Given in the table.
Safe spans for no 1 roof rafters.
The 1 grade material is more expensive than the 2 grade but if you can use fewer or smaller 1 grade joists or rafters in your design you may actually save money.
The tables below give maximum spans for rafters and beams.
Rafter table type 1.
This type is used to determine the length of the common valley hip and jack rafters and the angles at which they.
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.
Maximum floor joist span no.
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.
Type 1 figure 7 10 appears on the face of the blade.
So if your house is 26 feet wide and the roof ridge beam is centered on the house you will need a rafter that can span 13 feet.
For example 2 by 6 rafters made from select structural grade douglas fir that are required to support a live load of 20 pounds per square inch can have a maximum horizontal span of 11 feet 4 inches.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
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 grade of douglas fir and maximum span floor joists imperial units nails and spikes withdrawal force allowable withdrawal load for nail and spikes softwood and hardwood structural strength classes strength classes bending stress and mean density of hardwood and softwood.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
Contact a building control officerfor advice.
Span calculator for wood joists and rafters also available for the android os.
Span calculator for wood joists and rafters available for the iphone.
Let s use this example and find a size of rafter that will work.
The other type of table gives the actual length of a rafter for a given pitch and span.
1 psf lb f ft 2 47 88 n m 2.
Maximum clear span of rafters in metres for roof pitches of between 15 and 45 degrees roof pitch between 15 and 22 5 degrees with rafter spacing.
The maximum spans in the table above are for the horizontal distance the rafter can span not the diagonal distance or actual length of the rafter.
Decreasing the distance between rafters to 12 inches however increases the maximum span to 14 feet 4 inches.
Dead load weight of structure and fixed loads 15 lbs ft 2.
