Timber Roof Joists Sizes

Surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors.

Timber roof joists sizes. Permissible clear span metres. Lp solidstart i joist benefits. 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. 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.

The lengths and sizes of joists vary depending on the species and quality of the lumber used. Lp solidstart i joists are more versatile than open web floor trusses and more uniform and dimensionally stable than lumber. For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine. These tables can help calculate whether floor joists are strong enough to support themselves and the load they carry without the help of any walls underneath.

Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1. 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. Dead load per square metre in kn m supported by joists. Standard size of joists though there is no standard joist size for the ceilings in all buildings most average homes use ceiling joists in a board size of 2 by 6 inches.

For pitched roofs flat roofs and ceiling joists. The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches. Surveyors span tables for designing roof rafters. This is the distance between joist centres.

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 47 x 170 3 75 3 67 3 42 47 x 195 4 41 4 31 3 92 47 x 220 5 04 4 85 4 41 75 x 170 4 50. They can be trimmed on site and long lengths allow ceilings and floors to be designed with fewer pieces saving installation time.