Yes, it is possible to paint pressure-treated wood; however, if you want to achieve a good and long-lasting finish, you must ensure that the wood is dry, determine the moisture content in the wood and use the right primer and paint.
What Are Pressure Treated Woods and How to Use Them?
Pressure-treated woods are essentially lumber that is treated with chemical preservatives that help to protect the wood from moisture, insect infestation, fungus growth, mold, decay, and water damage.
In the process of pressure treatment, the wood (mostly softwood like pine) is placed in a pressure chamber that is sealed and depressurized by removing the air, which creates a vacuum.
The chamber is then filled with chemical preservatives like copper quaternary (ACQ), copper azole (CA) or micronized copper azole (MCA) and re-pressurized.
The high pressure forces the preservatives to penetrate the wood deeply, which blends with the wood and gives it properties that make it durable, decay resistant, and long-lasting.
Pressure treated wood is typically used for outdoor structures such as decks, fences, walkways, ramps, arbors, sheds, wooden swings, pergolas, stair stringers, picnic tables, etc., that are exposed to the elements.
Some of the different types of pressure treated woods and their applications include:
Borate Treated Lumber
Borates are basically sodium salts that are usually used in water-based pressure treatments for wood. They protect the wood from fungus growth and insects such as termites and mold and mildew.
The low toxicity of borate-treated lumber makes them suitable for indoor applications, including:
Alkaline Copper Quaternary (ACQ) Treated Wood
A widely used water-based wood preservative, alkaline copper quaternary (ACQ), contains quaternary ammonium and soluble copper oxide compounds. ACQ helps to prevent decay caused by insects and fungi.
ACQ is widely used in residential and other applications, including:
Fire Retardant Treated Wood
Fire-retardant wood is typically wood that is coated or infused with fire-retardant chemicals that help to resist ignition and slow down the spread of fire significantly.
Fire retardant wood is ideal for interior and exterior uses, such as:
5 Step-By-Step Process to Painting Pressure Treated Wood
Pressure-treated wood can be painted, and here are some steps to ensure that the treated wood is painted properly:
Step 1 – Check the Moisture Content (MC)
Before you paint pressure-treated wood, you must ensure that the wood is completely dry. Checking the MC of the wood can help to:
- Achieve a Better Finish: If the MC of the wood is very high, then painting it can be a bad idea because the moisture will be trapped inside the wood, and this will prevent the paint from adhering to the surface.
- Fight Rot: If the MC is around 35% or more, this encourages rot. So, keeping the MC in check can help to prevent rot.
You can check if the wood is dry by using the water test. To do this, pour a little water on the wood. If the water does not get absorbed and beads up instead, it means that the wood is not dry, and you must wait a little longer before you can paint it.
To be completely sure that the wood is dry, you can use a moisture meter to check the MC of the wood. The reading must be less than 14% for the wood to be ready for painting.
Step 2 – Start the Drying Process
Pressure-treated wood should be completely dry before painting it because if it is not dried thoroughly, not only will the paint not stick to the wood, but the pressure-treated wood will also bend and warp easily.
The new pressure-treated wood can take around 3-4 months to completely cure before you can paint it. The best ways to dry pressure-treated wood include:
- Kiln Drying: The quickest and most reliable method to dry pressure-treated wood, kiln drying essentially involves stacking the wood in a container to which heat is applied to aid quicker drying. But if you don’t want to wait a lot for the wood to dry before painting it, you can purchase kiln-dried after-treatment (KDAT) wood.
- Air Drying: Another way of drying the pressure-treated wood is by air drying lumber. In this process, the wood is dried naturally (outdoors or indoors). Air drying does not need any special equipment, but the drying process can take a long time, around 3 to 12 months, depending on the moisture content in the wood.
Step 3 – Thoroughly Clean the Lumber
Once the pressure-treated wood is completely dry, then you must clean it properly before painting it to remove any dirt, grime, and chemicals from the wood surface so that the paint adheres to the wood properly.
Cleaning the wood is very simple. All you need is a stiff brush, bucket or water with some mild detergent and a hose with a jet nozzle. Wet the wood, pour some soapy water and scrub with a brush and spray water with the hose to clean it off.
Avoid using a pressure washer for the job as this can gouge the wood and also damage the pressure treatment. The strong pressure may also cause the water to penetrate the wood fibers, delaying the drying further. Once cleaned, allow the wood to dry again.
Note: If the project you’re working on has a tight deadline, then it may be better to use kiln-dried pressure-treated wood, which can help to eliminate the need for long drying times, thus reducing your work time.
Step 4 – Use a Primer
Before painting or staining the pressure treated wood, it is essential to prime the wood. A high-quality primer will ensure that you get a flawless finish. A primer helps to create a smooth surface that allows the paint to glide easily.
Wood generally soaks up a lot of paint, which means more work and expense. A primer helps to form a protective barrier, helping to save time and money. The primer also ensures that the paint sticks to the wood surface properly without peeling.
Apply a coat of primer to the pressure-treated wood surface that you want to paint with a paintbrush or sprayer and allow it to dry for a day at least.
Step 5 – Apply a Top Coat of Paint
Once the primer has dried fully, then the wood is ready for painting. Using a good-quality exterior latex-based paint is best for treated wood, but if the wood is for an interior installation, then you can paint using interior paint.
Pressure-treated wood can be painted with any color of paint, but you might need to apply many coats to hide the brown or green-colored wood, especially if you’re using lighter colors, unless you’re using a primer.
But irrespective of whatever color you decide to paint the wood, plan two coats of the paint over the primer at least.
To ensure that the paint dries fully, wait for a day between the coats of paint because applying coats of paint without the previous coat drying properly can lead to adhesion issues.
How Long to Leave Pressure Treated Wood Before Painting?
Pressure-treated wood must be painted only after it is clean and completely dry. Typically, when pressure treating the wood, water is used to ensure that the preservative chemicals penetrate the wood fibers deeply.
This means that when the wood is removed from the treatment chamber, it is extremely wet. It can take many months for the pressure-treated wood to become completely dry before it can be painted.
The drying times of pressure-treated wood and when it can be painted depending on factors including:
When the Wood Was Treated
You might be able to estimate how long the wood has had to dry if you know when the pressure treated wood was brought into the lumber yard. But there are many more aspects to consider.
Often, hardware stores stack the pressure-treated wood in tight bundles, which prevents them from drying properly, so some wooden boards may be drier compared to others.
Where the Wood Is Stored
The place where the pressure treated wood is stored is an important aspect to consider when determining if the wood can be painted.
For instance, pressure treated wood stored in a cool and dark area will take a lot longer to dry compared to wood stored in a warm and dry place.
The Thickness of the Wood
Any type of wood can be pressure treated, but the thinner the wood is, the faster it will dry and be ready for painting compared to thicker wood.
If the Wood Is Kiln Dried
If you want wood that can be painted right away, then it is a good idea to purchase pressure-treated wood that has been kiln-dried. Although this is an expensive option, it is the best if you need to complete your project quickly.
Ways to Determine If the Pressure Treated Wood Is Dry
There are many ways by which you can determine if the pressure-treated wood is dry and ready for paint.
In this method, you examine the wood visually and feel it to assess if the wood is dry. Press the wood with your hand or a paper towel to see if you can detect any moisture. If the wood is very wet, the moisture will ooze out.
The limitation of the feel test is that it will help you assess if the wood is still wet, but it will not help you to determine if the wood is sufficiently dry to be painted.
Sprinkle drops of water on the wood’s surface. If the water is absorbed by the wood, it means that it is dry and is ready for painting. But if the water beads are on the wood surface, it means that the wood contains a lot of water within.
Digital Moisture Tester
The final method to test the moisture content in the pressure tested wood is using a digital moisture meter.
A moisture meter features two prongs that are pressed into the wood and helps to test the moisture content in the wood. But you must test the wood in various places to ensure that it is dry throughout.
- Accurately locate excessive moisture content within wooden materials including floors and walls with this moisture meters 2 pin precision system.
- With 8 calibration scales, you can easily assess any piece of lumber before cracks, splits, warping becomes a problem in everything from walnut to pine.
- Select from two different measuring modes to precisely assess the %MC (Moisture Content) and the potential moisture level growth.
- With its bright LED display, strong stainless steel pins, automatic shutdown, and memory function, this is the best budget moisture meter available.
What Happens If You Paint Pressure Treated Wood Too Soon?
You may be concerned about what might happen if the pressure-treated wood is painted before it has fully dried.
Typically, when it is just treated with chemicals, pressure treated wood contains high levels of moisture and is likely to be damp, unless it has been kiln-dried.
It is always recommended to wait until the wood is dry (around 2-4 months) before painting it. If you paint on the wood without waiting for it to dry, you will not get a good quality paint finish.
You will also face issues such as:
The Paint Will Not Dry Properly
Painting on pressure treated wood that has not dried completely means that the moisture has no place to escape and will get trapped in the wood.
This will cause the paint to remain damp and not cure properly and also cause it to chip and peel. Damp paint will not harden properly and remain soft, making the surface of the wood susceptible to scuffs, dents, and scratches.
The paint will not appear the way you want in terms of color and texture and will not look the way it should.
The Paint Will Peel
Painting over pressure treated wood that is not dry will prevent the paint from adhering to the wood fibers properly, causing the paint to start peeling and flaking.
Further, when the wood board dries, it will shrink in size, which will cause the paint to peel even more. This means that the painting effort is wasted, and you will have to remove the paint and start over.
The Wood Will Warp
As the pressure treated wood dries, it will shrink a little and may make the wood warp. This is because when one side of the wood shrinks more quickly compared to the other, the board will start pulling towards the side that’s shrinking.
And, if you paint the pressure treated wood before it is completely dry, then the non-painted side will dry faster than the painted one. When one side of the wood dries more quickly than the other, it will cause the board to warp.
The Bottom Line
It is possible to paint pressure-treated wood for a woodworking project, but when doing so, the vital aspect is to ensure that the wood is dried properly before you paint it.
There are many ways by which you can determine if the pressure-treated wood is fully dry and ready for painting. The key to painting pressure-treated wood is patience, and if you rush it, you will end up with a flawed paint job and a poor finish.
The paint may also end up cracking or peeling, which means you have to restart the entire project over, resulting in a loss in terms of time, effort and money.