Steel Purlin Roof Design

In timber construction purlins are nailed to the rafter or supporting trusses while in steel roof construction they are welded or bolted to the rafters or trusses by the means of cleats.

Steel purlin roof design.

The type and spacing of purlins is a design consideration which depends upon the incident roof loads as well as the limiting lengths of sheeting to be used. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Purlins are 2 by 4 feet and are installed much like metal roofing. In a structural steel shed the main portal frames and roof rafters are made from strong steel sections which are welded together and later bolted together.

They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Purlins are 2 by 4 feet and are installed much like metal roofing. Purlins traditionally support the roof deck cladding sheeting and are in turn supported by the principal rafters steel beams etc. In the past the majority of roof structures were of wooden construction but over the past 15 to 20 years there has been a vast shift away from wood to metal mainly steel roof construction.

Purlins and girts are used longitudinally to support the roof sheeting which they were originally designed for. Welded together they can be used as columns braces and ties. Metal roof purlins are installed horizontally under metal roofs. In structural steel or aluminum construction p urlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof.

Steel z purlins and z girts are also available with other depths and flange widths. Contact flexospan for information on custom purlin and girt structural steel dimensions. Engineered purlin metal mart offers a complete line of engineered purlin material. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.

This design is a lot stronger and more robust way of making a steel shed. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. We manufacture any component from 1 2 steel subgirts to 12 section up to 10 gauge. Purlins are installed horizontally under metal roofs.

Cee purlins are secondary steel framing members most commonly used as roof purlins wall girts and header jamb and sill for windows and doors on metal buildings. The shape of cee purlins does not allow end lapping they are butted together.