Abstract: A formwork for building bearing walls comprises a plurality of pairs of facing panels (PE, PI) connected together so as to form an inside space between them, said pairs of facing panels being arranged in superimposed rows, the panels of each pair being connected to each others by braces (6) of adjustable length with both the braces (6) and the panels (PE, PI) being left in the wall formed when a cementitious material poured in said inside space has solidified. The so formed walls are provided with bearing partition members and ventilating duct, and are strongly insulated and already finished (FIG. 6).