Flat Roof Timber Joist Sizes

Posts these span tables are designed for a minimum post size of 50 x 50 x 2 5mm up to a maximum height of 3 0m.

Flat roof timber joist sizes.

Common joists sizes are 200 x 50mm 175 x 50mm and 150 x 50mm. 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. Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1. In the majority of cases the covering will be plywood or osb timber which is more commonly called stirling board.

Timber floor joists shall be adequate for the spans and loads and be correctly installed. This is the distance between joist centres. Solid timber joist sizes are provided in the bs 8103 3 span tables. Centre to centre spacing of joists in mm joist size width depth mm 400 450 600 400 450 600 400 450 600.

Spantec has prepared these tables for use by people skilled in the design and specification of the. Flat roof span tables allow for a maximum roof pitch of 5º. The joists will normally be placed at 400mm centres but no more than 600mm centres. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading.

Permissible clear span metres. The construction of the flat roof is similar to that of the timber upper floor. Where the tables do not apply or where there are concentrated loads floor joists should be designed by an engineer in accordance with technical requirement r5. Timber and concrete upper floors.

Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Dead load per square metre in kn m supported by joists. 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 220 1 77 2 40 2 89 3 38 3 87 4 36 2 05 2 67 3 22 3 77 4 31 4 85 assumptions at 400mm centers. 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. The sizing and spacing will depend upon the loads imposed on them and the required span. Surveyors span tables for designing roof rafters. Use recommended minimum roof pitches as specified by roof sheet supplier.