Abstract: A building construction system that permits the erection of a modular-skeleton structure type building in a very short time utilizing relatively unskilled labor. The construction of vertical metal profile posts which extend from the foundation to the horizontal roof girders in a single unit of uniform cross-section. The roof girders are attached by means of slotted tension bolts. The one-piece vertical profile posts have a cross-section which is essentially the combination of a T-section and an U-section. In the lower part of the building, basement wall elements extend into the vertical profile posts with their angled legs on the inside of the building. In this position, they are secured by a bracing tube.