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.

This is the distance between joist centres. 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. Centre to centre spacing of joists in mm joist size width depth mm 400 450 600 400 450 600 400 450 600.

Lp solidstart i joists are more versatile than open web floor trusses and more uniform and dimensionally stable than lumber. For pitched roofs flat roofs and ceiling joists. Permissible clear span metres. 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.

Surveyors span tables for designing roof rafters. 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. 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. 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.

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. They can be trimmed on site and long lengths allow ceilings and floors to be designed with fewer pieces saving installation time. Dead load per square metre in kn m supported by joists. 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. 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.