Abstract: An assembly of structural elements capable of disassembly, capable of addition horizontally and vertically, capable of reduction in size horizontally and vertically, the entire structure accomplishing such purposes and objectives by the use of precast concrete elements, precast with wire tensioning bores therethrough, so that upon assembly of such elements the assembly can be post-tensioned in place; also being subject to ready disassembly or reduction in size by removal of individual elements by facile release of the tension wires. The entire assembly thus represents a composite of basic individual structural elements, which when attached together form the basic system of the complete building unit, are capable of receiving habitable precast modules or capable also of utilization in the formation of basic floor framing systems.