Flat Roof Joist Sizes

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.

Flat roof joist sizes.

Sizes of joists needed for flat roof construction. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc. 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. So any timber joists that are used need to be strong enough to support this weight.

2 are indicated below. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. 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. Dead load weight of structure and fixed loads 15 lbs ft 2.

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. 1 ft 0 3048 m. The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches. This is the distance between joist centres.

The lengths and sizes of joists vary depending on the species and quality of the lumber used. Rafter and joist span faq. 1 psf lb f ft 2 47 88 n m 2. K series joists range in depth from 10 to 30 and can span up to 60.

Usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size automatically calculate sizes suitable for supporting the loads below. These joists easily handle spans that wood systems cannot handle while their lightweight construction makes them much less costly than steel beams. These welded steel products are used to support a building s roof and floors.