Span tables use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.
Shed roof span tables.
Patio roof cover sheds water allows natural light.
You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.
View joist rafter tables.
For lesser grades spans should be shorter.
There is no standard spacing it depends on what size of rafters you want to use and the span of your shed.
For instance 2 grade 2x4s at 16 on center will span just over 9.
Joist and rafter span tables.
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.
Keep in mind that these are maximums in other words shortening spans slightly will result in a more solid structure.
For standard shed roof rafter spacing see rafter span chart.
Simplified maximum span tables for selected visual and mechanical grades of southern pine lumber in sizes 2 4 thru 2 12.
Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters.
The figures are based on quality materials.