Building block

Claim 1

A building block comprising an inner wall, an outer wall spaced from and parallel to the inner wall, a cavity defined between the inner and the outer walls, at least one web connection between the inner and the outer walls, two end portions, said end portions both including either a female recess or a male protrusion thereby forming a double-female block or double-male block respectively, said female recess tapering inwardly from a wider mouth and said male protrusion tapering outwardly from a wide inner portion whereby cooperating end portions of adjacent juxtaposed male and female blocks may interlock simply by butting one block against the other, and longitudinal projections extending one from an inner portion of the upper edge of each of the inner and outer walls, the longitudinal projections being aligned with the double recess or double protrusion of the block and having a length defined thereby, and the longitudinal projections each tapering from a wider inner portion to a narrower free edge, the blocks being adapted to be assembled together such that, in a structure comprised of a plurality of cooperating double-male and double-female blocks, adjacent blocks are simply butted up to one another to interlock with one another horizontally and vertically, load is transmitted to below through the outer portions of the inner and outer walls, and the longitudinal projections are disposed in the cavities of adjacent blocks above to locate one block upon the other.