View allowable load tables.
Timber pitched roof span tables.
For pitched roofs flat roofs and ceiling joists.
Span tables span tables can be used to determine the size of a timber member of a particular strength class required for a given span.
View joist rafter tables.
Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.
You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.
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.
Surveyors span tables for designing roof rafters.
Pitched roof timber sizes.
Also available for the android os.
View size selection tables.
The tables below give maximum spans for rafters and beams.
The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.
All the figures are based on roofing tiles or slates laid on timber laths over sarking felt.
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.
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.
They also tell you what the maximum spacing should be between each section or timber member size of joists mm clear span c16 joist m clear span c24 joist m 47 x 95 47 x 120 47 x 145 47 x 170 47 x 195 47 x.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters.
Span calculator for wood joists and rafters also available for the android os.
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.
In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
