Rather than having 2 4 purlins every 12 it would make far more sense economically to use 2 6 purlins every 24.
Roof rafter spacing 2x4.
Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.
For standard shed roof rafter spacing see rafter span chart.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
For instance 2 grade 2x4s at 16 on center will span just over 9.
Spacing in exterior exposure.
An syp rafter can span 11.
Both of these are for light roof loads.
1 psf lb f ft 2 47 88 n m 2.
Span calculator for wood joists and rafters also available for the.
Typical rafter spacing codes will specify a minimum spacing of 16 inches 19 2 inches or 24 inches.
2 are indicated below.
If you live in an area that requires a shed roof rafter to support a heavy load then an spf rafter can only span 7.
Live load psf dead load psf span calculator for wood joists and rafters available for the iphone.
Structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes.
As mentioned above a 2 4 spf shed roof rafter can span 11.
1 ft 0 3048 m.
Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.
It is always better to have a large rafter rather than be concerned with a sagging roof.
Rafters must be strong enough to hold the roof sheathing and the shingles.
Live load is weight of furniture wind snow and more.
Builders aren t bound by standard rafter spacing measurements.
Dead load weight of structure and fixed loads 15 lbs ft 2.
If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.
Without even running the calculations i would say there is a good chance the 2 4 purlins will not make the deflection criteria required for a roof framing member supporting steel.