Roof Timber Sizes And Spans

For pitched roofs flat roofs and ceiling joists.

Roof timber sizes and spans. Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in flat roof construction. Pitched roof timber sizes. These spans were calculated using our flat roof joist calculation.

This span table is to the format and methodology given in bs 5268 7 2. Find the column for your dead load and spacing and the row for your timber size to find the permissible clear span in metres. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. 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.

All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. 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. 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 figures are based on normal loading conditions found in domestic construction.

Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall.