Date:October 25, 2020

This Triangular House In Japan Looks Uninhabitable From The Outside, But It’s Quite Spacious From The Inside

In Tokyo, one of the world’s most overcrowded cities, land is expensive and it is always difficult to find and buy an ideal plot. So, building houses on difficult patches of land is not uncommon. At the same time, such challenges encourage Japanese architects to create impressive and ingenious buildings. This house on a tiny triangular plot in Horinouchi, designed by Architect Kota Mizuishi, of Mizuishi Architect Atelier, is an excellent example.

 Mizuishi Architects Atelier

The house is the residence of a furniture designer, his wife, who works from home, and their two young children. They had previously rented an apartment in the area, but their dream was to build a house. One day they were drawn to Mizuishi’s office nearby. They didn’t have a large budget but wanted to build a house in the same neighborhood. Mizuishi and the homeowners looked for a site and finally found this very small and narrow piece of land along the river.

 Mizuishi Architects Atelier

The site is a triangular plot sandwiched between the Zenpukuji River and a little lane. However, narrowness wasn’t the only challenge the lot presented.
Article 43 of the Japanese Building Standard Law stipulates that every property must be connected to a road at least 4 meters in width, either directly or by a driveway, in order to allow access for emergency vehicles. However, this was not the case here, as the lane next to the house is less than 4 meters wide. It was therefore necessary to contact the city and the surrounding neighbors, get a special permit and fit the design as much as possible to the regulation.

 Mizuishi Architects Atelier

A buyer for such a piece of land is hard to find, so, luckily for the owners, it was offered at a considerably lower price than the market average for the area. The current homeowners asked Mizuishi if it would be feasible to build a home there at all. After considering how much living space they would be able to extract from the site, they concluded that it could be done, with some ingenuity. The project began to take shape.

With such a narrow structure, however, there is the danger that the house might fall sideways in the event of an earthquake. Then again, too many pillars would have diminished the interior space. Instead, the structure was reinforced internally with small, load-bearing walls, which also help divide the interior into zones (pictured in later photos).

Due to budgetary constraints, the architect chose a wooden structure.

The house now nestles between the small lane and the river-bank promenade. “We cut off the sharp corners of the site’s triangle and placed windows on those sides, so we can see the river from three sides of the house,” the owners say.

The part of the first floor that appears to be indented allows for a parking space. “I was a bit surprised when I was asked to make space for a car on this tiny lot. It’s limited to a mini-vehicle, but I was able to make room here,” Mizuishi says.

Rows of ceramic siding cover the first floor, while the second story is encased in maroon-colored galvanized-steel plates, oriented vertically. The transitions of texture and color make the house look lighter and less dull than if it had had a monotone exterior. The switch to the different finishing material on the overhanging part of the second floor also emphasizes that area.

 Mizuishi Architects Atelier

Additionally, despite the steepness of the roof, the house lacks rain gutters. It’s a radical solution that makes it appear as though the roof and walls are one. “It’s quite courageous not to have a gutter, but we have U-shaped grooves on the outer perimeter of the foundation, so we won’t have problems with rainwater drainage,” Mizuishi says.

Because the ground of the site is lower than the riverside promenade, it is possible for passers-by to look into the first floor. Therefore, the main living area is situated on the second floor, which also allows the family to see the scenery of the path and the river. These photos show the house immediately upon its completion, but the trees have since matured, partly blocking the pedestrians’ sightline.

Given its location along a river, it is possible that floods may affect the site. For this reason, the first floor was raised 24 inches (60 cm) above the ground, and 24-hour underfloor ventilation was implemented to prevent dampness. A sliding door was installed on the entrance, approached by movable steps.

Additionally, the entrance threshold is 4 inches (10 cm) in height and depth and consists of concrete clad in stainless steel. The homeowners wanted to make sure any flood prevention measures would be as unobtrusive as possible.

The bedroom’s solid-wood flooring is made up of Japanese cherry birch, which “is good quality and reasonably priced. Even though the budget was limited, I wanted to use high-quality materials as much as possible,” Mizuishi says. The antique piece with small drawers is a family favourite – they owned it long before they moved into this house.

 Mizuishi Architects Atelier

Light enters the loft through skylights. The one on the south side was added after construction had already begun, at the last possible opportunity to introduce a new opening. Besides letting light in, it provides the room with fresh air.

Since it faces the south, however, there is also a risk of overheating the room. Still, the daring installation of the skylight on this side allows the family to take in views in three directions from the loft, as they are able to see the river from the windows on both sides of the house and look up at the sky from the skylights. It gives the feeling of a connection with the outdoors.

 Mizuishi Architects Atelier

Upstairs, a spare room is currently being used for storage. It is unobtrusively separated from the rest of the floor by the load-bearing walls mentioned above.

The lower shelves on the lane side of the living-kitchen-dining room (on the left in this photo) were made to accommodate the family’s love of music: They fit their audio equipment and CD collection. The computer desk in front is a workstation for the lady of the house, who works from home. A bench, installed on the riverside, serves as a sofa and its bottom compartments as storage. At night, curtains maintain privacy.

As there is a loft directly above it, the living room ceiling isn’t very high. However, thanks to the large windows on both sides, one never feels overshadowed.

 Mizuishi Architects Atelier

There is a loft, less than 6 tatami mats (about 105 square feet/9.7 square meters) in size, above the living room. It’s a fun, creative playroom for children, where one can still feel connected with family members in the kitchen and dining room. There are two load-bearing walls on each side of the loft.

 Mizuishi Architects Atelier

The sharp corner of the triangle hosts the kitchen and dining room.

Despite how small it is, the kitchen has a relaxed air thanks to the height of the sloped ceiling, which adheres to the shape of the roof. The ceiling’s dimensions are emphasized by the pendant light. The Nakajima Tatsuoki Lighting Design Laboratory designed the lighting, which consists of recessed lights throughout most of the house. These highlight the quality of the space without being overbearing.

 Mizuishi Architects Atelier 

 Mizuishi Architects Atelier

“When I start to design, I definitely want to create something of value,” Mizuishi says. He has certainly done that in this house in Horinouchi: By reading the merits of a quirky site that no one else wanted he succeeded in designing a comfortable living space.

 Mizuishi Architects Atelier 

Structural design: Ken.Nagasaka Engineering Network
Lighting design: Nakajima Tatsuoki Lighting Design Laboratory
Builder: Hirano Kensetsu

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