Pressure-treating wood is an essential step for preparing the surface before applying any additional protection onto it. Wood treated this way will have a lifespan of over 40 years which is much longer than untreated wood.
Although the chemicals used in the process leave some residual moisture behind, it usually doesn’t take the wood too long to dry. Staining after the treatment is necessary if the wood is to be used outdoors or in humid conditions.
However, if it’s done too soon after the treatment, it might not have the desired effect. Here we look at what happens if you stain pressure-treated wood too soon.
How does pressure-treating work?
The process begins by putting the wood into large cylinders in an industrial vacuum system. It removes air from the wood then floods it with preservatives.
These chemicals are forced inside the wood using high pressure, the process is repeated depending on the type of wood. Finally, the chemicals are then extracted, after which the wood is removed from the cylinder and left to dry.
Why is pressure-treating done?
Preservatives used during the pressure-treating serve the purpose of protecting the wood from insects and fungi. This wood can be later used safely indoors or outdoors, in any weather conditions.
Treatment with fire-retardants is also a common practice, as it helps the wood scorch more quickly, reducing flames during a fire. It’s used mainly on floors and roof structures.
Types of wood treatments and their effects
Borate treatment is the most natural way of long term pest control. Derived from a mineral deposit, borate prevents insects from advancing in the lumber, thus destroying it.
It doesn’t affect the wood’s color or further handling. It’s commonly used on floors and beams, as these are the most vulnerable parts of buildings.
PTI is one of the newest methods used in wood preservation. It’s probably also the most cost-effective one, as it requires a low amount of product. Used on wood intended for outdoors, PTI itself doesn’t have color, and it works fine with most stains and paints.
However, since a reddish pigment is often an addition to PTI, it’s best applied on cedar or redwood to bring out the natural tones. With the addition of a wax stabilizer, PTI will help prevent the wood from splitting.
MCA is a wood treatment with PTI with added copper, which helps prevent the wood from rotting. It goes deeper into the wood, providing more extensive mold protection.
ACQ is a preservative consisting of copper, ammonium, and insecticide. Known for exterior use, it needs a special type of sealing as the copper makes it highly corrosive.
Non-Com is fire-resistant, while the wood treated with it is exclusively for indoor use. The wood, when catching fire, will burn slowly, preventing spontaneous combustion.
Besides these, there are numerous other methods for wood protection. A lot of them are based on copper, and as such, they are considered outdated and used less frequently.
Natural treatments are getting more and more attention because of their ecological benefits. Some of these include thermal wood protection, biologically modified wood with agricultural waste or mud treatments.
Should pressure-treated wood be stained?
Although all treatment methods provide some level of protection internally, the wood surface suffers without sealing. This is particularly true for harsh weather conditions or high traffic areas.
As a rule, wood that’s intended for use in these sectors should be stained and finished. The stain will provide additional protection from mildew, usual wearing, and UV damage.
Pressure-treatment can also make the wood seem dull, so adding only a sealing agent will already make the surface look nicer.
Why wait after the treatment?
Freshly treated wood might be too damp, and it will prevent the stain from adhering to the surface properly. You also have the potential problem of those damp chemicals trying to escape the wood and leaving blisters.
This means your sealant won’t be effective and you put in all that effort for nothing.
That being said, most of the time you get wood from a treatment facility, it will already dry as it’s had time to do so.
Only if you acquire the wood within 24 hours after the treatment and plan to stain it before using it should you wait at least two additional days.
How to prepare your pressure-treated woods for staining?
Without a wash, staining might not adhere to the wood because of residue on the surface, even if the wood is new.
When it comes to fresh wood, it’s pretty simple. You take your pressure washer and rinse off any debris with clean water.
However, with older wood, the process is a little more complicated because you will need special cleaners to remove old stains and dirt accumulated over some time.
Depending on the type of contamination, you can use different types of cleaners.
What cleaning products should you use for wood?
If you only want to remove grime, use all-purpose wood cleaners that premixed or are available in liquid or crystal form. Apply it with a sprayer, scrub it in if it’s necessary, then rinse it off.
Use restorative cleaners for wood that’s discolored or has rust specks. These products contain oxygenated chemicals or bleach to help lighten the wood. Work best if brushed into stubborn discolorations, then washed off with a pressure washer.
Mildewcide cleaners are used to kill fungi, thus preventing wood decay. They are usually premixed and left to seep into the surface, without any rinsing.
Cleaners without ammonia are perfect to clean painted surfaces if you don’t want all the paint off. You only need to spray them lightly to the surface and wipe them off quickly.
When can you stain the treated wood?
Don’t be impatient by rushing the process of staining if the treated wood isn’t dry enough. The preservatives themselves will leave some dampness behind, and if you also washed the wood with water, the drying will be extended.
Without washing, wood usually dries in only 48-72 hours after the treatment. With the added water, however, it could take a week, depending on the environmental humidity.
To make sure your wood is dry enough before staining, do a moisture test. You can do this by dripping water onto the surface. If it beads, the wood still needs to dry, and if the water is absorbed in 10 minutes, you can begin staining.
Another method for testing the dryness is pressing a nail slightly into the wood. If water comes out around the nail, it’s still too soon for staining.
Additionally, you can buy kiln-dried lumber for a slightly higher price and save on the drying time. This wood is oven-dried right after treatment, making it ready for use almost immediately, unlike the air-dried variants.
Can you wait too long?
Yes, you can. Similarly to too much moisture, the lack of it will also interfere with the stain adherence. The ideal moisture level of the wood before staining should be around 15%.
Otherwise, you might have to use additional products to help the stain bond. Not to mention the fact that the more time passes before the staining, the less protected your wood will be.
It’s why it’s so crucial to check if the wood is dry enough and then apply the stain as soon as it is.
What kind of stain to use?
If you want to keep the natural color of the wood clear, transparent, or semi-transparent stain is recommended. Use semi-transparent stain only if you don’t mind changing your wood colors but you can get one that matches your existing color.
These look best on warm-toned surfaces or on ones that are tainted with preservatives.
The more opaque stains have longer-lasting protection. If your new wood is light, and you are not sure in which direction to go, stick to a transparent stain for starters.
You can always go darker later, unlike going from dark to light which takes infinitely more effort.
Copper-based preservatives will cause a greenish tint during their reaction with the wood. The green fades somewhat into a grayish color, but this will make the lumber permanently cool-toned, so you should use stains accordingly.
Some pressure-treatments contain a water repellent. If they do, you need to use oil-based stains because they adhere much better. This combination is often used for outdoor structures that are in contact with the ground, as the sealer will last longer and the preservative protects better from the mold.
Some types of stains and finishes require a more intensive penetration into the wood, and treatments may prevent that. It’s an excellent reason to consider every option before buying wood, stains, or paints.
You should wear gloves when handling chemically treated wood, especially touching it while it’s still damp. Wash your clothes immediately, in a separate cycle after being in contact with treated lumber.
Wear gloves and even a mask when cutting wood treated with harsher chemicals. It’s best to do it in a heavily ventilated place, of its possible outside in fresh air.
The same is true for staining, as the chemicals could get into a mild reaction with the stain, resulting in somewhat toxic gas.
After some treatments, cutting is not allowed, as the dust could be too dangerous for health. Don’t ever burn the scraps, but discard them instead with other construction materials.
Never use treated wood for surfaces that come into direct contact with food or drinks. This most likely won’t be an issue as you’ll be using a covering and/or plates.
Frequently Asked Questions
The wood dries about 48 hours after the treatment and will be good to go. Wait further only if you determine it’s still too wet but make sure to check it regularly so you won’t go beyond the required moisture level.
Kiln-treated wood is dried sufficiently in an industrial kiln after the pressure-treatment. It doesn’t require you to wait, as it is dry enough and you can stain it right away.
The choice of stain depends mostly on the natural tint of your wood and your preference for it. The color of the wood is might already be changed by the preservative. In that case, you should choose a stain that works best with it.
The most recommended ones are the quality, semi-transparent, water-based stains. They last long and protect better without discoloration.
No, the treatment will mostly depend on the intent of use. Wood meant to for outdoors and might receive different treatment than the one for the interior.
Also, lumber for above-ground use will have fewer preservatives in them. The lumber in contact with the ground will have more preservatives retained for more protection.
The wood needs to be dry enough before staining. You can determine your wood’s moisture level by putting a little water on it. If it soaks through, you are good to go.
If you don’t wait for a sufficient amount of time, the stain will not bond to the wood and will peel.
A stain is more likely to adhere to this type of wood than a paint. The chemicals used during the treatment can cause the paint to peel, particularly an oil-based paint.
You will have a better chance of bonding stain or sealer to the treated wood, just do your research to make sure you use the right kind of stain on a specific type of treatment.
It’s important to wait 2-3 days after the pressure-treatment of the wood before staining. If you stain it too early, your wood surface won’t have adequate protection.
Waiting too long can have the same effect, plus the costs of sealing the wood will be a lot higher, and the process much longer than needed.
You also have to keep in mind the freshness and the type of wood, the method of treatment, the finished product’s purpose, the type of stain and finish you want to use. These factors can all affect both the treatment process as well as the staining.