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Old 07-07-2009, 01:25 PM   #1
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Posts, in or on concrete?


Hi all, working on deck plans and have a few questions. Been getting conflicting info. from contractors (friends), and reading materials.

The deck in question will be elevated ~10ft. 23'X14'(or 15' if local will allow a 3' cantilever), doubled 2x12s for beam at 12' from house with 2x10s on 16's for joists. I like to overbuild and I'm coming up with numbers of 12" footings for the corners posts and the 2 intermediate footings would be 18" (local code is 36" deep, i'm thinking 42" to be on the safe side). There will be stairs, and I may add another section a step down, but I'll try to keep this as simple as possible for now.

I was planning on sinking the J-bolt into the concrete while wet and using a post base connector for my 6X6s. Now I'm hearing that because of the height, I'll want to put my posts down in the ground and pour my footings around them for lateral stability. Either way I will use 4x4s to brace between beam and post. Experience and opinions would be appreciated.

Also, what it typically considered far enough away from the foundation to not require digging to foundation depth for footings? Thanks!
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Old 07-07-2009, 02:12 PM   #2
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I don't put them in the ground ever
Properly installed the J-bolt will hold w/lateral bracing on the posts
You might want to go to 4x6 posts -

OOPs - you are alread using 6x6's as the posts




Last edited by Scuba_Dave; 07-07-2009 at 03:21 PM.
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Old 07-07-2009, 03:16 PM   #3
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No wood will ever get cast into concrete on my watch.

6x6 posts, properly braced to the beam and to the outer joists (2ftx2ft knee braces with proper connections), along with blocking at those outer braces, is good to go in my book up to 12 feet in height.

Footing depth is a frost line issue, but around existing foundations, I stick with 5 feet. Anything within 5 feet of the foundation gets dug down to the foundation footing depth.

12 inch diameter footings is kind of light for the dimensions you listed, unless you have pretty good soil. Check with local requirements. You'd need some darn good soil to have 12 inch diameter footings. If you describe your soil to me, I'll go into detail.
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Old 07-07-2009, 03:21 PM   #4
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Quote:
Originally Posted by Seriously View Post
I like to overbuild and I'm coming up with numbers of 12" footings for the corners posts and the 2 intermediate footings would be 18" (local code is 36" deep, i'm thinking 42" to be on the safe side). There will be stairs, and I may add another section a step down, but I'll try to keep this as simple as possible for now.

I was planning on sinking the J-bolt into the concrete while wet and using a post base connector for my 6X6s. Now I'm hearing that because of the height, I'll want to put my posts down in the ground and pour my footings around them for lateral stability. Either way I will use 4x4s to brace between beam and post. Experience and opinions would be appreciated.

Also, what it typically considered far enough away from the foundation to not require digging to foundation depth for footings? Thanks!
If attached to the house I was under the impression you need to dig down past the frost line?
Where are you located?



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Old 07-07-2009, 05:57 PM   #5
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Thanks for the input. I'll stick with original plan and keep the posts on the concrete instead of in it. I'm in southeast PA and the soil is mostly clay. I have no problem going with bigger diameter footings if needed.

I asked about the distance from the foundation because the house bumps out a few feet (after the 23' section) and there is the back of a fireplace preventing a ledger attachment. Therefore, if I add this section I would step down 1 step off the main deck. Without having a bandboard here I thought of making this section attached to the main deck, but not the house. However, I would have to dig near the foundation for posts, even with a 3' cantilever I'd be 2' short by digging out at 5'.

Alternatively, I could possibly attach a ledger into the wall studs instead of the bandboard. Is this a common practice or bad idea? Or, I suppose I could frame around the fireplace by using a ledger on both sides and a doubled joist, parralel with the house against that section of wall.

Also, I've been on some bouncy decks before and I'd like to build this one sans bounce. Is that possible with the beam at 12' from the house given the framing mentioned in original post? Thanks again fellas.
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Old 07-07-2009, 11:02 PM   #6
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I'm glad to see you are wanting a strong deck.

Doug.fir, 12' span- 2-2x12's post spaced 6'10"max, yours are 7'8"= Page 5- Table 3

20' footings required= Page 9- table 4

Ledger bolts possibly 12"o.c.= Page 12- table 5

Chimney cantilever solution= Page 19- Figure 35

http://www.awc.org/Publications/DCA/DCA6/DCA6.pdf

Be safe, G
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