Roof Beam Size

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.

Roof beam size.

Most interior beams need to include the roof load. Window door garage door headers supporting roof wall floor loads. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads. 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.

In the example d calculates to 7 75. Maximum rafter spans for a patio roof. Window door garage door headers supporting roof loads only. It has been my experience to never use a beam smaller than a two ply 2 x 8.

If you know the slope x in 12 you want to use for your roof framing design you can use it along with the run r to determine the height of the ridge beam for example if the slope is 4 in 12 and the run is 12 feet the ridge beam height m will be 4 feet. The finished ridge beam height z above the top of the wall will be m plus the y height. You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. If there is are any questions about anything else then you should contact your supplier or an engineer.

In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot. For heavy roofs or in. This calculator matches up with 90 of the applications in the 2012 international residential code book. Calculate the initial value for d then round it up to the nearest inch.