Why Fence Posts Slowly Lift Out of the Ground

It’s a strange thing to see — a fence post that was set solidly a few years ago is now visibly higher than it used to be, sometimes rising nearly an inch a year. The cause almost always traces back to how the concrete footing was shaped, not how deep it was set.

If concrete fills the hole all the way to grade, and the hole is wider at the top than the bottom (which is typical, since post holes are rarely perfectly straight-sided), that shape is exactly the wrong one for frost. Frost moves into the ground from the surface downward, and as moisture in the soil freezes, it expands. A footing shaped wide at the top gives frost heave something to grab and push upward on — and it doesn’t take much depth for this to happen. Whether the concrete goes down 32 inches or 42 inches barely matters if the top of the footing is still shaped like a plug sitting near the frost line.

The fix is simple: keep the concrete confined to the bottom portion of the hole, and backfill the upper portion with soil or gravel instead of concrete. That removes the wide “cap” shape frost needs to lift against, and lets the post move with the ground instead of getting jacked out of it.

One case worth remembering: this exact failure was found surrounding a municipal services yard — the very crew responsible for fence repairs in that township. It’s a reminder that this mistake is common even among people who work with fences professionally, not just first-time DIYers.