The 87 m2 (936 ft2) house is supported by a combination of cross braced steel framing and reinforced concrete. The tunnel is supported by an internal steel frame, suspended near its apex from the structure above.
Beneath the concrete curve is a parking space. Glazing encloses the entrance of the home.
Inside the glazed space, there are two freestanding steel boxes that contain a small private room and a shower room.
The semi vaulted enclosure forms a cave-like entryway.
The second-floor slab, a mere 105 mm (4.1 inches) in total thickness, is suspended from the ceiling by steel rods.
The absence of supporting columns not only creates the impression of spaciousness inside this compact house. It also strengthens the sculptural presence of the curved wall.
The space receives plenty of daylight from two distinct windows. A horizontal band of translucent glass – set above the tunnel – filters the light softly into the space. The tunnel creates gradational reflection of the light. Light from an open atrium in the center of the house fills every floor of the house.
Makiko Tsukada Architects is an architectural office based in Tokyo. Their recent works include Shakujii Pleats, Kozuki House, and Kondo House.