Steel Roof Purlins Spacing

Metal building roof purlins provide three structural functions.

Steel roof purlins spacing.

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. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Tin roofing also known as metal roofing is considered more durable than composition or wood shingles. The cos of the purlin spacing is because the load on the purlins is vertical and the purlin spacing is with the run of the roof.

Do all roofing projects require purlins. First the purlins support the roof. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. The width of metal panels will determine the rafter spacing.

Installing wood stripping under a tin roof. Secondly purlins tie the rafters together stabilizing and strengthening the structure s rigid framing. Purlin spacing for metal roofing the country inspector upon approving the plans seems to have written in per manufacturers specs regarding 2x4 purlins on 16 centers. For sake of discussion we will assume a minimal roof snow load of 20 psf pounds per square foot and a 4 12 roof slope.

Purlins are 2 by 4 feet and are installed much like metal roofing. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Dead load will be the actual weight of the roof steel and the roof purlins. Metal roof purlins are installed horizontally under metal roofs.

The roofing is manufactured in panels that. The metal roof purlins spacing must be done correctly within narrow tolerances. An engineer will use a load chart in order to determine the spacing between metal purlins. Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load.

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. Screw line spacing for metal roofing over metal purlins. Once the purlin spacing is determined then the metal roofing panels are typically attached to every line of purlins. There is a chance of damaging roofing sheets if you are failed to do so.

The building was built 24 on center. The wider the roofing panels the greater spacing distance you should put. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. We do recommend it however.