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Does Pressure Treated Wood Rot? (Read This First!)

The pressure-treating process makes the wood much more durable and less susceptible. We use pressure-treated wood in furniture, decks, posts, fences, outdoor exposures, interiors and etc. 

Actually, it is called pressure-treated because chemicals are applied under pressure on wood to reduce insect infestation and make it excessively long-lasting.

Does pressure-treated wood rot?

Pressure-treating does keep wood long-lasting but eventually, it’ll start to rot after two decades or longer. Actually, depending on the climate, wood, and amount of preservatives, pressure-treated wood lasts. But normally due to moisture, fungal spores attract and eat away the wood over time.

Pressure-treated wood is a process that ensures an intensely long-lasting life of the wood. The main reason why it lasts long is, on pressure-treated wood, chemical preservatives are used which prevent woods from directly connecting with moisture, water, dirt, or ground. 

But it doesn’t mean it’ll never be damaged. It depends on the climate, soil, type of wood, pressure, grades, amount of preservatives how long it will last.


Pressure-treated wood lasts long in-ground or soil but can’t last more than 40 years. It mostly depends on the wood that has been used and where it’ll be located. 

But on the dirt it’ll need more protection otherwise, it’ll rot within just a few years. While using pressure-treated wood in the ground you have to be careful choosing the right grade. 

Choose a higher grade; more than 60 will be appropriate so that it goes long run.

If buried/underground:

If the pressure treated wood is buried or underground, it may last 40 to 50 years looking at rot, bacterial or fungal, or insect damage. But in constant contact with water, it may completely damage the wood within 7-10 years. 

Before burying, applying an all-weather wood sealer will be a wise decision, as it will protect the wood from being damaged.

In concrete:

In concrete, the pressure-treated wood will actually rot quite speedily when exposed to wet conditions. It will absorb the moisture and can even swell from the moisture.

The moisture will be trapped inside and it may only last a few years in non-draining concrete. But a solution of copper, chromium, and arsenic subjected to the pressure-treated wood can slow the rotting process.

In water:

Though preservatives used in pressure-treated wood kindly seal it from the water its longevity also depends on the types of wood, amount of preservatives, and how closely it’s connected with water.

To prevent its early rotting, wood sealers can work well. Providing no entry points on wood’s grain can also accelerate the speed of rotting and it will last a minimum of 30 years.

Does pressure-treated wood prevent/resist rot?

The pressure-treating process prevents wood from rotting for a couple of years but in the end, it will rot. Actually, it’s a process that ensures the long life of the wood but it doesn’t mean it’ll never decay. 

Depending on the types of wood, how it has been used or maintained, pressure-treated wood can stay up to two decades.

In contact with moisture or water, it will more speedily rot. Bacteria, fungal spores, and insects affect wet wood mostly. They are attracted to moisture and damage the wood day by day. So placing the pressure-treated wood in a dry area will be a wise decision. 

Dry pressure-treated wood has more longevity and can be more easily repaired.

Why does some pressure-treated wood rot? What causes pressure-treated wood to rot?

Here are the reasons why pressure-treated wood rot:

Excessive water:

Trapped water or pooling water under the deck or on the concrete piles increases rot. With a post or beam, water directly gets connected with the bottom of the wood which damages the deck beam and the ledger. 

Also sometimes cupped wood causes cracks that allow water to enter the wood and damage it.

Galvanic rot:

When the galvanized screws are driven into pressure-treated wood, the galvanic rot happens mostly. This happens because of the affected lumber of the deck. 

Moreover, chemicals that have been used in the wood sometimes react with those nails or screws. It results in oxidation and causes corrosion on the wood.

Fungal and microbial Infestation:

It’s one of the main causes why pressure-treated wood rots quickly. Fungi or bacteria are tiny organisms that attract because of the air and moisture. They move on the wood and feed on it over time. 

They can propagate easily and increase their number. A large number of the tiny organisms continue feeding and the wood continues to soften and decay.

Painting before dry:

This one is one of the common reasons that people often do and let the pressure-treated wood rot. The moisture of the pressure-treated wood penetrated deeply on its fiber. 

So, the pressure-treated wood takes a few months to release its moisture in the air and properly dry. If you apply paint until the pressure-treated wood is thoroughly dried, it will be rotten very quickly.

How can pressure treated wood rot? How long for pressure-treated wood to rot?

How long the pressure-treated wood will last, completely depends on the weather, soil, pH level, moisture, and where it has been located. Trapped water inside the deck can harm the ledger that results in damage to the bottom of the wood. 

Again, when pressure-treated wood gets in contact with air and enough moisture, it causes fungal and microbial infestation. And the tiny organisms continuously feed away from the wood over time.

If the pressure-treated wood is perfectly prepared with the right wood, right grade, good amount of chemical preservatives, good nails, and screws, and perfectly sealed, it will last for a long time, more than 40 to 50 years. 

But if it gets air and constantly connects with water it will not last more than 7 to 8 years. Actually, in dry places, the pressure-treated wood lasts long.

How do you keep pressure-treated wood from rotting?

Pressure-treated wood doesn’t last for a lifetime but you can use the wood for almost two decades. It also depends on many factors how long it will last. But you can keep pressure treated wood from rotting for a long time if you follow the ideas:

Choose the right wood:

Heartwood and redwood are the best choices for making pressure-treating wood. They are full of natural oils and extractives that naturally make rot-resistant wood. They do not even attract fungi to grow there. 

Another kind of rot-resistant wood comes from cedar which has natural wood preservative. It also perishes fungi and repels insects.

Use sealers:

Sealers provide an extra layer of the wood surface that will keep it safe from air and moist and also will give enough protection. 

Stains, varnishes, and paints as well are included in sealers that work for improving their durability and longevity. But you have to frequently apply them.

Try UV Stabilizer:

Natural woods are not UV resistant and UV light can alter the appearance of pressure-treated decks and fences. To make the pressure-treated wood UV resistant, you can use a UV stabilizer, containing preservation coatings and other finishes.


The pressure-treated wood is mostly affected by the fungus. Mildewcides are one of the forms of fungus but surprisingly, it actually works to prevent the fungus from growing. 

You have to clean the surface and the lumber with mildewcides before coating and let it dry. It will actually give the best result. 

Frequently Check:

Frequently checking the pressure-treated wood deck will let you know when it started rotting. And thus it will aware you when you have to reapply coatings, paints, or other stains or finishes.

What is the pressure treated post life expectancy?

The post-life expectancy of pressure-treated wood is about 40 years. Though depending on the weather, temperature, soil, its way of using and maintaining the life length can go up or down. 

Actually, the pressure-treating process ensures the incredibly long-lasting life of the wood. It gives proper protection on the surface of the wood and keeps it safe from air and moisture.

But in constant contact with water or moisture, pressure-treated wood lasts for a few years. The reason is, water and moisture can cause fungus infestation. Fungus rapidly grows on the moist and eats away the whole wood so, they get rotten within 7 to 10 years.

Final thought

Pressure-treating is really an effective process that makes the wood very long-lasting. But depending on weather, type of wood, water exposure, and its maintenance, it will eventually rot one day. In wet wood, fungi and microbial infestation grow and they’re mainly responsible for rotting.