Home & Garden

Fence Posts - Sink in Concrete or just down deep?

  • Last Updated:
  • May 5th, 2008 6:53 pm
Tags:
None
[OP]
Deal Guru
Aug 2, 2001
13016 posts
3790 upvotes

Fence Posts - Sink in Concrete or just down deep?

I'm looking to replace a few fence posts this year, and I notice everyone seems to have a different strategy for it. Currently, my fence is probably 20-30 years old and most of the posts are still around, I don't know how deep they are in the ground but there is only 1 foot of concrete holding them in.

Being in Edmonton I need to ensure that it is dug in deep so they don't heave. I was thinking of just using 4x4's and going down 5 feet, which should eliminate the need for concrete. I'm not worried about the labour, as I'll use the existing holes which should save a lot of time.

Should this be OK without needing concrete?

As well, I'm a bit confused. When I put the posts in place, if I don't use concrete, what holds them in place while I build my fence? Assuming I dig down 5 feet, drop the post in, level it, backfill with whatever I dug out, what will hold the post level while I do the rest of the posts? I can't see the 5 feet of dirt being strong enough, as it'll be loose from the digging. Is there something I'm missing here?
7 replies
Deal Addict
User avatar
Mar 24, 2008
1028 posts
77 upvotes
Etobicoke
TrevorK wrote:
May 4th, 2008 7:44 pm
I'm looking to replace a few fence posts this year, and I notice everyone seems to have a different strategy for it. Currently, my fence is probably 20-30 years old and most of the posts are still around, I don't know how deep they are in the ground but there is only 1 foot of concrete holding them in.

Being in Edmonton I need to ensure that it is dug in deep so they don't heave. I was thinking of just using 4x4's and going down 5 feet, which should eliminate the need for concrete. I'm not worried about the labour, as I'll use the existing holes which should save a lot of time.

Should this be OK without needing concrete?

As well, I'm a bit confused. When I put the posts in place, if I don't use concrete, what holds them in place while I build my fence? Assuming I dig down 5 feet, drop the post in, level it, backfill with whatever I dug out, what will hold the post level while I do the rest of the posts? I can't see the 5 feet of dirt being strong enough, as it'll be loose from the digging. Is there something I'm missing here?

Yep..

At least use one bag of sacrete at the bottom of each post. It will give some rigidity to the post. You will also need to add some cross bracing from the 4x4 to the ground at about a 45* angle to keep the post straight.
Don't forget to layer the bottom of your hole with some stones for a bit of a solid base for the post to sit on.
Deal Fanatic
Jan 16, 2003
6224 posts
84 upvotes
TrevorK wrote:
May 4th, 2008 7:44 pm
I'm not worried about the labour, as I'll use the existing holes which should save a lot of time.
Have fun removing the existing posts... you'll end up with huge holes so you might need to use sonotubes with bell shaped bottoms to hold the new posts in place.
Newbie
Feb 14, 2008
87 posts
3 upvotes
If you don't feel like pulling up the posts then dig new holes beside them.

If you do then dig 6" below the top of the post, crack the concrete with a crowbar or chisel, loop a cord around it and attach it to a car jack. Lift it enough so that a couple of guys can wrap their arms around it and move it aside.
[OP]
Deal Guru
Aug 2, 2001
13016 posts
3790 upvotes
mart242 wrote:
May 5th, 2008 9:54 am
Have fun removing the existing posts... you'll end up with huge holes so you might need to use sonotubes with bell shaped bottoms to hold the new posts in place.
I don't know if the fence was done with quality in mind (Even though it's lasted decades). I had to temporarily repair a fence post in the fall (As I didn't have time to replace it) and it only took 15 minutes to break up the concrete/pull the post out.
[OP]
Deal Guru
Aug 2, 2001
13016 posts
3790 upvotes
Techhead wrote:
May 5th, 2008 9:25 am
Yep..

At least use one bag of sacrete at the bottom of each post. It will give some rigidity to the post. You will also need to add some cross bracing from the 4x4 to the ground at about a 45* angle to keep the post straight.
Don't forget to layer the bottom of your hole with some stones for a bit of a solid base for the post to sit on.
So that's the part I'm missing - is that everyone uses at least some concrete to hold the posts in place?

And I'm guessing it's best to put it at the bottom rather than the surface (Which is where it's at now) because it's more difficult for the concrete to heave through all the dirt and stuff overtop? Would I just use the quick-setting style concrete then (I think it says it's made for fences)?
Deal Addict
User avatar
Mar 24, 2008
1028 posts
77 upvotes
Etobicoke
TrevorK wrote:
May 5th, 2008 11:41 am
So that's the part I'm missing - is that everyone uses at least some concrete to hold the posts in place?

And I'm guessing it's best to put it at the bottom rather than the surface (Which is where it's at now) because it's more difficult for the concrete to heave through all the dirt and stuff overtop? Would I just use the quick-setting style concrete then (I think it says it's made for fences)?
Quick set is good, using this method allows you to build the fence in a day. If you use the reugular cement, do not desturbe for 24hrs.

At the bottom is best, less chance of heaving. What causes the heaving is water gets under the crete and then freezes, this pushes the post upwards.
Deal Addict
User avatar
Apr 14, 2005
1591 posts
66 upvotes
TrevorK wrote:
May 5th, 2008 11:41 am
So that's the part I'm missing - is that everyone uses at least some concrete to hold the posts in place?
Around here (SK) many people still use concrete, but many do not. My neighbor and I built a fence 5 years ago without any concrete.. sand & pea gravel mix.. lots of tamping.. 5 years later and lots of abuse and it is as solid as the day we put it up, straight as ever, etc. I realize 5 years doesn't tell the whole story though..

I think the movement is towards no concrete for people who are trying to build quality and long lasting fences.. a post set in concrete is pretty much guaranteed to rot eventually.. a post set in gravel/sand at least has a chance but will also probably rot.

can a post be set solid without concrete? Yep.
× < >

Top