Flat Roof Joist Sizes Uk

Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1.

Flat roof joist sizes uk.

Permissible clear span metres. Surveyors span tables for designing roof rafters. Sizes of joists needed for flat roof construction. So any timber joists that are used need to be strong enough to support this weight.

If the rafters of a flat roof need to span 18 feet with a deflection limit of their length divided by 360 l 360 they need to be 2 inches by 10 inches or 2 inches by 12 inches depending on the type and grade of timber used. For pitched roofs flat roofs and ceiling joists. These dimensions take into account a snow load of 9 07 kilogram per square foot psf. 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.

As you may imagine there is a fair amount of weight involved here in terms of boards felt etc. 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. Common joists sizes are 200 x 50mm 175 x 50mm and 150 x 50mm. 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.

Old asbestos roofs are often replaced with flat roofs. Dead load per square metre in kn m supported by joists. Timber floor joists shall be adequate for the spans and loads and be correctly installed. 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.

Centre to centre spacing of joists in mm joist size width depth mm 400 450 600 400 450 600 400 450 600. Clear spans for flat roof joists in metres size of roof joists spacing of joists 400mm 450mm 600mm 97 x 47 1 84 1 81 1 74 120 x 47 2 43 2 39 2 27 145 x 47 3 08 3 02 2 87 170 x 47 3 75 3 67 3 42 195.