Among the quirks of living in a city built on hills is that your garage—should you be lucky enough to have one—may reside on a street far removed from your front door. For one family living in San Francisco’s Eureka Valley neighborhood, hopping in the car means heading through the kitchen and out the back door, traversing the garden, and ascending a flight of stairs to an alley of similarly detached parking structures.

The garage once sat atop a storage shed that housed a pile of rubble, several species of spiders, “and a cacophony of ad hoc foundations,” says Cary Bernstein, the architect who oversaw the transformation from arachnid haven to children’s playroom. The garage’s dilapidated state provided the impetus to carve out some usable space below, and, for Bernstein, the chance to create a rapport between the 1908 house and the outbuilding.

Part of Bernstein’s unification plan called for a flow of like materials across the divide, such as ipe decking and anigre casework in both kitchen and playroom. A deck just outside the kitchen door used for alfresco dining descends three steps to a courtyard, where Bernstein had previously replaced a patch of lawn with sandstone pavers (more hospitable to small wheeled vehicles) while carefully protecting two of the primordial-looking tree ferns. Bitty plantings along each side were changed out for lush, green walls—–fast-growing Podocarpus and climbing jasmine—–that define the architecture of the outdoor room. Picking up across the courtyard, the ipe decking crosses the playroom threshold and continues inside with an interior-grade version. The proverbial borders between indoors and out are further blurred when the playroom’s Nana folding doors are pushed open.

The house’s verticality—1,850 square feet on three levels—helped dictate the renovation, since the children (now four and six) used to play on the lower level, neither seen nor heard. Directly across from the kitchen windows, the new playroom confers just the right balance of independence and proximity. There is plenty of storage for toys and art supplies, and a magnetized chalkboard wall encourages temporary exhibitions. Playful but sophisticated, the room was designed to evolve with the family, and defies the Disneyfied palette that makes adults gnash their teeth. When not doubling as a trampoline, a queen-sized Murphy bed offers respite to overnight guests, as does the wine cellar, which is below grade and thus stays naturally cool. The door to the left of the chalkboard leads to a washing-up room.

Overhead, the garage’s aluminum and laminated glass door differentiates it from the painted wood ones on the alley. “Sure, it could have been a Sheetrock box,” muses Bernstein. “But as the house’s most frequently used point of entry, it deserved the same architectural respect.” Before the engine is even turned off, three windows pull one into the domestic setting with framed views of the house. “It’s a pleasant transition,” says Bernstein, of the interplay between indoor and outdoor spaces. The visual connection continues during the trek downstairs, which is guided by an ipe wall on one side and the garden-reflecting laminated glass of the garage on the other. Sheltered but not severed from the elements, one can see clouds and stars through the skylight.

“There is no jarring contrast between the two buildings,” says Bernstein, who had previously removed the mullions from inside the Craftsman house, expanding the doors and windows for a greater connection to the outdoors. Indeed, the “decidedly modern” new form, clad in painted wood siding, sits easily amongst its elders. Says Bernstein, “It was really gratifying to pull up one day and overhear someone say, "Isn’t this the prettiest garage in the whole alley?’"