In most parts of the United States, summer’s glow has already faded to an ember. Yet in Northern California, the season lives on at a backyard paradise complete with a swim spa and workout room.

For Hwang DeWitt Architecture’s Chad DeWitt, who designed the project, the question was whether the new structure should mimic the architecture of the existing residence, a classic California ranch house, or oppose it. Ultimately, the architects chose to juxtapose the two, taking inspiration from modern additions to historic buildings they’d seen in Europe.

Unlike the relatively traditional residence, with its cement-tile roof and mullioned windows, the addition is clad in a cedar rain screen and its inside is lined with hypnotic marine-grade plywood.

These stylistic departures contrast old and new, but also respond to practical considerations. The addition’s non-orthogonal floor plan, one of its most immediately striking qualities, was chosen by the architects as a workaround to the site’s tricky build-able area constraints.