Flat Roof Joist Sizes And Spans

For pitched roofs flat roofs and ceiling joists.

Flat roof joist sizes and spans. 3 stud construction standard utility. The lengths and sizes of joists vary depending on the species and quality of the lumber used. 1 ft 0 3048 m. This is the distance between joist centres.

Dead load weight of structure and fixed loads 15 lbs ft2. 2x4 2x6 2x8 2x10 2x12. Usually 400 450 or 600mm but any value can be used up to 610mm max usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size. 1 psf lbf ft2 47 88 n m2.

Spacing in 12 16 19 2 24. L 720 l 600 l 480 l 360 l 240 l 180. 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.

Floor joists ceiling joists rafters snow load rafters roof live load deflection limit. 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. Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support. Live load 20 lbs ft2 956 n m2 maximum span ft in nominal size.

1 in 25 4 mm. 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. Live load is weight of furniture wind snow and more.