Abstract: A wall construction unit for buildings, said unit comprising a reinforced concrete layer with parallel, projecting flanges between which insulations are provided, and joists and an intermediate insulation preventing cold bridges are positioned on the free edge of the flanges by means of clamp-irons cast into the concrete flanges.At one longitudinal edge the wall construction unit also has a longitudinally extending projection which constitutes the external corner of a building and is cast integrally with the rest of the wall construction unit, said projection being provided with an insulation and an intermediate insulation preventing cold bridges and situated beneath the joist positioned on its outer flange.The wall construction unit is a pre-fabricated building component which is prepared to be ready for mounting by a casting process during which joists, intermediate insulation and other insulation are secured to the concrete by casting.