Abstract: A load-carrying building structure, particularly ceilings and floors, comprising an assembly of prefabricated box-shaped components made from appropriate non-viscoelastic material like wood, steel and concrete. The box-shaped components are held together to form a rigid structure by means of tensioning members, a plurality of rods made from high quality steel arranged in at least two crossing directions. The rods are positioned and tensioned to such a degree that the tensile stresses in the structure due to dead load and live load are entirely eliminated by the compression stresses brought to the structure by the tensioning members. The mentioned boxes are thin-walled with a ratio between length: thickness of at least 30:1, and the ratio between depth:length is between 1:1 and 1:4.