A pre-cast concrete wall system that incorporates a truss ledge for positioning a building floor system at a below-grade location. The truss ledge is defined by a vertical wall formed as a continuation of the exterior wall of the wall panel extending from the footer beam to the upper bond beam and projecting vertically above the upper bond beam to provide a support surface for the building floor members. A floor truss system can be supported on the upper bond beam with the truss ledge forming a concrete below-grade surface externally of the floor trusses. Galvanized steel stud facings incorporating fold-up reinforcing bar supports are used on the interior surface of the vertical wall beams. Insulated access holes are formed through the vertical beams for the passage of wiring and plumbing behind the wall finish to be fastened to the stud facings.