Using two walls and a roof, a dwelling in the Leuven region is extended. The roof consists of a steel plate onto which a grid of steel fins of varying height is welded. The plate is 5 mm thick, while the fins are 8 mm thick and only 60 mm high at the edges. The roof covers the dining area, the living area, and a covered outdoor space. The extension is fully open towards the garden and improves the connection to it by incorporating the existing level difference into its spatial organisation. The roof bulges at the location of the lower-lying living area, thereby helping to define the space. Owing to the position of this bulge at the centre of the roof, the plate also benefits from it structurally. The new volume, almost 6 m deep and more than 8 m wide, is spanned without additional structural elements, while the edge is kept exceptionally slender.