Roof Purlin Design

A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin.

Roof purlin design.

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. 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.

As structural members they resist loads and provide lateral restraints for truss members therefore it is important to design them properly against forces. A single shell roof is also called warm roof and it is an unventilated roof. A distinction is made between single shell and double shell roofs. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.

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

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

Roof purlin design roof purlin design.