Flat Garage Roof Timber Sizes

There are several variables to consider when determining the proper rafter size.

Flat garage roof timber sizes.

The joists will normally be placed at 400mm centres but no more than 600mm centres. 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. This sizing guide for roof rafters will help determine what you need for your small project. This is the distance between joist centres.

Wherever possible joists should span the shortest distance. 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. Supporting imposed load for access and repair only. The sizing and spacing will depend upon the loads imposed on them and the required span.

Common joists sizes are 200 x 50mm 175 x 50mm and 150 x 50mm. Completely flat roofs typically present weather proofing problems so the rafters or joists of some flat roofs are laid at a slight angle for drainage. If this is the case the slope of the.