Roof Timber Span Tables

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.

Roof timber span tables.

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. Span tables f7 rafters a maximum roof pitch of 25 degrees is assumed. For pitched roofs flat roofs and ceiling joists. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.

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. 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. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. 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.

Also available for the android os. Spacing should be interpreted as the centre to centre distance between adjacent parallel members. Other more complex load condition spans can be determined with our free hyne timber design 7 5 software. 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.

Required size for a given span. Span tables allow users to choose an appropriate size and stress grade to achieve spanning needs. 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. Roof load width rlw and floor load width flw can be determined from as1684 or from the images below.

These span tables apply only to flat roof and roof with a slope of up to 10 degrees. For simple construction such as domestic construction this can be determined from span table supplements in as1684 2 and as1684 3. Pitched roof timber sizes. Span calculator for wood joists and rafters also available for the android os.

Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.