The firm, founded 2009, was asked by a client to come up with a design for a 3.5-acre site that included a guesthouse where the client would live while the poured-in-place concrete main house was being completed. (The client sold the compound last summer to a Chinese media entrepreneur and his family.) Since the land came with 130 protected live-oak trees, Walker needed to design around their leafy presence. He did so by taking advantage of the rugged topography with a parti that gradually spills down a slope: the entrance, garage, and living and dining levels are located at the top, while the four bedrooms, plus gym, media room, and office of the main house are below. To make sure the lower level receives ample light, Walker pulled apart and cranked the plan, organizing one wing around a courtyard carved out of the terrain. 

The concrete structure allows long-span spaces and also helps the house meet seismic codes, offer strong acoustical insulation, and provide planted terraces and a vegetated roof deck for the occupants. (The roof over the kitchen/dining and living area employs steel and wood framing.) To obtain sandblasted or smooth finishes, the team used varied kinds of medium-density overlay (MDO) formwork for the concrete pour. Inside, walnut panels give the interiors warmth, while ample glazing ushers in dramatic views.