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This is related to a question I asked earlier regarding my deck footings.

I had a pool deck built last fall. The footings are 4' deep and 12" diameter. There are metal post brackets attached to the concrete, and the PT 4x4s are attached to those brackets.

The builder only poured the concrete to about 6" below grade. So now my posts are buried about 6" below grade. Well, not exactly buried, as the footings were dug out and left as holes. Those holes filled up with rain and are now my posts are sitting in blocks of ice. I assume I should fill the holes with something in ther spring when the ground thaws.

Is there anything I can do to help my wood posts from rotting? I know I need to regrade the area so water drains away from the footings, but I don't know if it's ok for the bottom of the posts to be buried. And if so, what material do i use to fill in the footing holes (sand, crushed stone, gravel, etc)? Should i coat the posts with some type of rubberized sealant to keeo away water?

I attached a photo (from the fall, it is all frozen now) for reference. Thank you!

enter image description here

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I'm answering from Australia so building practices may be different.

I'd call your builder and insist that he come back and install the footings properly. Post brackets are expressly to keep the posts above ground so the bottoms do not rot.

Installing them below ground is not a very good idea.

Edit

This need not be a difficult fix but it is my strong view it is the builder's responsibility. I'd wait for a time when the ground is reasonably dry. It will be a pain in the butt.

Instead of replacing the footings:

  1. Support the deck on jacks / trusses.
  2. Dig out around each post footing until the top of the existing footing and the bracket is exposed.
  3. Cut off the bottom of the post at the desired height, 4" - 6" above grade, or in line with local best practice .
  4. Unbolt the cut end of the post from the existing bracket.
  5. Obtain and, to the top of the existing bracket - bottom of the post, bolt an extension bracket. If some diligent fossicking at the local hardware store does not turn something suitable up you may need to get them fabricated. They should be externally and internally galvanised(a).
  6. Into the existing footing drill 4 x 5/8" holes at a 6" pitch ~12" deep.
  7. Smack a 2'(b) length of 5/8" rebar into each hole.
  8. Box the top of the existing footing to the appropriate height.
  9. Apply concrete.
  10. When cured release the support jacks(c).

a. This is a must. Copper Arsenate is a typical pressure treatment. In direct contact with steel (iron), depending on the pH of your soil, weird electrolytic things can happen.

b. The top of the rebar should be ~2" below the new top of the footing. 2' is a guestimate. Adjust appropriately.

c. Take some care with this. The post bracket extension must be installed firm so that the deck does not sag when the support is released. You may need to shim. A small piece of fibre cement sheet works a treat.

Good luck.

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  • 1
    The concrete footings should come several inches above grade. And there are fittings that will keep the end of the post off the footing to prevent wicking. – DaveM Mar 26 '19 at 18:23
  • @DaveM. What you said. – pHred Mar 28 '19 at 3:54
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I would not use sand or rock the hole will hold water, I might clean the holes out this summer and fill with fresh concrete to above grade. I put fence posts in with this method (just concrete around the post and sloped away from the post) and they last 20 year's or more.

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You can treat the posts with a preservative but sooner or later they will probably rot in such wet soil. Unless you dig up the posts annually to inspect, you probably won't know they're rotten until the deck starts to sink. So it's probably best to just fix them sooner rather than later.

This would involve building a temporary support around the post, cutting the post short, adding a post base to the post, and building the concrete up to meet the bottom of the post - a lot of work.

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  • I don’t think the meant the footings were removed; I think they meant there is no dirt above the footings which makes a hole 6” deep to where the footing starts. – UnhandledExcepSean Feb 23 '19 at 14:41
  • @UnhandledExcepSean - I see, that makes more sense, I will update. Thanks. – batsplatsterson Feb 23 '19 at 17:15
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Pressure treated 4x4's will last a very long time like that, but it's still not ideal. You can use Blueskin

Image from Home Depot website enter image description here www.homedepot.com it's a rubberized membrane, super strong. I always use the primer for it as well but I'm not sure if it's required. if done properly it will certainly keep it dry.

You can also pour concrete higher. Support the deck, cut off the post, slide a new sonotube over the existing concrete, attach a new post bracket to the bottom of the post, pour concrete up to it, remove the sonotube and Blueskin around the joint.

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  • Thank you! Would this work if I can only use it on the sides and not the bottom of the post (since it's already attached to the post bracket)? Also, any idea what material to use to fill in the dugout hole around the footings (sand, gravel, etc)? – Mainer Feb 23 '19 at 3:18
  • Yes you should be able to get a tight seal right on to the concrete. It's actually made for waterproofing foundations and comes in much larger rolls too. – Joe Fala Feb 23 '19 at 3:25
  • When you use pictures from some other site it is the policy of SE to have the poster reference the source site as an acknowledgement or attribution. The appropriate link should be plain text under the picture such as: <sup>*(Picture Source: <URL HERE>)*</sup> – Michael Karas♦ Feb 23 '19 at 5:19
  • How do you protect it from sunlight, as required by the manufacturer? Will it lock moisture in? – Kevin McKenzie Mar 25 '19 at 20:15
  • The easier way to do columns that will last a very long time is driveway sealer on the wood stopping 6 inches above grade or so. Of course concrete around it from below frost line to grade with a slope on the top to guide the water away. The only thing to fail then is the wood. ;) – user68386 Mar 26 '19 at 0:29

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