Roof Timber Sizes And Spans

Surveyors span tables for designing roof rafters.

Roof timber sizes and spans.

These spans were calculated using our flat roof joist calculation. 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 figures are based on normal loading conditions found in domestic construction. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.

All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. Click on a span to generate a full calculation you can adjust the exact span. 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. Pitched roof timber sizes. In any other situation you should refer to trada document span tables for solid timber members in floors. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.

For pitched roofs flat roofs and ceiling joists.