Located in the hills above California’s Sonoma Valley, Sonoma Mountain House occupies a high, sloping site shaded by towering trees. “You climb a long, winding drive to get to the site,” says architect Richard Schuh, “then you’re surrounded by these classic California trees: firs, redwoods, oaks, and madrones.” Schuh insisted on saving as much of that standing timber—and of the site’s existing topography—as possible in this project, designing the house as a largely transparent platform for living, entertaining, and, most important, simply being here.

Schuh’s clients, a couple embarking on post-retirement life, envisioned a casual mode for their new home. “This was to be their transition from living in the city, a place where they could just relax and absorb the setting,” Schuh says. To accommodate frequent visitors without cramping the open-plan lifestyle they sought, Schuh divided the program into two separate structures—a main house and a guesthouse—linked by a linear deck that runs the length of both buildings. “The grade drops off dramatically,” he says, “so the deck can bridge to the guest house. It’s this spine that holds things together.” 

The main house’s L-shaped plan orients its private wing upslope, where it digs into the hillside. “By the time you get back to the master bedroom, the back wall is a fairly high retaining wall,” Schuh says. “It gives you the sense of tucking into the site—kind of the opposite of the guesthouse, which hovers above the site.” The topography falls away along the entry wall of the house’s great room wing as well, permitting on-grade access to the garage below. Schuh located the kitchen and dining areas at the hinge of the L, where they open onto the linear deck and a pool terrace at the house’s northeast side. Like the house itself, the pool meets the grade at its uphill side, Schuh says, “but then it shoots out into the landscape.”

Schuh heightened the tree house atmosphere inside with a shed roof that floats over a tall, glazed clerestory. Tubular steel struts shorten the effective span of the rafters, which also benefit from the cantilever effect of the roof’s 12-foot overhang, permitting the use of relatively small 6-inch-deep, wide-flange I-beams. “We used steel because we wanted to keep the framework as light and airy as possible,” Schuh says. Laminated fir decking boards span the 8-foot bays without purlins, “so we were able to keep the roof profile really thin.” And while the ceiling plane’s skyward trajectory draws one’s gaze out into the treetops, the roof structure asserts its own sculptural presence. “Most of the walls don’t go up to the main roof—just two interior walls do—so there’s always this sense of it hovering over the space,” Schuh says.

A similar roof tops the two-story guesthouse, whose upper level shares the floor elevation of the main house. “It has a living room upstairs and bedrooms downstairs,” Schuh says, “but they’re not connected inside,” an arrangement that allows the guest living area, with its small kitchen, to serve also as an overflow living space for the main house. Despite their close connection, however, the two structures offer subtly different experiences of the site. The main house is grounded by its board-formed foundation walls, which extend outward from the building to become site retaining walls. In contrast, the guesthouse perches lightly on a scaffoldlike steel framework. As the building rises into the forest canopy, Schuh says, “the site just flows through underneath.”