Flat Roof Joist 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.

Flat roof joist span.

Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. 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. 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. Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.

Span tables for flat roof joists to bs 5268 7 2 imposed loads of 0 75 kn m for maintenance and snow load are applicable where there is no permanent access no fixed ladder or staircase and most areas where the altitude does not exceed 100 metres refer to bs 6399 3. For pitched roofs flat roofs and ceiling joists. Live load is weight of furniture wind snow and more. Dead load weight of structure and fixed loads 15 lbs ft 2.

Use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size. 1 psf lb f ft 2 47 88 n m 2. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope. 1 enter joist details 1 1 span and joist spacing.

Surveyors span tables for designing roof rafters. This is the distance between joist centres. These span tables apply only to flat roof and roof with a slope of up to 10 degrees. Span calculator for wood joists and rafters also available for the android os.

2 are indicated below. Joists under each partition. 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. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. The full version allows any size. Flat roof joist calculator. Also available for the android os.