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Old 03-29-2011, 05:31 PM   #1
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Minimum Deck Joist Size?

I'm building a 6' x 6' free standing deck with a deck height of 32.25" to stand next to a mobile home. I've decided to use two 2"x6"s for the beams which will be set on top of four 6"x6" posts.
My first question is can I use 2"x6"s for the joists if I set them at 12" oc or am I required to use 2"x8"s?
Next, what are the advantages or disadvantages to hanging my joists directly on the beam (as opposed to having them cantilever past the beam and hang from a header)?
My county uses the 2006 IBC. In the "Design For Code Acceptance", there is no mention of joist span for anything less than 2"x8", but it doesn't directly say that 2"x8"s are the minimum. Everything else I have read (published post-2009) has joist span tables and the what-not for 2"x6" and up, but I have no idea if they're going off of the 2006 IBC rules or not.

Thanks for helping!


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Old 03-29-2011, 05:38 PM   #2
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My town uses the 2006 IBC as well. In my town, the minimum joist size is 2x8. The minimum design in my town is set forth in the Design for Code Acceptance document, which I assume is the same one you are using. You may want to check with the local building inspector as to whether they will permit lesser sized members than the ones specified in the design guide, when I built my deck the inspector was quite clear that if I wanted to deviate from the guide, I needed an engineer's letter explaining how and why the deviation would occur.


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Old 03-29-2011, 08:03 PM   #3
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Originally Posted by BBaker View Post

Next, what are the advantages or disadvantages to hanging my joists directly on the beam (as opposed to having them cantilever past the beam and hang from a header)?
Can't help with the other parts, but if you cantilever the joists over the beam then you reduce the span, so you will reduce any likelihood of bounce or sag. Also, if you cantilever (or just put the joists on the beams with no cantilever) you won't need joist hangers.

Other factors to consider:

Appearnce -- how will you finish the overhang.

Stairs -- if this is the entrance, then make sure that the way you'll tie in the stairs will work.
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beam , deck , joist , rim joist

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