This is a two-story traditional wooden house located on a sloped site in Yokohama. To create a stable structure on the sloped terrain, the existing steps in the ground were utilized. This resulted in four levels of floors within a two-story structure, as the floors were stacked while being shifted. By connecting these four levels of floors in a spiral, and allowing light to penetrate between them, a cohesive and unified space was achieved.
Structurally, a large keel truss beam were employed to create a column-free, open-plan space. The keel not only serves as the primary structural element of the house, but also acts as an environmental control device. In the summer, it blocks direct sunlight while allowing indirect light, providing both shade and brightness. In the winter, it allows direct sunlight to enter, ensuring brightness and the warmth of the sun.