Calculations to bs 5268 2.
Flat roof timber sizes uk.
2002 bs 5268 7 5.
Order helpline 01752 692 760.
Subject ceilings and flat roofs timber sizes and construction details 09 issued 01 04 13 rev page 1 of 2 the following tables give details of the allowable spans and spacing for some of the more common timber sizes used in ceiling and flat roof construction.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
Surveyors span tables for designing roof 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.
Structural calculations for timber joists timber beams glulam beams flitch beams using the latest design codes.
Here the number is 1166 66 inches.
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.
Here the number is 941 86 inches.
All the figures are based on the normal loading conditions.
Supporting imposed load.
Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak.
Flat roof joists.
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.
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.
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.
Rafter run outer wall this should be measured starting from the center of the roof span and then extending to the very edge of the exterior wall.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
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.
C16 timber is commonly used in floor and roof joists for intern.
