Under One Roof

­A concept house with a faceted top offers people living together a sense of solitude.

The mountain range—that massive geological phenomenon of peaks and valleys—hardly seems an apt inspiration for the intimacy of the domestic realm. But mountains are the surprising metaphor of the Tokyo-based architect Akihisa Hirata’s new diminutive concept house, recently on display at the Yokohama Triennale. Called Ienoie, which translates to “a house within a house,” the design features an oversize roof with three distinct summits, Hirata’s curious means of allowing many people to share a single living space without entirely sacrificing privacy.

The 37-year-old architect clarifies the connection with aerial pictures that reveal the topographical similarities between a mountain range and the rooftop landscape of a residential neighborhood. “A roof is an artificial thing but could be seen as a type of nature,” says Hirata, who worked in Toyo Ito’s office for eight years until starting his own firm, Akihisa Hirata Architecture Office. “Roofs and mountains share the generative principle of a ridgeline, which takes care of efficient water drainage.” By simulating that dipping profile and pulling down the large top of his 1,324-square-foot model home in certain spots, he provides each imagined resident with his own private mountaintop.

Inside, the three individual areas are split into two stories—a closed lower room and an open upper level—with common space between them. The drops in the roofline visually divide the second floor, though louder voices from other rooms can still be heard. “The valley lines slope gently, so what comes into view completely depends on your position on the upper level,” he explains. “When you stand straight, you cannot see the common spaces, so it just feels as if you are in your own private room. But when bending a little or kneeling down, you are able to see glimpses of the common space and the other residents.”

The Ienoie model can be adapted for families of any size, and because each resident is provided with designated second-story personal space, the exterior reveals the number of people dwelling inside. “In reality they all live under one roof, but that seems different from within,” Hirata says. “When looking from your window toward the next peak, you feel as though your cohabitant is your next-door neighbor.”

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