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jjmartin1340 10-06-2012 09:40 AM

The wrong way to anchor fence posts in concrete
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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.

BridgeMan 10-06-2012 01:04 PM

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.

nealtw 10-06-2012 03:55 PM

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.

CallMeVilla 10-06-2012 05:36 PM

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

Blue Jay 10-06-2012 07:16 PM

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.

nealtw 10-08-2012 11:54 PM

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.

CallMeVilla 10-09-2012 12:34 AM

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Hey Neal . . . strongest might be the carport saddle with rebar into the cement.

Another version has two prongs that are pushed into the cement of the sonotube.

Wuzzat? 10-09-2012 06:36 AM


Originally Posted by jjmartin1340 (Post 77959)
4 feet deep
now some of the fenceposts are about 4" higher than they were. See photos.

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

JoeD 10-09-2012 06:55 AM

Saddle would never hold up to the wind forces on a fence. Those things are only for decks.

jjmartin1340 10-09-2012 10:21 AM

"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.

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