Roof Joist Size Table

Use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.

Roof joist size table.

If this is the case with your structure use the floor joist table to determine maximum joist length load. 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. 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. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.

For uninhabitable attics without storage we will use table r802 4 1 and for uninhabitable attic with limited storage we will use table r802 4 2. These span tables apply only to flat roof and roof with a slope of up to 10 degrees. Ceiling joists of the first floor of a two story structure often serve as floor joists for the second floor. For pitched roofs flat roofs and ceiling joists.

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. Joist span tables use these tables to determine lengths sizes and spacing of 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. Surveyors span tables for designing roof rafters.