Post hole question

Old 11-07-07, 07:13 PM
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Post hole question

I'm replacing an old picket fence that has fallen down due to age and rotting. In the process, I'm digging up the old cement foundation that held each post in place.

Unfortunately, whoever put in the original fence, used a ton of cement on each post. As a result, when I finally get the cement out, I've got a huge hole leftover. You can probably see where I'm going with this.

Obviously, I'm going to have to fill the holes back in and re-dig a new hole for the new fence posts. Something a lot narrower than the original builders did.

What I'd prefer to do is put something in the hole, like a 6x6 disposable tube, then fill the hole around it with the dirt I dug out, water it, pack it, get it solid again so it will support new cement, then at some point remove the 6x6 tube so I can easily drop in the new fence post with new cement.

My question is: does anyone out there have a recommendation as to what I can use to preserve the post holes while I fill in the excess dirt around it?

One of my friends suggested duct taping a couple of coffee cans together and sticking them down in the hole. Unfortunately, I don't drink coffee and I don't know where I'd get some empty cans (I'd need several.) If anybody out there has any creative ideas, I would really appreciate the input.

Thanks a bunch.
Old 11-08-07, 04:20 AM
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Biggest problem, I think, would be to use something that will slip back out fairly easily, i.e. low amount of friction. I'm thinking large diameter piece of pvc pipe. Check HD/Lowe's plumbing section to see what might work.

I take it whacking off the old posts at/below ground level, leaving the concrete in the ground, and offsetting the new posts is not an option?

If you had wanted to salvage the entire hole and keep it clean I would have said to drop a big gargage bag down the hole and inflate it, but that wouldn't work in this case.
Old 11-08-07, 06:13 AM
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Another possibility is a chimney thimble. This is a piece of terracotta pipe w/an inside diameter of 6" - usually available in various lengths up to 24".

You probably won't find this at any of the box stores but a good local building supply should either have it or be able to get it.
Old 11-08-07, 06:39 AM
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Thanks all. Great suggestions. The reason I didn't dig new holes is because here in Dallas, we've got this really tough clay bedrock that's not easy to get through if you don't have a motorized post hole digger. All I've got is my two arms and a lot of determination.

So I felt the best course of action was to dig up the old posts (which was fairly easy), pop out the cement plugs, and use these as my new fence post holes. What I wasn't prepared for is the amount of cement the original builders of the house used. No matter. They're all dug up. Now I just have to prepare them for the new fence posts.

Thanks again everyone. I do appreciate it.
Old 12-04-07, 10:47 AM
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When i have to pull an old post out, I set the new posts in a 5 gallon paint pail then install in the hole adding concrete if you need to. it's sure a lot easier to get out when you need to move the fence.
Old 12-04-07, 11:15 AM
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Why pull the tubes out just get a tube big enough to hold concrete and the post and install them in the tubes. I used sono-tubes on a couple of holes and so far so good.
Old 12-04-07, 01:19 PM
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Post hole question

Whenever you embed a wood post in concrete, make sure the top of the concrete os sloped away from the wood to shed the water. Also have the concrete slightly above grade.

What really rots wood is the alternating wetting and drying cycles. Keep the moisture constant and have won most of the battle.

If you look at wood deterioration (post, piling for piers, etc.), most is in the area where the moisture content of the wood varies with storms or tides.

Sonotubes are great because the do not let the frost attach to the sides (waxed forms) and lift them. A rough dug hole is very susceptible to frost lifting (from the sides) as opposed to frost heaving (from the bottom). The ground freezes from top to bottom, so frost lifting happens before the frost heaving.


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