How Long Does a Wood Fence Last in the Carolinas?

What our soil and summers do

Most yards around Charlotte, Union County and York County sit on red clay. Clay holds water. After a summer storm the top of the ground dries in a day, but the hole a post sits in stays wet for much longer. Wood that stays wet rots, and the rot happens right where the post meets the air, at the ground line, where the wood is wet below and dry above.

Our summers make it worse. Hot, wet months are what fungus likes. A post can look fine at eye level and be soft as bread at the ground. That is why a fence here most often fails from the bottom up and from the posts out, not from the boards.

The post is the fence

Everything hangs on the posts, and the posts are the only part in the ground. So the single biggest thing that decides how long a wood fence lasts is how the posts were set.

• Ground-contact rated treated pine. Not all treated lumber is the same. A post should be rated for burial, which means more treatment deeper into the wood. A post that was only rated for above-ground use rots fast in clay.
• Gravel at the bottom of the hole. A few inches of gravel under the post lets water drain away from the end grain instead of sitting against it.
• Concrete that sheds water. Concrete poured level with the ground, or sunk below it, makes a cup that holds water against the post. Concrete crowned a little above the ground, sloped away from the wood, sends rain off.
• Deep enough for the fence. A 6 foot privacy fence catches wind like a sail. A shallow post works loose in a season of storms, and a loose post lets water in. Depth depends on the fence height and the soil.

When we replace a post, this is how we set it. It costs the same visit as setting it badly, and it is the part of the repair you never see again.

Cedar, treated pine and the boards

Pickets and rails live above the ground, so they get rain and sun, not soil. Both woods handle that, in different ways.

Treated pine is what most fences here are made of. It costs less and takes stain well. Left bare it turns gray, and some boards cup, twist or split as they dry out over the first year or two. Sealed, it stays flat longer and keeps its color.

Cedar costs more. It has natural oils that resist rot and bugs, it holds its shape better as it dries, and it weathers to a soft silver that many people like without any stain at all. Sealed, it keeps its red and gold. Cedar pickets on treated pine posts is a common and sensible mix: the wood that looks good where you see it, the wood that is treated for burial where it is buried.

Either way, the boards that touch the ground are the ones that go. A kickboard along the bottom, or pickets held an inch or two off the soil, keeps the picket ends out of the wet.

The care that buys years

• Seal or stain every few years. A water-repellent stain or clear sealer keeps rain out of the end grain, which is where boards split and rot. New treated pine should dry for a few months before the first coat.
• Move the sprinklers. A sprinkler head that soaks the same boards every morning rots them faster than any storm. Aim the heads away from the fence, or shorten the run.
• Keep soil and mulch off the boards. Beds that pile mulch against the pickets keep them wet. Pull it back a couple of inches.
• Trim what leans on it. Vines and shrubs that lie on the fence hold water against it and hide rot until it is bad.
• Fix the first bad post. A leaning post pulls on its neighbors and racks the gate. Fixing one post when it goes keeps it from becoming three.

Signs a post is going

Walk the fence once a year, after the spring storms, and do three things at each post.

• The push test. Push the top of the post sideways with your palm. A sound post does not move. One that rocks, or leans and stays leaned, is loose in the ground or soft below it.
• The thumbnail test. Press a thumbnail into the wood right at the ground line. Sound wood resists. Rotten wood gives, and may feel damp or crumbly.
• Look at the rails. A rail that has pulled away from the post, or screws that have backed out, usually means the post has moved.

One or two posts like that is a normal repair visit: the post comes out, a new one goes in with gravel and crowned concrete, and the same boards go back on. The visit is $225 to $600, installed, plus tax, confirmed after the final measure. When most of the posts fail the push test, read repair or replace for the rule we use.