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.
Flat roof timber span tables.
You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.
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.
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.
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.
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.
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.
Span tables use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.
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.
For pitched roofs flat roofs and ceiling joists.
Joist and rafter span tables.
Span tables for ceiling joists to bs 5268 7 3 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.
Span tables allow users to choose an appropriate size and stress grade to achieve spanning needs.
Other more complex load condition spans can be determined with our free hyne timber design 7 5 software.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
For simple construction such as domestic construction this can be determined from span table supplements in as1684 2 and as1684 3.
Attached flat roof 1ao page14.
