Porch Roof Beam Span Chart

Window door garage door headers supporting roof loads only.

Porch roof beam span chart.

This post may contain affiliate links. Lumber species southern pine douglas fir douglas fir larch hemlock fir spruce pine fir redwood western cedar ponderosa pine red pine. If you move up to 4 by 8 you re usually allowed to span up to 10 feet between posts. You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.

This tells you the size of the beam needed to support the porch s roof. A 4 by 10 can usually span up to 12 feet between posts. Tables providing size selections for various beam spans and loading combinations for southern pine dimension lumber and southern pine glued laminated timber are available for the following applications. Beam span calculator for help simply click on the beside the section you need help with watch this tutorial video.

Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads. Patio roof maximum beam rafter spans. For more information see our disclosures here. In general the maximum span for a 4 by 6 beam is 6 feet between 4 by 4 posts.

This means the example porch would need a 6 inch by 8 inch beam. Window door garage door headers supporting roof wall floor loads. The smallest beams for patio covers are typically 4 by 6.