Abstract: An improved economical, easily assembled, prefabricated building structural system is disclosed in which practically no on site construction is necessary as compared with the substantial site preparation necessary in the prior art. Substantially every portion of the main structure may be prefabricated on or off site, prior to assembly. The system is characterized in the use of materials which render it fireproof, weatherproof and termite proof and not subject to buckling or warping. It has structural details and connections at the footings, floor slab, vertical columns, roof trusses and interior and exterior walls, for example, which render the finished structure flood and earthquake resistant and give it a life expectancy far superior to prior art prefabricated or conventional housing.