Abstract: The invention relates to a modular element used in the construction of buildings, constituted by a floor, a ceiling and vertical walls extending between the floor and the ceiling so as to define at least one parallelepipedic box-shaped compartment, the interior of which may be entirely finished, wherein the floor is constituted by a reinforced concrete slab covered by a layer of supple material on which rests a false floor or layer, connected to the vertical walls at their base, dismountable fixing means being provided between said slab and said false floor at least in each of the angles of the element.