Roof Joist Sizes

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Roof joist sizes.

This ceiling joist span table is based on the 2012 irc for uninhabitable attics with limited storage. These welded steel products are used to support a building s roof and floors. Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1. For example the highlighted cell below shows that a 2 x 6 southern yellow pine joist with a grade of 2 and spaced 24 apart can have a maximum span of 10 feet 0 inches 10 0 if you are designing your structure to support a plaster ceiling.

Although 2 x 4 s are included in the official table they are not listed because it is never advised to use them. K series joists range in depth from 10 to 30 and can span up to 60. It covers 2 common lumber species and sizes at 20 pounds per square foot load. Centre to centre spacing of joists in mm joist size width depth mm 400 450 600 400 450 600 400 450 600.

These joists easily handle spans that wood systems cannot handle while their lightweight construction makes them much less costly than steel beams. Permissible clear span metres. A 2 by 4 inch joist for instance hangs into the room by 4 inches which may leave the ceiling high while a 2 by 12 inch joist in the same position hangs 12 inches into the room which decreases the ceiling height by 8 inches. 2 x 12 s are not listed because you can span pretty much whatever you want.