Abstract: A pre-formed building panel comprising a metal core substantially completely encapsulated in a low density material and acting as a reinforcement member therein, that member comprising first and second sets of lengthwise-extending segments at different elevations within the panel and connected to adjacent segments of the opposite set by generally vertically extending segments, the panel optionally being provided at its side edges with portions adapted to be overlapped with corresponding portions of an adjacent panel, the panels being provided with metal edge plates at top and bottom, those edge plates optionally having a width less than the width of the panel, the general vertically extending segments being provided with relatively large holes spaced lengthwise therealong while the segments of the first and second sets are substantially free of holes, with the metal reinforcement member optionally carrying a vertical wall extending from a side edge of said member, the segments of said first and second sets, t