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The FAQ`s of ACQ Treated Lumber

Update: Since this article was originally published in 2004, ProWood Micro CA treated lumber has become the primary alternative to CCA treated lumber.

Why is CCA lumber no longer being sold?
In early 2004, Sutherlands, along with most other retail lumber dealers in the United States, began phasing in ACQ (Alkaline Copper Quaternary) lumber to replace CCA & Wolmanized® treated lumber, which are no longer being manufactured for residential use. The Preservative manufacturers are voluntarily taking this action based on negative public perception of CCA, media coverage and growing consumer interest in using an alternate wood preservative.

What is ACQ Lumber?
ACQ is a copper based preservative system that is the most cost-effective alternative to CCA. ACQ has been researched and tested since the late 1980s. It was introduced commercially in 1992. ACQ provides dependable performance and is building code compliant (Acrobat Reader Required NER 628). It treats a wider range softwood lumber species, and is quality assured by a third party (TPI or SPIB). Like CCA, it is treated against decay and insect damage.

What is ACQ lumber approved for?
ACQ is ideal for structural uses, sill plates, outdoor furniture, playground equipment, patios, decks, garden edging and landscaping structures. The preservatives in ACQ products meet American Wood Preservers Association standards.

Are there different grades of ACQ lumber?
Yes. The same formula used for CCA lumber applies to ACQ treated lumber for the following applications:

  • Above Ground (.25)
  • Ground Contact (.40)
  • Fresh Water Contact (.40)

Can I use the same metal fasteners used for CCA lumber?
The chemicals used in ACQ will corrode ordinary galvanized fasteners, therefore special consideration must be taken when working with ACQ lumber. Hot dipped or stainless steel fasteners MUST be used with ACQ.

The two most important things to remember when selecting deck fasteners, framing nails, decking nails or screws are: (1) holding capacity, and (2) resistance to corrosion. Using the wrong fasteners can compromise the appearance, longevity, and safety of an outdoor project.

Many fasteners traditionally used with treated lumber are no longer recommended for this application. Dacrotized, electroplated, brass, and aluminum fasteners should not be used in treated lumber when the appearance of rust or the likelihood of corrosion is unacceptable.

Hot Dipped Galvanized - Fasteners galvanized to meet ASTM A 153 class D are acceptable for use with treated lumber. It is important to point out that galvanized fasteners are rust-resistant and not rustproof; there is no guarantee that these fasteners will remain rust-free.

PrimeGuard +10-Coated® This is a patented coating that carries a 10-year guarantee against rust and corrosion when used with treated lumber. For maximum performance we suggest PrimeGuard Plus Stainless Steel or PrimeGuard Plus coated fasteners. PrimeGuard Plus Exterior Fasteners are a complete line of premium fasteners for all outdoor projects, and available at most Sutherlands retail locations. All PrimeGuard Plus fasteners are guaranteed not to rust or corrode.

The following products are available at most Sutherlands locations for use with ACQ products. Manufacturers recommend these lines of product to be used with ACQ treated lumber:

Please note: One-half inch (12.7mm) or greater steel bolts are acceptable and do not require special coatings.

Aluminum should NOT be used in direct contact with ACQ preserved wood. Spacer materials or some other physical barrier are recommended to prevent direct contact. A poly barrier is recommended for any applications where ACQ will meet aluminum flashing. Do not use aluminum fasteners.

Will ACQ lumber look the same as CCA?
When purchased, freshly treated ACQ is normally a green color like CCA. It will weather to a tan/brown color in months and eventually weather to gray over time.

For more information about ACQ lumber, check these other resources:
Universal Forest Products (
Simpson Strong-Tie

Sutherlands® provides these project tips and guides as a service to our visitors. Due to possible variance in conditions, equipment, materials and individual skill levels, Sutherlands® assumes no responsibility for losses or injuries incurred during maintenance or repair of your property. Sutherlands® assumes no liability for errors or omissions in the Resources section of this website. Please read and follow any safety precautions provided by tool and equipment manufacturers, and consult a building professional in your area if you have any questions about a repair project. Always check your local codes before building, and obtain the required building permits.