We begin to understand why site-built, platform-frame houses have persisted so long in America. Site-built is site-rebuildable, much more than factory-made housing, even mobile homes. Platform frame—2-by-4 wood stud walls raised a floor at a time—is an amateur medium. You can build or rebuild an entire house with a power saw and a hammer (I did so once in Nova Scotia). For reasons unknown—perhaps our frontier history—Americans revel in doing major home projects themselves, and so we stick with forms that give us that freedom.
