Pressure-treated wood is a fantastic option for projects where the wood will be exposed to factors such as moisture and insects that can damage it and cause it to rot and decay.
Fences and decks are two examples that instantly come to mind due to their constant exposure to moisture and insects, which are perfect use cases for choosing pressure-treated wood.
Unfortunately, pressure-treated wood comes with a disadvantage of its own. During the manufacturing process of pressure-treated wood, the wood is immersed in a solution that gives it moisture and insect resistance capabilities, which causes the wood to become wet.
While it’s possible to find pressure-treated wood that has been kiln-dried after treatment (KDAT), this form of wood is usually quite expensive. As a result, there is a good chance that the wood you buy ends up being quite wet, meaning that you can’t stain or paint it until it’s dry.
So, how to dry pressure-treated wood to make it ready for staining or painting?
- Kiln-drying – Kiln-drying is the fastest and most reliable way to dry pressure-treated wood, but it requires a large enough kiln that can accommodate your wood. If you don’t have a kiln, it’s still possible to get your wood kiln-dried by finding a kiln-drying service.
- Air-drying – The air-drying process involves letting your pressure-treated wood dry stay outside to dry. While anyone can use the air-drying process as it requires no special equipment, the process can take quite a while, depending on the moisture content of your wood.
As both methods will successfully dry your pressure-treated wood, factors such as time and budget constraints usually decide which drying method you will have to use.
Now, let’s inspect both methods in greater detail to see the advantages and the disadvantages they come with to have a clearer picture of how pressure-treated wood is dried.
Drying Pressure Treated Wood
The two methods you can use to dry pressure-treated wood are kiln-drying and air-drying.
Even though both methods work quite differently than one another, you can use either to dry your pressure-treated wood.
Kiln-drying is the process of drying wood in a closed environment where variables, such as temperature and humidity, can be controlled. Controlling these variables allows the moisture level of the wood to be brought down to desired levels rather quickly and consistently.
While kiln-drying has the advantages of speed and consistency over air-drying, it also costs more, which creates a trade-off between kiln and air-drying.
Alongside the trade-off between drying methods, there is also a decision to be made for the way you will be utilizing kiln-drying, with each having a different speed, effort requirement, and cost.
Here are the four different ways you can benefit from the kiln-drying method.
- Buying Kiln-Dried Pressure-Treated (KDAT) Wood – KDAT stands for Kiln Dried After Treatment, which refers to wood being kiln-dried after being pressure-treated. While this form of wood costs more than regular pressure-treated wood, it saves you from the trouble of having to dry it. If you haven’t bought your pressure-treated wood yet, this method will most likely prove to be the most effective in every way.
- Using a Kiln-Drying Service – Kiln-drying services dry your pressure-treated wood for a certain cost, which can come in handy if you bought regular pressure-treated wood that requires drying as soon as possible. Since it’s possible to find this service in most areas, you should easily be able to find one that is close to you by searching online.
- Buying a Kiln – If you regularly find yourself having to dry pressure-treated wood, buying a kiln is the most cost-effective way to do so in the long run. As a kiln can be quite expensive to buy, ensure that you will be able to make good use of it before proceeding.
- Building a Kiln – Technically speaking, a kiln is nothing more than a closed environment where you can control temperature and humidity, meaning that with some effort and time, it’s entirely possible to build your own kiln and dry your pressure-treated wood in it. Compared to buying a kiln, building one is usually far more cost-effective, and it allows you to fully customize things such as the size of the kiln and the energy source it uses.
If you are planning on using a kiln-drying service, buying a kiln, or building one, it’s vital to know the differences between kiln types as each type of kiln comes with strengths and weaknesses of its own.
Let’s take a quick look at different kiln types and how they operate.
- Conventional kiln – A conventional kiln is very similar to an oven, where the chamber of the kiln is constantly kept at high temperatures to vaporize the water contained in the wood. Due to the way they operate, conventional kilns are highly inefficient in terms of energy consumption.
- Dehumidification kiln – Dehumidification kilns dry wood by circulating heated air in the chamber. Due to their ability to recycle heat, dehumidification kilns are highly energy efficient. Combined with the fact that they require almost no attention to dry wood without defects, dehumidification kilns are popular with both experienced and amateur lumber dryers.
- Solar kiln – Solar kilns use solar energy to dry the wood, but they also require electrically powered fans to circulate air. Due to their reliance on the climate, solar kilns are highly inconsistent. While climates that are too hot cause the wood to dry excessively, climates that are too cold prevent the wood from drying. As it can take quite a while for a solar kiln to dry wood due to these inconsistencies, it usually becomes energy inefficient due to the power requirement of the fans.
- Vacuum kiln – Vacuum kilns take advantage of the relationship between atmospheric pressure and the boiling point of water to operate, which allows them to dry wood faster than any other kiln type. That being said, these kilns usually have small chambers, and they cost a lot more to both build and operate compared to other kiln types.
If you have the budget for it, we highly recommend going with a kiln-drying solution for quicker drying times and a lesser risk of warping.
Air-drying is the process of drying wood purely by using airflow, with no additional heat sources in play.
To air-dry your pressure-treated wood, stack them on top of each other and leave them out to dry. As all parts of the wood need to dry evenly to avoid warping, you will need to ensure that the airflow is distributed equally.
Since distributing the airflow requires all parts of the wood to be exposed, stacking them in a criss-cross pattern with extra padding between rows is often the best way to conduct this process.
While air-drying is cheaper than kiln-drying, it offers less consistency and speed.
The speed of air-drying depends on how humid your pressure-treated wood is and the temperature of the environment, meaning that the process can take anything between a week and a few months.
The consistency of the air-drying method purely depends on distributing the air evenly across all parts of the wood, which often isn’t as easy as it sounds even when you take all the necessary steps.
While it’s entirely possible to air-dry pressure-treated wood with absolutely no warping, many woodworking enthusiasts face warping-related issues after the air-drying process due to factors that they can’t control.
Due to the possibility of warping-related issues and the amount of time it could take, we don’t recommend air-drying your pressure-treated wood unless it’s a last resort solution.
How Long Does It Take for Pressure Treated Lumber to Dry?
The amount of time it takes for pressure-treated lumber to dry depends on many factors, such as how humid the wood is, the drying method, and the type of the wood.
As a result, it’s simply impossible to say anything about it without knowing the variables in play.
That being said, the shortest amount of time it takes to dry PT wood with either kiln or air-drying is often at least a month unless the wood has already spent some time drying.
Should You Let Pressure Treated Wood Dry Before Installing or Building?
Installing pressure-treated wood before it dries is a double-edged sword, which is why it’s possible to find opinions that are both for and against it.
The main argument for installing pressure-treated wood before it dries mostly applies to those who aren’t planning on kiln-drying the wood. Due to the long amount of time air-drying wood can take, some woodworking enthusiasts believe that the best way is to install the wood before it dries and let it naturally dry while it’s already in place.
On the other hand, the argument against installing pressure-treated wood before it dries is warping and shrinkage due to uneven drying. As wet wood shrinks (and possibly warps if it doesn’t dry evenly), your project could completely be ruined when the wood completely dries.
Our opinion is that you should wait for your pressure-treated wood to completely dry before installing it, as wood shrinking or warping after you have spent time and effort on your project is the worst thing that could happen.
What Happens if You Stain or Paint Pressure Treated Wood Too Soon?
If you stain or paint the pressure-treated wood too soon, the stain or the paint won’t stick to the surface of the wood properly. As a result, the wood will look nothing like how it should, and the stain or the paint will most likely wear out very quickly.
To understand whether your wood is dry enough for staining or painting, you can use the sprinkle test.
All you have to do is to splash a few drops of water on the wood and wait to see if the wood absorbs the water. If the wood doesn’t absorb the water drops for a long time, the wood isn’t ready for staining or painting just yet.
Kiln-drying and air-drying are two techniques that you can use to dry pressure-treated wood, with kiln-drying being the winner in terms of speed and consistency.
While you can technically use both of these techniques to dry your pressure-treated wood, the long waiting times and the chance of experiencing warping often make air-drying an undesirable choice unless it’s an absolute last resort.
Here is a quick recap of our recommendations, depending on the situation.
- If you haven’t bought the wood yet, we recommend buying KDAT wood for a smooth experience where you don’t have to worry about drying the wood and any problems that may come with it.
- If you have already bought the wood, we recommend using a drying service where you can get your pressure-treated wood dried professionally.
- If you need to dry wood regularly, we recommend buying or building a kiln to save money in the long run.
- If budget is your absolute priority, we recommend going with the air-drying method as it doesn’t have any costs associated with it.