Abstract: Modular housing units each including identical floor and roof structures as well as walls made up of panels of identical size assembled together with some of these panels including window structures and door structures. Ceiling panels are of the same shape and size as the wall panels. The floor and roof structures are such that the floor structure of one unit can be placed on the roof structure of a next-lower unit. Thus modular units can be assembled at a common elevation enabling a number of the modular units to be combined to provide a given housing area of any desired size and in addition the modular units can be assembled vertically to provide both vertical and horizontal assemblies of the modular units.