Post depth is where most fence failures start. A fence can have good lumber, tight fabric, straight rails, and still lean within three years because the posts were not set deep enough or were tamped in dirt instead of set in concrete. In Conway’s clay-heavy soil, this failure happens faster than it does in sandier ground.

The One-Third Rule and Why It Matters

The standard guide for fence post depth is to bury roughly one-third of the total post length. A six-foot fence uses an eight-foot post, with two feet in the ground. That two-foot rule works in well-drained sandy soil. In Faulkner County’s clay soil, we go deeper.

Conway and the surrounding area sit on heavy clay. Clay holds moisture against the post base, which accelerates rot on wood posts and, more importantly, expands and contracts with temperature and moisture changes. That expansion and contraction is what heaves posts out of level over time. We dig to 30 inches minimum on standard residential fences and 36 inches on anything taller than six feet, heavier, or in a spot with poor drainage.

Concrete Is Not Optional in This Soil

Post depth gets you part of the way there. The other part is what goes around the post in the hole. We use concrete every time. Tamped dirt, even done carefully, does not resist the lateral pressure that wind, kids, and dogs put on a fence. Concrete does. We fill the hole with mixed concrete, let it slope slightly above grade so water sheds away from the post base, and give it the cure time it needs before the fence goes up.

The most common objection we hear is that concrete traps moisture and rots the post faster. That was true of old installation methods where the concrete was flat with the grade or slightly below it, which pooled water at the post base. The fix is simple: slope the concrete above grade so water runs off rather than pooling. Done correctly, a concrete-set post in Faulkner County clay outlasts a tamped-dirt post by years, sometimes decades.

Frost Depth in Faulkner County

Arkansas is not Minnesota, but Central Arkansas does see freeze-thaw cycles in winter that affect shallow posts. The frost depth in Faulkner County runs around 12 inches, meaning the ground can freeze to about that depth in a cold winter. A post hole that only goes to 18 inches puts the bottom of the post at the frost zone, where freeze-thaw cycling pushes it up and back down over the course of a winter. A few years of that and the post has moved.

Going to 30 or 36 inches puts the post base well below the frost zone. The post stays put through winter, and the fence stays plumb.

Post Spacing and What It Has to Do With Depth

Post spacing affects how much load each post carries and therefore how deep it should be. The standard spacing for a residential wood or vinyl privacy fence is 6 to 8 feet on center. At 8 feet, each post carries a full panel’s worth of wind load. On exposed lots near open ground on the west side of Conway, we sometimes tighten spacing to 6 feet and go a bit deeper on the corners and terminal posts because those carry the most stress.

Gates get their own treatment. A gate post takes repeated opening and closing force on top of the wind load, which is why we over-build gate posts: deeper hole, more concrete, sometimes a larger diameter post. A gate that starts to sag almost always traces back to the gate post, not the hinge or the hardware.

What to Ask Any Fence Contractor in Conway

Before you hire someone, ask them how deep they dig and whether they use concrete. If the answer is 18 inches and compacted fill, that fence will move. If they say concrete but cannot explain the above-grade slope detail for drainage, they may be pouring it correctly or they may not. A good contractor will tell you exactly how they install and why without being defensive about it.

Kade sets every post in concrete at the right depth for the soil and the fence. We have been building across Faulkner County long enough to know what this ground does to a shallow installation over three or four winters, and we build to avoid it.