Tricking the Wind, and Other Tips for Setting Posts

Q: DEAR TIM: What is the preferred method to set fence posts? My five-foot-tall, solid-picket privacy fence has had some issues over the past 10 years. The latest problem is posts set in concrete that have snapped. I have installed some temporary steel 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 posts? --Ron W., Maumee, Ohio

A: DEAR RON: Fence posts can be a real hassle. I have fixed my fair share of them over the years.

Your fence posts have a tremendous amount of force pushing against them whenever the wind blows. To get an idea of what I am talking about, lift a four-by-eight sheet of plywood and take it outdoors on a windy day. If you are not prepared, the wind may 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 eight feet.

The average wood fence post seems to be a square four-by-four or six-by-six-inch timber. The surface area of the post in the soil is what determines how quickly a fence will tip in the wind. A smaller fence post will yield much faster than a larger one, assuming they are buried at the same depth.

About 15 years ago I discovered a method of setting wood fence posts that appears to work well. Use crushed, angular gravel to trick the wind into thinking a massive fence post is installed. Crushed gravel is affordable, and it's easier to use than concrete. (You are about to discover how hard it is to deal with concrete that's as solid as a rock and deep in the ground right where you need to fix your fence posts. My guess is that you will be swearing like a sailor by the time you have removed the concrete around your third post.)

My method of setting fence posts is quite simple. If I am installing a four-by-four wood fence post, I dig a hole 10 inches in diameter. The depth of the hole is also important. My tests over the years have shown that the buried part of the post should be half the length that extends above the ground. I'm guessing that your fence posts were taller than the fence, so your wood fence posts should be at least three feet in the ground.

When it's time to install the fence post, be sure it's in line with the other posts and that it's plumb. It's also important that the fence post be centered in the hole. Start to add the crushed gravel in five-inch lifts. In other words, add five inches of gravel around the post and use a long, heavy two-by-four to tamp and compact the gravel. Each time you're finished tamping a lift of gravel, check to make sure the fence post is still in the correct position.

Continue to install the crushed gravel until it's just a few inches from the top of the hole. You can add topsoil to finish filling the hole if 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 decorative colored gravel to finish off the hole.

The mass of interlocking gravel acts like an anchor when wind blows against the fence. It also helps drain water away from the fence post as the soil moisture drops in spring and summer.

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

Tim Carter can be contacted via his Web site, http://www.askthebuilder.com/printer_Submit_Question.shtml.

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