Purlins On A Roof

Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building.

Purlins on a roof.

A traditional purlin strictly by definition is a horizontal structural member in a roof. Metal building roof purlins provide three structural functions. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

Purlins are an important component in a pre engineered steel structural kit. There is a chance of damaging roofing sheets if you are failed to do so. The metal roof purlins spacing must be done correctly within narrow tolerances. The purpose of purlins.

In structural steel or aluminum construction p urlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof. These structural supports run perpendicular across the rafter beams. Purlins traditionally support the roof deck cladding sheeting and are in turn supported by the principal rafters steel beams etc. The width of metal panels will determine the rafter spacing.

Purlin plates are beams which support the mid span of rafters and are supported by posts. A common arrangement is a rafter and purlin system which combines purlins and rafters. The purlins of a roof support the weight of the roof deck. Purlins are 2 by 4 feet and are installed much like metal roofing.

The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge. Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern. By supporting the rafters they allow longer spans than the rafters alone. Purlin plates in wooden construction.

The term plate means a major horizontal supporting timber. 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. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. In the past the majority of roof structures were of wooden construction but over the past 15 to 20 years there has been.

The wider the roofing panels the greater spacing distance you should put. The roof deck is the wood panel ply board or metal sheeting that creates the surface of the roof.