The fence is only as good as its posts
Here's a trade secret: when a fence fails, it's almost never the pickets' fault. It's the posts. Posts lean, rot, heave, or sink — and they take the whole fence with them. Everything about a fence's lifespan comes down to what happens in the hole in the ground, where nobody's looking.
So if you want to judge a fence installer's quality, don't look at the pickets. Ask about the posts.
How a post should be set
Dig deep enough. The rule of thumb: one-third of the post underground, or below the frost line — whichever is deeper. For a 6-foot fence, that usually means holes 30 to 36 inches deep. Shallow holes are the number one cause of leaning fences. In Maryland, winter freeze-thaw cycles push shallow posts right out of the ground — a process called frost heave.
Below the frost line. The frost line is the depth to which the ground freezes in winter. Water in the soil expands when it freezes, and that expansion lifts anything sitting above the line. Set the concrete footing below the frost line and the frozen ground can't grab it. In our part of Maryland, that means getting the bottom of the footing a good two-plus feet down.
Concrete, mixed right. Posts should be set in concrete — not just dirt packed back in the hole. The concrete should fill the hole around the post, slightly mounded or domed at the top so water runs away from the post instead of pooling against it. Water pooling at the base is how wood posts rot.
Drainage at the bottom. A few inches of gravel at the bottom of the hole lets water drain away from the post base instead of sitting there. In heavy clay soil — which is much of Charles County — this matters a lot, because clay holds water like a bowl.
Clay soil: our local challenge
Waldorf sits on a lot of heavy clay. Clay has a split personality for fence posts. On the plus side, it's dense and grips posts tightly — a well-set post in clay is very stable. On the minus side, clay drains terribly. Water collects in the post hole and sits against the wood, which accelerates rot. And clay expands and contracts dramatically with moisture changes, which can shift footings over time.
What good installers do about it: dig the hole wider than the minimum, put gravel at the bottom for drainage, dome the concrete at the top to shed water, and keep the wood post itself from sitting in a puddle — some even set the post slightly above the concrete or use post anchors. Ask your installer how they handle clay. If they look confused, that's your answer.
Why posts fail
Rot at the ground line. The most common killer of wood posts. The spot where the post meets the soil stays damp, and damp wood rots. Pressure-treated posts resist this much longer than untreated, but even treated posts eventually lose at the ground line — typically the first failure point on an aging wood fence.
Too shallow. Posts set 18 inches deep for a 6-foot fence will lean. It's physics: the fence is a sail, the wind pushes, and a shallow footing can't resist. Every leaning fence section you see is telling this story.
No concrete — or bad concrete. Posts set in packed dirt alone loosen within a few years. Concrete mixed too wet, or poured into a muddy hole full of water, cures weak. Good concrete in a clean hole cures strong.
Frost heave. Footings above the frost line get lifted a little every winter. A quarter inch a year doesn't sound like much until the post is two inches high and the fence looks drunk.
Gate posts and corner posts: the heavy lifters
Gate posts carry moving weight and take abuse every time the gate swings. They should be bigger, deeper, and set in more concrete than line posts — and wide or heavy gates may need steel posts or additional bracing. Corner posts take pull from two directions. If an installer sets every post identically, the gates and corners are where it'll show first. See our fence gates page for gate-specific details.
What to ask your installer
When you're choosing a contractor, ask these post questions: How deep do you set posts for a 6-foot fence? Do you use concrete on every post? How do you handle drainage in clay soil? How do you set gate posts differently? The answers tell you more about the installer's quality than anything else on the quote.
We set every post like the fence depends on it — because it does. Fill out the form below for a free site visit, and ask us about our post footings. We'll show you exactly what goes in the ground.