Spiral stairs puncture hilly floors inside Takeshi Hosaka's House in Byobugaura

A spiral staircase rises through the trough-shaped floors of this concrete residence in Japan by local studio Takeshi Hosaka Architects (+ slideshow).

House in Byobugaura by Takeshi Hosaka

Takeshi Hosaka designed the Byobugaura House for a couple with two children in a residential area of Yokohama, Japan.

Situated in a densely populated area, the property faces neighbours on three sides and backs onto a three-metre-tall retaining wall for a grassy knoll to the rear.

House in Byobugaura by Takeshi Hosaka

In response, Hosaka designed a reinforced concrete structure with three storeys, one subterranean and two above ground-level, each formed from a curving concrete slab.

House in Byobugaura by Takeshi Hosaka

The ramped floors were devised to give privacy to the inhabitants, while maximising space inside the property. From outside, the curves give the impression that residents might be crushed below the concrete.

House in Byobugaura by Takeshi Hosaka

"The site at first looked like it was buried by the surroundings," said the architects. "In response, the design sought to pull in an equal amount of light and wind in section to both the basement and the ground level."

House in Byobugaura by Takeshi Hosaka

As the floors scoop upwards, they meet the top of glass doors and windows that bracket the front and rear of each floor. This also allows light to come into each floor from above.

House in Byobugaura by Takeshi Hosaka

"The oppressive feeling exuded by the three-metre-tall retaining wall on the east side is skilfully minimised by the rising floor, directing the eye to the green that is beyond," said the architects.

House in Byobugaura by Takeshi Hosaka

Inside, each concrete level is covered with wooden floorboards. A circular hole cut through each level reveals the thickness of the concrete and wooden layers, and makes way for a spiralling steel staircase.

House in Byobugaura by Takeshi Hosaka

An open-plan bedroom on the upper floor features a bath and shower room with a glass surround, taking advantage of the privacy provided by the swooping concrete bays.

House in Byobugaura by Takeshi Hosaka

The wooden walls of a toilet cubicle to one side stop shy of the ceiling, where they are topped by a piece of acrylic that allows natural light to filter through.

House in Byobugaura by Takeshi Hosaka

A kitchen on the middle level features built-in wooden fittings and, in keeping with the rest of the building, exposed concrete walls and ceilings.

House in Byobugaura by Takeshi Hosaka

In the basement, small white grips allow the couple's two children to climb the walls of their basin-shaped bedroom to a back garden where a small sand pit has been dug into the landscaping.

House in Byobugaura by Takeshi Hosaka

The roof plane follows the upward curvature of the floors below, channelling rainwater away from the windows into the centre of the roof, where it drains to ground level through a slit in the southern wall.

House in Byobugaura by Takeshi Hosaka

Photography is by Koji Fujii/Nacasa & Partners.


Project credits:

Architect: Takeshi Hosaka
Structural engineers: Kenji Nawa
Client: Toshiyuki Kondo

House in Byobugaura by Takeshi Hosaka
Site plan – click for larger image
House in Byobugaura by Takeshi Hosaka
Basement floor plan – click for larger image
House in Byobugaura by Takeshi Hosaka
Ground floor plan – click for larger image
House in Byobugaura by Takeshi Hosaka
First floor plan – click for larger image
House in Byobugaura by Takeshi Hosaka
Section – click for larger image