Roof Purlin Design

Purlins are 2 by 4 feet and are installed much like metal roofing.

Roof purlin design.

A distinction is made between single shell and double shell roofs. The term plate means a major horizontal supporting timber. Purlin plates are beams which support the mid span of rafters and are supported by posts. Metal roof purlins are installed horizontally under metal roofs.

The typical use case for a warm roof is the flat roof. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Roof purlin design roof purlin design. The roof frame work mainly consists of purlins inferior purlin central purlin and ridge purlin ridge collar rafter and roofing battens.

By supporting the rafters they allow longer spans than the rafters alone. 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. 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. 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. 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. The designis based on the maximum yeild strength mn fysx as stated in the aisc manual 13th ed.

Purlin plates in wooden construction.