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Discussion Starter #1 (Edited)
Hi All.

I am rehabbing a deck in southern Maine and would appreciate some ideas regarding solutions for the sinking and rotting posts, and inadequate footers. Deck dimensions and specs are below.

The deck is attached to the house, with one single beam made of three 2x6's sandwiched together. The deck is not level, seemingly due to the posts sinking. The beam needs to be raised about 1.75" to bring it to level.

The posts are 6x6 and are buried inside 10" concrete footers. The top of the footers are 12-15" below grade, and the wood exposed to the soil has areas of rot. I'm not sure how deep the posts are buried into the footers, and I'm not sure how deep the footers go - but presumably below the frost line.

I put the specs into this calculator and it seems that the current footers are significantly inadequate given the size of the deck, which likely explains the sinking. I don't know how old the footers & posts are, but they look newer than the original parts of the deck which are likely 30 years old.

Specs:

  • Total size: 16'x12'. 16' is the length of the ledger and beam.
  • Distance from ledger to center of beam: 9'4"
  • Distance from beam to edge of deck: 2'6"
  • Distance from outside post to edge of deck: 1'8"
  • Distance between posts (center to center): 6'
  • Footer size: 10" round
  • Post size: 6x6 (Three posts)
  • Beam size: Triple 2x6
 

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Not clear what you're looking for. I think most folks will tell you to do a complete demo and start from scratch, paying close attention to local codes.
 

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retired framer
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Hold the deck Up and cut the post off at the top of the concrete.
Jack up the deck where you want it. Dig out some of the rotted wood as best you can set a sono tub on top of the concrete and add new concrete to above ground level and install and new post saddle then install a new post.
 

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If they are sinking, they have to be put in deeper and correctly.
Jack the beam up.
Remove the existing posts.
Remove the joists on either side of there the posts had been to give clearance to work.
Pull the existing concrete with a backhoe.
Install new sonotube at the local/required depth, or deeper if it is original un-compacted backfill.

Get an estimate for that versus remove the entire deck and start over.

Bummer when the "foundation" is wrong...
 

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Discussion Starter #5
Bummer when the "foundation" is wrong...
So true^

Thank you all for your replies thus far! I also spoke with a local contractor this morning who has similar ideas, suggesting something to this:

  • Pour two new additional 12" footings between the existing 10" ones - in the end there will be five posts.
  • Cut each of the existing three posts off at footer (as Nealtw explained)
  • Jack beam up to proper height
  • Install the two new posts on the new footers
  • Repair the existing three posts/footers one at a time.
If the above will work, I guess it'd be down to figuring out the best method of repairing/replacing each post once the additional support is in place.


Please keep the responses coming... I appreciate your feedback!
 

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retired framer
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So true^

Thank you all for your replies thus far! I also spoke with a local contractor this morning who has similar ideas, suggesting something to this:

  • Pour two new additional 12" footings between the existing 10" ones - in the end there will be five posts.
  • Cut each of the existing three posts off at footer (as Nealtw explained)
  • Jack beam up to proper height
  • Install the two new posts on the new footers
  • Repair the existing three posts/footers one at a time.
If the above will work, I guess it'd be down to figuring out the best method of repairing/replacing each post once the additional support is in place.


Please keep the responses coming... I appreciate your feedback!
The ground below those posts has compacted, just add to the height of the concrete so the concrete is out of the dirt and install new post.


Do all three at the same time, that deck is not heavy now. You don't need 2 more. Just don't make the new section of concrete bigger than the old. or it will catch frost.
 

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Are you sure the deck is sinking? It could have been built out of level. Some believe that a deck should be sloped so that water readily runs off it. (And others argue that since the deck boards are spaced, water flows right off anyways.)


Do you know the bearing capacity of the soil in your area? I'm not going to try to analyze how that calculator came up with it's numbers, but 3 could be light, but eyeball test says not grossly light.


As I see it, the only difficulty in putting more posts is that the beam is in the way of the auger. About equal the trouble to temporarily move the beam, add the posts and then move the beam back, compared to just putting a second beam just in front of the first.
 

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Are you sure the deck is sinking? It could have been built out of level. Some believe that a deck should be sloped so that water readily runs off it.
Ayuh,.... That's Me,...... I run the boards in-line with the pitch too,.....
 

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Discussion Starter #10
Are you sure the deck is sinking? It could have been built out of level. Some believe that a deck should be sloped so that water readily runs off it. (And others argue that since the deck boards are spaced, water flows right off anyways.)

Do you know the bearing capacity of the soil in your area? I'm not going to try to analyze how that calculator came up with it's numbers, but 3 could be light, but eyeball test says not grossly light.

As I see it, the only difficulty in putting more posts is that the beam is in the way of the auger. About equal the trouble to temporarily move the beam, add the posts and then move the beam back, compared to just putting a second beam just in front of the first.
I don't think it was intentionally built out of level. If so, they'd surely have sloped it less dramatically than 2" over the 12 feet -- especially since there is a second deck on the house (connected by a walkway) that is perfectly level. You can really feel the difference as you walk from one deck to the other.

Re bearing capacity of the soil - I went with 2000 psf in the calculator ref'd in my original post. The soil is rich and somewhat sandy - perfect for gardening and relatively easy to dig. Compared to the red clay I dug for 10 years in NC, about anything is easy to dig, though.

I don't know how accurate the calculator is, but (using the specs in my original post) it says that even had they used larger 12" footings, three is inadequate. And the 10" footings they used are 'grossly' inadequate.

I'd prefer to do this once and not have to do it again 10 years from now so over-engineering is my strong preference. The idea of a second beam is a good thought... I'll keep it in mind if I'm not able to manage digging under the current beam which is roughly 4.5' off the ground.
 

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I'll keep it in mind if I'm not able to manage digging under the current beam which is roughly 4.5' off the ground.

I predict your attempts to hand dig those holes will last about 15 minutes.
Then call a fence company or an outfit that builds deck to auger the holes.
 

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You don't necessarily need 5 posts. If you can't pull your existing footings, you can sink a new pair adjacent (to correct depth and dimension) and use a grade beam across the top of the existing footing. Then the post can be attached to the grade beam.
 

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retired framer
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Unless the deck was still sinking last week it is sunk all it is going to sink.
Starting over with new is starting over on questionable soil when compacted soil is available and proved to hold the weight after it compacted.
 

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First thing I would do is dig around the concrete supports in the ground to see for myself how deep they are. If they are the required depth for the frost line I would follow Neals plan to build on top of the existing concrete supports.
 

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First thing I would do is dig around the concrete supports in the ground to see for myself how deep they are. If they are the required depth for the frost line I would follow Neals plan to build on top of the existing concrete supports.
If digging is daunting, you could try probing with a piece of rebar to get an approximate depth based on the angle of the rebar.
 

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If digging is daunting, you could try probing with a piece of rebar to get an approximate depth based on the angle of the rebar.

" Whatever we're talking systematic's here, find the depth of the existing supports go from there however you like . Just do it."
 
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Discussion Starter #18
The ground below those posts has compacted, just add to the height of the concrete so the concrete is out of the dirt and install new post.


Do all three at the same time, that deck is not heavy now. You don't need 2 more. Just don't make the new section of concrete bigger than the old. or it will catch frost.

Got 'er done so I figured I post a follow up. It turns out that the posts weren't buried in the concrete after all. It was a bit of an optical illusion as there was caulking along the bottom of the post / top of the footer. The caulk appeared to be displaced concrete that had risen up the post - was so glad to discover I was mistaken!


So I jacked up the deck, cut off the rotted wood, drilled into the existing footers for rebar, 'glued' the rebar into the existing footers using two part epoxy, and used sonotubes to extend the footers up out of the ground.

Thank you all for the advice and feedback. I really appreciate it!
 

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retired framer
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Got 'er done so I figured I post a follow up. It turns out that the posts weren't buried in the concrete after all. It was a bit of an optical illusion as there was caulking along the bottom of the post / top of the footer. The caulk appeared to be displaced concrete that had risen up the post - was so glad to discover I was mistaken!


So I jacked up the deck, cut off the rotted wood, drilled into the existing footers for rebar, 'glued' the rebar into the existing footers using two part epoxy, and used sonotubes to extend the footers up out of the ground.

Thank you all for the advice and feedback. I really appreciate it!
Success is always an option. Looks good.:biggrin2:
 
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