Abstract: A mortarless, lightweight building block and walls formed therefrom. The block is generally rectangular and comprises side walls, end walls, and an interior wall which divides the interior of the block into two vertical passages through the block. In certain blocks, parts of the end and interior walls are removed to form horizontal channels through the blocks. The blocks are provided with projections and recesses having rectangular cross sections by which means they may be interlocked together to form walls. In such a wall, the vertical passages and horizontal channels may receive reinforcing structures to impart added strength and load bearing properties to the wall.

Abstract: A family of interlocking polyurethane foam building blocks configured similarly to conventional concrete building blocks. Tongues and grooves are formed on the end faces of a universal block in such a manner that the end faces of two identical blocks will engage with one another when the blocks are longitudinally aligned and the end faces are in abutment. The tongues and grooves are configured so that the building blocks may be rotated about any axis of the block and still interlock with an identical block. The upper and lower surfaces of the universal block are formed with projections and recesses configured to engage with the projections and recesses on an abutting surface of an identical block that is longitudinally offset by one-half the length of the block. The projections and recesses are configured and arranged to allow the universal block to be rotated about any axis of the block and still interlock with an identical block.