Usually 400 450 or 600mm but any value can be used up to 610mm max.
Span flat roof joist wood.
Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
Dead load weight of structure and fixed loads 15 lbs ft 2.
Live load is weight of furniture wind snow and more.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
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.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
1 enter joist details 1 1 span and joist spacing.
Span calculator for wood joists and rafters also available for the android os.
This is the distance between joist centres.
2 are indicated below.
While every effort has been made to insure the accuracy of the information presented and special effort has been made to assure that the information reflects the state of the art neither the west coast lumber inspection bureau the american wood council nor its members assume any responsibility for any particular design prepared from this online span calculator.
Also available for the android os.
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.
1 ft 0 3048 m.
Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support.
You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.
Because i joists are straight and true it s easier for builders to avoid crowning and maintain a level framing surface.
Span tables for flat roof joists to bs 5268 7 2 imposed loads of 0 75 kn m for maintenance and snow load are applicable where there is no permanent access no fixed ladder or staircase and most areas where the altitude does not exceed 100 metres refer to bs 6399 3.
Flat roof joist calculator.
Common i joist applications i joists are used extensively in residential floor and roof framing.
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.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
1 psf lb f ft 2 47 88 n m 2.