Whether you’re completing a large construction job or have leftover scraps from a DIY home project, many people wonder if they can burn pressured, or treated, wood.
Large bonfires or backyard firepits might seem like a logical place to dispose of pressured wood.
However, you should learn all of the facts before striking that match.
Can You Burn Pressured Wood?
No, you should never burn pressured wood.
According to the U.S. Environmental Protection Agency, pressured wood is considered a hazardous material, especially when it’s fresh and new.
When burning this type of wood, the chemicals used to treat it, including arsine, release their bond creating toxic ash.
Instead of the preservatives burning along with the wood, the heat releases these chemicals into the air.
Any amount of arsenic that is breathed in can cause serious health issues and environmental damage.
Plus, the various other chemicals used in the treating process are also hazardous and can easily seep into the ground and water systems once they are released.
It’s even illegal to burn pressured wood in the United States.
What Is Pressured Wood?
Pressured wood, also sometimes called treated or pressure-treated wood, is lumber that has been treated with chemicals and preservatives to withstand and preserve itself against aging and environmental damages.
The pesticides included in the chemicals increase the durability and longevity of the wood’s life and prevent premature rotting.
The chemicals protect against damages caused by weather, insects, microbial species, and rot.
The treatment also protects against termites, fungus, and moisture.
From the 1940s to the early 2000s, chromated arsenical (CCA) chemicals that included preservatives containing chromium, copper, and arsenic were used to treat wood.
However, as of 2004, most manufacturers have changed their CCA lumber usage from residential to commercial use only.
Today, the most common chemicals used in treated wood are alkaline copper quaternary (ACQ), copper azole (CA), and micronized copper azole (MCA).
These compounds, lower in toxicity than their predecessors, interact with wood fibers to preserve the wood’s integrity and lifespan.
Types Of Treated Wood
There are generally two types of treated wood: above-ground and ground-contact.
Above-ground and ground-contact pressured woods are treated chemically differently, with ground-contact receiving twice as much chemical treatment than above-ground.
Because of the added treatment, ground-contact pressured wood should be used when making contact with the ground or within six inches of the ground.
It can also be used in poor ventilation and in areas where the wood is difficult to reach and maintain.
Due to the added level of protection, ground-contact treated lumber is used frequently for fence posts and deck columns, as the chemicals protect it from ground damage.
On the other hand, above-ground pressured wood contains fewer chemicals, making it half as protected as ground-contact.
This allows it to be used six inches off the ground and in areas with proper ventilation.
It should also be used in areas that are easy to maintain or replace.
Examples of above-ground usage include fence slats, deck boards, and railings.
Above-ground treated lumber has an average life span of ten years, whereas ground-contact can last up to forty years.
In addition to above-ground and ground-contact, there are also oil-based groupings and water-based.
Most commonly used treated wood has a water-based solution, but oil-based treated wood is still used for some commercial purposes, including utility poles, pilings, and railroad ties.
Oil-based treated wood has a stronger odor and is treated with different chemicals, including creosote and pentachlorophenol.
What Is Pressured Wood Used For?
Pressured wood is used effectively for several building projects.
Residentially, it’s most commonly used for building fences, decking, and accessibility ramps.
Commercially, its uses include construction projects, telephone poles, and railroad ties.
It’s also used frequently in coastal regions for boardwalks, freshwater docks, and other walkways.
Specific treated wood can also be used in and around salt water.
Ground contact pressured wood is even suitable for use in raised flower beds, or other ornamental plant beds.
However, it’s not recommended to use treated wood around edible plants, as the chemicals can seep into the soil.
If you are going to use treated wood to build vegetable garden beds, line the bed with plastic first to avoid chemical leakage.
Treated wood should never be used for interior home projects.
When determining which wood type to use for a certain project, look at the end of the board.
There should be an end tag stapled on that tells you everything you need to know, including brand, use description, inspector, retention, treating company, preservative, and use category.
Using the proper type of pressured wood is imperative to maintain safety and environmental health.
If used for commercial purposes, the International Code Council-Evaluation Service (ICC-ES) can write up an evaluation report, confirming that certain treated woods meet building codes.
Categories Within The Types
There are different chemicals for different purposes.
Many treating companies go by standard grades distributed by the American Wood Protection Association (AWPA).
The AWAP is a nonprofit organization that, though it is only informational, has set the standard for residential and commercial pressured wood uses.
However, the AWAP standards and grades are determined by wood durability, not potential health risks.
The categories are broken down by service conditions, use environment, common agents of deterioration, and typical applications.
Examples of category titles are UC3B Above Ground, UC4A Ground Contact, UC4C Ground Contact, etc.
There are even three categories approved for saltwater marine use and two categories for fire retardant pressured woods.
The AWPA also goes on to inform users of commodity specifications for wood use.
This table includes the use, exposure, and use categories.
The specific commodities include balconies, decking, flooring, ties, guardrails, and many more.
The association also lists dozens of lumber species and what they can be preserved with and what for.
In addition, the AWPA lists all of the possible preservatives that can be used in the various categories.
This helps to see abbreviations and chemical components.
The specificities and attention to detail in this information are beneficial to the consumer as well as environmental agencies.
There is also a grading system based purely on cosmetic appearance.
For instance, boards with few blemishes or knots receive a higher grade, while those with dings and more knots get a lower grade.
Higher grade boards are more expensive but may last longer.
Lower boards may be cheaper but due to the drying process, these boards are more likely to split or reveal hidden blemishes than their more expensive counterparts.
How Is Pressured Wood Made?
Today’s manufacturers have mastered and simplified the process of treating wood, ensuring that building codes are met, along with proper wood standards.
After wood, typically pine, fir, or cedar, is received from sourced mills, the treatment center places the lumber inside a vacuum or pressure chamber, which looks like a large steel cylinder.
An industrial vacuum then pulls the air out of the chamber.
After the air is removed, the chamber fills with whichever preservative solution is to be used on that specific wood and pressured into the lumber.
Cycle times are adjusted for the types of wood and the types of solution being used.
The cylinder then drains before a final vacuum runs to remove excess preservatives from the wood.
After the wood is removed, it’s placed on a drip pad for 24-48 hours for drying.
After the allotted time, the treated wood is ready to be shipped to distribution centers.
Since the wood takes several weeks for drying, it may be delivered to stores still wet.
However, the preservatives are retained by the wood as the water evaporates out.
Wood that has been treated expands due to the preservatives it is absorbing.
However, when it dries, the wood will shrink a bit, which may lead to splintering or warping.
It’s good to consider this during building.
Is Pressured Wood Safe To Handle?
Yes, in small amounts.
Since manufacturers changed their processes at the end of 2003, treated wood is much safer to work with.
It is however advised to use hand and eye protection, as well as a face mask when handling treated wood.
Goggles, gloves, and breathing masks are useful to have on hand when working with treated wood.
Breathing in sawdust from freshly cut treated wood can cause harmful effects.
Make sure you work outside or in a well-ventilated area when handling or sawing treated wood.
When finished sanding, sawing, or cutting treated wood, it’s a good idea to sweep up and properly dispose of the sawdust so it doesn’t mix in with the soil.
It’s also a good idea to wash your hands or skin after contact to avoid ingesting any chemicals.
Some people may react to the pesticides used in the preservatives, but the risk depends on the type of exposure and which chemical they were exposed to.
Some chemicals are much more potent than others, such as chromium, which can cause eye and skin irritation.
How Do You Know If Your Wood Has Been Treated?
In the store, check for the end tag attached to the ends of the board.
It should state which preservatives it was treated with.
It might also have stamps or markings on the surface.
If you’re not in a store and the tags may have been removed, or the wood is older, you can smell or touch the wood briefly.
Pressured wood typically has an oily or chemical odor and can feel sticky or wet.
Treated wood usually has a greenish or brown tint to it, as well.
Pressured wood can also have half-inch splits on the side, where the preservatives were injected.
Can Chemicals From Pressured Wood Leech Into Soil And Water?
Yes, but certain factors affect the likelihood of this occurring.
Considerations such as type of wood, type of chemicals, and manufacturing process should all be taken into account.
Soil factors need to also be taken into consideration, such as soil acidity levels, soil type, and type of contact.
Because chemicals can bind to soil, they may not be able to travel far throughout the ground.
This can mean the preservatives might not necessarily reach groundwater.
The North Carolina Coastal Federation states that “toxic ash” from burning pressured wood can easily leak into the coastal salt waters creating environmental havoc.
This can cause much damage to fish and wildlife populations.
Can You Paint Pressured Wood?
Water-based pressured wood can be stained or painted once the wood is completely dry.
However, the drying process can take months even after construction.
It’s often recommended that homeowners wait at least ninety days or three months before staining or painting newly built fences or decks.
To test whether or not your treated wood is dry enough and ready to be stained, drop some water on it.
If it gets absorbed, then it’s ready to go.
If the droplets stay on the surface, the wood needs more days to dry.
Staining treated wood will help protect against splitting or warping from age, especially when the weather changes.
Staining also adds another barrier of protection from moisture, mold, mildew, insects, and decay.
Any stain for exterior use will work, but oil-based stains are a favorite for homeowners.
Oil-based stains absorb completely into the wood, allowing for the best defense against water penetration.
Clean the wood for any debris or use specially developed wood cleaners prior to staining.
After staining, allow 24-48 hours to dry.
Be sure to check the weather and make sure you allot enough dry weather time before starting.
Sealing pressured wood is a good idea, not only because it prolongs the wood’s lifespan even longer, but it helps keep the preservatives in.
This way they are less likely to seep into the surrounding soil and stay in the treated wood for a longer life span.
Oil-based pressured wood is not always paintable due to the types of chemicals used in it, so check if it is possible before attempting to stain.
What Happens If You Do Burn Pressured Wood?
Since breathing in toxic ash and smoke are both extremely dangerous, there are many health risks if this wood is burned.
The Journal of American Medical Association reported what happened when a family burnt treated plywood in their home stove that contained CCA.
According to the 1985 report, the family suffered alopecia, as well as a “variety of diverse and nonspecific complaints.”
Other symptoms included headaches, nosebleeds, fatigue, seizures, and disorientation.
If you accidentally inhale smoke or ash from burning pressured wood and start noticing symptoms like headaches or respiratory and breathing issues, it’s a good idea to seek medical help.
Burning these types of chemicals, such as arsenic, are extra dangerous because they don’t necessarily give off specific odors or taste like anything, making them harder to detect.
How Should You Dispose Of Pressured Wood?
Rules about treated wood disposal are different for every state, so you should check with your local guidelines before disposing.
However, most guidelines direct pressured wood to be disposed of in a landfill or construction debris disposal site.
Do not use treated wood as mulch or throw it in the compost either, as this can also transfer chemicals into the soil.