Roof Purlin Design

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

Roof purlin design.

In structural steel or aluminum construction p urlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof. As structural members they resist loads and provide lateral restraints for truss members therefore it is important to design them properly against forces. The typical use case for a warm roof is the flat roof. By supporting the rafters they allow longer spans than the rafters alone.

A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. 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. A single shell roof is also called warm roof and it is an unventilated roof. The roof frame work mainly consists of purlins inferior purlin central purlin and ridge purlin ridge collar rafter and roofing battens.

They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Purlin plates are beams which support the mid span of rafters and are supported by posts. The term plate means a major horizontal supporting timber. Purlins are 2 by 4 feet and are installed much like metal roofing.

Purlin plates in wooden construction. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. This spread sheet can only be used for load combinations with two variables. The designis based on the maximum yeild strength mn fysx as stated in the aisc manual 13th ed.

Metal roof purlins are installed horizontally under metal roofs.