A strong fence starts with posts set in the right way: deep enough, plumb, and on a gravel base. Getting the posts right keeps the rest of the fence straight and stable for years.
Setting a fence post looks simple — dig a hole, drop the post in, pour concrete. But a fence that sags or leans within a year usually fails at the post, not the paneling. The difference is in a few details that don’t cost extra time but make the build last. Here is the exact sequence that works for standard wood and picket fencing, with the numbers you actually need.
Mark the Fence Line Before You Dig
Skip the string line and your posts will wander off course. Drive stakes at the start and end of the fence run, then stretch a tight mason’s line between them. Mark every post location along the line. This keeps the whole row straight even before the first shovel hits the ground.
Standard post spacing for wood and picket fences runs 6 to 8 feet apart. If you’re working with pre-assembled panels, divide the total fence length by the panel length, then add two posts (one for each end). Measure twice — correcting a mis-spaced post after concrete sets means starting over.
Dig the Holes Right (Depth and Width Matter)
The one-third rule is the reliable starting point: dig the hole about one-third of the post’s above-ground height. For a post that will stand 4 feet above ground, that means a hole roughly 18 to 24 inches deep. Most picket and lattice fences land in the 24- to 30-inch range. A shallower hole risks frost heave in colder climates or a lean from wind load over time.
Make the hole about three times the post’s width, which works out to 8 to 12 inches wide for typical 4×4 posts. That gap gives room for gravel drainage and enough concrete or packed soil to hold the post firm. Local building codes may specify minimum depths or frost-line requirements, so check before digging — that five-minute call can save a full re-do.
Gravel Base and Setting the Post Plumb
Pour 4 to 6 inches of gravel or crushed stone into the bottom of the hole and compact it. That layer drains water away from the post’s base, which is the single best defense against rot for wooden posts. Skip this step and the post sits in standing water after every rain.
Set the post in the hole and check vertical alignment with a level on two adjacent faces. Temporary wood braces — simple 2x4s staked into the ground and screwed to the post — hold it steady while you backfill. Re-check plumb after the first few shovelfuls of concrete or soil; the weight of the fill can nudge the post off-center. Adjust while the mix is still workable, because once it firms up, the post is locked in place.
Footing Choices: Concrete vs. Packed Soil
Most US homeowners use concrete for gate posts and corner posts where extra stability matters. This Old House and Home Depot guides both describe using dry Postcrete or bagged concrete mix poured directly into the hole and watered in. Mound the top surface so it slopes away from the post, or keep it below ground level — either choice sheds water rather than pooling it against the wood. Allow at least 24 hours for the concrete to cure before attaching rails or panels; 48 hours is safer in cooler weather.
For lightweight fences or temporary runs, tamped soil works if you have clay-heavy ground. The trade-off is less holding power and faster rot at the base, since the post absorbs ground moisture directly. If you take the soil route, pack it in 4-inch lifts and tamp each firmly.
Want to browse the best fence posts and panels for your project? Our tested roundup of garden fence and posts covers the options that hold up through real winters and summers.
Common Mistakes That Shorten a Fence’s Life
Three errors cause most premature fence failure. Skipping the string line produces posts that are visible out of alignment even from a distance. Setting posts too shallow or too close to each other leaves them vulnerable to wind leverage. And the most common one: running construction before the footing has cured, which breaks the concrete’s bond with the post. Each of these adds a year of work to a one-day job.
Also worth noting: T-posts are a different system. They use anchor plates and driven installation, not dug holes and concrete. The steps above apply to wood posts and the standard metal fence posts intended for concrete footings.
FAQs
Can I set fence posts in just gravel without concrete?
Yes, for lightweight fences or well-drained sandy soils. You dig the hole wider, fill with compacted gravel in 4-inch lifts, and tamp hard. The post won’t be as immovable as one set in concrete, but the drainage is excellent and removal is much easier later.
How long does concrete take to dry before I can hang fence panels?
Bagged concrete mix needs at least 24 hours of curing before any weight goes on the posts. In cool or damp weather, wait 48 hours. The concrete is not fully cured until several days later, but the initial set is strong enough within 24 hours for rails and light panels.
Do I need to treat the post before setting it in concrete?
Pressure-treated lumber rated for ground contact is the standard choice and does not need additional treatment. If you use untreated wood, brush a wood preservative onto the section that will sit underground and let it dry fully before installation. Either way, the gravel base and sloped concrete top are what really prevent rot.
References & Sources
- This Old House. “How to Install Fence Posts.” Covers the full process from layout to concrete curing times.
- Home Depot. “How to Build a Fence.” US-specific guidance on panel-based fences and post spacing rules.