Flat Roof Joist Sizes Uk

The joists will normally be placed at 400mm centres but no more than 600mm centres.

Flat roof joist sizes uk.

Sizes of joists needed for flat roof construction. For pitched roofs flat roofs and ceiling joists. Solid timber joist sizes are provided in the bs 8103 3 span tables. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc.

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. Flat roof with no permanent access and altitude not exceeding 100m 0 75 kn m udl 0 9 kn point load most areas exceeding 100m but not exceeding 200m excluding parts of scotland pennines north east england refer to bs 6399 3 1 kn m udl 0 9 kn point load. Centre to centre spacing of joists in mm joist size width depth mm 400 450 600 400 450 600 400 450 600. Common joists sizes are 200 x 50mm 175 x 50mm and 150 x 50mm.

Dead load per square metre in kn m supported by joists. Permissible clear span metres. Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1. Old asbestos roofs are often replaced with flat roofs.

Surveyors span tables for designing roof rafters. 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. 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 47 x 195 4 41 4 31 3 92 47 x 220 5 04 4 85 4 41 75 x 170 4 50.