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Fence post

Posted: Sat May 11, 2019 12:14 pm
by mikeyitis

I am building a fence and I am in the process of setting the posts in the ground. I dug 3-1/2 foot holes and I am planning on putting about a 1/2 a foot of gravel in the bottom to help with drainage and fill the rest with concrete. I figured since I had a bunch of extra landscape river rock, that I could put that at the bottom of the hole instead of purchasing pea gravel like what is usually recommended. Do you think it would be ok to use the landscape rock or should I use pea gravel? Does it make that much of a difference since 3 feet of the hole is going to be solid concrete (not sure if the landscape rock will cause a stability issue)?


Re: Fence post

Posted: Sat May 11, 2019 1:54 pm
by A. Spruce
IMHO, you don't need to bother with gravel in the bottom of the hole, if your soils are that wet, the post is going to rot off at ground level before it ever has a chance to rot from the bottom up. Concrete around the post will rot it faster as well because concrete holds moisture against the post and will actually wick moisture from the surrounding area.

The reasons for using concrete to set a post are primarily stability, the larger base that the concrete provides makes it more stable in wet soil. The other major reason is speed, it's faster to pour concrete than to dry pack a post.

To answer your question about using larger gravel, that will be fine, if you want to. Dirt will be able to get in around the bottom of the post faster with large rock than small rock, other than that, it doesn't matter.

Re: Fence post

Posted: Sat May 11, 2019 2:53 pm
by Nick M.
It might be ok, don't use anything bigger than a quarter and make sure u tamp it down before u put in the post and concrete.

Hopefully it's a vinyl fence and you won't have to worry about rot....

Re: Fence post

Posted: Sat May 11, 2019 3:07 pm
by mikeyitis
This is the type of rock. 1" to 1-1/2" in size. ... 321218.htm

Re: Fence post

Posted: Sat May 11, 2019 6:08 pm
by emtnut
Something my father taught me was that a post never rots in the ground, it always rots at grade level.
We were replacing 30+ year old fencing, and the part of the post in the ground looked like new.

The only reason to put in crushed stone at the bottom would be for water drainage to prevent frost heave. If you are below the frost line (or not in a frost area), there would be no need for the gravel IMO.

Re: Fence post

Posted: Sat May 11, 2019 6:57 pm
by mikeyitis
I live in Minnesota. I know all about rot and how to prevent it as best as possible at ground level by bringing the concrete slightly above ground level and to slope it away from the post, as well as keeping dirt and mulch away from the post.

The holes have been dug, the dirt has been hauled out, the posts are 10 feet and I need them right around 7 feet out of the ground, and I already put the rock in the holes a few days ago. Just trying to figure out if I need to pull the landscaping river rock out and put pea gravel in. I could pull the rocks and put dirt in to fill it to 3 feet deep, but might as well put drainage down there just in case it works.

Probably just going to leave the river rock in unless someone knows of how it would be a bad idea as far as stability. I cant see how it would cause a problem since there is going to be 3 feet of concrete above it.

Thank you all for your help.

Re: Fence post

Posted: Sat May 11, 2019 8:23 pm
by A. Spruce
I doubt that rock under the post is going to help with frost heave, in fact, if anything, it would be a place for water to collect and freeze, thus increasing the likelihood of frost heave. At a depth of 3', you're probably pretty safe though, even in the climate of MN.

As far as rot prevention goes, you can eliminate it completely if you used Postmaster, or similar style posts. These are galvanized steel and have perforated "wings" to allow the attachment of wood rails. The advantage of a Postmaster style post is that it is about the same depth as a fence rail, so you can easily cover the posts with your pickets. The alternative would be cyclone fence posts, those ugly round things with the even uglier brackets to attach the rails.

Re: Fence post

Posted: Sat May 11, 2019 9:49 pm
by mikeyitis
I was contemplating using those nifty postmasters for a bit, but I was worried they wouldn't be a good match for my 7 foot board on board fence. I plan on being out of this house within the next two years, so I am not really worried about rot. However, I still want to build it as best and correct as I can for the next owners. I just wanted a short L shape privacy fence that came off the side of my house and blocked out the neighbor's house up to their deck so that I had a private little nook.

The old neighbors are moving out within the next week or so, so I figured it was a good time to put up my fence without offending anyone. I have got to get this project done in the next couple days and I have 10 holes already drilled in my yard, so no turning back now.

Re: Fence post

Posted: Sat May 11, 2019 10:27 pm
by A. Spruce
No worries. 8-)

I admire the fact that you're trying to do the best job you can. Also, any investment you make on a property has to have some sort of return for you, whether it is creature comfort (cost be damned), or improvement with resale value in mind. The fact that you're not here for the long term means that any significant investment isn't likely going to show any returns, so doing a good job while still maintaining a reasonable budget is the way to go. If this were a forever property, then I'd definitely go with steel posts, heavier framing, etc. 8-)