Fence Posts

By Tim Carter
©1993-2009 Tim Carter

Summary: Fence posts have to withstand a tremendous amount of wind force. If the fence post is not properly set, your fence will not hold. Discover a method for your setting wood fence posts so your fences will stand up to the pressure.

DEAR TIM: What is the preferred method to set fence posts? My 5-foot-tall solid-picket privacy fence has had some issues over the past ten years. The latest problem is posts set in concrete that have snapped. I have installed some temporary steel fence posts to stabilize the fence as winter winds have caused it to lean. How would you install wood fence posts? Should I be using treated fence posts? Ron W., Maumee, OH

DEAR RON: Fence posts can be a real hassle. I have fixed my fair share of them over the years. My guess is there are as many opinions as to the right way to set fence posts as there are posts encircling a one-acre field! But about fifteen years ago, I stumbled upon a method of setting wood fence posts that appears to be working really well.

Your fence posts have a tremendous amount of force against them each time the wind blows. You may not think a 5-foot-tall fence is high, but in terms of wind load, it is substantial. To get an idea of what I am talking about, lift a 4x8 sheet of plywood up and take it outdoors on a windy day. If you are not prepared, the wind may either knock you over or rip the plywood from your hands. Imagine the pressure on the entire fence being held back by a single fence post every 8 feet!

This 4-foot-tall fence post is as straight as the day it was installed. It was not set in concrete.  PHOTO CREDIT: Tim Carter
This 4-foot-tall fence post is as straight as the day it was installed. It was not set in concrete. PHOTO CREDIT: Tim Carter
The average wood fence post seems to be a square timber that is a 4-inch by 4-inch post or possibly a 6-inch by 6-inch post. The surface area of the post in the soil is what determines how quickly a fence will tip in the wind. Smaller fence posts will yield much faster than larger posts assuming both are buried at the same depth.

The trick I discovered is that you can use crushed, angular gravel to trick the wind into thinking a massive fence post is installed. The crushed gravel is affordable and it is easier to deal with than concrete that becomes as solid as a rock. You are about to discover how hard it is to deal with concrete that is deep in the ground around your fence posts. My guess is that you will be swearing like a sailor by the time you get to removing the concrete around your third fence post.

My method of setting fence posts is quite simple. If I am installing a 4x4 wood fence post, I dig a hole 10 inches in diameter. The depth of the hole is important. My tests over the years have shown that the amount of buried post should be half the length that extends above the ground. In your case my guess is your fence posts were taller than the fence, so your wood fence posts should be in the ground at least 3 feet.

When it is time to install the fence post, be sure it is in line with the other posts and it is plumb. It is also important that the fence post is centered in the hole. Start to add the crushed gravel in 5-inch lifts. This means add 5 inches of gravel around the post and use a long heavy 2x4 to tamp and compact the gravel. Each time you are finished tamping the gravel, check to make sure the fence post is still in the correct position.

Continue to install the crushed gravel until it is just a few inches from the top of the hole. You can add top soil to finish off filling the hole in case you want vegetation around the fence post. Some people like the look of gravel, so it can extend to the surface. You can even use a decorative, colored gravel if you like to finish off the hole.

The mass of interlocking gravel acts like an anchor when wind blows against the fence. It also can facilitate drainage of water away from the fence post as the soil moisture drops in late spring and all summer long.

The gravel is also easier to remove than solid concrete in the event you need to work on the fence in the future. A metal spud bar will quickly loosen crushed gravel that has been in the ground for many years.

Fences that are not solid have less wind load against them. A split-rail fence or a regular picket fence that has spaces between the individual pickets allows much of the wind to pass through the fence thus lowering the tipping force. In these instances the fence posts do not have to be buried as deeply.

If you decide to use treated fence posts, be sure to use the proper timbers. Not all treated lumber is approved for burial in the ground. The treated fence posts should be labeled that they are approved for direct burial.

Always be sure to call the national Call-Before-You-Dig Number a few days before you start your fence project. Simply dial 811 or go to their website www.call811.com. You may prevent death, serious injury or substantial expense by doing this. You would not be the first person to strike an electric line, phone line or even a buried natural gas line with a posthole digger!



Comments:

Shelley Brunet
19 Apr 2008, 14:07
We moved into a home with a fence that is only about 3 years old. The entire fence is in good shape except one post is loose, what is the easiest way to fix it.
Thanking you in advance
Shelley Brunet
Tiffany
19 Jul 2008, 16:39
I came across someone selling sections of heavy steel fence for a really good price. The only problem is that it doesn't come with the posts.
I was wondering if I bought heavy duty aluminum fence posts, if they would be able to hold the steel fence.

Tiffany
OK Fence
10 Aug 2008, 16:35
I am putting up a 7ft dog-ear fence, how far does the metal fence poles need to extend above the ground or how far from the top of the board should the pole reach.
Gucci
27 Aug 2008, 20:11
Dear Tom,

My home was hit by car that first took down a light post and fire hydrant. I'd like to prevent this from happening again but do not want to build a fortress looking wall in front of my home. What do you recommend? I'm considering bolders but they are pretty expensive. I've started considering fence posts and rails between that are less then a car width apart but not sure of what type of fence post would look good and withstand the force of a car going up to 35 miles per hour. (The house is on a court so speeding is not the issue.)

Thanks,
Gucci
Mike Kemp
05 Oct 2008, 12:31
The idea of using crushed gravel instead of concrete is fantastic. Do you think installing into a asphalt driveway will give you the same stability using crushed gravel instead of concrete? I've also had neighbor problems with my car getting hit. According to our bylaw the fence can only be 5ft between the houses and 3ft to the end of the driveway. Do you think a wooden fence would protect my property? Thanks so much, really enjoyed that article!
Arusha Stanislaus
08 Nov 2008, 23:02
I need my wood fence repaired, rechipped and painted. For replacement of 15 rails, 15 fence posts, 25 post caps, prep work on fence--e.g. loose paint, mildew, scraping, sanding and powerwash, plus application of 2 coats of solid white stain, I've been quoted a total price of $3500. Is this a fair price? The fence covers a one-acre lot.
Karen Manus
13 Nov 2008, 09:48
Dear Tim
The crushed angular gravel you recommended for setting fence posts, is that a processed gravel with fines mixed in or is it straight gravel without the fines?
thanks a bunch! karen
Darryl
20 Nov 2008, 15:54
just need a estimate on a 8ft 2inch post and what it would cost for labor no concrete
sally
07 Feb 2009, 02:02
Is there any way to remove a fence post in winter?
David
02 Apr 2009, 03:15
I had a 6ft privacy fence professionally installed and then had wind damage. After inspecting further, the fence posts were only placed 15 inches in the ground and not with solid concrete. The fence builder is returning to repair the fence. Instead of replacing the posts, they are digging a large 12-15 inch hole around the posts and filling with lots of concrete. What kind of issues will this cause in the future? I live in KY and am concerned about the ground freezing and pushing the posts out of the ground.

     View all comments
*Name:
Email:
Notify me about new comments on this page
Hide my email
*Text:
Security Image:

Visual CAPTCHA


 
Contact us to Advertise on this site.
Have a Suggestion?

Ask the Builder Comment Help

Helpful Comment Tips: If you need help with a problem, please try these things now before you type in a comment. You could discover your answer in just minutes.
Don't show this alert again.