For saddle roofs of halls up to span 24 m. Type production of prestressed joining beams with I cross section, structural length 18 m and 24 m. These joining beams have indented gridiron for putting on a pole or girder. Type joining beams are designed for frame module 6 m (for roof cassette iron-concrete panels) for calculation load stable + random 3,16 kN/m2. Thorns protruding from the upper collar can be alternatively replaced by built-in steel plates for weld fixation of steel binding rafters or trapezial sheet metal. Under joining beams a lower ceiling can be suspended with total weight up to 50 kg/m2. Above the bottom collar are in 150 cm distance hole couples for lower ceiling fixation, lighting or installations. Joining beams with other dimensions are handled in an individual production documentation.