Guest house

Nendo’s Oki Sato builds spectacular new tunnel-shaped guesthouse by pre-stressing plant and assembling culverts on site stacked on top of each other combining civil engineering with product details

Nagano, Japan

Oki Sato, Noritaka Ishibayashi, Ryota Maruyama and Daisuke Maeda of nendo have designed a new storage facility with an adjoining guest house for archiving furniture, products and artworks in Miyota-machi, Nagano Prefecture.

Set in a quiet, nature-rich environment where streams meander through thick red pine forest, the tunnel-like architecture took shape through a combination of precast and prestressed construction methods.

For prefabricated construction, the common parts are molded in the factory and assembled on site.

An example of its applications in infrastructure projects is the culvert (box-shaped concrete structures), used to store waterways, tracks, power lines and communication lines buried underground.

However, since the process itself does not allow for leak-free composition or stacking, both of which are necessary for this architecture, prestressing was also used to connect the parts together.

The prestressing method is a technique used in civil engineering works such as bridges, in which the parts are aligned and then tightened with wires to connect them.

    Culvert Guest House by nendo studio

This results in a consistent and smooth surface finish, achieving a tight seal and durability.

The common square-shaped pieces weigh about 12 tons each, and a total of 63 such pieces were used.

The size of the parts was derived from the loading size of the delivery truck and the weight that could be lifted by a crane.

    Culvert Guest House by nendo studio

The 45 degree brace at the entry corner, also found in general box culverts, serves as bracing and improves earthquake resistance.

By connecting these parts, a slender tunnel-like space with an interior dimension of approximately 2 x 2.3 m was created.

Fourteen wires were used to connect each “tunnel” and care was taken to apply even tension to each wire at all times.

    Culvert Guest House by nendo studio

The work involved gradually tensioning the wires over time until a tension of 46 tonnes was finally applied to each one.

The building is made up of four stacked “tunnels” covered with a roof in the center.

In addition to a long, narrow storage room approximately 40 meters deep, there are two smaller storage rooms, but it is expected that more will be added to the site in the future as the collection is growing.

The kitchen, bathroom, toilet and other water facilities are concentrated on the first floor, and a compact bedroom and study are located on the second floor.

    Culvert Guest House by nendo studio

The windows were made without metal frames as much as possible, and high-transparency glass up to 10 meters long was fixed in the grooves in the same way as shoji screens.

The gravel and plantings used on the exterior were also laid out on the interior to draw the exterior environment inside.

To facilitate walking, the gravel has been partially hardened with resin.

    Culvert Guest House by nendo studio

Instead of just pouring resin over the gravel, which is usually the case, the resin was first applied to the base and then gravel was laid over it so that the surface did not become shiny.

In addition, the door handles would have seemed abrupt if they had been installed as they are, which is why an original handle was designed, which hides in the small gap between the door and the wall.

The tub is dug into the ground, so the water surface lines up with the ground, creating the appearance that the shape of the tunnel is continuous.

The resulting space is less architectural, but more of a project that combines civil engineering concepts with product design details.

Project: Culvert Guest House
Architects: studio nendo
Collaborators: Noritaka Ishibayashi, Ryota Maruyama and Daisuke Maeda
Customer: Private
Photographers: Takumi Ota and Daici Ano
Video: Toru Shiomi, Takahisa Araki and Masaya Yoshimura