Abstract: In the construction arrangement of building composite double or multiple walls, two or more load-bearing walls are built together by means of panels which are prefabricated of concrete or other strong hardenable material and of noncorrodible molds of various shapes that can be combined in various ways and which remain integrated in the final construction assembly. All the elements of the construction are of such size and weight that can be easily handled by two laborers without the need of special or heavy equipment. The separation between walls is pre-determinable in accordance with the specifications of the construction and the space between walls is fillable with any material suited to the purpose of the construction, which remains fireproof regardless the material used as filler. The composite walls can be fabricated with capability for bearing permanent overloads.