Abstract: A generally U-shaped channel member is positioned on top of the top surface of a plurality of foam plastic blocks in a horizontal wall segment, and vertically aligned concrete confining openings are formed through both the channel member and the plastic blocks. Concrete or the like is poured into the U-shaped channel and is funneled therefrom into the vertical openings. Once the concrete sets as a rigid supporting structure, the U-shaped channel is permanently retained in the wall structure. The U-shaped channel member is employed for attaching means to the exterior of the completed wall structure. Additional horizontal segments of the wall structure are formed by placing another horizontal layer of plastic blocks and a U-shaped channel member on top of the previously completed horizontal segment.