How To Tell If Wood Is Treated? Useful Tips for Recognizing Treated Lumber

Nowadays, pressure treatment is a common practice. Every construction enthusiast saw stamps or end tags on wood with rather cryptic words. Fortunately, behind these words lies a safe and reliable process of making the lumber sturdier and more durable.


How to tell if wood is treated?

Pressure-treated wood has many distinguishable features: color, stamps, smell, and modified size.

How To Tell If Wood Is Treated

How pressure treated wood made?

First of all, avid woodworkers should know what pressure treating consists of. The wood is soaked with specific chemicals (we will discuss categories further). Then, it is placed inside a vacuum chamber.

High pressure within the chamber makes chemicals permeate the wood and alter its properties.

How to tell if wood is pressure treated?

When wood is pressure treated, it has a few specific features listed below:

1. Added chemical preservatives can alter the treated wood color

CCA wood has a green tint (remember, direct contact with such wood is extremely dangerous). Wood, which went through ACQ (Alkaline copper quaternary) pressure treatment, has a brown color. It is also easy to identify borate-treated lumber – it saves the natural color.

2. Information from the end tag allows us to know the proper handling

Whether ground contact is possible or not. If there is a retention level, it signifies how many chemicals are left after the pressure treatment. In other words, if there is no retention level, you have untreated wood.

3. Use a wood testing kit

Contemporary wood testing kits allow ensuring that there is no poisonous arsenic. We use them to detect whether wood went through the treating process and distinguish between salt-treated lumber (in most cases – sodium borate) and alkaline copper quat-treated lumber.

4. There is a quick chemical smell test

Unlike untreated lumber, wood that recently went through the treatment process should smell oily. The old wood doesn’t have such a specific chemical smell. Please do the smell test after you are sure that the treatment process was done without using the chromated copper arsenate.

How to tell if plywood is pressure treated?

  1. It has a green or brown tint.
  2. It has a specific oily smell.
  3. It is accordingly labeled. Pressure-treated plywood should have a “UC” label, followed by a category describing the proper use of the wood.

What is stain-exposed treated wood?

Sometimes, when the wood is pressure treated besides the green or brown color, it might have additional tints. This tint often demonstrates that a protective barrier covers your pressure-treated wood.

Why should you never burn treated wood?

Burning pressure-treated timber poses risks. The preservatives in pressure-treated timber are not destroyed when burned; they are released with smoke and pose a serious threat to human health and the environment.

Additionally, the ash and ashes from burned treated wood are hazardous and contain fatal toxins. 

How To Tell If Wood Is Treated

Why can such common practice sometimes be dangerous?

Pressure-treated wood requires certain precautionary measures. It would help if you remembered that some conditions could cause the release of dangerous chemicals.

  1. Pressure-treated wood should be completely dry to prevent inhaling the chemicals.
  2. Make sure that chosen materials are either made after 2003 or are not CCA treated wood.
  3. You should wear full equipment, protecting skin and lungs, including a dust mask and goggles. Please, avoid any direct contact with toxic chemicals.
  4. You should never burn pressure-treated wood!
  5. Don’t use chemically active substances, such as bleach, acids, and bases, during the work. The chemical reaction caused by their contact with treated lumber can release poisonous gases.
  6. Out of caution, always wash your hands even after minor construction work, and collect the remaining dust when the work is done.
  7. Always do the correct disposal of pressure-treated wood. As mentioned before, never burn it; it is recommended to call the local landfill, consult with them and find legal ways of disposal.
  8. Contacting the local landfill would also help you know the safe and approved disposal methods for treated lumber. For example, you shouldn’t recycle commercial wood materials since it is very dangerous for people and the environment.
  9. Cover pressure-treated wood with a protective barrier, if possible, so the wood preservatives and other chemicals would be sealed better.
  10. If you have the fact sheet, look at used chemicals, and evaluate their safety.

How can we know that we have CCA lumber?

We can check the end tag, stamps, and wood markings. The following information helps us to tell if the wood is safe or not:

  1. Code acceptance symbol
  2. Proper use (GC, LP-22, LP2 – specially prepared for ground contact, AG – use it above ground, UC1 – interior with dry conditions, UC2 – interior with damp conditions, UCFA – above-ground interior, fire protection)
  3. Used wood preservatives
  4. Treating company and plant location
  5. Trademark of a third-party inspection agency
  6. Retention level (how much chemicals remained after the pressure treatment)
  7. You should never use wood tagged as CCA treated wood or any wood whose list of wood preservatives contains words such as “chromate copper arsenate” or “chromated copper arsenic.” Beware the green tint! The information above helps you to know if the wood is pressure treated.
How To Tell If Wood Is Treated

The stamp says my pressure-treated wood belongs to the UC3 category, what is the meaning behind it?

As long as it isn’t exposed to excessive moisture or humidity, UC3-treated wood can be utilized in any application and has a preservative content of at least 1.75 pounds per cubic foot. Common applications for this kind of pressure-treated wood include decks, fences, playground structures, landscaping timbers, etc.

What is UC2?

The preservative content of UC2 pressure-treated wood ranges from 1.0 to 1.75 pounds per cubic foot. We can use it outside but not in ground contact, for decking, fences, playground equipment, etc.

What about UC1?

The preservative content of this type of pressure-treated wood ranges from 0.5 to 1 pound per cubic foot, and we can’t utilize it for exterior or ground-contact applications. You might use it for shed flooring but not for landscaping timbers or other items that will come into direct touch with the ground.

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What is ACQ?

ACQ stands for Alkaline Copper Quaternary. Brown or tan-colored pressure-treated wood was produced using ACQ. It is a safe and modern solution. However, it’s crucial to distinguish pressure-treated wood from wood that has been painted or stained.

What is borate?

Borate is another chemical used in pressure-treated wood products. Borate pressure treatment for wood preserves the wood’s natural color. If borate was used, it would be more challenging to tell if the wood had been pressure treated. So, another test should be applied to treated wood.

What are the chemical reactions behind the process?

The key reaction in the pressure treatment process – is oxidization. This reaction’s most frequently used chemicals are alkaline copper quaternary, sodium borate, copper azole, and copper naphthenate. Liquids inside the wood and air react with the chemicals; the oxidization appears at the deepest levels. That’s how the wood is pressure treated.

Is chromated copper arsenate safe for human health?

This preservative contains an arsenic derivative. Because of this, its usage in decks, playgrounds, and other such structures in an outdoor residential context has been restricted since 2003. CCA pressure-treated wood is extremely dangerous for your health!

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What kind of treated wood is referred to as salt-treated lumber?

Pressure-treated wood that has been maintained with sodium borate, copper naphthenate, and other salts is referred to as salt-treated timber. When the wood is placed in a pressure chamber, the salts are driven into the wood.

What are the small holes on pressure-treated wood?

Small holes that resemble markings are intentionally positioned to ensure that the preservative enters the wood fibers. If you’re asking, “why does pressure-treated wood have markings,” look no further than this explanation.

What colors are the most popular among pressure-treated wood?

Depending on the type of oil and treatment method, the color of the pressure-treated wood ranges from light brown to a tint to dark green. The smell of the oil may be detectable close to the treated wood. If the lumber isn’t pressure treated with a mild oil, it’s tough to paint or stain.

What is AWPA?

Spreading voluntary wood preservation standards is the responsibility of the American Wood Protection Association (AWPA). The International Residential Code (IRC) and the International Building Code both exclusively relate to AWPA requirements (IBC). AWPA is responsible for CCA pressure-treated lumber.

What is the retention level?

Retention level is a great helper in recognizing pressure-treated wood. If lumber is not pressure treated, it simply wouldn’t have a retention level since it is only placed on treated wood. Retention level is a measure of remaining chemicals volume. Pressure-treated wood with greater retention levels underwent harsher processing.

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If it can be so dangerous, why do we continue using it?

  1. Maintaining safety precautions can eliminate the risks of chemical release.
  2. Compared to untreated wood, treated wood is less susceptible to moisture; hence, it is more resistant to mold, fungi, and other wood-decaying organisms.
  3. Besides this, treating wood allows us to eliminate insects inside the wood fibers and natural pathways.
  4. Some chemicals also allow for enhancing fire resistance (for example, house fire protection)

What wood requires more thorough pressure treatment: softwood trees or hardwood trees?

  1. Understanding the differences between softwood and hardwood lumber is necessary before learning how to detect pressure-treated wood. Most pressure-treated wood is softwood timber made from coniferous trees like spruce, douglas fir, and yellow pine.
  2. Softwood trees produce more sap than hardwood trees, resulting in naturally wetter lumber. It seems reasonable that the softwoods would need pressure treatment to lengthen their lifespan because of the increased sap. Additionally, the sap’s inherent channels ensure that the pressure treatment chemicals penetrate farther into the wood.
  3. It is doubtful that the lumber has been pressure treated if you know it is hardwood. The type of wood also helps us to tell if wood went through the treating process.

What are the major differences between treated and untreated wood?

  1. Untreated wood is commonly cheaper since it doesn’t undergo chemical procession. It also has greater availability at local shops. For many construction solutions, it is a cheaper option – no need for additional preventive measures, for example, a wood testing kit.
  2. Untreated wood requires less effort when it comes to recycling and disposal. No need for careful handling; we can burn it without harming the environment.
  3. Untreated wood can be safely used within the home.
how to tell if lumber is treated


Why is wood treated with copper azole relatively expensive?

Out of all wood preservatives, it is one of the most eco-friendly materials, and that’s why it is so expensive.

What if the pressure-treated wood is old and its color is faded?

If a color test can’t be applied to pressure-treated wood, you can always do a smell test, wood testing kit test, swipe test, and check the stamps and the dimensions of the lumber. They will help tell if wood is pressure treated just as a faint olive green hue.

What are the most popular uses of pressure-treated lumber?

1. Railroads
2. Utility poles
3. Floor foundation material (also known as a base underneath home flooring)
4. Bridges
5. Structural support
6. Docks

In these applications, the durability of treated wood is very beneficial for making the construction sturdier. 

Cases in which we definitely shouldn’t use treated wood

Due to potential health risks, direct contact with people, animals, and water is strictly prohibited, even for the wood using newer wood preservatives. We can’t use treated wood to construct:

1. Bed frames
2. Chopping boards
3. Playground equipment
4. Picnic tables

Final thoughts

Always do preliminary research on the wood you want to purchase. Evaluate all the risks, and make a weighed decision! Analyze the wood’s color and smell, use the wood testing kit, and check the end tag and fact sheet. Follow the advice from the article, and you will gradually get used to all the check stages, even if they seem overwhelming at first glance.

Feel free to ask questions if something still needs to be clarified!

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