Table 9 1 in span tables for joists and rafters figure 5 gives a required compression value of 237 psi for a span of 16 feet and bearing length of 1 5 inches.
Porch roof beam span table.
Simplified maximum span tables for selected visual and mechanical grades of southern pine lumber in sizes 2 4 thru 2 12.
In the article it is stated that a 12 joist span corresponds to the double beam span a length equal to the 2x width.
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.
The tables permit a bearing length of up to 3 5 inches but since 1 5 is probably the worst case that you ll encounter for joist or rafter bearing it s a safe value.
Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters.
The smallest beams for patio covers are typically 4 by 6.
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 figures are based on quality materials.
Michael t 5 17 2017 12 53 19 am reply.
F stands for the beam s fiber strength in bending which depends on the species of wood.
Includes size and spacing tables for load bearing and links to related articles.
However this seems to match the 6 joist span column of the table.
In the example the beam spans the 10 foot width of the roof.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
The tables below give maximum spans for rafters and beams.
A 4 by 10 can usually span up to 12 feet between posts.
L stands for the span of the beam in feet.
Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.
For the initial calculation f can be estimated at 1 000.
In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
Download a pdf.
Fill in the parts of the formula that are already known.
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.
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.
You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.
Jan 15 2017 a simple buying guide for beams and rafters that support patio roofs.
