Avoid Wobbly Fence Posts: Backfill Holes Securely

Want sturdy fence posts? Some extra effort and patience backfilling the holes makes a big difference in the ultimate strength of the posts and the fence.

by J. Keeler Johnson
PHOTO: Daniel Johnson

Through the years, I’ve dug a lot of holes for fence posts, some by hand with a post-hole digger and others with the aid of a tractor-driven auger. I’ve installed many posts of different lengths and diameters, including some 12-foot 6-by-6 posts that required two people just to lift each post into its hole.

Along the way, I’ve realized you can’t rush the process of backfilling holes and securing posts in place. If you want your posts to sit firmly, without wobbling back and forth, you need to commit adequate time and effort to fill the holes properly.

Here’s why. Most of the time, you dig holes not much wider than the posts you  install. This means the spaces between the post and the walls of the hole are narrow—maybe an inch or two wide, yet several feet deep.

Filling Holes of Fence Posts Too Quickly

If you hurriedly shovel dirt back into the hole, you quickly run into issues. Small rocks lodge in the narrow gaps, preventing dirt from evenly reaching the bottom of the hole. Clumps of dirt held together by roots can be even more problematic. Before you know it, the hole appears to be “filled.” When you tamp down the soil with a tool or your foot, it all feels sturdy enough.

But push on the post to test its strength, and… surprise! It wiggles like it’s barely set in the ground at all. Rock it back and forth, and the hole quickly reopens. It’s so wide, you can pull the post back out with no trouble whatsoever.

What’s With the Wobble?

What gives? Rocks and clumps of soil prevented dirt from reaching the bottom of the hole, so the bottom of the post is hardly set in the ground at all. Large air pockets surround the post, so essentially you’ve generated an off-center seesaw. The post is secure only near ground level. Above and below this point, it freely rocks back and forth as it pleases.

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Backfill Securely and Thoroughly

Although it’s tempting to quickly backfill a fence post hole, I recommend you take the time to do it properly. Sift through the dirt with your hands to remove rocks that could cause issues. Break up chunks of clay or roots so that dirt falls freely down the hole. After you’ve added a few inches, use a metal rod or a slim piece of wood to pack down the dirt as tightly as possible along the post. Because you’ll pack it all down securely, you might need some extra dirt, too.

Repeat the process until the hole is filled and you can’t compress the dirt any more. Now give the post a push—doesn’t that feel nice and sturdy? Sure, it takes more time, but you’ll be rewarded in the long run with reliable fence posts that won’t lean this way or that at the slightest whim. And even this extra effort is still simpler than bringing in concrete or gravel, right?

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