Roof Joist Sizes

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Roof joist sizes.

2 x 12 s are not listed because you can span pretty much whatever you want. Not more than 0 5 more than 0 5 but not more than 0 75 more than 0 75 but not more than 1. It covers 2 common lumber species and sizes at 20 pounds per square foot load. 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.

The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches. K series joists range in depth from 10 to 30 and can span up to 60. The difference in the joist sizes applies to the width of the boards which determines the height of the ceiling. 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. 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. These joists easily handle spans that wood systems cannot handle while their lightweight construction makes them much less costly than steel beams.