In most multistory homes, stairs connect floors. But in the 921-square-foot Coil house, located in a quiet residential neighborhood in Tokyo, they are the floors. Defined by 44 steps of varying depths and widths, Coil is a dynamic swirl of continuously ascending spaces, designed by local architect Akihisa Hirata for Sakura and Ryo Sugiura, a young couple with two children.

Keen to trade their rental apartment in the suburbs for a home of their own, the couple purchased a 15-by-47-foot site, commonly known in Japan as an “eel’s nest.” To maximize the tiny, oblong lot, Hirata divided the permissible building volume with conventional walls and floors as little as possible. Instead, he planted three beefy, square-shaped wooden columns along the plot’s center axis and wrapped each one with stairs. “Big columns are uncommon in contemporary houses, but we needed them to anchor the treads,” explains Hirata. While large, open landings act as rooms, level changes eliminate the need for partitions and doors. “The winding of the stairs separates spaces,” says the architect.

Balancing the steps’ orientation and dimensions (they had to be big enough to hold furniture, such as the clients’ Fritz Hansen dining table and Kartell storage units) with programmatic requirements, such as off-street parking, a terrace, and built-in bookshelves, the three-story climb begins at the wedge-shaped foyer. Four steps descend to the bathroom, while 13 broad treads, ranging in depth from two to five feet and doubling as the library, ascend to a series of large landings, designated as living and sleeping areas. At the top of the house, the sequence culminates in a compact galley kitchen, followed by an elevated dining area. Per the clients’ request, this last room abuts a south-facing terrace, overlooking a leafy shrine precinct. Expansive views from all sides of the house help it feel bigger.

As with traditional Japanese homes, Coil’s floor plane is not only a surface for walking but also a versatile platform for living. Devoid of heavy furniture, each landing accommodates a multitude of activities on a daily basis. “[This] fits our ‘futon lifestyle,’” says Ryo, explaining that the family freely spreads out their mattresses on any of the large landings at night. But during the day, after the bedding is stowed in a deep closet (one of two large storage areas tucked beneath Coil’s giant stairs), the spaces become an informal study for Sakura and Ryo or an impromptu play area for Gen and Ran, ages six and three. While inhabiting a giant staircase might not be everyone’s cup of tea, Hirata’s clever strategy turns a tiny interior into an efficient and refreshingly innovative living space.

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