Solid timber joist sizes are provided in the bs 8103 3 span tables.
Timber roof joist span tables uk.
This table uses commonly available uk regularised timber depths.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
Usually 400 450 or 600mm but any value can be used up to 610mm max usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size.
Flat roof joists rafters purlin.
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 imposed loads of 1 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 exceeds 100 metres but does not exceed 200 metres.
Timber and concrete upper floors.
Pitched roof timber sizes.
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.
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.
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.
This is the distance between joist centres.
Surveyors span tables for designing roof rafters.
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 pitched roofs flat roofs and ceiling joists.
The floor joist span tables are based on the loadings given in the amended version of bs 6399 1 which is an imposed load of either a uniformly distributed load of 1 5 kn m or a concentrated load of 1 4 kn.
The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.
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.
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.
All the figures are based on roofing tiles or slates laid on timber laths over sarking felt.
The weight of the timber floor itself consists of the timber joists the plasterboard ceiling underneath it except for suspended timber ground floors the floorboards and the nails or screws used to fix both of the aforementioned coverings.
