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Thread: Setting fence posts--put the concrete in dry?

  1. #1
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    Setting fence posts--put the concrete in dry?

    I'm building a small picket fence to screen an AC unit. Its only about 3' high, L-shaped, 54" on each side, with 3 posts. I read somewhere you can just dump dry concrete mix in the holes around the posts. Does this really work?


  2. #2
    I've heard of the same thing, but have never tried it. It probably depends upon how wet the ground is. Right now it my back yard a post hole would fill with water as fast as you can dig it. I know that concrete will set up in the bags after a while if they are stored in a damp location for very long, so I would guess the ground dampness would make it set up as well. How strong the non-water method might be as compared to the manufacturers instructions is anybody's guess. Pouring dry concrete mix into a hole will create clouds of concrete dust.
    Lee Schierer - McKean, PA

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  3. #3
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    Quote Originally Posted by Matt Meiser View Post
    I'm building a small picket fence to screen an AC unit. Its only about 3' high, L-shaped, 54" on each side, with 3 posts. I read somewhere you can just dump dry concrete mix in the holes around the posts. Does this really work?
    I can personally attest that this works. As you get rain the groundwater will seep into the concrete and cure it. You can also pour the mix in and dump some water into it and mix it a bit to accelerate the process.

  4. #4
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    I've never heard of just putting the concrete in and not add water. I know you can put the post in, add the dry concrete and then add water and just poke it with a stick to get the water around.

  5. #5
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    I do this for line runs, but that for gates and corners I like to mix and pour.

    For a fence as small as you're doing, I honestly wouldn't even use conrete at all if it were my place, but some poured in dry mix is easy enough to do, it can't hurt.
    - Bob R.
    Collegeville PA (30 minutes west of Philly)

  6. #6
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    I bought it already so I might as well use it. As wet as it is here, it will get plenty of moisture. I expect they'll fill with water like Lee's would. There was standing water 30' away yesterday--mostly dried up today, but still very wet.


  7. #7
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    The concrete mix should say right on it if it can be done this way. Quickrete make a "fence post" mix that you dump in dry...add water...you're done.
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  8. #8
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    I put up 300' of fence ten years ago using Quickrete some with water, some without. Both worked very well, but the Quickrete is eating away at the wood now. If I was to do it over, i'll use pea gravel, in your case it doesn't need to be sturdy.

  9. #9
    I've always been told to put a few inches of gravel in the bottom of the hole first, then the post, then the dry concrete, then some water. The gravel keeps the bottom of the post from sitting directly on a wet surface. Obviously, if the ground is saturated it'll be wet no matter what. But in times when the soil is simply moist, this will reduce rot.

  10. #10
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    Here you pour a layer of concrete in the bottom of the hole and use dirt to fill around the post. That way the frost doesn't have any thing to grip to and lift the post.

  11. #11
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    Yes, Matt, it works just fine. Would I do it for something structural? No, but for fence posts it works. I've done it successfully.
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  12. #12
    Matt.... I would actually suggest not doing what Jerome suggested in post #10. You do not want the end of a fence post encapsulated in concrete. Put gravel in each hole so the bottom inch or two of the post is set in gravel. Then put the concrete above it, like Ben said. That way any moisture can drain off the wood instead of the concrete acting like a cup that holds water from above.

  13. #13
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    I've never tried it that way, but for the last 45 years I've filled the hole about 3/4 full with water, and then dumped the dry mix in and punched into it a few times with the shovel handle, and haven't had a failure yet. I doubt we would have very good results "Here" just putting the dry mix in because we just don't get much rain anymore.

    The drought is so serious in West Texas currently, our city recently passed a new ordinance that became effective May 01, 2011 that states, "if you are caught watering on other than your assigned days, OR, at hours other than the designated night hours, the FINE is $2,000", (and they are very serious about enforcing it).
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  14. #14
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    I have always done the "dry" method for using concrete with fence posts and it's usually only for corners and other posts that are either under stress or in ground that's less than ideal.
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  15. #15
    I've done concrete in situ (dry) and you can have problems with it. You get the strongest concrete by mixing the proper amount of clean water with the concrete and by agitating it to make sure the aggregate is well distributed through the mix. When you do concrete in place, you risk putting too much or too little water in the mix. Too little water results in weak concrete. And if you put too much water, the aggregate will work through the mix to the bottom, especially if you do anything to stir the mix. You can also get dirty water into the mix which will adversely affect the strength of the mix.

    For most fence posts, you'll get a strong enough mix. But for gate posts, or for posts where the fence direction changes (such as corner posts) I recommend you mix outside the hole and then put a stiff mix into the hole.

    Mike

    [I've especially had problems doing it the way Norman Hitt describes above. If you put a lot of water into the hole first, then dump the concrete mix in, the concrete and aggregate separate, with the aggregate going to the bottom and the concrete to the top. Also, it's almost impossible to keep the water clean so you get dirt incorporated into the concrete.]
    Last edited by Mike Henderson; 05-09-2011 at 9:21 PM.
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