How to Treat Untreated Pine

I absolutely love iced coffee. I especially love a certain coffee chain’s caramel macchiato. The problem with iced coffees is that they condensate quite a bit, and I tend to nurse my drinks. When that sweat drips down onto my wooden table, it can create a hideous water stain that would ruin the look of my table. Fortunately, my picnic table (where I spend a lot of time working) has been treated and finished properly, which helps to repel the moisture from any drinks with which I forget to use coasters.

Pine is a very common wood that is used when making furniture. It’s also a very popular wood for DIYers who want to build their own things. The problem is that untreated pine wood will slowly discolor and rot. To prevent wood rot, you want to be sure to protect it from the elements, especially moisture. To protect pine, it is pressure treated by the lumber companies prior to sale. You can treat untreated pine at home, but the process takes patience and time. Once you have treated the wood, you may choose to finish it, which also requires some time and patience.

how to treat untreated pine

There are a few options for finishing off pine, and we’ll take a look at some of those options today. We’ll also look at the best way to treat pine wood projects with as little hassle to you. We’ll look at what happens to pine that is left untreated outdoors and how long it will last. Most importantly, should it even be used for projects?


What Is Treated Pine Wood?

You will often hear of wood being pressure-treated. This means that it has gone through the proper cycle to make it rot- and bug-resistant. To pressure treat wood, lumber yards mill the wood, in this case pine, and put it into a tank that depressurizes the wood.


The air that is removed from the pine is then replaced by element-resisting chemicals. The problem is that these chemicals are not safe for humans, so they should only be used in outdoor projects and must be handled with care.

Treated pine works much better for longevity than if you were to purchase a preservative and treat untreated wood yourself. By using the pressure treated method, the chemicals will penetrate the wood more deeply, providing better protection and longer life for your build.

Treated Pine Applications

Most of the time, builders use treated pine in home building. Treated pine is typically what is used when building exterior walls, sheds, and decks. It works well for these applications because it is resistant to water and dirt, while untreated wood should never come into contact with the ground.

Because it is treated against wood rot, it can even be placed within the ground, making it perfect for wooden fences. Posts can be placed deep into the ground and will last a long time compared to untreated wooden posts. This is also why it is used by government agencies for telephone and light poles, as well as railroad ties.

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How Long Will Untreated Pine Last Outside?

The reason that treated pine should be used only outside is because of the chemicals. These chemicals help to preserve the wood and protect it from the elements. Without treating the pine, the wood will only last for about five years before it begins to be replaced. It will show wear and tear from the elements (wind, rain, bugs, sun, dirt) much more quickly.

Moisture and bugs are not the only thing that can damage wood: sun and wind are also dangerous to the wood’s condition. In fact, the UV rays from the sun deplete natural wood oils in untreated pine, which could cause splitting or cracking. On the opposite end of the spectrum, treated wood will last about 25 years outside.

How Can I Tell Treated Pine from Untreated?

The easiest time to distinguish between treated and untreated pine is during the purchase. Besides most companies having tags that are labelled with the type of wood and price, lumber yards are required to attach tags to the base of all treated pine pieces. These tags are required to include the name of the treatment company, the AWPA code, and the chemical agent used to treat the wood.

But what if you’re inheriting some reclaimed lumber and you’re unsure whether it is treated? There are a few other ways you can tell whether the pine has been treated and is for use outdoors. The first step is to check the color and odor of the lumber. Most pressure treated pine will have a green or blue hue and will smell strongly of chemicals. Fresh lumber will usually be a pale yellow and smell like freshly cut wood.

However, some chemicals are not easy to pick up by sniffing. The final test that can aid you is a testing kit. These are sold by many retailers (check online if all else fails). Typically, you’ll just swab the wood and use the testing kit to tell you whether certain chemicals are present.

What Are the Grades of Treated Pine?

The American Wood Protection Association (AWPA) are the ones who have a grading system for treated woods. The Environmental Protection Agency (EPA) recognizes these codes and many building permits require a specific type of wood coding to pass for permits.

In fact, the International Code Council recognizes only the AWPA’s standards for coding for both commercial and residential building codes. Typically, for exterior projects, you’ll want to use a UC2, UC3, or UC4 code. These codes are then broken down further based on the usage of the wood.

  • UC2 – Interior usage that will come into contact with moisture
  • UC3 – Exterior use but only above ground
  • UC4 – Exterior use touching the ground

On top of the codes used for where the treated pine can be used, the wood is also graded on appearance and quality. More knots or an uneven grain will lead to a lower grade. Most high-grade, premium woods will be used for decorative purposes, like flooring.

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However, lower grade woods are best used if you are unconcerned about appearance and minor warping, like it sheds and treehouses.

What Chemicals Are Used?

As mentioned, several time, these chemicals are typically hazardous to humans and animals, so some chemically treated wood has been banned for use around animals and humans, like wooden playgrounds or picnic tables. These specific chemicals are referred to as CCAs, or chromated copper arsenate.

Even the name strikes a little fear because of arsenic. In 2003, this chemical composition was banned, so only older wood will be treated with this. However, reclaimed wood is a popular trend for builders and DIYers, so always be sure to check.

Some of the older chemicals are still in use for commercial purposes, such as pentachlorophenol and creosote. However, the most common chemicals used today are borate and alkaline copper quaternary (ACQ).

ACQ is water-based and leaves a dry fungi-resistant wood that can be stained or painted. Borate is the least hostile of the chemicals and can actually be used when building interior projects. These are not the only two that are used today, and the lumber industry is always looking for new ways to treat wood.

Should I Use Treated Pine on Projects?

Treated pine is an excellent product to use when you want to build furniture or structures for outdoors. Since it lasts so much longer, it is also better for the environment. Since untreated pine might only last five years, you’ll need to replace it as it begins to degrade. So, if you have decking boards that need replaced every five years, you’ll go through five times the amount of lumber than you would in the 25 years that the pressure treated pine would last. That’s a lot more trees that need to be cut down and milled.

What Safety Precautions Should I Use?

Because of the chemicals used, most builders recommend you use appropriate safety gear when building with treated pine. Use googles, gloves, and a dust mask when cutting or carving the wood. The chemicals in the wood are also too dangerous to burn. This means you should never use pressure treated pine for a bonfire or in your fireplace. Also, scraps and sawdust should never be burned but should instead be treated as trash and disposed of properly. You should note that even though it sounds like a dangerous product, the chemicals used by today’s standards are safe for people in small amounts, but it’s always better to take precautions.

How Can I Treat Untreated Pine?

Of course, the title of this article asks what we should do when we have untreated wood and need to treat it personally. If you chose not to use treated wood on your project, you’ll want to seal and finish the final product to extend the lifetime of the wood. This will typically protect it from moisture, but it can still attract bugs and fungus growth.

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To treat pine on your own, you can follow a couple of techniques that will help to treat the wood. The first option is to purchase a safe borate powder that can be dissolved in water. You can then soak the wooden pieces in the solution for the allotted time, and then allow the wood to dry completely before using.

The other option is better for those who are attempting to treat wood that has already been used to build. Many companies sell copper coating stains that can be used to treat the wood. Otherwise, simply look for the best stain and sealant that works for you. The process for sealing is arduous but worth it as it will prolong the life of your projects. To seal wood:

  1. Check your wood for any mold or rot already happening
  2. Wash down the wood to remove any dirt or escaped sap
  3. Allow the wood to dry fully (allow it to air dry, since this works best for wood)
  4. Sand down the entire piece of wood and vacuum or wipe away all loose sawdust
  5. Using a paint brush, apply the store-bought sealant on the entire piece of wood (including ends)
  6. Allow the sealant to dry
  7. Apply stain or polyurethane layers to finish the project.
  8. Allow it to dry for several days before using.

Can I Paint Treated Pine?

The chemicals in treated pine make it difficult to paint. Because the chemicals swell the wood at first, the moisture content is quite high. This will likely make the paint peel rather quickly. After the wood has sat, it will contract a bit, which can cause any paint that did not peel to crack and splinter. However, after a good amount of time (up to a year), the wood should have settled to its final size. You can then paint or stain the wood, even finishing it off with polyurethane. Some lumber companies even pre-dry or kiln-dry the treated wood so that it is ready to stain and paint immediately. However, if it is not kiln dried, wait at least four months before painting (longer is always better).

Depending on the chemicals used in the pressure treated process, you’ll find that certain paints or stains may not take on the wood, for instance water-resistant chemicals will repel latex paints and water-based stains. Luckily, most commercial and residential treated pine use water-based chemicals that will take paint and stain of all kinds.

For outdoor applications, consider using an oil-based paint or stain. These are best for using on outdoor projects anyway because they help the wood stay water resistant. Oil-based paints also work really well on high traffic areas that take abuse, like sheds and fencing from falling sticks and high winds. Oil-based paints provide a very hard shell for the wood, preventing chips and cracks more easily than latex paints. Also, since oil-based paints and stains are so high in VOCs, it is best to work outdoor for plenty of ventilation anyway.