Abstract: A composite lightweight building element comprises a first layer of aggregate based material (7, 8 and 9) extruded, sprayed, molded or cast onto a lightweight base form (1) which becomes an integral part of the element. This element can be manufactured in a panel to emulate common face brick (52), a smooth or chipped surfaced cut stone (60) or a floor tile. Integral with the first and second layers are cooperating dovetail ridges and grooves (4) respectively which serve to provide mechanical locking between the layers and a strengthening to the first layer. Integral with the second layer are male and female interlocking members (6 and 6a) to facilitate installation, to resist air or water infiltration between the panels and to provide mechanical locking between panels.