Abstract: A planar building panel core having two main faces coated with a cementitious material wherein the core includes an extruded, non-containing formaldehyde closed cell foam insulation board that is chemically inert, of high compressive strength, and of a low moisture absorbing quality. The board also includes an upper surface with opposite ends, a bottom surface of a length substantially equal to that of the upper surface and parallel side surfaces, and has a generally congruent sheet of metal lath on each main face, with each sheet having diamond-shape openings formed therein. Additionally, the building panel core includes a plurality of spaced commonly shaped metal furring vertical channel members which are to be fastened to a support structure and a steel reinforcing sheet spanning each board face.