The hayloft of La Grange de la Haute Vallée has an inverted boat hull structure. This technique makes it possible to build roofs more easily and free up all the space in the attic. The frames consist of a succession of load-bearing beams linked together by ribs. The beams are formed of short, curved planks supporting the battens on which the slates are fixed. The inverted boat hull frames are often made of poplar, a wood that bends easily and usually grows near rivers.