Pole Barn Roof Purlin Spacing

The most common method of installing purlins in a pole barn is to lay them flat.

Pole barn roof purlin spacing.

Here is the formula for calculation of a roof purlin. 384 x e modulus of elasticity for the lumber being used x i moment of inertia for the lumber size plugging in the variables. Purlins are dimensional lumber that are fastened to the top chord of trusses connecting them together for bracing purposes. Investigators have found that post frame structures fare surprisingly well in the tornado prone areas of the central united states.

Truss spacing roof purlins and roof sheathing is listed below with the roofing finish options. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. Vinyl siding trim on 7 16 sheathing and house wrap additional 2x4 vertical nailer 4 on center for 4x8 sheathing painted steel siding trim w matching screws 29 ga. Installation of pole barn purlins.

I am wondering if a 2 x 6 x 16 rafters 2 oc will work. I ve had roof truss manufacturers try to convince me it is impossible to place wood trusses at spacings of over every 4 feet. Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof. I am wanting to make it 14 deep and 22 wide with no center post in the 14 span.

With this design change roof trusses could be placed 12 feet apart making it possible for roofs to support the loads to which they would be subjected. Fyi we run purlins on 3 5 feet on center depending on size of purlin. This is typically done with 2x4s. Cos of live load dead load x cos of the purlin spacing x purlin span squared 8 x sm section modulus of the member x duration of load 1 15 in areas with snowfall x cr repetitive member factor of 1 15 where members are 24 on center or less fb fiberstress required.

Purlin spacing is dependent on profile of the metal and gauge plus snow and wind load plus what the rafters are designed to carry. It will have a metal roof over purlins. The pt posts are 6 x 6 spaced either 6 or 8 apart on the high and low load bearing side walls. 5 x 18 98 psf 144 has to be divided by 144 to give psi x 24 x 70 5 4 384 x 1 400 000 x 0 984 0 795.

Since the weather is a critical factor how well do these hold up in the severest of weather conditions. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. 5 x ps roof snow load adjusted for slope factors x purlin spacing x purlin span 4. Without a set of blueprints with a pe s seal you have no option but to follow the inspectors gig.

The purlins are nailed to the trusses with two 20d galvanized ring shank nails. Many post frame or pole barn construction use 8 foot spacing between trusses. Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load. Nails trim basic plans.