Roof Timber Sizes And Spans

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

Roof timber sizes and spans.

The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Pitched roof timber sizes. For pitched roofs flat roofs and ceiling joists. Find the column for your dead load and spacing and the row for your timber size to find the permissible clear span in metres.

This span table is to the format and methodology given in bs 5268 7 2. Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. In any other situation you should refer to trada document span tables for solid timber members in floors. Click on a span to generate a full calculation you can adjust the exact span.

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

All figures are based on normal loading conditions found in domestic construction.