House in a car park by Alts Design Office hides a covered passage behind its walls

A secluded passage extends along one edge of this house in Japan by Alts Design Office, bringing natural light into the interior (+ slideshow).

Kusatsu House by Alts Design Office

Japanese studio Alts Design Office, whose previous projects include a house filled with pointed doorways and openings, designed the two-storey Kusatsu House for a site beside a car park in Shiga.

The close proximity of neighbouring residences and apartment blocks made it impractical to add glazing on the south-facing facades, so architects Sumiou Mizumoto and Yoshitaka Kuga instead created an open-air passageway along the north-western wall.

Kusatsu House by Alts Design Office

"A house with southern exposure is not good because the client wants to secure the privacy," explained the architects.

Kusatsu House by Alts Design Office

"Therefore, we arranged the exclusive path inside of the house. We gave importance to designing an outside space in the inside space, and produced a diverse and interesting space," they said.

Kusatsu House by Alts Design Office

Flanked by a windowless concrete wall, the passageway is glazed at both ends and has a skylight overhead, allowing daylight to permeate the building throughout the day.

Kusatsu House by Alts Design Office

A traditional Japanese tatami area is located within the space, alongside a small rock garden. Glazed doors open the passage to the open-plan living room, dining area and kitchen, which takes up most of the ground floor.

Kusatsu House by Alts Design Office

"We didn't separate into inside and outside of house simply," said Mizumoto and Kuga. "By doing so, we brought a feeling of strangeness in a good sense."

Kusatsu House by Alts Design Office

The room features simple furnishings that define the different areas. A wooden dining table offers seating for four people, while a selection of plants sit beside the walls and a low white wall defines the kitchen.

Kusatsu House by Alts Design Office

Wooden panel flooring runs throughout the interior. Chunky timber surrounds doors and windows, while a steel-framed staircase leads up to the first floor.

Kusatsu House by Alts Design Office

This upper storey is divided up into four rooms. The largest is the master bedroom, which leads out to a balcony positioned above the passageway.

Kusatsu House by Alts Design Office

Two smaller rooms accommodate the family's children, while the fourth space is a bathroom, with a separate WC alongside.

Kusatsu House by Alts Design Office

Photography is by Yuta Yamada.

Kusatsu House by Alts Design Office
Site plan – click for larger image
Kusatsu House by Alts Design Office
Ground floor plan – click for larger image
Kusatsu House by Alts Design Office
First floor plan – click for larger image
Kusatsu House by Alts Design Office
Section – click for larger image
Kusatsu House by Alts Design Office
Elevation – click for larger image