Purlins are horizontal secondary beams that carry loads from light roofing material and transfer it to the main beams. Reinforcement of the purlins is prestressed strands. Concrete cover provides a fire resistance limit of up to 60 minutes. Purlins have a wide scope of application: warehouses, industrial shops, logistics and shopping centers, where light roofing materials are used for covering. As a rule, the spacing of the purlins is 3 to 4.5 m.