Abstract: A modular building panel comprising a single, monolithic, planar slab having a thickness and parallel inner and outer surfaces, the slab being formed primarily of cellular concrete and a pair of parallel linear members. Each of the linear members has outer and inner opposed parallel edges, a web connecting the edges, and an outer flange at the outer edge extending substantially perpendicular to the web. The slab extends between the webs of the outer side linear members, the outer edges and the outer flanges being embedded in the slab inwardly of its inner surface, and the outer surface of the slab being uninterrupted. The panel can additionally include at least one inner linear member intermediate and parallel to the outer side linear members.