How to Set Fence Posts That Last in Florida
Jax Fence Builders — a family-owned fence company serving Duval County, FL. Every job is run by the owner personally. No subcontractors, no franchise crews.
The short version
Set fence posts so that about one-third of the post is below ground — for a 6 ft fence that means a hole roughly 2 to 2.5 ft deep — in concrete, over a few inches of gravel for drainage. In Jacksonville's sandy soil, concrete is what keeps the fence from leaning after the first storm. Dig corner and gate posts deeper.
The post is the fence. Everything else — pickets, panels, rails — just hangs off it. Get the posts right and the fence stands for decades. Get them wrong and no amount of nice cedar will save it. In Jacksonville, almost every leaning fence we are called to fix has the same root cause: the posts were driven into the sand instead of set in concrete.
This is the guide we wish every homeowner read before they rented an auger. It is the same method our crews use on paid installs, written so you can do a short run yourself.
Why fences lean in Florida
Three things work against a fence here, and they compound. First, our soil is sand — it drains fast but holds a post about as well as a beach holds an umbrella. Second, we get real wind; a solid privacy panel acts like a sail, and every gust torques the posts. Third, the water table is high, so a bare wood post sitting in wet sand rots from the bottom up.
Concrete solves the first two by giving the post a wide, heavy footing the sand cannot push around. A few inches of gravel under the post solves the third by letting water drain away instead of pooling against the wood.
How deep should fence posts be
The rule of thumb is to bury one-third of the post's total length. A standard 6 ft fence uses 8 ft posts, so about 2.5 ft goes in the ground. For a 4 ft fence, 2 ft is usually enough. Whatever the height, do not go shallower than 2 ft in our soil.
Dig the hole about three times the width of the post — roughly a 10 to 12 inch diameter for a standard 4×4. Corner posts, end posts, and any post carrying a gate take more load, so dig those deeper and wider. A gate post that is set too shallow is the number one reason gates start to drag within a year.
How to set a post, step by step
Once the holes are dug, the process is the same for every post:
- Add 3 to 4 inches of gravel to the bottom of the hole for drainage and tamp it down.
- Stand the post in the hole and brace it with two scrap boards so it stays put hands-free.
- Check plumb on two adjacent sides with a level — not just one — and adjust the braces.
- Pour or mix your concrete around the post, keeping the post plumb as you go.
- Slope (crown) the top of the concrete up to the post so water runs away from the wood.
- Re-check plumb, then leave the braces on and let the concrete cure before you hang anything.
Set all your posts and let them cure first. Trying to hang rails or panels before the concrete sets is how a whole run ends up out of line.
Concrete: how much and which kind
Fast-setting concrete is the easiest option for DIY: you pour the dry mix into the hole, add water per the bag, and it sets in under an hour. Plan on one to two 50 lb bags per hole for a standard post — more for wider corner and gate holes. Manufacturers like Quikrete publish set and cure times on the bag; let posts cure at least a few hours before adding load, and a full day before hanging a gate.
One thing we see go wrong: people fill the hole with concrete all the way to the surface and leave it flat or dished. Water sits there and wicks into the post. Always crown the top so it sheds water.
When to call a pro instead
A short, straight run of fence on a flat lot is a reasonable weekend project. Some jobs are not, and we would rather tell you before you start:
- Long runs or sloped yards, where keeping dozens of posts plumb and in line is harder than it looks and mistakes multiply.
- Anything needing a permit. New fences in Jacksonville usually do — see our fence cost and permit guide.
- Heavy gates, automatic gates, or pool-code fences, where a mistake is a safety and code problem, not just a cosmetic one.
- An existing fence that is already leaning. That is usually a repair question — and sometimes the posts are too far gone to save.
If you want a second opinion before you dig, ask. We will tell you honestly whether your project is a good DIY candidate. More free guides live in the DIY Fence Academy.
FAQ
How deep should a 6-foot fence post be?
About 2 to 2.5 feet deep — roughly one-third of an 8 ft post — set in concrete. Go deeper for corner, end, and gate posts, which carry more load.
Do fence posts need concrete in sandy soil?
In Jacksonville, yes. Sand does not grip a driven post, so concrete gives it a wide footing that resists wind and leaning. Add a few inches of gravel under the post so water drains instead of rotting the wood.
How long should concrete cure before attaching panels?
Let fast-setting concrete cure at least a few hours before adding rails or panels, and a full day before hanging a gate. Check the bag for exact times.
How much concrete do I need per post?
Plan on one to two 50 lb bags of fast-setting mix for a standard line post, and more for wider corner and gate holes.
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