A pressure-treated wood fence is a great investment for privacy, security, and safety—but how long can you expect it to last? The answer depends on lots of factors, but the biggest one is the fence posts. While fence panels can last for many years with minor repairs, the posts are the weak point. Moisture in the ground slowly rots the posts over time, eventually leading to structural failure- a fence falling over.

At MKW, we specialize in building high end, long lasting pressure-treated wood privacy fences using 4x4 or 6x6 posts. Let’s take a look at what affects the lifespan of a fence, how long you can expect different materials to last, and what you can do to extend the life of your fence.

Why Do Fence Posts Rot?

Fence posts rot mostly due to excessive moisture exposure. The section of the post right at ground level is constantly in contact with soil and water, which leads to a very slow rot. There are things that can speed up the process. Here are a few things to watch for:

Poor Drainage– This is the main issue for most fence posts. If water pools around the base of the posts, they’ll rot much faster. A properly sloped yard that drains water away from the fence can significantly extend its lifespan.
Soil Conditions– Heavy clay soils can hold water longer, leading to increased moisture exposure. If your fence post is set without concrete, more of the post will be exposed to the moisture.
Old vs. New Pressure Treatment– Older pressure-treated posts (especially before 2004) contained arsenic, which made them last over 20 years. Arsenic was a great preservative, but a harsh chemical not good for the environment. Today’s copper-based treatments are much more environmentally friendly but not quite as effective. The downside is the posts are susceptible to breaking down a little faster, meaning newer 4x4 posts may only last around 10 to 15 years.

4x4 vs. 6x6 Fence Posts: Which Lasts Longer?

If longevity is your priority, 6x6 posts are the obvious winner. Here’s why:

4x4 Posts

Typically last 10-15 years (sometimes longer in dry conditions).
More likely to break in strong winds once they begin to rot.
Although 4x4s may not last as long, using them will significantly reduce the cost of your fence.

6x6 Posts

Typically last 15-25 years due to their larger size.
Take longer to rot through, meaning by the time they do, the rest of the fence is usually old and in poor condition anyway.
Create a much stronger, much more durable fence—one of our clients called it a “fortress.”

At MKW, we always drill 12” diameter holes for 6x6 posts and set them 4 feet deep allowing room for more concrete. This makes the fence far more resistant to shifting, leaning, and long-term rot compared to how other contractors install them.

Can You Extend the Life of Your Fence?

Yes you can! While you can’t stop fence posts from eventually breaking down, you can slow down the process:

Ensure proper yard drainage– Keep water from pooling at the base of posts.
Use professional installation methods– We go the extra mile with deeper holes, wider concrete footings, and stronger framing.
Repair instead of replacing– If a few posts fail, we can replace only the damaged posts while reusing the existing fence panels.

When to Repair vs. Replace a Fence

Often times, you can extend the life of the fence with post replacements instead of tearing the whole thing down and doing a whole replacement.

When a 4x4 post rots, it often snaps during a windstorm, but the fence panels may still likely be in good condition. If only a few posts have failed, we can:

Remove the old post and concrete footing.
Ensure the hole is 4 feet deep (if it isn't, we dig until it is).
Install a new post with quick-set concrete that firms up in about an hour.
Reattach the existing panels, giving your fence an extended life.

This is a great option if most of your fence is still solid. We charge a few hundred dollars per post for this service, making it an affordable way to extend your fence’s life. However, if too many posts are failing, it may be more cost-effective to replace the entire fence.

At MKW, we do 75-100 post replacements per year, helping homeowners save money while keeping their fences standing strong.

Should You Paint or Stain a Fence?

Some homeowners choose to paint or stain their fences for a fresh look and added protection. While its not necessary for pressure-treated wood, it can defintely help in a few ways:

Improve appearance– A fresh coat of stain or paint can make an older fence look new again.
Provide some moisture resistance– While pressure-treated wood is already resistant, a good stain can offer even more protection.
Require maintenance– Keep in mind that staining or painting a fence means ongoing upkeep —you’ll need to restain every couple of years to keep it looking good.

Final Thoughts: How Long Will Your Fence Last?

A well-built 4x4 post fence can last 10-15 years, while a 6x6 post fence can last 15-25 years or more with proper care. The key to a long fence life is a quality installation, a little bit of maintenance, and good drainage to prevent rot.

If you’re dealing with a few broken posts, replacing them might be the best option. But if your entire fence is reaching the end of its life, investing in a brand-new 6x6 post fence will give you a stronger, longer-lasting solution.

At MKW, we build fences to stand the test of time backed by the best warranty in the industry. If you’re unsure whether to repair or replace, reach out to us! We’d be happy to assess your fence and help you choose the best option for your property.