Flat Roof Joist Sizes Uk

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 joist sizes uk.

More common timber sizes used in flat roof construction. All the figures are based on the normal loading conditions. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. Flat roof construction for residential.

In terms of rules on ventilation bs 5250. Although flat roofs are cheaper to build than pitched roofs they have a shorter life span. 2011 control of condensation in buildings is the document to view. Surveyors span tables for designing roof rafters.

A flat roof usually consists of the following. 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. 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. The size of rafters for a flat roof depends on the horizontal span of the building the type and grade of timber used and the load on the roof.

Put simply a warm flat roof has insulation of some kind packed into every available void and a cold flat roof allows air to circulate between the joists. Automatically calculate sizes suitable for supporting the loads below or. Solid timber joist sizes are provided in the bs 8103 3 span tables. Maximum clear span of flat roof joists in metres for sc3 timber spacing between joists size of roof joist 400mm 450mm 600mm 47 x 97 1 84 1 81 1 74 47 x 120 2 43 2 39 2 27 47 x 145 3 08 3 02 2 87.

Waterproof membrane to prevent water penetrating the structure and interior of the. For pitched roofs flat roofs and ceiling joists. Flat roof joist calculator. A roof is considered to be flat when it is of a slope of 1 5 o to the horizontal.

Flat roof with asphalt finish with felt. All figures are based on. They are nailed securely to exterior wall plates and to each other. This air is vented at either end of the roof to allow a continuous air flow.

Supporting imposed load. Enter a specific joist size 2 loadings. These span tables apply only to flat roof and roof with a slope of up to 10 degrees.