Abstract: Element of construction designed to be laid without mortar comprising a block (B1-B4) with six faces (1-6) opposite two-by-two and of which at least one face (1, 2) is punched so as to form open internal cells (7, 7a, 7b, 7c) separated by walls (8), characterized in that said block comprises ribs (9, 9a, 9b) and grooves (10) which extend in parallel to the edges (1a, 1b) on at least two faces with a length at the most equal to the greatest dimension of said block as well as a transversal channel of V-shaped cross-section disposed perpendicularly between the longitudinal edge and said rib on the upper face of said block.