The concrete walls of this Tokyo house were designed by architect Hugo Kohno to step in and out, giving the building extra structural support while creating built-in shelves and seating (+ slideshow).
Tokyo-based Hugo Kohno Architect Associates designed the three-storey house for a site in Edogawa, an area on the east bank of the Edo River.
The client requested a concrete house. But the ground condition in the area is very soft, so a complex structural system that integrates timber had to be developed to achieve this without making the building too heavy.
"For a three-storey reinforced-concrete building, we would need to install pile foundations driven deep into the support layer, which would be unrealistic due to the large construction cost," explained Kohno.
"In order to decrease the weight of the building, we [instead] adopted a composite structural system comprised of reinforced exterior concrete walls and conventional timber infill."
To give the external walls additional strength against seismic and wind loads, different sections were pushed back and forth. This creates the stepped profile, which is visible both inside and out.
Kohno describes these steps as "cranks" and named the building after them. Inside, they double up as work surfaces, benches and shelves. They also provide frames for large windows.
"The 'cranks' continue throughout the interior and exterior, creating a sense of ample spatial continuity," said Kohno. "At the same time, the crank-shaped walls create a new expression of reinforced-concrete architecture, and accentuate the space and the building with patterns of deep shadows."
The house's other features include a courtyard concealed behind the concrete walls, which is overlooked from various rooms within the building, as well as secluded balconies on both of the upper floors.
The main living and dining spaces occupy an open-plan room on the middle floor, which opens out to one of the balconies. There is also a traditional Japanese-style tatami room on this level.
Bedrooms and bathrooms take up the uppermost floor, while the ground floor accommodates a entrance lobby, as well as sheltered parking spaces for both cars and bicycles.
Photography is Seiichi Ohsawa.
Architect: Hugo Kohno Architect Associates
Structural engineer: Kentaro Nagasaka