Flat Roof Timber Joist Span Tables

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

Flat roof timber joist span tables.

Span tables for solid timber joists. Should refer to trada document span tables for solid timber members in floors ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice. For timber floors between homes. Tables 1 and 2 in this chapter are derived from the trada technology ltd.

View joist rafter tables. The section sizes are based on regularised als or cls timber. Simplified maximum span tables for selected visual and mechanical grades of southern pine lumber in sizes 2 4 thru 2 12. Joist spans over 4 5m provide 2 rows of strutting at third span positions.

Flat roof with no permanent access and altitude not exceeding 100m 0 75 kn m udl 0 9 kn point load most areas exceeding 100m but not exceeding 200m excluding parts of scotland pennines north east england refer to bs 6399 3 1 kn m udl 0 9 kn point load. For pitched roofs flat roofs and ceiling joists. Span tables span tables can be used to determine the size of a timber member of a particular strength class required for a given span. 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.

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. 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. Solid timber strutting to be at least 38mm thick and be a minimum of three quarters of the joist depth.

Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. Joists are to have minimum end bearing of 40mm. Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters. 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.

They also tell you what the maximum spacing should be between each section or timber member 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. 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. Proprietary strutting is to be used in accordance with manufacturers recommendations.