more than 200% of the existing roughly 800sf (80m2) usable floor area, totaling 2400sf (240m2) after completion. The ground floor is extended into the hill, thereby hiding much floor area under ground and forming a terrace with lake view for the first floor.

The entrance to the house is relocated into the wintergarden-connection. A double-high space stretches along the facade and incorporates the central staircase. Together, these elements form an inviting and representative new entrance to the house.

The first and second floors of the new annex are conceived as a lightweight wood construction, resting on the first floor as a solid, water-tight concrete box. The wood structure allows for large wall openings that create a spacious feeling, despite the comparatively small footprint. 


The existing house is located in the historic center of the town Thalwil, close to Zurich, Switzerland. Built in 1925 for workers of the local textile fabrication, it accommodates only 800sf (80m2) on two floors. According to local building regulations, the existing house had to remain the primary element of the project. This is achieved by offsetting the new volume from the old; at the same time, the design achieves a balance of both volumes by coordinating floor level heights and window proportions.

Services Delivered
· Architecture 
· Construction Supervision


Thalwil, Switzerland

Time Frame 
April 2018 – August 2021

Project Status 
Under Construction