Abstract: A sustainable, prefabricated building system, including prefabricated wall panels, load bearing beams, and prefabricated roof panels, and methods of assembly are presented herein. In one aspect, a prefabricated building assembly includes a number of prefabricated wall panel subassemblies mounted to a concrete foundation with a desired offset distance between the bottom of each prefabricated wall panel assembly and the foundation. Each prefabricated wall panel includes a metal base angle subframe coupled to structural wood subassembly. In another aspect, a metal base angle subframe includes end caps welded to each end of the structural angle to facilitate weather proofing and isolation of the wall panel assembly from the ground. In some embodiments, a wall panel subassembly includes any of an interior facing finishing layer, one or more utility chases, a weather resistive membrane, an insulation layer, one or more flashing elements, and an exterior finishing layer.