Standard Flat Roof Joist Sizes

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.

Standard flat roof joist sizes.

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. Flat roof joist calculator. 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. The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches.

Enter a specific joist size 2 loadings dead load. But they do tend to space rafters in one of several industry standard increments typically. The lengths and sizes of joists vary depending on the species and quality of the lumber used. 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.

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. Rafter and joist span faq. The difference in the joist sizes applies to the width of the boards which determines the height of the. Builders aren t bound by standard rafter spacing measurements.

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. The full version allows any size. 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. Surveyors span tables for designing roof rafters.

Code of practice for permissible stress design materials and workmanship and bs 5268 7 2 1989 structural use of timber section 7 2. Supporting imposed load. This demo version is fixed at 1m clear span. 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.

1 enter joist details 1 1 span and joist spacing.