joist spacing


Old 08-09-06, 12:06 PM
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joist spacing

I have installed the joists at 16" oc and then the owner changed the design to a diagonal deck pattern. Ive switched to 2x6 treated decking, is this adequate for strength?
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Old 08-09-06, 01:12 PM
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Should be fine. Treated 2x6 boards on a diagonal (assume you mean 45 degrees) should span that without difficulty. My own deck has 2x6 cedar boards laid at 45 degrees.

Waste goes up slightly with diagonal cuts, but laying the decking diagonally adds considerable resistance to the deck "racking" (moving side to side). Deck boards laid perpendicular to the joists do not provide much resistance to racking, and require either braces on deck support posts, or some angular braces under the joists. Diagonal decking acts like dozens of braces.

Laid at a 45, a 12' board will span 8' of joists with just the corners cut off. You will waste about 1' of every 12' board. If you change direction of the diagonal every 8', it makes a nice herringbone pattern, and the pieces you cut off as the boards get shorter (heading for the corners), fit in closer to the corners, so the waste doesn't go up any.
Old 08-09-06, 03:14 PM
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I just finished my deck with 2x5/4's laid 45 degress to 16" O.C. joists and it is very solid. I still haven't had the final inspection done, but the initial drawings were approved with this design.

Also, my Dad had a new deck built 9 months ago with 16" O.C. joists and 2x5/4's laid at a 45 and his too passed inspection and has absolutely no bounce or weak feel to it.

45 looks great, but does create a lot of waste, but in the end it is well worth the extra effort and cost.

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