Flat Roof Joist Sizes Uk

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 47 x 170 3 75 3 67 3 42.

Flat roof joist sizes uk.

Suitable for uk building regulation approval. Code of practice for permissible stress design materials and workmanship and bs 5268 7 2 1989 structural use of timber section 7 2 joists for flat roofs. Supporting imposed load. Where a new flat roof abuts an existing external wall the joists can be hung on metal joist hangers which are fixed to a horizontal timber plate wall bolted to the wall.

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. Timber floor joists shall be adequate for the spans and loads and be correctly installed. Ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice. For pitched roofs flat roofs and ceiling joists.

Flat roof joist calculator. Boarding to be fastened on top of flat roof joists with a depth to width ratio greater than 4 the allowable clear spans have been calculated in accordance with bs 5268 2 2002 structural use of timber part 2. Surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors. But any value can be used up to 610mm max.

Solid timber joist sizes are provided in the bs 8103 3 span tables. A cavity closer should be provided to the top of the walls to prevent fire spread and to stop damp air entering the roof space. 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. The rafters in a flat roof serve as ceiling joists for the space below.

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. 1 2 timber strength class and joist size automatically calculate sizes suitable for supporting the loads below or. Enter a specific joist size. Surveyors span tables for designing roof rafters.

They are nailed securely to exterior wall plates and to each other. 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.