Flat roof joist calculator.
Flat roof joist sizes uk.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
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.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
Enter a specific joist size 2 loadings.
Flat roof construction for residential.
A roof is considered to be flat when it is of a slope of 1 5 o to the horizontal.
Automatically calculate sizes suitable for supporting the loads below or.
Supporting imposed load.
The rafters in a flat roof serve as ceiling joists for the space below.
Surveyors span tables for designing roof rafters.
In terms of rules on ventilation bs 5250.
Put simply a warm flat roof has insulation of some kind packed into every available void and a cold flat roof allows air to circulate between the joists.
Flat roof with asphalt finish with felt.
The size of rafters for a flat roof depends on the horizontal span of the building the type and grade of timber used and the load on the roof.
Although flat roofs are cheaper to build than pitched roofs they have a shorter life span.
For pitched roofs flat roofs and ceiling joists.
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.
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.
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 47 x 120 2 43 2 39 2 27 47 x 145 3 08 3 02 2 87.
2011 control of condensation in buildings is the document to view.
They are nailed securely to exterior wall plates and to each other.
More common timber sizes used in flat roof construction.
Solid timber joist sizes are provided in the bs 8103 3 span tables.
Waterproof membrane to prevent water penetrating the structure and interior of the.
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.
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.
This air is vented at either end of the roof to allow a continuous air flow.
