Timber Roof Joist Sizes

For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine.

Timber roof joist sizes.

Pitched roof timber sizes. Where the tables do not apply or where there are concentrated loads floor joists should be designed by an engineer in accordance with technical requirement r5. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. For pitched roofs flat roofs and ceiling joists.

Solid timber joist sizes are provided in the bs 8103 3 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. The lengths and sizes of joists vary depending on the species and quality of the lumber used. Usually 400 450 or 600mm but any value can be used up to 610mm max usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size.

Flat roof joists rafters purlin. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. Timber floor joists shall be adequate for the spans and loads and be correctly installed. Greater than 2400 mm and 3 6 kn load per metre width of floor for spans less than 2400 mm to ensure that very small joist sizes do not result from the calculations for smaller spans.

These span tables apply only to flat roof and roof with a slope of up to 10 degrees. Rafter and joist span faq. Surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors. These tables can help calculate whether floor joists are strong enough to support themselves and the load they carry without the help of any walls underneath.

Bs 5268 7 1 was published before bs 6399 1. And the row for your timber size to find the permissible clear span in metres. 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. This is the distance between joist centres.

Surveyors span tables for designing roof rafters.