Are you confused about whether to go for kiln-dried or pressure-treated wood? We’re here to help. Our thorough examination will give you the clarity you need to make the right choice. Let’s unravel the mystery together.
Kiln drying reduces moisture and warping. Pressure-treating infuses preservatives to protect against rot, lasting over 40 years outdoors. For decks, pressure-treated is better. For indoor use where looks matter, kiln-dried is recommended.
Want to know the secret to choosing a suitable wood for your project? It’s all about understanding wood treatments. We’re here to guide you through it. Continue reading to become a wood selection pro!
Contents
- 1 How long does pressure-treated wood last?
- 2 What preservatives are used for the pressure treatment of wood?
- 3 How to pressure treat wood?
- 3.1 Step 1: Vacuum pressure tank
- 3.2 Step 2: Seal the pressure tank
- 3.3 Step 3: Pump the air out and control Moisture
- 3.4 Step 4: Preservative solution
- 3.5 Step 5: Apply pressure
- 3.6 Step 6: Use the correct time and pressure
- 3.7 Step 7: Drain the tank
- 3.8 Step 8: Remove excess preservatives
- 3.9 Step 9: Wait 1 to 2 days
- 4 Frequently asked questions (FAQs) about kiln-dried wood and pressure-treated wood:
How long does pressure-treated wood last?
Pressure-treated wood is the best material for outdoor construction, such as benches, decks, pergolas, fences, and gates, as it has a long, useful life span that will beat all kinds of weather conditions and is much less costly than its alternative wooden construction material.
Pressure-treated wood can last more than forty years altogether. The pressure treatment process involves placing a load of wood in a vast cylindrical chamber called a retort or vacuum pressure vessel.
It’s important to remember that the kiln drying process is crucial in preparing the wood for this treatment. It has a door on one end that can be sealed airtight, and then some waterborne chemicals are forced into the timber under high pressure.
• Understanding the Properties of Different Wood Species
A handful of species of wood are commonly used to construct structural framing, and their properties affect how far they can span as joists. Most timber used to build the deck is considered fresh and wet.
It has over thirty percent water-weight moisture content. This is where the kiln-dried lumber comes into play, as it’s dry and has a consistent density, making it an ideal building material. Greenwood will shrink as it dries out and is less solid and stable, which can cause it to check and warp.
If you plan to use greenwood, you might want to consider the advantage of kiln drying vs. heat treatment. The temperature used in the kiln drying process helps reduce the moisture content of the wood, but kiln drying is a much longer process than heat treatment.
What preservatives are used for the pressure treatment of wood?
For decades, the pressure-treated timber industry faced a deservedly bad reputation for preservatives that included environmentally toxic chromate copper arsenic (CCA). In 2003, the pressure-treated timber industry voluntarily suspended chromated copper arsenic CCA for residential use.
Although it continues to be used for commercial applications, paying attention to the type of preservatives used in the wood you plan to use is essential. Moldex 45 Mildewcide is an isothiazolinone chemical that temporarily controls mold and mildew on pressure-treated wood-building products.
Moldex 45 is 100% environmentally friendly and does not persist in the environment. This is an essential factor to consider, primarily if the wood is intended for use in pallets or other items that might come into contact with people.
• Overview of Six Preservatives for Pressure Treatment of Wood
Today’s pressure-treated wood preservatives still include some form of copper, which is not toxic, inhibits mold and mildew growth, and repels insects. Some manufacturers avoid the telltale incisions used to help preservative chemicals penetrate the wood.
Instead, they employ new high-pressure techniques that drive the preservatives deep into the heart of the timber.
Below, I will discuss 6 different preservatives used for the pressure treatment of wood; they have the following features: low environmental toxicity, easy to incorporate, common dosage requirement, cost-effectiveness, good supply, and online availability, and above all, global production capabilities.
● ACQ
ACQ (alkaline copper quaternary) is used to pressure treatment raw, organic timber. It is a water-based wood preservative that prevents decay from fungi and insects (fungicide and insecticide). It also has relatively low risks, based on its components of copper oxide and quaternary ammonium compounds.
Water-based preservatives like ACQ leave a dry, paintable surface. ACQ (alkaline copper quaternary) is officially registered on buildings, utility poles, and other wooden structures.
From an environmental perspective, kiln drying uses energy but doesn’t introduce chemicals into the wood, unlike pressure-treating, which uses chemicals that can be a concern if not handled properly.
● Borates
Disodium octaborate tetrahydrate (DOT) is used to treat raw, organic timber pressure. It is specially formulated as a water-based wood preservative and is registered by EPA and government agencies throughout Asia, North America, and Europe. Typical applications include furnishings and joists.
● Copper Azole
Copper azole is used for pressure treatment of raw, organic timber. It is a water-based wood preservative that prevents fungal decay and insect attack; it is a fungicide and insecticide. It is widely used throughout the USA and Canada.
Water-based preservatives like copper azole leave wood with a clean, paintable surface after it dries completely.
Copper azole is officially registered for treating millwork and other wooden products used in above-ground, ground contact, freshwater, and saltwater splash (aquatic) decking applications.
● Copper Naphthenate
Copper naphthenate is used for pressure treatment of raw, organic timber. It was officially registered in 1951 and is used to brush, dip, spray, and pressure treat wood used in ground contact, water contact, and above the ground, such as utility poles and landscape timbers.
Copper naphthenate is effective in protecting wood against insect damage.
● Copper- HDO
Copper–HDO is also used to treat raw, organic timber pressure. It was first officially registered in 2005 and is used today for the pressure treatment of wood used as decking and posts.
It is restricted from use in aquatic or marine areas, construction of beehives, or any other application associated with the packaging of food or feed.
In my two decades of experience, I’ve found that the main difference between kiln-dried and pressure-treated wood lies in their processing; the former is dried in a kiln to reduce moisture, while the latter is infused with chemicals to resist decay and insect damage.
● Polymeric Betaine
Polymeric betaine is a preservative for pressure treatment of raw, organic timber. It was first officially registered as an active ingredient in the United States in 2006. It is a borate ester that, when applied to the pressure treatment of wood, breaks down to DDAC and boric acid.
Today, polymeric betaine is commonly used for pressure treatment on forest products. Adding water repellants to the preservatives to help the timber fend off moisture is very useful.
No matter what pressure-treated wood you choose, you must always wear a dust mask, eye protection, and gloves when handling the material and cutting pressure-treated lumber.
How to pressure treat wood?
Step 1: Vacuum pressure tank
Move the wood into a large steel cylinder called a vacuum pressure vessel or tank.
Step 2: Seal the pressure tank
Once the wood is loaded into the cylinder, you must close all the doors and seal the cylinder tightly.
Step 3: Pump the air out and control Moisture
Use an industrial vacuum pump to remove the air from the cylinder, including pulling air out of the wood.
Step 4: Preservative solution
The cylinder must then be flooded with the preservative solution.
Step 5: Apply pressure
The pressure must be applied to the solution to force the preservatives deep into the wood cells.
Having worked with both types of wood, I can tell you that kiln drying involves reducing the wood’s moisture content in a kiln, while pressure treating involves a vacuum process to remove air and moisture before forcing a preservative into the wood.
Step 6: Use the correct time and pressure
Cycle times and pressure settings must be adjusted based on the retention levels needed and the wood species being treated.
Step 7: Drain the tank
Once the cycle has been completed, the cylinder must be fully drained; then, the industrial vacuum pump must be used to remove excess solution from the wood, which is returned to the work solution storage tank.
Step 8: Remove excess preservatives
A final vacuum must be run within the cylinder to extract the excess preservatives returned to the work solution storage tank.
Step 9: Wait 1 to 2 days
Now open the doors and remove the wood. Wait for 24 to 48 hours.
Frequently asked questions (FAQs) about kiln-dried wood and pressure-treated wood:
1. How do I dispose of kiln-dried wood and pressure-treated wood?
Kiln-dried and pressure-treated wood may be disposed of in landfills or burned in commercial or industrial incinerators or boilers. But you must carefully follow the federal, state, and local regulations.
2. How can I remove stamps from kiln-dried wood and pressure-treated wood?
Sawmills mark their kiln-dried wood and pressure-treated wood with an ink stamp that indicates the species, sawmill, moisture content, and other information about the kiln-dried wood and pressure-treated wood. You can easily remove the stain of the stamp by using a palm sander.
3. What is meant by KDAT?
KDAT means kiln dried after treatment. Following the pressure treatment of the wood, it is placed in a kiln, where its excess moisture content is removed, and the wood is returned to its original moisture content.
The kiln offers a strictly controlled environment, and the timber is dried evenly. This process helps minimize the natural tendency of wood to crack.
Can you pressure treat wood at home or does it need to be done professionally?
Pressure treating wood at home is not recommended due to the specialized equipment and toxic chemicals involved. It’s best to have it done professionally to ensure safety and effectiveness.
I didn’t realize how important it is to wear protective gear when working with pressure-treated wood.
Thank you, Juan! It’s essential to prioritize safety when working with pressure-treated wood. Your awareness will help prevent potential health risks.
This article helped me understand the difference between kiln-dried and pressure-treated wood.
Thank you, Mary! I’m glad the article helped clarify the differences between kiln-dried and pressure-treated wood for you. If you have any more questions, feel free to ask!
What are the environmental impacts of pressure treating wood?
Pressure treating wood adds preservatives for protection against decay, insects, and rot. The preservatives used are non-toxic and environmentally preferable. Kiln-drying reduces moisture content. Both processes have their benefits.
Is it better to use kiln-dried or pressure-treated wood for outdoor furniture?
Pressure-treated wood is best for outdoor furniture due to its long-term protection against decay and insects. Kiln-dried wood reduces weight for easier shipping but lacks the same durability.
I didn’t know that pressure-treated wood can last over forty years, that’s impressive!
Thank you, Levi! Kiln-drying and pressure treating wood serve different purposes but can complement each other well for long-lasting results.
How long does the pressure treatment process take for wood?
The pressure treatment process for wood typically takes about 1 month, and the preservatives used are non-toxic and environmentally friendly.
The comparison between kiln-dried and pressure-treated wood was very helpful.
Thank you, Alfredo! I’m glad you found the comparison helpful. Feel free to reach out if you have any more questions or need further clarification on the topic.
I had no idea there were so many different preservatives used in pressure treatment, it’s good to know the options available.
Thank you, Dylan! It was great to share information about the different preservatives used in pressure treatment. Feel free to reach out if you have any more questions.
How long does pressure-treated wood need to dry before it can be used?
Pressure-treated wood can typically be used in about 1 month after treatment, as it is often first kiln-dried to lower moisture levels for better absorption of the preservative.
What are the benefits of using borates for pressure treatment of wood?
The benefits of using borates for pressure treatment of wood include long-term protection against decay, rot, insects, and termite attack. It is environmentally friendly and certified as an Environmentally Preferable Product (EPP).
I never considered the process of pressure treating wood before, it’s fascinating.
Thank you, Lucille! Both kiln-dried and pressure-treated wood have their benefits. Kiln-dried maintains the natural color and is lighter, while pressure-treated offers long-term protection. It’s all about choosing the right option for your project.
I feel more confident now about choosing the right type of wood for my projects after reading this article.
Thank you, George! I’m glad the article helped you feel more confident in choosing the right wood for your projects. Happy woodworking!
Can you pressure treat wood that has already been painted or stained?
Thank you for your question, Lauren. Pressure treating wood that has been painted or stained is not recommended as it may not properly absorb the preservatives, affecting its durability and effectiveness.
Is it safe to handle pressure-treated wood without gloves?
It is always best to handle pressure-treated wood with gloves, even though the preservatives used are non-toxic and environmentally friendly. Safety first!
Very informative video links provided, thank you for sharing.
Thank you for watching! I’m glad you found the video links informative. If you have any more questions, feel free to ask!
Will kiln-dried wood still need to be treated with preservatives?
Kiln-dried wood does not need to be treated with preservatives. The low moisture level achieved through kiln-drying makes the wood resistant to decay and insects.
Great explanation of the pressure treating process, it seems like a complex but important step.
Thank you, Leonard! It is indeed a vital step in protecting wood. Appreciate your interest in the article.
I appreciate the detailed explanation of different preservatives used for pressure treatment.
Thank you, Juan! I’m glad you found the explanation helpful. If you have any more questions or topics you’d like me to cover, feel free to let me know.
Is there a difference in cost between kiln-dried and pressure-treated wood?
Kiln-dried wood is typically more expensive than pressure-treated wood due to the additional processing involved in removing moisture from the cells of the wood.