How to Tell if Wood is Treated

Image of a treated wood,color is one way of How to Tell if Wood is Treated

During pressure treatment of wood, the wood is placed in a de-pressurized tank to expel the air and replace them with the preservatives, which effectively protect the wood against fungus, mites, insects, and vermin. How to tell if wood is treated is never a problem recently as most wood treating companies label them to help curb any potential chemical contamination on people.

Today, pressure-treated lumber comes with end tags or stamps that indicate chemicals present in them. A pressure treated wood is either green or brown due to the treatment process. Furthermore, treated wood can have an oily smell, unlike the pleasant natural scent of a non pressure treated wood.

Provided lumber is subjected to pressure treatment; it can last for several decades, sometimes up to 40 years. If you are looking to build a garage, a treehouse, or a shade, you must use durable wood products. 

Here are some of the things that you need to know so that you can tell whether or not wood is pressure treated.

Know About Softwoods

Before you can tell that wood is pressure treated or not, you should familiarize yourself with softwood and even the hardwoods. Virtually all pressure treated wood are softwoods with the majority coming from the coniferous trees such as Douglas fir, yellow pine, white pine, and spruce.

Softwood trees produce lumber that is naturally wetter because softwoods contain much more sap compared to the hardwoods. The presence of excess sap in the softwood explains why the softwoods call for pressure treatment in a bid to prolong its service life. Furthermore, the natural pathways for the sap make it possible for chemicals from pressure treatment to find their way deeper into the wood’s cells.

Therefore, if you are looking at wood and you can tell that it is a hardwood, there is every chance that it is not pressure treated.

Check for an End Tag

You need to assess the piece of your lumber to see if there is a stamp or label that indicates it is pressure treated. An end tag that is found on treated wood should bear the name of the preservative used for the treatment, its rating, preservation company, and every other related information.

If you see any wood that is treated using Chromated Copper Arsenate (CCA), avoid it by all costs. This particular preservative contains a form of arsenic and is thought to increase the risk of causing cancer. Woods treated with CCA is prohibited for use in decks, playgrounds, and all structures of residential areas.

Find The Stamp

Contractors and other commercial builders still use CCA-treated wood for industrial projects and structural supports. If your wood was treated after CCA was prohibited in 2003, it means that the likely used chemical, in that case, is alkaline copper quaternary (ACQ).

If you look keenly, you will notice that somewhere on that wood, there is a stamp that reads “L P22” which indicates that the wood was treated using arsenic, which is one of the safe variety. Treated wood can withstand direct contacts with the ground, such as structural support or a fence post. Wood with a stamp that reads “L P2” is not that toxic, however, you must not use it for building a playset or even home furniture.

The safest types of pressure treated come stamped with an “FDN” for the foundation. It is the favorite of many builders when it comes to using it as the base underneath home flooring.

Furthermore, a wood that has undergone pressure treatment with borate as the chemical is also safe for internal usage in homes and has no causes no harm to humans. You can identify borate-treated lumber by looking, look for the stamp with the following abbreviations “Bor,” “Hi Bor,” and or “Tim Bor.”

Check The Color of the Wood

In case the wood that you are looking at has no end tag, You may wonder how to tell if wood is treated. However, this should not worry you. 

One of the easiest ways to determine if wood has no stamp is treated is by carefully looking at the colors, if it has a faint olive-green hue, then it is a pressure treated wood. If your wood is too old and weathered so that the only color you can see is gray, you can go ahead and cut a piece of the wood at an angle and see the color.

Note: A borate-treated wood has a blue color.

Most builders and DIY woodworkers love using it a borate treated wood in homes as it is excellent against termites. Even though this wood is considered safe with low levels of toxins, it’s still not great for open usage, especially in the outdoor areas.

Carry Out The Smell Test

If you can not see a stamp or end tag at all, and you also find it hard to identify any blue or green tint on a wood surface, you can opt to pick up a chunk of wood and sniff it deeply. If the wood is not treated, it will have a pleasant, fresh, natural smell. Most pressure treated woods have oil or chemical smells.

CCA treated wood remains as the most dangerous one even for smelling because it contains no distinct odor. If you suspect that the wood you are using or intend to use is older than 2003, you can cut a piece and see if it is pressure treated.

Chemicals Used for Pressure Treatment of Wood

  • Woods that were treated before 2003 contains a chemical called Chromated Copper Arsenic. Today, this chemical is considered harmful, yet the most effective substance to treat lumber. It comes with resistance against ultraviolet (UV) hence protecting the wood against discoloration, etc.
  • Copper azole is another excellent wood preservative, it has a low level of toxins and does not affect the soil even if its elements go into the soil
  • Copper Naphthenate is another compound used for the treatment of woods such as fences, greenhouse, railroads, etc. It is excellent for woods that are used in ground and water contact.
  • Borate is one of the safest chemicals to use in the pressure treatment of wood; it has low levels of toxicity to the environment and humans. Its components prevent the growth of molds and fungi.
  • Creosote preservative is preferred for wood types that are majorly used for industrial purposes only like the railroads because it contains a high amount of coal.
Watch the video below on important things you need to know about pressure treated wood:


Pressure treated wood has a long life, which is why most people prefer using it on different woodworking projects. Wood that was treated before 2003, contains CCA, which is a toxic compound. Be extra careful if you suspect that your wood is older than 2003.

How to Tell if Wood is Treated

I have comprehensively explained the steps that you can use to tell if the wood you are using is treated. Such methods include:

  • Checking for end tags
  • Smelling the wood
  • Checking stamp
  • Discerning between soft and hardwood and a lot more

 I believe that at this point, you will find it easy to tell if the wood that you want to use is pressure treated or not. 

If you found this post helpful, please share with me your thoughts on the comment section below.

Image of a woodworker wearing hearing protectors for woodworking

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.

2 thoughts on “How to Tell if Wood is Treated”

  1. Thanks for this info. I would like to re-cycle some pallets for use in bee hives. How can I be sure that the timber is not treated as to effect the bees.
    It has no smell, nor discoluranation. Do you think it will be safe?

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