For roofs that will experience heavy snow or wind and will span the same distance use 2 6 rafters.
Gable roof span.
The tables below give maximum spans for rafters and beams.
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.
To calculate a gable roof.
Wood beam calculator american wood council website rafter and joist span faq.
F stands for the beam s fiber strength in bending which depends on the species of wood.
So this table could accommodate a house with a total rafter span or house width of 32 feet.
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.
The lengths and sizes of joists vary depending on the species and quality of the lumber used.
If you have a simple gable shed roof then using 2 4 rafters makes more sense unless you have a very large shed.
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.
This is the horizontal distance from the inside surface of the supporting wall to the inside surface of the ridge board.
2 you must determine the snow load for your region.
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.
Use the saltbox roof to calculate a two sided roof with different slopes spans and or overhangs for each side of the roof.
The total load is 4 000 pounds.
L stands for the span of the beam in feet.
In the example the beam spans the 10 foot width of the roof.
The span would be 11 5 3 4.
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.
Trusses can be constructed with smaller sized lumber than rafters and often their cost is not significantly higher than normal rafters.
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.
So consider a simple gable roof on a 24 foot wide ranch framed with 2 6 exterior walls and a 1 1 2 ridge.
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.
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.
Use of manufactured roof trusses can dramatically cut labor costs when framing a gable roof compared to building rafters.
