The wrong way to anchor fence posts in concrete

Discussion in 'General Home Improvement Discussion' started by jjmartin1340, Oct 6, 2012.

  1. Oct 6, 2012 #1

    jjmartin1340

    jjmartin1340

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    Some years ago, a friend was installing a fence. He dug holes 4 feet deep and anchored the posts in concrete. But first he put an 8" Sonotube (a heavy cardboard tube 8" dia., 4' long) in the hole. I had never seen Sonotubes used this way. He said it made the concrete with smooth sides, so when the ground froze and heaved up, it would not lift the post up too. Made sense to me. I never had to install a fence, so didn't know if it was really necessary. Found out last spring it IS a good idea. Saw a fence down the street where they had not used Sonotubes. We had a mild winter, lots of freeze-at-night/thaw-during-day cycles, and now some of the fenceposts are about 4" higher than they were. See photos.

    Fence Post Concrete Lifted 1 s.jpg

    Fence Post Concrete Lifted 2 s.jpg
     
  2. Oct 6, 2012 #2

    BridgeMan

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    Classic examples of "junk" concrete work--improper consolidation, cracking, delaminations and missing (or incorrect) top-slope. Sonotubes wouldn't have helped at all.

    I've never understood why people spend good money on materials and then don't bother learning the proper basics of how to use them.
     
  3. Oct 6, 2012 #3

    nealtw

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    This picture is a good sample of concrete not deep enough. The idea for concrete is to fill the gaps around the post so it drys firm to the undisturbed soil around it. If you use a sono tube you are then going to fill around that with dirt, what's the point.
     
  4. Oct 7, 2012 #4

    CallMeVilla

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    While we are piling on (pun) where are the galvanized saddles for the posts? If you are going to the trouble of sonatubes, why not install the saddles so you can easily replace the posts without having to destroy of the old concrete?

    Get the guy who did this work on the phone and read him these posts .... :D
     
  5. Oct 7, 2012 #5

    Blue Jay

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    I don't understand using concrete to set a fence post, all my years on the farm we never did. Did not have any come out of the ground that were put in properly, even ones that had a gate hanging off it did not move. Guess people now days just don't know how to tamp the ground so the post does not move or don't want to put forth the effort.
     
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  6. Oct 9, 2012 #6

    nealtw

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    Blue Jay; I agree 100%, built lots with out concrete but after some people start sprinkling a little dust in the hole and the puplic is convinced it is the only way to go, the rest of us have to go along.
    Villa: Have yet to see a saddle that will hold a six or seven foot panel fence.
     
  7. Oct 9, 2012 #7

    CallMeVilla

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  8. Oct 9, 2012 #8

    Wuzzat?

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    Is the frost line in your area deeper than 4'?
     
  9. Oct 9, 2012 #9

    JoeD

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    Saddle would never hold up to the wind forces on a fence. Those things are only for decks.
     
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  10. Oct 9, 2012 #10

    jjmartin1340

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    "Is the frost line in your area deeper than 4'?"

    This is Keswick, ON, Canada (north of Toronto).
    Water pipes, etc must be 4 feet deep, so I assume the frost line is maybe 3 feet deep, probably less now with the warmer winters. The fence in the pictures is a couple of blocks away from me, don't know anything about it. I've been going for walks around the area for 5 years now. The fence was there when I started. It never heaved up until this spring, which is also the warmest winter in ages. Instead of -25C to -35C at night in February, we only had a few nights at -20C, and in March there were many days above 0C with nights -10c.
     
  11. Oct 9, 2012 #11

    Wuzzat?

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    Thanks for your answer.

    At my latitude/longitude the outside design temp is -10C/+14F so it maybe gets colder than that 1% or 5% of the time.

    I imagine these kinds of temps can be dangerous if you are not acclimated.

    Your freezing and thawing seems somehow to have compacted the soil more than it was when the fence was installed.
     
    Last edited: Oct 9, 2012
  12. Oct 9, 2012 #12

    Wuzzat?

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  13. Oct 10, 2012 #13

    nealtw

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    If your pipes are at 48" the fence wants to be a 48".
    The fence coming out of the ground on a warmer winter will have more to do with the amount of water just below the concrete as compared to other years, warmer may have been wetter.
     
  14. Oct 11, 2012 #14

    bemugg124

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    I think so, the concrete not deep enough
     
  15. Oct 11, 2012 #15

    Wuzzat?

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    Assuming the posts were vertical when first installed, I'd think:
    -if the soil surface is sinking because of compaction the posts will still be vertical.
    -if the posts are being pushed up they should be becoming crooked, like old tombstones.
     
  16. Oct 12, 2012 #16

    jjmartin1340

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    This seems to be getting a lot of interest. Here's 2 pics of the fence. It's becoming rather crooked from the post heaving.

    Fence Post Concrete Lifted 4s.jpg

    Fence Post Concrete Lifted 3s.jpg
     
  17. Oct 12, 2012 #17

    nealtw

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    So the red fence was planted deeper.
     
  18. Oct 13, 2012 #18

    Daryl in Nanoose

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    This has been an interesing thread, I just realized that the guy who used Sonotube has no problem with his fence but the guy who didn't has problems and yet everyone is picking on the guys who's fence is still good. Am I nuts here or??? Really not trying to make trouble here just not making sence to me
     
  19. Oct 15, 2012 #19

    nealtw

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    Like Blue Jay said; we used to just tamp the fill back in around the post. If you use a tube, you are not filling the whole hole so your back to tamping the fill back around the concrete, so why bother with the concrete?
    Any way if both fences were planted at the correct depth then both would have popped for the same reason, but the red one did not.
     
  20. May 20, 2015 #20

    postanchor

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