The object of the invention is to obtain prefabricated modules of reinforced concrete corresponding to a dwelling with or without compartments, with its six wall structures consisting of single elements, achieving in this way a 100% monolithic structure, which eliminates any vibrations or dilatation and prevents the formation of cracks or humidity in the module. To this end, an internal permanent formwork is manufactured in the plant on the basis of six elements—floor, walls and ceiling, which are fixed along their edges by means of high-resistance putty and provided with distancing pads (9) on the bottom base on the floor or on the selected supporting surface with the service installations (11) mounted on the external face of the permanent formwork (1, 2, 3, 4, 5 and 6) and over them the insulation material (12), where it is necessary, then a structural frame (13), and finally an external recoverable formwork (14).