How Far Apart Are Trusses In A Flat Roof

Reader dave in michigan writes.

How far apart are trusses in a flat roof.

The higher the snow load the closer the purlin spacing required. I ve had roof truss manufacturers try to convince me it is impossible to place wood trusses at spacings of over every 4 feet. Their defense is our engineers will not allow us to. Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches.

For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet. In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot. These standards are as follows.

Typically pole barn style buildings in my area have bays distance between trusses of 5 feet to 12 depending on pitch insulation and height. If you move the rafters closer together at 16 o c then your syp rafters will span 11 and spf up to 10. Spf 2 6 rafters can span 8. Once you ve calculated the number of trusses you will need you should purchase the lumber.

Typical roof truss spacing means that they are usually about 24 inches from centre which means at the centre of one truss there will be a two foot gap or twenty four inch gap until the centre of the next truss. Most economical when the difference in slope between the top and bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch. 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. We suggest 5 on center trusses with flat purlins to be restricted to 30 ground snow loads or less in most instances.

That is exactly what i have double trusses on each side of a post on 12 centers. The trusses should be a little longer than the exact width to allow for overhang and you will need sufficient trusses to mount across the length. Truss spacing for metal roof. Most are spaced between 18 26 inches apart.

The same concept holds true for roof trusses. The tables below give maximum spans for rafters and beams. It all comes down to engineering. The figures are based on quality materials.

If purlins are laying flat on top of the truss 5 or 6 feet is the max on 2x4 s edge up can go to 12 feet or more.