a system for constructing a building is disclosed which employs various side wall , corner and roof forming elements adapted to be joined in interlocked sealed relation without need for nails or skilled craftsman . the various elements may be made from relatively inexpensive materials , such as reclaimed materials indigenous to the site of construction , generally lighter than conventional building materials such as brick and mortar , and are therefore particularly suitable for use in countries of relatively low economic wealth . furring clips may be formed on the internal surfaces of the wall and corner forming elements to facilitate attachment of interior wallboards and the like , while the external surfaces of the various elements may be textured to simulate a desired exterior appearance .