Timber Roof Joists Sizes

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 roof joists sizes.

Dead load per square metre in kn m supported by joists. Centre to centre spacing of joists in mm joist size width depth mm 400 450 600 400 450 600 400 450 600. Permissible clear span metres. This is the distance between joist centres.

They can be trimmed on site and long lengths allow ceilings and floors to be designed with fewer pieces saving installation time. The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches. 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. Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1.

Holes bored in the joists or rafters shall not be within 2 inches of the top or bottom and the diameter of any such hole shall not exceed one third the depth of the member. Lp solidstart i joists are more versatile than open web floor trusses and more uniform and dimensionally stable than lumber. Section 91 2308 8 2 joists 91 2308 10 4 2 rafters b notches at the ends of joists or rafters shall not exceed one fourth the depth. 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.

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. Lp solidstart i joist benefits. Surveyors span tables for designing roof rafters. 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.

The lengths and sizes of joists vary depending on the species and quality of the lumber used. 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.