The residential architecture of Atherton, California, is nothing if not eclectic. Peeking out from behind the town’s ubiquitous fences are modernist glass boxes, French chateaux, and Italianate villas. But a just-finished house in this leafy Silicon Valley suburb, by San Francisco–based architect Craig Steely, defies stylistic categorization. The enigmatic one-story structure on a long and skinny lot is defined by a sinuous, almost windowless wall clad in vertical cedar planks. Although about half of the 5,900 square feet behind the curving enclosure are sheltered under flat roofs, the architect has dubbed the residence the Roofless House, since the remaining space is devoted to courtyards and is open to the sky.