Porch Roof Beam Span Chart

L stands for the span of the beam in feet.

Porch roof beam span chart.

Patio roof maximum beam rafter spans. In general the maximum span for a 4 by 6 beam is 6 feet between 4 by 4 posts. If you move up to 4 by 8 you re usually allowed to span up to 10 feet between posts. The smallest beams for patio covers are typically 4 by 6.

Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads. Window door garage door headers supporting roof loads only. A 4 by 10 can usually span up to 12 feet between posts. For the initial calculation f can be estimated at 1 000.

In the example the beam spans the 10 foot width of the roof. 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. An essential part of planning a patio roof or gazebo project is determining the number size and spacing of rafters beams and posts according to the loads they will carry. This post may contain affiliate links.

F stands for the beam s fiber strength in bending which depends on the species of wood. Fill in the parts of the formula that are already known. You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. For more information see our disclosures here.