Minamiboso is a city on the Boso Peninsula at the southern end of Tokyo Bay. Overlooking the Pacific Ocean and with wooded hills and valleys behind it, Minamiboso attracts many tourists, and nowadays has numerous vacation homes and accommodation facilities.

Takeshi Hirobe Architects has designed a vacation home here on a site whose constraints and opportunities became uniquely defining elements of the final design. The obvious opportunities stem from the superb position of the lot, which offers ocean views to the southeast. The constraints, however, concern a difference in level in the middle of the site of almost five feet (1.4 m), where there’s an outcrop of bedrock, and an unbuildable area on the street side of the property.

As a result, the home has two buildings. On the eastern side of the lot, where the difference in elevation is minimal, a detached volume comprises a double garage and an upstairs guestroom. The other building, the main one, is the house itself.

At the request of the client, the main volume was woven around the limitations of the site. Working to achieve this from the beginning of the design process, the architects initially proposed a design made up of interconnected triangles that was flexible enough so that it could easily be modified in the later stages of the project. The approach made it possible to adjust the forms by “pinching” the roof ridges as the architects developed a more detailed plan of the interiors. As discussions with the client progressed, the shapes were modified, resulting in a close correspondence between the interiors and the shape of their section of the roof, with each section containing a space scaled for its particular purpose.

Modal planning

This approach, which Takeshi Hirobe calls “modal planning” and has used on other projects, is flexible and makes it possible to change the size of spaces according to their function, with their shape reflected outside, avoiding any rigidity in the size of the planned volumes. The triangular roof slabs are supported by load-bearing partitions and polygonal columns that vary in shape throughout the house.

On the side of the house facing the sea, the roof lifts to extend the height of the windows and the breadth of the views from inside. Both on the ground-level floor and the upper floor, the living areas connect to one another in a sequence of spaces so as not to interrupt the views of the sea while flooding the interior with morning light.

The relationship between external forms and internal spaces is reflected in the choice of materials, with wood and concrete used for the façade and the interior finishes, alternating cooler shades of gray with warmer tones of brown. The home has been designed so that the focus of all the living areas is the sea.

>>> Read an excerpt from an article about the Phase Dance home, published in THE PLAN 130.

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