The Drusch House marks a decisive step in Claude Parent’s approach in that it brought the dynamism of the volumes into reality by introducing the diagonal. Built for industrialist Gaston Drusch on a narrow plot of land of approximately 1 200 m² on the edge of the Forest of Versailles, the house is composed of two major parts, one designed for the living area, the other, more classic one, housing the bedrooms, bathrooms and kitchen. The concrete structure of the living room volume is in the shape of a rhombus, one side of which is covered by a roof sloping down to just below the gable of the other structure. The 120° angle created by the fracture between the two volumes is evident in both the plan and the elevation, with the reshaping of the terrain also contributing to the tipping effect. While the two forms are highly differentiated, the interior space is thought out as a continuum from the bedrooms up to the mezzanine. The open areas between the various elements are entirely glazed. Here, Claude Parent explored instability by using an “overturned” cube balancing on one of its edges. The diagonal introduced as a line of force of the volume, modifies both perception and use, which are usually determined by horizontality.