In the example the beam spans the 10 foot width of the roof.
Gable roof span.
So consider a simple gable roof on a 24 foot wide ranch framed with 2 6 exterior walls and a 1 1 2 ridge.
Gable roof a gable roof has two opposite sides with equal slopes and equal spans that meet in the center of the roof at the ridge.
Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
2 you must determine the snow load for your region.
This is the horizontal distance from the inside surface of the supporting wall to the inside surface of the ridge board.
To calculate a gable roof.
Use the saltbox roof to calculate a two sided roof with different slopes spans and or overhangs for each side of the roof.
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.
Trusses can be constructed with smaller sized lumber than rafters and often their cost is not significantly higher than normal rafters.
The lengths and sizes of joists vary depending on the species and quality of the lumber used.
After they re up you can snap a line to mark and trim the tails in a nice straight line to make up for any ridge warp or marking cutting and fixing errors.
The spans in this table are based on a maximum supported rafter span of 16 feet where the supported span is the total horizontal distance spanned by the roof rafters divided in half not the diagonal distance or the length of the rafter.
Use of manufactured roof trusses can dramatically cut labor costs when framing a gable roof compared to building rafters.
The 1 grade.
The tables below give maximum spans for rafters and beams.
For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2.
Wood beam calculator american wood council website rafter and joist span faq.
L stands for the span of the beam in feet.
F stands for the beam s fiber strength in bending which depends on the species of wood.
For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
The total load is 4 000 pounds.
For roofs that won t experience heavy snow loads a gable roof can span up to 22 with 2 4 rafters.
Gable roof framing calculator plan diagram with full dimensions for a good straight fascia add an extra inch or 2 to the tails of all your rafters total length.
For roofs that will experience heavy snow or wind and will span the same distance use 2 6 rafters.
