Author Topic: Metal Fence Post - Southern MN  (Read 998 times)


  • Stubble
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Metal Fence Post - Southern MN
« on: July 27, 2017, 01:16:09 PM »
I'm looking to build my first fence and I'm running into the advice that posts should be dug 6" below the frost line.  Here in southern MN the frost line is 3'6"... so do I really need to put 4 feet of pole into the ground?  So for the 6 foot section I'd need to buy 10 foot poles?  And the 4 foot section would have to be 8 foot poles?


  • Stubble
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Re: Metal Fence Post - Southern MN
« Reply #1 on: July 27, 2017, 01:38:43 PM »
If you're putting a footing down, you want to go that far to avoid frost heaves.  It's very important for structural building, since you don't want floors or walls to crack or buckle.  For a fence, however, I don't think it's that big of a deal, especially if you hammer metal poles directly into the ground or backfill with gravel.  They might move a bit in the winter, and if the lateral structure is strong enough, they'll mostly bounce back in the spring.  Worst case, you might have to dig up a post every couple of years and reorient it.  If that idea bothers you, go down to 4 ft.


  • Walrus Stache
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Re: Metal Fence Post - Southern MN
« Reply #2 on: July 28, 2017, 08:54:34 AM »
For what it's worth: Our frost line here in the South is measured in inches.  I use 8 ft poles for 4 ft fences where the pole is structural.  In other words: If I am putting in a 4 ft chain link fence, the corner post is 8 ft.  I'd probably do the same for a wooden fence, as those can be supporting quite a lot of weight (and the wood will be catching quite a lot of wind).  For chain link, I use 6 ft poles for line posts on a 4ft fence.

...but I do have a tendency to over build things.  It's just that a "6 ft pole" is really 5 ft 6 in.  This means on a 4 ft section of fence, you'd have 1.5 ft in the ground... and that just seems like not a lot when you add weight or wind load or you start stretching chain link.
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  • Walrus Stache
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Re: Metal Fence Post - Southern MN
« Reply #3 on: August 13, 2017, 03:30:53 PM »
Your hole with the concrete needs to be 4 ft (or more) deep.   The pole needs to be deep enough in that to bet strong structurally, but does not need to go to the bottom of the concrete foundation hole.   Kind of like your house has foundations the structural support is anchored to.