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.
Flat roof rafters span tables.
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.
Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall.
Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.
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.
For pitched roofs flat roofs and ceiling joists.
Flat roof span tables allow for a maximum roof pitch of 5ยบ.
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.
Roof pitch use recommended minimum roof pitches as specified by roof sheet supplier.
Surveyors span tables for designing roof rafters.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.