Flat Roof Joist Sizes Uk

In terms of rules on ventilation bs 5250.

Flat roof joist sizes uk.

Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. 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. Although flat roofs are cheaper to build than pitched roofs they have a shorter life span. They are nailed securely to exterior wall plates and to each other.

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. Automatically calculate sizes suitable for supporting the loads below or. For pitched roofs flat roofs and ceiling joists. All the figures are based on the normal loading conditions.

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. Flat roof construction for residential. Waterproof membrane to prevent water penetrating the structure and interior of the. This air is vented at either end of the roof to allow a continuous air flow.

Size of joists mm clear span c16 joist m clear span c24 joist m 47 x 95 47 x 120 47 x 145 47 x 170 47 x 195 47 x 220 1 77 2 40 2 89 3 38 3 87 4 36 2 04 2 75 3 47 4 20 4 93 5 66 floor joists flat roof joists assumptions at 400mm centers supporting permanent load excluding self weight of joists up to 50kg m2. More common timber sizes used in flat roof construction. A roof is considered to be flat when it is of a slope of 1 5 o to the horizontal. 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.

Enter a specific joist size 2 loadings. Subject ceilings and flat roofs timber sizes and construction details 09 issued 01 04 13 rev page 1 of 2 the following tables give details of the allowable spans and spacing for some of the more common timber sizes used in ceiling and flat roof construction. Flat roof with asphalt finish with felt. Flat roof joist calculator.

These span tables apply only to flat roof and roof with a slope of up to 10 degrees. Solid timber joist sizes are provided in the bs 8103 3 span tables. Surveyors span tables for designing roof rafters. A flat roof usually consists of the following.

2011 control of condensation in buildings is the document to view. Supporting imposed load. 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.