Abstract: An assembly consisting of a first building construction block with a substantially parallelepipedal shape and a second building construction block with a substantially parallelepipedal shape, said first and second blocks being able to fit together by mortice and tenon, each block comprising a first opening in the form of a splayed U on each of the transverse sides of the parallelepiped and a second opening extending over at least part of the surface of the longitudinal side, the first and second openings being joined together in the top part of the splayed U, at least one edge forming the junction between the longitudinal side and the top part of the legs of the splayed U of the first block forming a recess intended to receive a predetermined quantity of mortar binder and the second block comprising at least one protuberance situated at the base of the splayed U enabling the construction block to nest and slide, the protuberance on the second block coming into contact with the mortar binder and participating