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.
Roofing span tables timber.
Stress grades and timber sizes combine to determine the spanning ability of load carrying members.
Required size for a given span.
Table assumes a maximum flooring mass of 40kg.
Surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings.
Member tables for seasoned timber stress grade f17.
Roof load width rlw and floor load width flw can be determined from as1684 or from the images below.
Span calculator for wood joists and rafters also available for the android os.
For simple construction such as domestic construction this can be determined from span table supplements in as1684 2 and as1684 3.
Also available for the android os.
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.
Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope.
Technical diagram on page 35 30mm m aximum allow able sp ans mm sheet roof spacing mm rafter size 600 760 900 1000 1200 66 x 30 850 750 700 700 600 90 x 30 1200 1050.
Span tables allow users to choose an appropriate size and stress grade to achieve spanning needs.
For pitched roofs flat roofs and ceiling joists.
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.
Span tables f7 rafters a maximum roof pitch of 25 degrees is assumed.
Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size.
Spacing should be interpreted as the centre to centre distance between adjacent parallel members.
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.
Surveyors span tables for designing roof rafters.
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.
