Abstract: A roof ballast block having generally rectangular top and bottom faces and two parallel edges bevelled at substantially identical angles of 12.degree. to 23.degree. from the vertical, the remaining two edges being substantially vertical, the block having a plurality of parallel spaced channels in its bottom face and being characterized by a density of 85 to 155 pounds per cubic foot, a compressive strength of at least 2500 psi, a flexure strength of at least 300 psi, and a capability of undergoing at least 100 freeze-thaw cycles without cracking.

Abstract: A roof construction comprising ballast blocks each having two parallel edges bevelled at substantially identical angles of 12.degree. to 23.degree. from the vertical, the remaining two edges being substantially vertical, the blocks being laid in a pattern adjacent each rectangular corner of the roof so that downwardly and outwardly bevelled edges are adjacent each roof edge at the corner.