Roof Joist Size Table

These span tables apply only to flat roof and roof with a slope of up to 10 degrees.

Roof joist size table.

As mentioned above the span tables within the code list the allowable ceiling joist spans for common lumber sizes based on what design load scenario is applied. If this is the case with your structure use the floor joist table to determine maximum joist length load. 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 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.

For pitched roofs flat roofs and ceiling joists. Joist span tables use these tables to determine lengths sizes and spacing of ceiling joists. 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. 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.

Ceiling joists of the first floor of a two story structure often serve as floor joists for the second floor. Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size. Surveyors span tables for designing roof rafters. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.