Architects understandably yearn to be their own clients, especially when it comes to their homes. But Remo Halter of the Luzern, Switzerland, firm, Lussi + Halter, couldn't afford to build his ideal house—a cubic volume of poured-in-place concrete. Yet he had found a tranquil setting—over a third of an acre in the wooded residential district of Kastanienbaum, not far from downtown Luzern. So he and his Brazilian wife, Cristina Casagrande, a psychoanalyst, looked for a “roommate”—that is, someone to share his design for a 6,652-square-foot two-family house divided vertically down the middle.

Halter found adventurous partners for his project: a physician-and-artist couple. “The doctor wanted something new and quite brave,” says Halter about his plan to create an anthracite-hued concrete house. A far cry from the gemütlich gabled houses of the neighborhood, the three-level structure's poured-concrete walls, floors, and piers form a crisp, brooding mass floating above the voids for open-air carports, terraces, and walkways.