In the past, pressure-treated wood was fairly hard to paint, or at least to make it look good when painting. Improvements in the treating process mean that it can be painted or even stained.
It’s a good idea to paint pressure treated wood, as the treatment doesn’t render the wood waterproof. Eventually, unpainted pressure treated lumber will turn gray and start to splinter, which will actually speed up the weathering process.
Yes, you can paint pressure treated wood, if you allow it to dry correctly and use a good primer and 2 coats of paint.
Pressure treated lumber does require some special considerations and the whole process may take longer than you would like. Allowing the wood to dry thoroughly and using both a primer and paint will take time, but this type of wood requires that you take the extra time and effort.
This is because the pressure treatment involves chemicals injected into the wood under high pressure, and it takes time for all the moisture to evaporate completely. If you’re too impatient and don’t allow the proper drying time, you won’t get the results you want, and you may well end up having to repaint much soon than you expected. The paint may even start flaking off as the wood dries. In addition, the wood will be less protected than you would like.
When Can You Paint Pressure Treated Wood?
Pressure treated wood has a special type of liquid, usually a copper azole compound, that is injected into the wood while it’s subjected to high pressure. The copper helps in preserving the wood. Because of this, the wood may look and feel dry on the outside, but it must be completely dry all the way through before you try to paint it. This is because paint locks in any moisture that may be inside the wood.
Stain, on the other hand, is a bit breathable. This means that only the surface must be thoroughly dry before staining. The moisture still inside will still have a chance to evaporate, and the wood will keep drying.
There is a type of pressure treated wood that you can purchase that will skip the drying part. This is called kiln-dried wood. It’s basically dried in an oven at the mill. This process thoroughly dries the wood, both inside and outside. Of course, this type of wood costs a bit more, but if you don’t want to wait or don’t have a suitable place to store it while it dries, you may want to look into this option.
If the wood is not kiln-dried, you will need to store the new wood in a warm, dry place. Your shed can be used if there is no dampness inside. An enclosed garage will also be a good place as long as you don’t leave it open during winter or damp weather. Stack the wood with thin wooden strips separating each layer to enable air to reach all sides.
Placing a small heater inside either the shed or garage will help, as the process is aided in a warm environment. Even so, the drying process may take as long as two to four months. Check out my article What is Pressure Treated Wood? A Comprehensive Guide to get all the information and safety risks with pressure treated wood.
What Kind of Paint Do You Use on Pressure Treated Wood?
It’s important to use the right type of paint for pressure-treated wood. This is because some paints might contain ingredients that will react with the chemicals used in the treatment process and it may produce some unwelcome results with the paint.
Oil-based primers will provide a good, sealing coat, but most authorities recommend using a latex-based or water-based primer and a compatible latex-based paint. Look for both a primer and paint meant for exterior use. Some are even rated for use on pressure treated wood.
Latex-based paint and primer are preferred for several reasons. One is that the latex coating is more flexible than oil-based paint. It will handle the slight swelling and contracting that wood undergoes due to changes in humidity and temperature. The latex primer and paint will flex with the wood rather than the movement stressing the finish. Over time, oil-based paints will crack with these changes.
Latex-based paints are also slightly breathable. This ensures that while most moisture will be repelled, if any does get under the paint, it will eventually evaporate. Oil-based paint does not have this breathability. If any moisture gets trapped behind the paint, it will stay there and eventually cause blistering and flaking.
Latex-based primers and paints also offer better protection against UV rays, meaning that the paint won’t age and fade. Sun will eventually deteriorate it, but it will last longer than oil-based products.
Can You Spray Paint Pressure Treated Wood?
Spray painting is fine, as is using a roller or brush. Be sure to let your primer dry for the recommended time period before applying the paint. This may take as long as three days, so be prepared. The primer should contain information on the recommended drying time on the can.
Two coats of paint are recommended to help protect your wood. Again, make sure your first paint coat is completely dry before applying the topcoat. The paint will also have the recommended drying time on the label.
Be aware that pressure treated wood may take an extended drying time, at least for the primer. It wouldn’t hurt to wait an extra day than that indicated on the label. It’s always better to take a little more time to prevent having to repaint much sooner than you had anticipated.
If you do use a paint sprayer, it would be a good idea to use a brush first around the trim or in any recesses or inward-facing corners before using the sprayer. This way, you’ll be sure to get everything thoroughly covered and protected. Also, the sprayed paint will cover these areas and the touching up won’t be so obvious to the eye.
One tip for using a paint sprayer: if it’s your first time using one, you might want to practice a bit before tackling your main painting project. It can take a little time to get the hang of it. You need to spray an even coat to avoid applying the paint too thinly in spots or too thickly. You want to get good coverage without having to deal with drips.
This is especially important when changing direction, as it’s too easy to get the paint sprayed on too thickly and have drip problems. Try practicing on some scrap lumber first until you get comfortable with it.
How to Prepare Pressure Treated Wood for Painting
Many people suggest lightly sanding the wood surface to be painted. This helps the primer and paint adhere better. Make sure you clean all the dust off with a damp cloth. Some authorities recommend using a soap and water mixture with a scrub brush to ensure that any dust, oil or dirt is thoroughly removed from the wood.
This is a good idea if the wood has been stored outside for any length of time, such as at most lumber mills or home improvement stores. Even things that you can’t see can interfere with the adhesion of the primer and paint. This will take quite a bit of time, but it ensures that the primer will adhere properly, and nothing will interfere with the primer that might cause it to separate from the wood. It also ensures a smoother finish.
If you do sand the wood, be sure to do it in a well-ventilated area and wear a long-sleeved shirt, eye protection and a dust mask. This is because the chemicals in the sawdust flying around can be hazardous to your eyes, skin, and lungs.
Long pants would be a good idea as well, as you’ll want to sweep up all the dust left after you’re finished and before you take off your protective gear. This is also the reason why you should never try to burn scraps of pressure-treated wood. The smoke and fumes it will produce can carry a long way and cause harm.
Do I Need to Prime Pressure Treated Wood Before Painting?
It’s always a good idea to use an exterior, latex-based primer first. The primer contains more resin than does the paint. This creates a smoother surface for the paint to adhere to and helps with protection against moisture. In addition, there are primers that have stain-blocking properties, keeping any impurities in the wood from discoloring the paint or affecting it in other ways.
Paint, on the other hand, is basically pigment with less resin. It may also contain such ingredients as a fast-drying agent, glossy agents, and other things. If you use paint without using a primer, the paint has a tendency to sink into the wood.
This will lead to an uneven pigment distribution, and you’d find yourself requiring more coats of paint to achieve the finish and look you want. A good primer keeps the paint above the wood and provides an opaque base to show off the paint’s color to its best advantage.
There are plenty of products on the market that are touted as being paint and primer in one, but this is not a good idea to use when you have pressure-treated wood. Primer and paint basically have different functions, which is why they contain different ingredients. You won’t get good adhesion with an all-in-one product on this type of wood.
A paint and primer combination are also usually thicker than either paint or primer, meaning that it will take longer to dry. In addition, a thinner coat of primer and paint will adhere much better to the wood than a thicker coat.
It’s much better to take the time to use a separate primer to get the results you want. It will also make the final finish last longer, so you won’t really save anything by trying any shortcuts. You want the finish to last as long as possible before having to repaint, and you also want the wood thoroughly protected.
Do I Need to Seal Pressure Treated Wood Before Painting?
You don’t need to use a separate sealant. The resins in the primer will take care of that for you. The pressure treatment actually makes the wood repel paint. The primer will prepare the surface so that the paint firmly attaches. It will also protect the surface from stains. You can even add extra insurance by getting primer containing a stain blocker.
Avoid using a thick coat of primer. Besides the fact that it will dry more quickly, a thin coat of primer will actually attach more effectively than a thick coat.
What Happens if You Paint Treated Wood Too Soon?
The chemicals in the wood will ooze out of the wood grains as it dries, although this happens so gradually that you may not realize that it’s happening. If you prime or paint too soon, the moisture will repel the coating.
The coverage will end up being poor, it will look bad, and the adherence will be less than optimal. Worst of all, the coating will peel after the wood dries. You’ll just have to repeat the process, costing you more both in time and materials.
How to Tell if Pressure Treated Wood is Dry?
To test the wood to see if it has thoroughly dried, try using a moisture meter. They are readily available at most home improvement or hardware stores and don’t cost much. In fact, it would be a good idea to have one if you plan to do much working with wood.
A reading of a 12 to 14% moisture content is considered to be dry enough, but 14% is the upper limit. A more homemade method is to try sprinkling some water droplets on the wood. If the water soaks completely into the wood within ten minutes, it’s ready to paint. If the water beads on the surface, that means that there is still some moisture inside and it will have to have some more drying time.
Working with pressure treated wood does take extra care and extra time, but the added protection for anything that you build with it makes using it worth the extra effort. If you’re using it to build something outside like a shed or deck, it’s definitely worth using for the extra life you’ll get out of it and the extra reassurance that your project will be well protected from the elements. Just be prepared to spend some time and care with it, and it will do the job for you.