One of the most common—and most misunderstood—questions we hear at Ozark Fence is:
“How deep should I set my fence posts?”
Whether you’re installing a wood privacy fence, a steel post chain link fence, or you’re using driven posts, getting the depth right is crucial. Too shallow and your fence may lean or fail over time. Too deep and you might be overworking (and overspending) unnecessarily.
In this blog post, we’ll break down proper post depths based on industry standards, and what that means for your fence project here in Springfield, Missouri. Don’t feel like reading? Watch this video instead.
Where These Recommendations Come From
All of the depth and installation standards we follow at Ozark Fence are based on ASDM (American Society for Testing and Materials) specifications, which are widely accepted throughout the U.S. fencing industry. These guidelines ensure your fence is built to last, especially in variable weather conditions like we experience here in the Ozarks.
Wood Fence Posts: How Deep is Deep Enough?
When setting wood posts for a standard 6-foot privacy fence, here’s what the ASDM standard says:
1. Post Hole Width:
- Should be 4 inches wider than the widest dimension of the post.
- For a typical 4×4 post (actual size is 3.5” x 3.5”), that means a 7.5” diameter hole.
- At Ozark Fence, we use an 8-inch auger, which works perfectly.
2. Post Hole Depth:
- Should be half the finished fence height, minus 6 inches.
- For a 6′ fence: 6 ÷ 2 = 3 feet – 6” = 30-inch deep hole.
- Posts should be floated 6 inches above the bottom of the hole in concrete, not touching the dirt.
3. Frost Heave Consideration:
- In frost-prone areas (like Springfield, MO), bell the bottom of the hole (wider at the bottom than the top) to prevent heaving.
- Ensure the bottom of the post is at least 6 inches below the frost line.
- For Greene County, MO, frost depth is typically 18 inches, so you’d want a 24-inch minimum depth in those cases.
Steel Fence Posts: Stronger, but Require Specific Depths
Steel posts—often used for chain link fencing and even some wood fences—have their own rules.
1. Hole Width:
- Should be 4x the post diameter.
- For a 2.5″ diameter steel post, you’ll need a 10-inch wide hole.
2. Hole Depth:
- 24 inches + 3 inches for every foot over 4 feet of fence height.
- For a 6′ fence: 2 feet extra = 6 inches more → 30-inch depth.
3. Frost Line Rule Still Applies:
- Bell the hole’s bottom to reduce frost heave.
- Make the bottom of the hole 4 inches wider than the top.
- Greene County’s frost line (18”) + 6” = minimum 24 inches deep to be safe.
Driven Posts: Go Deeper for Long-Term Hold
With driven posts (usually steel posts, often used for chain link or agricultural fencing), ASDM suggests you go even deeper:
Post Depth for Driven Posts:
- Use the same base as steel: 24” + 3” per foot above 4’ (which gives us 30” for a 6’ fence).
- Then add 6 more inches → Total 36-inch driven depth.
Why the extra depth? Driven posts don’t have the benefit of concrete, so depth = strength.
So… How Deep Should You Set Your Fence Posts in Springfield, MO?
Here’s a quick summary for a 6-foot tall fence:
| Post Type | Hole Width | Hole Depth |
|---|---|---|
| Wood Post | 8″ diameter | 30″ deep (plus bell if frost risk) |
| Steel Post | 10″ diameter | 30″ deep (bell if frost risk) |
| Driven Steel | No hole—drive post | 36″ driven depth |
Why This Matters for Springfield Homeowners
In Southwest Missouri, frost heave, rocky soils, and wet springs make proper post depth even more important. Setting posts too shallow could result in a fence that leans, wobbles, or collapses over time.
At Ozark Fence, we’ve installed thousands of fences across the Springfield area. We follow industry-best practices (like those above) to make sure your fence is built to last through all four Missouri seasons.
Need Help Installing Your New Fence
Whether you’re going DIY and just need expert advice—or want a local pro to take care of the heavy lifting—Ozark Fence is here for you. Get a free quote today.
Remember: Good fences make good neighbors—but only if they’re set deep enough to stand tall.
Let Ozark Fence help you build yours right the first time.