As of January 2004, there was a change in the chemical preservatives used for pressure-treated lumber available for residential use in the United States. Up until that time, almost all pressure-treated Southern pine lumber was preserved with Chromated Copper Arsenate (CCA), which contains arsenic, a known carcinogen. With this new change in place, all pressure-treated lumber manufactured for residential use (and available to the general public) after January 2004 has been treated with different chemicals. The new pressure-treated lumber is preserved with Alkaline Copper Quaternary (ACQ), also known as Copper Azole (CBA). Both of these chemical treatments are to have fewer environmental and health risks, but they’re also more corrosive to nails, screws, and any other metal fasteners that come in contact with lumber.
You’re now probably wondering how you’re supposed to use ACQ Lumber for your new pole barn or post-frame building. We’ll explain the differences between the two lumber preservatives next.
What is ACQ lumber, and how is it different from CCA?
Chromated copper arsenate (also known as CCA) is a wood preservative that has been used for timber treatment since the mid-1930s. It is a mix of chromium, copper, and arsenic formulated as oxides or salts, and is recognizable for the greenish tint it imparts to timber. Alkaline Copper Quaternary (also known as ACQ) is a water-based wood preservative method recently introduced in countries where there is a demand for alternatives to chromated copper arsenate (CCA).
Is CCA Lumber Still Available?
Although existing stocks of CCA-treated lumber continued to be sold, all pressure-treated lumber manufactured for residential use and available to the general public after January 2004 has been treated with different chemicals. One of the new pressure-treated lumber uses the preservative Alkaline Copper Quaternary (ACQ).
CCA-treated lumber is still manufactured and sold for certain industrial and marine applications, including agricultural posts and poles, and some builders prefer CCA lumber for poles and posts. However, a considerable amount of ACQ lumber is being used, including posts and dimension lumber (2x4, 2x6, etc). You can almost guarantee that any pressure-treated lumber that you buy from a lumber yard today is not the CCA lumber that we’ve all been familiar with for so many years.
This is why it is extremely important for you (as the buyer of a new pole barn) to know what type of lumber is being used in your building and where. If problems were to arise, would you know what steps to take to get them solved?
What Does More Corrosive Actually Mean?
It means that most of the fasteners commonly used in the past, whether galvanized or not, are likely to be corroded by the chemicals in ACQ lumber at a higher rate than in CCA-treated lumber. Using the wrong fasteners could have an adverse effect on the structural performance and service life of the post-frame building, or any type of building for that matter.
When you’re choosing a professional builder to put up your new farm shop or pole barn garage, it’s perfectly normal to question them about what types of fasteners they will be using in your building. This is one topic that they should be knowledgeable about and be able to explain the difference to you as to why they use certain nails and screws over others.
Should You Be Concerned About CCA Wood?
According to the EPA, one of the major health concerns about CCA wood is the daily, long-term contact with arsenic leached from CCA-treated wood, which might lead to an increased risk of lung, bladder, skin, and other cancers or other health effects.
A draft EPA study released in November 2003, young children who regularly came in contact with CCA-treated wood have a risk of cancer that is greater than 1-in-1-million, which is the EPA's threshold of concern for the effects of toxic substances. Children in warm climates who play both at home and at school on treated decks and play structures have a risk of 1-in-100,000 of contracting cancer. The risk is also increased for children who frequently put their hands in their mouths as they play.
This study is still under scientific and public review. For additional information, see the EPA, Chromated Copper Arsenate (CCA): Questions and Answers.
Currently, the EPA does not recommend that people remove existing structures made with CCA-treated wood or the soil surrounding those structures. However, they do recommend that people reduce their potential exposure to arsenic.
Touching arsenic-treated wood is not considered a significant health hazard; ingesting it is the main concern. Many children put their hands in their mouths, and their hands may have arsenic on them if they play on CCA-treated wood structures. Tests have shown that the arsenic comes off the wood, whether it is wet or dry.
Even old playground equipment may still have high levels of arsenic. The soils below decks and play structures can also become contaminated. To be at risk of long-term health effects, a person would have to actually eat the soil or put wood chips in their mouth.
When is it Safe to Use ACQ Treated Wood?
ACQ preservatives penetrate into and remain in pressure-treated wood for a long time. However, some preservatives may migrate from the preserved wood into the surrounding soil over time, and there may be incidental contact with the skin during construction or use.
Follow the safe practices listed below when working with pressure-treated wood. Specific work practices may vary depending on the environment and safety requirements of individual jobs.
Use
- Wood pressure-treated with ACQ preservatives may be used inside residences as long as all sawdust and construction debris is cleaned up and disposed of after construction.
- Do not use treated wood under circumstances where the preservative may become a component of food or animal feed. Examples of such sites would be structures or containers for storing silage or food.
- Do not use treated wood for cutting boards or countertops.
- Only use treated wood that's visibly clean and free from surface residue for patios, decks, and walkways.
- Do not use treated wood for the construction of those portions of beehives that may come in contact with honey.
- Do not use treated wood where it may come in direct or indirect contact with public drinking water, except for uses involving incidental contacts, such as docks and bridges.
- Do not use treated wood for mulch.
Handling
- Wear gloves to protect against splinters.
- Wear a dust mask when machining any wood to reduce the inhalation of wood dust. Avoid frequent or prolonged inhalation of sawdust from treated wood. Machining operations should be performed outdoors whenever possible to avoid indoor accumulations of airborne sawdust.
- Wear appropriate eye protection to reduce the potential for eye injury from wood particles and flying debris during machining.
- Wash exposed areas thoroughly with mild soap and water after working with treated wood.
- If preservatives or sawdust accumulates on clothes, launder them before reuse. Wash work clothes separately from other household clothing.
Important Reminders
The switch to ACQ-treated lumber may be a good move for a safer environment, but problems with the structural stability of the buildings could result if the proper fasteners and connection materials are not used in conjunction with the newly treated lumber.
The building industry now recommends that fasteners or other metal contacting the lumber either be treated with the heaviest galvanize possible, be ceramic coated, or be type 304 or type 316 stainless steel. It’s important to know that you never want to mix galvanized and stainless steel in the same connection.
No fasteners should be used unless they are clearly labeled as approved for use with ACQ-treated lumber. Your local lumber supplier should have a list of fasteners that are approved for use with ACQ-treated lumber by brand name and type.
It is imperative that your builder understands the fastening requirements to follow when ACQ lumber is used. It is also imperative for you as the owner to understand the consequences of using the wrong fasteners.
For more information, check out the following websites:
References:
Alkaline Copper Quaternary - ACQ
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