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How Long Will a Treated 4×4 Post Last in the Ground?

Woods have always been an important part of our lives, spanning back to the dawn of civilization.

Wood has been our constant companion in making our lives better every now and then, from the usage of wood in constructing bonfires to the everyday necessities such as making architectural structures employing wood, tables, chairs, beds, other furniture, etc.

Wood is a fundamental component in all of it, from kitchen needs like wooden spoons, bowls, and forks to crafting decorative items that symbolize many cultures.

However, many of us may be unaware of the pressure-treated woods that are available on the market for use in various aspects of our lives, whether personal or commercial.

So, let’s talk about how long a treated 4×4 post will survive in the ground, as well as some helpful maintenance tips and other fascinating facts about it.

What is pressure treated wood?

The term “pressure treated wood” refers to wood that has been processed to make it more resistant to rot, insect infestation, mildew, and water damage. Some pressure treatments may even make the wood more fire resistant.

Pressure treated wood comes in a range of varieties, each of which may be used for a variety of purposes.

The most important thing to understand about this pressure treatment is that it has been proven as the most efficient method for preventing rot and insects, but it does not protect against weathering and rust.

Chemical infusion, usually chemical preservatives, is also used on pressure-treated wood to keep it from decomposing and rotting.

The wood is stored in a depressurized storage tank with an air-replacement preservative.

160 pounds of pressure is applied to initiate the treatment chemicals into the cellular structure of the wood inside the depressurized storage tank. Depending on a number of conditions, this pressure may fluctuate.

Following the pressure treatment, the pressure treated wood is placed on a drip pad to cure and dry following the pressure treatment. The length of time it takes to dry is determined by the surrounding environment and the quantity of sunlight it receives. 

How long will a treated 4×4 post last in the ground?

A treated 4×4 post can endure 20 to 25 years in the ground, depending on how favorable the soil and climatic circumstances are. The weathering qualities or favorableness of the soil, as well as harsh weather conditions, will affect the durability of 4×4 posts in the ground.

Wood that has been treated with chemicals or has undergone particular treatment to protect it against decay and insects is known as pressure-treated wood.

As previously stated, buried pressure-treated wood can last for 20 to 25 years without showing signs of decay.

But, it is only possible when the soil and weather conditions are favorable and don’t change drastically overtime.

Now that you know what pressure treated wood is, you might start thinking that maybe every piece of wood we see on our furniture, tables, and chairs is some sort of treated wood as well.

However, that is not true at all. It is true that pressure treated wood is made to fulfill a variety of purposes. However, it is also important to remember that, pressure treated wood is not suitable for use in every application.

For example, pressure treated wood is absolutely perfect in terms of burying them in the ground.

As normal woods would be prone to faster decay and rotting due to insect invasions, pressure treated woods are considered the ideal choice when it comes to burying a 4×4 post in the ground.

Pressure treated wood is usually used in places, where the wood comes into direct contact with environmental elements such as direct sunlight, air, water, soil etc.

Other than that, for interior work or indoor purposes, normal woods such as pine, fir, or spruce can be used, which are much more reasonable in terms of price than pressure treated woods.

Pressure treated wood is completely safe to use and there is nothing harmful about it.

However, it is highly recommended not to burn the pressure treated wood on fire as it might trigger the chemical on it to mix with the air, causing you respiratory discomfort and minimal damage to your eyes and nose.

How long will a treated 4×4 post last in concrete?

A treated 4×4 post would last up to 40 to 75 years in concrete if the weather conditions and the soil remain favorable enough in a particular area.

Suppose you live in an area where the rate of soil erosion is quite high. The decaying capabilities of soil are also very high. Besides, the climate conditions change drastically, and the area is prone to different natural disasters.

Therefore, if this description matches the area you are living in, then the treated 4×4 post in the concrete might have less durability than the average time span.

Again, imagine a situation where you live in an area where both the soil conditions and the climatic conditions are quite favorable and don’t change that much from time to time.

Therefore, your treated 4×4 post in the concrete will have longer durability in situations like this.

Thus, how long a treated 4×4 post lasts in the concrete is highly dependent on the type of environment you live in.

What Factors Cause a Treated 4×4 to Deteriorate Faster?

There can be many reasons why the treated 4×4 deteriorate fast. Let’s get to know them.

Moisture in the soil:

The moisture in the soil is one of the prime factors in initiating deterioration in treated 4x4s faster. Whether normal wood or pressure treated wood, none of those can escape the amount of danger they possess from moisture in the soil.

Additionally, this moisture creates a perfect environment for the fungus and molds to grow on the pressure treated wood.

Furthermore, if the soil contained arsenic, the arsenic would consume and degrade all of the chemical preservatives in the pressure-treated wood.

As a result, the treated 4×4 would start deteriorating quite faster.

Humidity in the climate:

Humidity in the climate is another influential factor that would cause treated 4x4s to deteriorate faster. This humidity increases the moisture in the soil as it represents the concentration of water vapor in the air.

Those who live in a region with high humidity will find that their treated 4×4 is likely to deteriorate faster than in a region with low humidity.

Type of wood:

The type of wood that you are using for your treated 4×4 is another significant factor in determining its deterioration rate. You have two viable options in terms of choosing the wood for your treated 4×4.

You can get either hardwood or softwood. Hardwood is far more resistant to decay than softwood.

If you are using hardwood, you are ensuring a long-lasting durability of your treated 4×4 post. But, if you are using softwood for your treated 4×4 post, then you are already starting off with a short span as softwood decays and deteriorates faster compared to hardwood.

How do you keep pressure treated wood from rotting in the ground?

To keep the pressure treated wood from getting rotten, you need to make sure that you take care of it properly. Let’s get to know how you can prevent it from rotting.  

Let the wood dry fully:

People often think that pressure treated wood is ready to use right after it comes out of the depressurized chamber. That, however, is not the case.

Therefore, after the treatment, allow your wet treated wood to get fully dry, at least for a month or two. The more time you allow for drying, the better.

Fully dry pressure treated wood would prevent it from rotting under the ground.

Use wood sealer:

The use of a wood sealant preserves pressure-treated wood from decaying. Clean it thoroughly when it has dried fully to ensure that no dirt remains on its outside surface.

Make sure there’s no moisture remaining on the pressure-treated wood’s surface. Then, to keep it safe under the ground, apply a water-based, transparent, oil-based, semi-transparent, soft, or solid wood sealer.

Keep the wood separated from the soil:

It is very important to keep the pressure treated wood separated from any direct contact with the soil. Because, soil contains moisture and this moisture slowly starts to affect the surface area of the treated wood.

As a result, it becomes prone to fungus and mold infections. Therefore, in order to prevent the pressure treated wood from getting rotten in the ground, separate it from any direct contact with the soil.

You may use several techniques in order to secure your treated wood under the soil. You may use concrete rings, gravel and plastic to secure your treated wood under the ground.

Besides, you can make a strong base for your treated wood by pouring the cement mixture at the very bottom of the foundation so that it doesn’t come into direct contact with the soil.

Final thoughts

A treated 4×4 post could remain in the ground for 20 to 25 years. However, soil condition has a significant role in influencing the 4×4 post’s durability. Moreover, climate circumstances, which vary from place to place, would also have a crucial effect in deciding the durability of a treated 4×4.