In compliance with new building regulations that mandate orthogonal walls and gabled roofs, the house takes the form of a nagaya (traditional row house): a linear sequence of rooms contained in a long, narrow volume aligned perpendicular to the street. The house expands in section to follow the slope: single-story at the street façade, expanding to two stories at the rear of the site. This allows the gabled roof shape to define the interior spaces rather than simply sit on top of them. The bedrooms are half buried, whereas the living area is oriented toward the mountains.
The overall nagaya form remains as abstract as possible, made entirely from bare concrete. The roof has no cladding or surface membrane (an invisible waterproofing compound has been applied to the exposed slab) and there are no projecting eaves, making the house volume akin to something sliced from a block of tofu. There are no drains, downspouts, or gutters — or more precisely, the entire roof plane has been subtly shaped to become an enormous rainwater channel. The roof perimeter slopes gently upwards, creating subtle parapets that prevent water from falling down the long walls, channeling it all to the building’s north and south ends where it may fall freely to the ground.
This area can receive heavy snow in winter, and so long-term durability and insulation was a primary concern for the clients. All the windows are double-glazed. With the exception of the storeroom (adjacent to the parking) and the sunroom (adjacent to the entry hall), all the exterior walls are insulated. They have been lined with 30mm-thick polystyrene foam spray, then finished with painted plasterboard. The roof and floor slabs have been lined with 50mm-thick expanded polystyrene sheets. The sunroom has been left in exposed concrete because it is intended as a semi-outdoor space, used as a greenhouse. Oriented to the southeast, it receives a great deal of direct sunlight through the glass walls and roof, and the exposed concrete wall visible inside acts as a heat sink that helps to warm the house at night.