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Old 07-12-2010, 11:33 AM   #1
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cantilever ?

Good afternoon all. I'd like to add a few feet (4'-5') to an existing deck without adding any posts. Existing beam is 3- 2x12's x 14' with 3 piers 4'-6" apart.(piers are 8x8's on top of concrete) Joists are 2x8 16' oc. Currently the 2x8s cantilever about 2' past the 2x12s. What I am thinking of doing is using 2x8x8' long on either side of the existing 2x8s. extending 5' past the 2x12 beam and thru bolted to the existing joists. Where the existing joist ends I would add a 3rd piece of 2x8 (about 3') in between the 2 new 2x8's and again bolted together. The rim joist would be a 2x12 to match the existing face board on the one side of the deck. There will also be a 4' wide x 5 step high stairs at one end of the extended deck. I have read the rules on cantilevering but with triple 2x8's I wondering what people think.

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Old 07-12-2010, 12:14 PM   #2
Join Date: Jul 2010
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cantilever ?

I think you've got a good idea, but I also think you are really pushing the limits to the rules of canterlivering. I don't think you should do it but if you do I would put some good supports from type existing columns the new rim joist. Good luck and keep the traffic on the deck on the oppposite side of the addition

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Old 07-12-2010, 02:09 PM   #3
Newbie Bill
Join Date: Dec 2008
Location: Alberta, Canada
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cantilever ?

A 5 foot cantilever is fairly significant and personally I wouldn't go beyond what you already have without a new beem and posts.

I just checked the codes for our area and maximum deck cantilever is 24 inches when using 2X10 or 2X12.

A DIY Noob that knows just enough to be dangerous.

Last edited by drtbk4ever; 07-12-2010 at 02:24 PM.
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Old 07-12-2010, 03:05 PM   #4
Join Date: Feb 2010
Location: MI's Western UP
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cantilever ?

if you triangulate it back to the existing piers with a diagonal brace, maybe, but 5' seams like too much.

a 5' cantilever is something like a 10' simple span. your current span is less than 5'
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Old 07-13-2010, 05:10 AM   #5
Join Date: Sep 2008
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cantilever ?

Thanks all for the input. I think I'll just get out the shovel and add a couple of piers and posts. Like you all said, much safer. Again thanks for the replys.
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