Abstract: A foundation unit which, when assembled, can be collapsed for compact storage and shipping and later can be elevated to a fully expanded state. The foundation unit includes a rectangular, grid wire top bearing structure, a rigid bottom substructure such as a wooden frame, and a series of spaced, parallel rows of substantially flat support members extending between the top bearing structure and the bottom substructure. The support members are hingedly secured to the top bearing structure and bottom substructure to permit reduction of the foundation unit to the collapsed state with the rows of support members lying essentially prone. In the elevated state, the foundation unit includes stabilizers which are oppositely reactive and which prevent relative longitudinal translation between the top and bottom of the foundation unit.