Composite Pre-Formed Building Panels

A composite building panel including a central body, substantially parallelepipedic in shape, comprised of an expanded polymer matrix, having a first surface and an opposing second surface; and one or more structural reinforcing elements longitudinally extending across the central body between said opposite faces, having a first side portion embedded in the expanded polymer matrix, and a second side portion extending away from the first surface of the central body and one or more expansion holes located in the reinforcing member between the first side portion of the reinforcing member and the first surface of the central body. The central body includes a polymer matrix that expands through the expansion holes.