Roof truss span chart.
Flat roof timber sizes and spans.
Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
1 ft 0 3048 m.
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 floor joists shall be adequate for the spans and loads and be correctly installed.
Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall.
Spans in feet to out of bearing spans in feet to out of bearing 5 12 38 47 57 39 51 59 42 56 63 45 54 68.
In any other situation you should refer to trada document span tables for solid timber members in floors.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
Live load is weight of furniture wind snow and more.
The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in flat roof construction.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches.
Surveyors span tables for designing roof rafters.
1 psf lb f ft 2 47 88 n m 2.
Solid timber joist sizes are provided in the bs 8103 3 span tables.
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.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
All figures are based on normal loading conditions found in domestic construction.
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 heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.
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.
Dead load weight of structure and fixed loads 15 lbs ft 2.
All the figures are based on the normal loading conditions.
