Roof Purlin Design

By supporting the rafters they allow longer spans than the rafters alone.

Roof purlin design.

A single shell roof is also called warm roof and it is an unventilated roof. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. As structural members they resist loads and provide lateral restraints for truss members therefore it is important to design them properly against forces.

Purlin plates in wooden construction. The roof frame work mainly consists of purlins inferior purlin central purlin and ridge purlin ridge collar rafter and roofing battens. This spreadsheet is to be used to check the adequacy of roof purlins for a specified combination of loads. Roof purlin design roof purlin design.

Metal roof purlins are installed horizontally under metal roofs. Purlins are 2 by 4 feet and are installed much like metal roofing. This spread sheet can only be used for load combinations with two variables. In structural steel or aluminum construction p urlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof.

The typical use case for a warm roof is the flat roof. Purlin plates are beams which support the mid span of rafters and are supported by posts. 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. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

A distinction is made between single shell and double shell roofs.