What Is Pressure Treated Wood?

What Is Pressure Treated Wood?

Pressure treated lumber refers to the wood with infused protective chemicals in a pressure treatment process.

During pressure treatment, wood is placed in a pressure chamber with liquid preservative where the chemicals are forced into the wood under high pressure.

You can determine that wood is pressure treated by cutting deep into one end and observing the color of the wood.

Usually, the pressure treated lumber is characterized by green color.

Chemicals used in the pressure treatment process are fungicides and insecticides. The role of these chemicals is to repel insects such as termites that can damage the wood.

Usually, these chemicals in the modern pressure treated lumber offer no threat to animals or even humans.

Table of Contents

Different Types of Pressure Treated Wood

Pressure Treated Wood. can you paint pressure treated wood?Pressure treated wood is categorized based on its “level of retention,” in other words, the number of chemicals in the following pressure treatment.

The retention level of treated wood is measured in pounds of chemical per cubic foot of the wood(PCF). 

The amount of chemical retained inside pressure treated increases with the time the wood is in the treatment chamber.

There are set standards of retention for different types of pressure treated wood. You can always tell the type of pressure treated wood by reading the end tag on the wood.

When discussing types of pressure treated wood, I can classify them into the two most common types: They are:

  • Waterborne Wood Treatment
  • Oil Based Wood Treatment

Waterborne Wood Treatment

Until 2004, Chromated Copper Arsenic (CCA) was the most common treatment bearing a distinct color synonymous with many of us. 

Arsenic is the main protective chemical though no longer used in most residential projects due to its health and environmental concerns.

As much as Arsenic is banned for residential wood usage, it is still applicable in marine usage.

Here are some of the water based wood treatment chemicals:

Alkaline Copper Quat (ACQ). This chemical replaced CCA for applications in decks. 

This preservative protects wood used for above-ground and ground contact projects, making it an excellent option for a backyard deck.  

When ACQ is formulated with copper-ammonia or copper ethanolamine and mixed with various types and percentages of chloride, you get the A, B, C, and D in labeling.

Copper azole (CBA). This formula is a mix of amine copper and co-biocides. 

It is majorly used in hard to penetrate wood like Douglas Fir.

MCA (micronized copper azole) and CA (copper azole) – These two chemicals are copper-based though they have a high level of penetration for uses in the above-ground, below-ground, and freshwater construction

Ammoniacal copper zinc arsenate (ACZA). The preservative works best with the Douglas fir making it prevalent in the Western United States.

Borate is a salt based wood preservative. It is effective in interior application though it will leach out of the wood if exposed to water.

Leaching of Borate makes it less suitable for deck construction. The leaching also makes it bad for ground contact application.

Oil Based Wood Treatments

Here the chemical preservatives include: 

  • Creosote
  • Pentachlorophenol
  • Copper naphthenate

Considering how they are dangerous to the environment and can cause health effects, the oil-based pressure-treated wood is less used for domestic projects.

Can You Use Pressure Treated Wood Indoors?

Treated wood contains toxic chemicals making people cautious about where to use them with questions like can you use pressure treated wood indoors?

The answer is yes! You can use pressure treated wood indoors except for cutting surfaces and kitchen structures like countertops constantly in contact with foodstuff!

As it is, these wood have chemicals infused in them during the treatment process. 

The chemicals are dangerous when consumed and can cause different health complications.

Pressure treated wood is an essential part of woodworking; they offer resistance against animals like rodents and insects like termites.

If you use pressure Treated Wood for different projects around your home, ensure that your safety is a priority.

Keep reading the article for more information about pressure treated wood and its uses.

Should You Stain Or Paint Pressure Treated Wood?

As we already know, pressure treated wood contains chemicals that protect it against destructive insects such as termites. 

However, the treatment does not protect the wood against other damaging elements like water, which begs the question of staining vs painting it.

Staining pressure treated wood is the best choice compared to painting. Stains, especially for exterior purposes, come with waterproofing properties.

Additionally, transparent and semi transparent stains preserve the natural beauty of the wood as they expose wood grains.

Painting, on the other hand, fully covers the surface of the treated wood, compromising the grain’s natural beauty.

So you need to stain your treated wood for more benefits.


Sometimes you are in a hurry and end up staining your wood before it dries. Is it a good thing? 

Let’s look at what happens if you stain pressure treated wood too soon.

Staining pressure treated wood too soon is not a good idea because the stain will not adhere to the surface of your wood correctly. 

You must allow your pressure treated wood to dry before you apply a stain. 

Usually, the drying time of pressure treated wood is between a few weeks to a few months, depending on the prevailing environmental conditions.

How to Stain Pressure Treated Wood

  • A few simple steps will help you stain your treated wood and get the best results possible in the long run. These steps are:
  • Allow your new pressure treated wood time to dry, about 30 days before considering staining it.

Clean your wood by removing the old stain, any form of mold, or mildew that might be on the surface of your wood. 

You can use a pressure washer or a deck cleaning liquid. 

If you use a pressure washer, set it between 1500 and 2500 PSI to limit your deck’s chance of getting damaged.

  • Allow your cleaned wood about 3-5 days to dry thoroughly.
  • Using your roller or paintbrush, apply your stain evenly over the surface.

 You should also have the ends of the board; this will help prevent moisture from entering through these points.

  • Apply a single coat of color-based stain and a second coat after a year.
  • If you are using a transparent stain, then apply two coats. You can apply the third coat after 6-10 months of the previous staining.

Here’s A Video On How to Stain Pressure Treated Wood

Benefits of Staining Pressure Treated Wood

Some of the benefits that come with the staining of pressure treated wood include:

  • Prevention of Rotting

Wood is susceptible to rotting every time you use it in the exterior environment without staining to protect it. 

Rotting does a lot to your wood. First, it makes the surface appear less appealing and can also collapse the structure. 

So, how does rot develop on the surface of the wood? 

Some of how wood can decay include the infestation of molds and mildews; also, termites play a critical role in the rotting of a wood surface.

Staining your woodworking projects right after installation and follow up maintenance practices is crucial in protecting them from causes of rot.

  • Protection Against the Sun and Moisture 

Whenever water enters your wooden structures, it increases the chances of rotting taking place. 

Once your wood freezes after absorbing water, it will start to break; the breaking builds up to slow destruction of your project, especially if it repeatedly happens.

On the other hand, sunlight contains UV lights that cause discoloration of wooden structures. 

Staining with an exterior deck stain will help protect your wood against the two elements.

Most exterior wood stains come with features that inhibit both water and UV destruction.

  • Preservation of Wood’s Natural Beauty

The aesthetic appeal of wood is in its natural beauty; therefore, staining wood with the semi transparent deck stains helps maintain the beauty.

Besides exposing the grains, semi transparent deck stain offers protection against destructive elements like rain and UV rays from the sun. 

Water repellency of the stains prevents rotting.

The UV blockers prevent discoloration of your wooden structure hence prolonged service life.

Should You Sand Pressure Treated Wood Before Staining?

Yes, all wood types, except for the manufactured products like composite decking, needs sanding for the stain to adhere.

How do You Know If Pressure Treated Wood Is Dry Enough to Stain?

One simple method you can use to tell whether your pressure-treated wood is dry and ready for staining is the “sprinkle” test. 

In this test, sprinkle water over the surface of your wood; if the wood absorbs that water in less than 10 minutes, it is ready for staining. 

If you notice water beading or pools on the surface of your wood, it means that the wood has not dried and needs more time to dry.

What Kind of Stain Do You Use on Pressure Treated Wood?

If you want to stain your pressure-treated wood, I recommend using an oil-based, semi-transparent exterior wood stain. 

See some of the best stains for pressure treated wood here:

How to Dispose of Pressure Treated Wood

There are several ways in which you can dispose of pressure treated wood they include:

Giving them out free of charge, once you have completed your projects and are left with treated wood you have no use for, you can always give them for free.

Look for Landfills and Dump them: Landfills present one great way of disposing of your treated wood. 

If you cannot locate one easily, contact your local environmental agency and have them help you find a landfill.

Find more on how to dispose of your pressure treated wood:

Note: You must burn pressure treated wood at all costs. 

Woods older than 2003 contain a harmful compound called CCA, which the U.S. Environmental Protection Agency banned for its ability to cause cancer.

How Long Do Pressure Treated Fence Posts Last?

A properly pressure treated pine fence posts, for example, can exist for 20–35 years if well installed, while the untreated one only lasts between 3–7 years. 

In a case where large numbers are supposed to be installed, it is practical to drive them into the ground using a hydraulic post driver. 

Ensure that the small end is driven first. 

Why Did My Pressure Treated Lumber Rot?

Whenever any treated wood decays, it’s always because of a fungal issue. 

These fungi are microscopic organisms; they get right into the wood and feed on it as time passes by. 

This continuous eating of the wood makes it decay, soften, and turn into rot. 

Fungi behave the same way with all kinds of timber, resulting in the same problem.

So what are the factors that facilitate the rot and the growth of fungi?

Moisture: Moisture on wooden surfaces over an extended duration facilitates the growth of fungi which multiply in size to promote wood decay.

Pests: Several pests eat wood; the most common pest is the termite. 

These pests bore inside and around wooden structures allowing water to penetrate the wood fibers. 

The extensive water inside the wood can lead to the growth of fungi which promotes rotting.

Will Pressure Treated Lumber Rot In Concrete?

Yes, pressure treated lumber can rot in concrete. 

However, it would take some time for that to happen, and only if the conditions are favorable-wet conditions facilitates rotting. 

So, what exactly makes pressure treated lumber rot? 

When treated board of wood contacts moisture, damp soil, or water, the chemical used for treatment can leach out of the wood, leaving it vulnerable to fungal activities.

How Do You Keep Pressure Treated Wood from Rotting? 

Pressure-treated wood is an excellent product because it is less susceptible to damaging elements. 

However, it will rot with time if not protected due to constant exposure to moisture and other destructive elements. 

Therefore, you need to know how to keep your pressure treated from rotting to avoid future issues. 

You can use various methods to protect your pressure-treated wood from rotting, like using paints, stains, oils, waxes, and more.

But let’s focus on stains. 

Step 1: Choose Your Preferred Stain

First, equip yourself with an appropriate stain for the job.

If you have old pressure-treated wood, opt for darker stains to help conceal the surface imperfections. 

But if you have a new one, choose semi-transparent colors as they add more color to your deck. 

For the best outcomes, choose oil-based stains because they soak into the wood entirely to create a barrier against moisture. 

Step 2: Clean the Pressure Treated Wood

Next, clean your wood thoroughly, as any contaminants will prevent the wood stain from adhering as expected.

Apply defy wood cleaner to your surface, and let it sit for 3 minutes to act. 

Using a scrubbing brush, you gently rub the wood cleaner throughout the surface. 

After that, make a second pass over the surface for more precise results, then rinse your wood with a pressure washer and let it air dry for 24 hours. 

You can also use a soap solution with a pressure washer, mainly if your treated wood stays in a shaded place and exhibits signs of fungal growth. 

Note: if you’re dealing with old wood, please take extra steps to remove the stubborn build-up of dirt and grime. 

Step 3: Test the Stain

Before staining, apply a small portion to your treated wood using your scrubbing brush and allow the stain to adhere properly.

Doing this allows you to determine whether the stain has the right shade for your job or not.

Step 4: Apply the Stain

It’s now time to stain your pressure-treated wood. 

So, take your paintbrush, soak it in a dish containing the stain, then start coating your wood. 

Avoid thick coats as they will dry and crack before you finish coating. 

Also, don’t stain your wood under direct sunlight, as your stain will dry before soaking up in the wood. 

After the first coat, pull back and check for possible irregularities. 

If any, fix them and proceed with a second coat for maximum durability.

After that, leave the stain to dry according to the operator’s manual. 


Remember that back brushstrokes result in additional coats and can cause color variation. 

So, if you’re staining any vertical surface, begin at the top to ensure you cover any runs as you proceed downwards. 

Also, never stain your pressure treated too soon as the stain won’t fully absorb in the wood. 

Safety Steps When Using Pressure-treated Wood

  • Wear a face mask to avoid inhaling harmful dust when cutting or drilling treated wood. 
  • Never burn treated wood as its harmful chemicals can present serious health problems. 
  • Don’t use treated woods for food prep surfaces because they are not food safe. 
  • Avoid using pressure-treated wood for indoor projects. 
  • Always collect and dispose of sawdust from treated wood. 

How Long Will Pressure Treated 4×4 Last In the Ground? 

Under favorable conditions, a 4×4 pressure-treated wood should last for 20 to 25 years. 

But this duration can increase to above 40 years if you mount the treated 4×4 wood in a cement ring instead of the soil. 

Several factors can make your 4×4 treated wood degrade prematurely. A good example is humidity. 

Your pressure-treated wood can easily succumb to humidity if available in excess, wearing down the sealants that protect the 4×4 treated wood from water. 

So, if you live in high humid areas, use other materials apart from wood. 

How Long Does Green Treated Lumber Last? 

Green treated lumber exposed to wet-dry cycles without proper maintenance will only withstand ten years of use. 

The same lumber will last more than forty years if you treat it right and practice good maintenance like cleaning with mildewcide at the first signs of mildew growth.

How Long Will Pressure Treated Wood Stay Green? 

 Pressure-treated wood stays green for about 4 to 6 months. As the wood dries, the green color fades away.

 So, after this duration, it’s recommended that you stain your wood with an appropriate product for added protection and durability. 

If not, your treated wood will succumb to the destructive elements. 

Can You Stain Pressure-treated Wood Immediately? 

Staining pressure-treated wood too soon is ineffective as the stain won’t fully penetrate the wood. 

This means your treated wood will have ugly cracks, splinters, splits, and patches. 

But if you had already stained too soon, check out these valuable tips: 

For light-colored stain

  • Give the wood ample time to dry, then reapply a darker stain as a remedy.

For dark stain

  • Peel down the top layer of stain using medium-grit sandpaper or chemical stain stripper. Then allow the wood to dry before staining again. 

What Happens If You Stain Pressure Treated Wood Too Soon?

The stain will not adhere properly to the surface of a wet pressure treated wood. 

Ultimately, your wooden structure might not get the utmost protection from the stains. 

Additionally, you will be forced to restrain your surface faster than if you stain the surface when the wood is completely dry.

How to Protect Pressure Treated Wood from Natural Problems

Upkeep of your treated wood and other outdoor structures is crucial as it keeps them in good condition for an extended lifespan. 

Here are some common problems with pressure-treated wood and how to solve them. 

  • Shrinking and Swelling

Continuous exposure to water can cause your pressure-treated wood to suffer natural defects like warping, twisting, swelling, and more. 

You can minimize water movement in and out of your treated wood by applying a coat of semi-transparent deck stain. 

  • Ultraviolet Protection

If you plan to maintain the original color of your pressure-treated wood, you will not only need to clean it regularly but also apply a finish with a UV stabilizer.

 The UV stabilizer will not wholly prevent discoloration but will slow down the process.  

How Can You Maintain Your Treated Wood?

Regular monitoring of your railing, wood deck, fence, and other structures in your yard is critical in keeping your pressure-treated lumber in the best shape.

Here are some of the common and naturally occurring problems and how you can protect your wood against them:

Shrinking and Swelling

Constant absorption and loss of water by your pressure treated wood can result in natural deformations such as cupping, warping, twisting, or splitting. 

You can apply a sealer or opt for a semi-transparent stain for pressure-treated wood to minimize this free movement of water into your wood.

Growth of Mildew

Each time wood gets moist or exposed to humid conditions, there’s an occurrence of mildew growth. 

So that you don’t experience this less pleasing growth in your pressure treated wood, you’ll have to clean and stain it.

 Use a cleaner with a mildewcide; this way, your treated wood will retain its brightness and beauty.

UV Protection 

Wood needs protection against UV light.

 If you want to conserve the original color and appearance of your pressure-treated wood, clean your deck periodically. 

Other than that, apply a water-repellent sealer with an ultraviolet stabilizer. 

This stabilizer does not entirely prevent eventual discoloration of the wood. However, it slows the process of discoloration.

How Does the Strength of Pressure Treated Wood Compare to that of Regular Wood?

Treated and non pressure treated wood of the same species have no difference in strength.

The pressure treated wood only comes top because of its ability to resist destructive elements like termites; this cannot be said for non treated wood.

Therefore, the excellent reputation of pressure treated wood is not based on its strength but on the ability to resist rot and rot-causing agents.

How Much Does Pressure Treated Lumber Cost?

On average, it will cost you about $15 to $25 to acquire basic pressure treated pine.

If you want to buy the premium brands of pressure-treated wood, you should prepare to part ways with $25-$30 per square foot.

What Fasteners Should You Use On Pressure Treated Wood?

From my years of experience working with pressure treated wood, I recommend that you strictly use hot-dipped galvanized or stainless-steel nails. 

If your project needs screws, bolts, anchors, and connectors as fasteners, ensure they are also galvanized or stainless.

So, why do I advocate for galvanized and stainless-steel nails?

It’s because most wood treatments today are corrosive to aluminum.

Does Pressure Treated Lumber Shrink?

Yes, just like any other wood, pressure treated lumber will shrink to some degree across its width during its drying process.

Therefore, it is important to consider this slight shrinkage when building fence boards or decking. 

How to Tell If Wood is Pressure Treated

All wood can have almost similar color, so it shouldn’t be a problem as there are ways you can tell whether the wood is treated or not.

You should consider some things when identifying treated and untreated wood.

1. Check for an End Tag

The end tag is a stamp telling you the wood is pressure treated.  

The end tag identifies the preservative used, it’s rating and the preservation company.

You should try at all costs to avoid wood treated with Chromated Copper Arsenate (CCA). 

The preservative is linked with severe health complications and was banned from residential use in 2004.

2. Identify the Stamp

Treated woods comes with stamps, like in the case of borate treated wood markings. 

A stamp should inform you of the wood type and suitable areas for its uses.

For example, and abbreviation “FDN,” which means foundation, indicates one of the safest types of pressure-treated wood. 

Woodworks and deck builders, in general, use these as the base for deck and underneath home flooring.

Wood treated with Borate is safe. You can use such wood inside the home. 

Their stamps have inscriptions like Bor, Hi Bor, or Tim Bor.

You can use them in the interior as they offer protection against termites. 

When you use borate treated wood outside, the preservatives will leach into the soil. 

Also, they are susceptible to rot when used outside.

Avoid wood with stamps like L P22. They have arsenic as the preservative.

Woods bearing L P2 stamps are less toxic but unsafe for home furniture.

3. Check with Your Fact Sheet

A fact sheet lists chemicals used in the pressure treatment of wood. 

If these chemicals include Copper and Tebuconazole, then the wood is treated.

4. Observe the Color

What is the color of pressure treated wood? Well, pressure-treated wood can be green or brown. 

Some treated woods have tan or olive-like appearances. 

The appearances are affected by the chemicals used.

5. Smell Test 

Smelling represents another way of identifying pressure treated wood. 

If you can’t spot the color, sniff a piece of your wood. Pressure treated wood has an oily smell or smells like chemicals.

The CCA treated wood, however, does not have a distinct smell.

6. Wood Dimension

Most wood designated for residential construction measures 8 (244 centimeters) to 16 ft. (488 cm).

Others like 2x4s and 2x6s are sold as precut 92 5/8” long option, the standard length of wall studs.

Woods containing chemicals is a bit wider and thicker compared to regular wood. 

7. Wood Testing Kit or Swipe Test Kits

You will find commercial labs offering a swipe test that you can use to identify treated wood.


Up to this point, I want to believe that you have learned much about pressure-treated wood. 

You know that pressure treated wood is tough and offers high resistance to insects and pests, still needs protection and proper maintenance. 

It is, therefore, your responsibility to ensure that you give your structure the best protection so it can last longer.

To Summarize our discussions today…

What Is Pressure Treated Wood?

Pressure treated lumber is wood with infused protective chemicals in a pressure treatment process.

During pressure treatment, lumber is placed in a pressure chamber containing liquid preservatives.

Then, the chemicals are forced into the wood through high pressure.

You can determine that wood is pressure treated by cutting deep into one end and observing the color of the wood.

If you have a structure constructed using a treated lumber, ensure that you follow the maintenance practices discussed in this article. 

That way, you will be smiling for as long as you want.

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Tyron Otieno

Tyron is an avid woodworker and writer. He founded this website to help other woodworkers, whether hobbyists or professionals by sharing his knowledge and experiencie after a decade of woodworking.

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