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Old 12-12-2010, 03:25 PM   #1
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At Grade Deck


I'm planning to replace an existing deck that is at grade.
Currently constructed with 2"x10" rim joists, 2"x8" joists, 2"x6" decking and 4"x4" support posts (every 5' or less) nailed to the rim joists and ledger bolted to the CBS/Brick foundation. The 2"x10" rim joist are right on the ground or in some spots under grade slightly. It has lasted approximately 25 years and is weathered/nasty though still very sturdy. I can't seem to find any code information for defining/constructing such a deck and the county had no code information either since it is so rare in this area of the country/world (Raleigh, NC).

Does anyone have suggestions with some on-line specifics I can read.
For example all the standard plans include a support beam and there is no room for one unless I make it out of 2"x2" ( yes two by two) and then it'll sit on the ground. Also I keep thinking the massive concrete foundation (16"x16"x8") is way over kill for a deck that is almost completely supported by the rim joists.

Thoughts and information appreciated.

TIA.
Jon

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Old 12-12-2010, 03:38 PM   #2
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At Grade Deck


I would have a series of sonotubes with standoffs supporting the decks frame. If you can, excavate the soil away from the framing members and put in some sort of drainage under the deck to keep the framing above the water and wet soil.
Ron

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Old 12-12-2010, 10:18 PM   #3
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Thank you Ron

Poured concrete sonotubes in place of the 4"x4" on top of the footings or just the concrete sonotubes down to the frost line ?
What spacing between the sonotubes ?
The existing decks posts are spaced 5' OC or less with joists 16" OC.
I was thinking of making the joists 12" OC to make the deck a little deeper.

Jon
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Old 12-13-2010, 09:11 AM   #4
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Can you post some photos of the support setup you have now and the current size of the deck?
Ron
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Old 12-13-2010, 01:20 PM   #5
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The current deck is 12'6" x 20'
The posts are buried approximately 19" with frost at 12"
There are no footers under the posts and I've never noticed any frost heave.
The rim joists are 2x10 and the joists are 2x8 and 16" oc
They did tack a trim piece at the bottom of the rim joists to
accept the joists I'm sure just to make installing the joists
consistent and easier.
The rim joists are right on the ground.
I'm amazed at how well it's lasted.


I've attached images but can't seem to insert them.
I hope this is OK

Thank you,
Jon
Attached Thumbnails
At Grade Deck-dscn1575.jpg   At Grade Deck-dscn1576.jpg   At Grade Deck-dscn1577.jpg  
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Old 12-17-2010, 07:28 PM   #6
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Ron

Were you looking for something different in the pictures ?

Thank you,
Jon
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Old 12-17-2010, 08:19 PM   #7
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A little reading 'til Ron gets back: http://www.lancova.com/deckinfo.pdf

And the 2009 up-date: http://www.awc.org/Publications/DCA/...eckarticle.pdf

Gary
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Old 12-18-2010, 08:01 AM   #8
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Quote:
Originally Posted by fornews View Post
Ron

Were you looking for something different in the pictures ?

Thank you,
Jon
I was just wondering how it was framed. Setting sonotubes with standoffs keeps the wood off the ground. For a 12 ft deep deck I would pour 2 sets. One 6 ft from the house and one at the end. At the 6 ft line I would set up a double beam resting on the standoffs. So essentially two deck frames. I would excavate under the deck so the wood was above the ground a few inches. If the water couldn't be drained away, I would dig a dry well under the deck for the water to go into. Plastic would be spread over the ground under the deck covered by gravel, pitched to the well opening.
Ron
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Old 12-19-2010, 11:10 PM   #9
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Thank you Ron

With the old deck removed I was planning on installing a french drain to help with the ground water. If that doesn't sound wise please make a suggestion.

I think I can dig out enough around the perimeter of the deck to clear 2x8s and maybe 2x10s but that will be close. I'm not sure how I can place a beam of any size on top of concrete pillars that extend above grade and still have room for 2x8 joists. This is the biggest problem I have for sizing everything. 2x8 joists can extend over 12' between supports when 16"oc which leaves very little clearance above the ground. None of the code guidelines I've read covers this scenario.

The current structure has a rim joist attached to 4x4 posts spaced every 5'. The joists are then nailed into the rim joist 16"oc The 4x4 posts are buried approximately 19" with out any footer which seems to be an appealing option at the moment.

Jon
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Old 12-20-2010, 02:57 PM   #10
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Quote:
Originally Posted by fornews View Post
Thank you Ron

With the old deck removed I was planning on installing a french drain to help with the ground water. If that doesn't sound wise please make a suggestion.

I think I can dig out enough around the perimeter of the deck to clear 2x8s and maybe 2x10s but that will be close. I'm not sure how I can place a beam of any size on top of concrete pillars that extend above grade and still have room for 2x8 joists. This is the biggest problem I have for sizing everything. 2x8 joists can extend over 12' between supports when 16"oc which leaves very little clearance above the ground. None of the code guidelines I've read covers this scenario.

The current structure has a rim joist attached to 4x4 posts spaced every 5'. The joists are then nailed into the rim joist 16"oc The 4x4 posts are buried approximately 19" with out any footer which seems to be an appealing option at the moment.

Jon

I agree with Ron, sonotubes/ footings every 6'.

You can place your double beam (use 1/2 cdx pt in between) flush with joists if there is no room to be placed under.
Keep your footings leveled and only few inches of the ground (if you don't have a laser level use a clear water hose) and set the double beam right on top of the ABA4x4 standoff, with a 1/2 ply in between beam will fit perfectly.
Connect your joist to the beam with joist hangers ...no screws use 10d and 16d galv nails..
I've had a job where i had to do the same ...there was no room for the beam to be placed under ... village gave me two options either construct beam flush with joist or use smaller beam and smaller joists 12 o.c. Either way you should be fine ,just keep the structure of the ground.
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Old 12-20-2010, 10:05 PM   #11
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Quote:
Originally Posted by Ron6519 View Post
Setting sonotubes with standoffs keeps the wood off the ground. For a 12 ft deep deck I would pour 2 sets. One 6 ft from the house and one at the end. At the 6 ft line I would set up a double beam resting on the standoffs. So essentially two deck frames.
Ron
It didn't make sense at first but I think I get it now.
When you say "two deck frames" you mean side by side such that the beam resting on the posts at the 6' line from the ledger would act as the ledger to the second frame. Do I have that correctly ? With a 6' joist span I could use 2x6 for the framing which would easily clear the ground then.

Sound good ?

Thank you,
Jon
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Old 12-21-2010, 06:31 AM   #12
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Quote:
Originally Posted by fornews View Post
It didn't make sense at first but I think I get it now.
When you say "two deck frames" you mean side by side such that the beam resting on the posts at the 6' line from the ledger would act as the ledger to the second frame. Do I have that correctly ? With a 6' joist span I could use 2x6 for the framing which would easily clear the ground then.

Sound good ?

Thank you,
Jon
Sounds good.
Ron
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Old 12-21-2010, 11:15 AM   #13
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Using this central beam approach and assuming it's made of 2- 2x8s and 2x8 joists (16" or 12" oc) what span between the supports ?
With nominal lumber for 2x8s (thinking joist lengths) at 12' or 16' I was thinking of staying with 12' from the house and make it wider then 20' which dictates the number of posts.
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Old 12-21-2010, 02:39 PM   #14
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Quote:
Originally Posted by fornews View Post
Using this central beam approach and assuming it's made of 2- 2x8s and 2x8 joists (16" or 12" oc) what span between the supports ?
With nominal lumber for 2x8s (thinking joist lengths) at 12' or 16' I was thinking of staying with 12' from the house and make it wider then 20' which dictates the number of posts.
I'd string 4 supports for up to 24 feet. That's one every 8ft. Over 24 ft, I'd go to 5 supports.
Ron
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Old 12-21-2010, 11:23 PM   #15
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Can you give me your thoughts on another approach.

Use a single rim joist made up of 2 - 2x8s set on top of sonotube/footings spaced about 4'10" and 2x8x12' joists ? Use joist hangers in both the ledger and the rim joist. Joists 16" oc See a problem with that approach ? This would allow a 12'x24' deck with 1 beam/rim joist and 5 versus 8 sonotube/footings. Beam/Rim joist set on stand offs.

Jon

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