Standard Flat Roof Joist Sizes

The lengths and sizes of joists vary depending on the species and quality of the lumber used.

Standard flat roof joist sizes.

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. The full version allows any size. Surveyors span tables for designing roof rafters. Builders aren t bound by standard rafter spacing measurements.

For pitched roofs flat roofs and ceiling joists. 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 joist calculator. Rafter and joist span faq.

But they do tend to space rafters in one of several industry standard increments typically. The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches. 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 47 x 195 4 41 4 31 3 92 47 x 220 5 04 4 85 4 41 75 x 170 4 50 4 38 3 99. Code of practice for permissible stress design materials and workmanship and bs 5268 7 2 1989 structural use of timber section 7 2.

Though there is no standard joist size for the ceilings in all buildings most average homes use ceiling joists in a board size of 2 by 6 inches. Compare click to add item 24 spreadweb residential roof truss 5 12 pitch 87 to the compare list add to list click to add item 24 spreadweb residential roof truss 5 12 pitch 87 to your list sku 1889754. For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine. Enter a specific joist size 2 loadings dead load.

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. This demo version is fixed at 1m clear span. 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. 1 enter joist details 1 1 span and joist spacing.

Rafter and roof joist spacing is only one part of a complex roof design that works together to form a structure that meets building codes and can hold up the weight of the roof and roof load.