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I have no idea how to resolve this, the posts are all wobbly and move at the bases, one area in middle starting to cause a lean. I installed this fence, 6' H, roughly 7' post spacing, only 3 months ago...but it was wet, now that we've had no rain for 2 months, as you can see the dirt is pulling down from kick board and away from the posts...the ground just shrunk. All these posts are a minimum 28" deep, most are 30"-32" deep. If I add concrete/product right now...it seems when it rains it might heave it out.

  • What are your soil conditions? You state minimum 28” deep but how big around and did you fill the entire hole with concrete? I see a nice sized top but not sure if I see dirt or concrete going down. I have never had rain heave a fence post but have seen many that wobbled because there was not enough concrete. – Ed Beal Sep 4 at 21:48
  • We call it black gumbo, it's a black clay mixture. The holes are 12" all the way down – Mlrs Sep 5 at 3:51
  • And I used high psi concrete for the entire hole, 2ish 80lb bags per hole...even got a concrete mixer so I could mix a good peanut butter consistency – Mlrs Sep 5 at 4:02
  • Well since you accepted an answer already , you have your answer , but clay soil that deep 6” diameter has worked for me your “metal post” I would probably use a 4 “ auger with a good mix in clay. I think your cement, rock & sand ( concrete) mix was not properly hydrated (or mixed with water). – Ed Beal Sep 5 at 4:17
  • The concrete is hard as can be....I can barely break off the thin chips that are on the edges of the pour at the top. The concrete isn't the issue, it's the ground opening up around the concrete that's the issue...but I do greatly appreciate the time you took to respond – Mlrs Sep 6 at 5:05
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The simplest solution here is to dig out a few inches around your existing concrete post footings and add additional concrete mix to the dug out area. If you do this now that the ground is dry you should be good-to-go for the longer term.

Note that even though the post holes were originally 28" to 32" deep you would not really need to dig down that full depth when you enlarge the holes to make things more sturdy. If you were to enlarge each hole 5"-6" all around to a depth of 10" to 12" and full that entire enlarged area with concrete the fence will be a lot sturdier.

The reason this would work is that the greatest area of motion on the posts as they wobble is at the surface of the ground and not at the very bottom of the original holes.

Depending upon your geographic location you may have to consider frost depth onto the ground in winter. It may be that your original hole depth is not even adequate for your climate zone. In addition the proposed shallow fix may be detrimental to your fence if the frost can get under the shallow added concrete and push it up during winter. If you have serious frost conditions you would actually want to have the greater mass of concrete in the bottom of the post holes at a level below the frost line to prevent heaving and destruction of your fence.

  • I may try this...I'm just concerned about the concrete larger at the top than the bottom it will heave the post upwards when the soil expands. I'm in Texas, frost is not a concern. I'm just amazed the soil retreated this severely. The void (about 1") goes about 6" down right now, so I've still got 22"+ in good soil, I just dont like the movement I'm seeing – Mlrs Sep 5 at 3:56
  • Just check any fence line from the west to the east and the top is usually wider in fact 2 to 3x the width of the bottom, if you search you will find many posts on how to pull them out and how to put them in. – Ed Beal Sep 5 at 4:23
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Quikcrete makes fence post mix that does not require mixing, but after you pour the dry into the hole, you then soak it in with water. http://www.quikrete.com/AtHome/Video-Setting-Posts.asp

You might want to enlarge a holes a bit.

  • I used a post hole digger that is 10-12"...pretty standard I would imagine...I suppose if I watered the yard when no rain like this it would be good to go – Mlrs Sep 5 at 3:59
  • Used this product many times in clay soil to sandy loam, the later it was best to put water on the hole with the post in place and add the mix then more water, clay if dry just some water in the bottom then the mix + – Ed Beal Sep 5 at 4:27

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