Purlins On A Roof

The purpose of purlins.

Purlins on a roof.

By supporting the rafters they allow longer spans than the rafters alone. Purlin plates in wooden construction. Purlins traditionally support the roof deck cladding sheeting and are in turn supported by the principal rafters steel beams etc. Purlins are an important component in a pre engineered steel structural kit.

The width of metal panels will determine the rafter spacing. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Metal building roof purlins provide three structural functions.

The roof deck is the wood panel ply board or metal sheeting that creates the surface of the roof. There is a chance of damaging roofing sheets if you are failed to do so. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. In the past the majority of roof structures were of wooden construction but over the past 15 to 20 years there has been.

A traditional purlin strictly by definition is a horizontal structural member in a roof. 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 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 purlins of a roof support the weight of the roof deck. The metal roof purlins spacing must be done correctly within narrow tolerances. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. When made of wood it is usually covered with some sort of weatherproofing and sometimes an insulation material.

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. The wider the roofing panels the greater spacing distance you should put. Purlins are 2 by 4 feet and are installed much like metal roofing. A common arrangement is a rafter and purlin system which combines purlins and rafters.

These structural supports run perpendicular across the rafter beams. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.