Roof Joist Sizes Building Regs

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.

Roof joist sizes building regs.

Timber floor joists shall be adequate for the spans and loads and be correctly installed. 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. This span table is to the format and methodology given in bs 5268 7 2. For pitched roofs flat roofs and ceiling 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 47 x 195 4 41 4 31 3 92 47 x 220 5 04 4 85 4 41 75 x 170 4 50. These spans were calculated using our flat roof joist calculation. 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. Solid timber joist sizes are provided in the bs 8103 3 span tables.

Click on a span to generate a full calculation you can adjust the exact span.