On a long lake-side site between Kleinen Wannsee and Königstrasse a historic villa was restored and complemented by a new residential building with six units. The polygonal form was defined as a direct reaction to the site, taking reference from the site boundaries and the orientation of the existing villa. Simultaneously the form is reflected in the plan where it creates spacious central hallway spaces forming the organisational back-bone of the apartments. Precise incisions into the building volume create the entrance area and provide daylight for the staircase. The rear-ventilated scale façade in slate emphasizes the compact form through its intricate texture. The south façade is largely characterised by large openings towards the lake fronted by a long balcony band. A highly insulated, diffusion-open building shell in natural building materials with a pre-fabricated timber structure minimises heat loss from the building, while ensuring a healthy room climate throughout.