This house by Japanese architect Shogo Aratani clambers over a steep rocky site in Hyogo, so it was named Krampon after the spiky devices that strap onto shoes to improve grip for climbing (+ slideshow).

Shogo Aratani designed the two-storey house for a site with an 11-metre change of level from front to back, so he divided the building into a series of blocks that stagger up to follow the slope of the hill.

"We decided to place volumes along the sloped ground to minimise excavation," said the architect. "We designed the spatial sequence in relation to the landscape by placing three volumes along contour lines."

The three rectilinear volumes fan out around a triangular central section that accommodates the houses's main staircase, but which also functions as a small library. Books can be stored on shelves around the three edges of the space, as well as within the gaps between treads.

The living rooms are all positioned on the upper floor of the house to offer the best views of the surrounding neighbourhood, and open to a large wooden roof deck.

A skylight above the living room reveals the branches of a camphor tree and cherry tree at the top of the site, while the kitchen features a stainless steel countertop and glass doors leading out to a narrow balcony.

Black powder-coated metal panels clad the exterior walls. There's also a concrete retaining wall framing a driveway at the lowest level of the site.

Photography is by Yutaka Kinumaki.

Here's a project description from Shogo Aratani:

Krampon

This is a residential area where the magnificent nature still remains. The site is situated on a sloped land among natural forest. Two large trees with beautifully shaped branches (one is a camphor tree and the other a cherry tree) stand on top of the site. These trees are integrated into the residential design.

The entire site is steeply sloped, and the gap between the top and the bottom is as large as approximately 11 meters. And the ground composed of a rock bed is extremely hard. Considering these landscape conditions, we decided to place volumes along the sloped ground to minimise excavation.

In order to provide the best view, the main spaces are located on the top floor and the other interior spaces are connected along the slope down to the street level. We designed the spatial sequence in relation to the landscape by placing three volumes along contour lines.

The upper volume is placed right underneath the two large trees. A skylight is provided in the living room to see the trees above. The volume on the north is allocated for bathroom. The volume on the lower level contains private rooms on the first floor and a wood-decked terrace on the roof, accessible from the living room. We place stairs with the same inclination as the ground at the intersection of the three volumes. The stair space is used as a library, while the stairs are designed to accommodate a large number of books.

By designing the three volumes along the landscape, diverse activities are generated and one can enjoy unique spatial sequences as they are.

A sizeable volume of rock was excavated upon construction of the garage, and it is reused as exterior finish on pavements and steps along the entryway.

Location: Hyogo, Japan
Principal Use: House
Structure: timber frame
Site Area: 360.35 sqm
Building Area: 104.53 sqm
Total Floor Area: 136.65 sqm (84.05m2/1F, 52.60m2/2F)
Structural Engineer: S3 Associates Inc.
Construction: Amerikaya Co.,Ltd.

Material Information
Exterior Finish: Lap Siding / Oil Paint
Floor: Ash Flooring t18 / White Oil Paint
Wall: Plasterboard t12.5 / Emulsion Paint with Sand
Ceiling: Basswood Plywood t4