Roof Purlin Design

As structural members they resist loads and provide lateral restraints for truss members therefore it is important to design them properly against forces.

Roof purlin design.

The term plate means a major horizontal supporting timber. 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. A distinction is made between single shell and double shell roofs.

The typical use case for a warm roof is the flat roof. Purlins are 2 by 4 feet and are installed much like metal roofing. Metal roof purlins are installed horizontally under metal roofs. By supporting the rafters they allow longer spans than the rafters alone.

They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Purlin plates in wooden construction. Purlin plates are beams which support the mid span of rafters and are supported by posts. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.

This spreadsheet is to be used to check the adequacy of roof purlins for a specified combination of loads. A single shell roof is also called warm roof and it is an unventilated roof. The designis based on the maximum yeild strength mn fysx as stated in the aisc manual 13th ed. This spread sheet can only be used for load combinations with two variables.

The roof frame work mainly consists of purlins inferior purlin central purlin and ridge purlin ridge collar rafter and roofing battens.