Located in one of San Francisco's most exclusive residential areas, this traditional home relies on some non-traditional structural engineering. To provide more openings and light, and to accommodate some of the challenges of the architectural design, the structure includes three different types of steel frames, as well as plywood shear walls and concrete walls. Special high-strength floor diaphragms transfer high earthquake loads across the floors, and the use of steel plate shear walls allow for some unusual conditions without excessive cost.