Using touch latches and drawer-pulls instead of hardware on FSC-certified cabinets yielded a clean aesthetic and saved money. Bovee and Kirkpatrick then used the leftover cabinet wood to craft the coffee table, dining table, and a side table for the kitchen.

The yard, for example, augments the home’s limited square footage with a series of “rooms,” including a front garden behind a basalt retaining wall and a sheltered patio made of pervious pavers. (There are plans afoot for a native-plant shade garden, too.) Inside the entryway, a narrow staircase on the right leads down to the diminutive basement, currently used for projects and storage. But up a handful of steps to the left are the living quarters, entering on what is essentially the Harpoon House’s great room, combining kitchen, dining room, and lounging area. The space lives much larger than its 250 square feet with a 10-foot-high ceiling, floor-to-rafters windows, and largely unadorned white walls. The kitchen is a sleek strip of custom cabinets and appliances that were selected for maximum efficiency and minimum noise. The room itself is divided by a vintage sleeper-sofa and a dining table, set back to back. “During the summer, we move the table outside to expand our livable space,” Bovee says, pointing to the tidy deck visible through sliding doors.

When scouting plumbing fixtures during construction, the couple fell in love with the onzen, a western version of a Japanese soaking tub. This singular nod to the spatial hedonism of a larger house—the tub’s four foot-by-four foot proportions dominated the tiny floor plan—pushed Kirkpatrick and Bovee to divine one of the Harpoon House’s most charmingly efficient innovations: a partition wall originally designed to be two and a half feet thick including shelves on both sides was shrunk to one foot thick. “We realized that if we made the wall itself a foot thick,” Kirkpatrick recalls, “we could nest the book shelves and bathroom shelves together inside the wall, saving some pretty valuable floor space.” In addition to the dual-purpose wall, another solution emerged: a dual-flush Caroma toilet-sink combination in which fresh water first used for hand-washing then flows into the cistern for flushing. (To compensate for the system’s “slight awkwardness for things like brushing teeth and shaving,” Kirkpatrick added a larger sink one floor above.)