Ask the Experts - Preserve® CA-C and ACQ

  • What are the similarities and differences in Viance Preserve CA and Preserve ACQ?

    Preserve® CA and Preserve® ACQ

    Preserve CA-C

    • CA-C is a copper-based wood preservative that has been used to pressure treat wood products worldwide. The first form of copper azole (CBA-A) was standardized by AWPA in 1995 followed by CA-B in 2002. CA-C was first standardized in 2009.
    • CA-C contains a soluble copper component as the primary biocide and two triazole fungicides propiconazole and tebuconazole as co-biocides to help control attack from copper tolerant fungi.

    Preserve ACQ

    • ACQ is a copper-based wood preservative that has been used effectively around the world for over 25 years and was initially introduced in 1987. ACQ was introduced to the US in 1992.
    • ACQ is composed of a soluble copper component and a quaternary ammonium compound (Quat) as a co-biocide.


    • Both are water-based wood preservatives.
    • Viance’s brands, Preserve CA-C and Preserve ACQ are both made from 100% recycled copper and are soluble formulations capable of penetrating deeper in the wood cells. Not all competitors’ products contain recycled copper.
    • Both leave a dry, paintable surface.
    • Because the appearance and performance of CA and ACQ treated wood is very similar, they have been used interchangeably in many instances. It is rare for the average consumer to notice any significant difference in appearance between CA and ACQ treated wood.
    • The EPA states, “These wood preservatives have lower toxicity profiles when compared to older wood preservatives."
    • Both preservatives meet the stringent industry standards of the American Wood Protection Association (AWPA), the leading authority on wood preservation science. Both are standardized by the AWPA for a wide variety of residential, commercial and agricultural construction projects including above ground exposed use (UC3B), ground contact general use (UC4A), freshwater immersion (UC4B), and salt-water splash applications (UC4B)
    • Both are field-tested, proven-to-last, accepted as an industry standard, and are building code compliant (IRC and IBC).
    • Both are NAHB Home Innovation Research Labs Green Certified Products for Resource Efficiency and are eligible to contribute points toward a building’s certification under the National Green Building Standard™ (NGBS).


    • The main difference between the two types of treated wood is the co-biocides that are used to combat copper tolerant fungi. Copper Azole uses a blend of azoles as the co-biocide. ACQ uses a quaternary ammonium compound (Quat) as a co-biocide.
    • The differences are few and any differences typically only affect the producers. When properly produced, the differences in the treated wood are insignificant to the point where the retailer and consumer will not notice.
    • The performance of CA treated wood and ACQ treated wood is basically equivalent when properly treated and used in the correct application. When choosing between CA treated wood and ACQ treated wood, the purchaser should consider the following:
      • Performance history of the treating company
      • Quality of the substrate treated and results of treatment
      • Support available

    Fasteners and Connectors

    CA and ACQ treated wood are in the “excellent range” as defined in the Corrosion Engineering Handbook. Viance provides the following guidelines regarding fasteners used with Preserve CA and Preserve ACQ treated wood:

    • Use building-code approved, corrosion-resistant fasteners and connectors suitable for use in pressure-treated wood.
    • For fasteners, use of hot-dipped galvanized (meeting ASTM A 153) or stainless-steel fasteners.
    • For connectors, use G185 hot-dipped galvanized connectors for exterior applications.
    • For Permanent Wood Foundations and corrosive environments, such as Coastal areas with saltwater spray, use code approved stainless steel fasteners and connectors.
    • CA and ACQ are not suitable for direct contact with uncoated steel or aluminum building products.


    Preserve CA and Preserve ACQ treated wood are covered by a Lifetime Limited Warranty from fungal decay and termite attack when installed in accordance with applicable building codes. See details of their Lifetime Limited Warranty for terms and conditions.

    More Information

    See the bulletin at this link.

    Todd Schoffstoll, Western Regional Manager

    704.340.3376 (Office and Mobile)

    Check out Todd's bio here.

    Todd Schoffstoll, Viance, LLC

  • Is an ICC ESR needed for Preserve ACQ or CA-C Treated Wood?

    An ICC ESR is not needed or required for Preserve® ACQ and CA-C pressure treated wood products if they have been treated to American Wood Protection Association (AWPA) standards. The AWPA Book of Standards are the accepted standards to meet applicable building code requirements. An ICC ESR would simply be a duplication of current practices and results.

    Preserve ACQ and CA-C pressure treated lumber are produced to the exacting standards of the AWPA Standards:

    • U1-11, Use Categories UC1, UC2, UC3, and UC4
    • M2 Standard for Inspection of Wood Products Treated with Preservatives
    • M4 Standard for Care of Preservative-Treated Wood Products
    • Preserve ACQ and CA-C preservatives meet the current requirements of the American Wood Protection Association (AWPA) P26-P29 and P48 standards respectively.
    • Preserve ACQ and CA-C meet the AWPA Standards mandated in sections 2303.1.8 and 2304.11.2 of the International Building Code (IBC),and sections 2303.1.8 and 2304.11.2 of the current California Building Code.
      • Numerous field studies and decades of commercial use have shown that material treated to the AWPA standards will provide wood structures with proper protection from rot and termite attack. An ICC ESR would yield no additional or different use information than what is currently available for Preserve ACQ and CA-C wood treated to AWPA standards.

      Preserve ACQ and CA-C treated wood that has been processed per AWPA standards are third-party inspected by an ALSC approved inspection agency. Treating plants that process Preserve ACQ and CA-C treated wood per AWPA standards are required to have an on-site quality control management program that involves inspections and quality control sampling of every production batch.

      You can assure your wood meets national consensus standards for pressure treated wood by looking for the distinctive CheckMark logo which appears on end labels or stamps on quality treated wood products (see example of CheckMark logo below). The CheckMark logo signifies that the wood has been produced under third party oversight and inspection to ensure that minimum requirements for preservative penetration, retention, and quality control have been met.1


          Todd Schoffstoll, Western Regional Manager

          704.340.3376 (Office and Mobile)

          Check out Todd's bio here.

        • Can you use pressure treated lumber for raised garden beds?
          Viance treated wood with Preserve CA for garden beds

          While there is scientific consensus that it is safe to use for vegetable/garden beds, the information in this article explains what chemicals are used in Viance ground contact treated wood for residential use and the results of numerous scientific studies. 

          The American Wood Protection Association (AWPA) specifies the use of treated lumber for horticultural purposes to be Ground Contact. In the AWPA Book of Standards, copper azole (CA) and alkaline copper quaternary (ACQ) are listed preservatives for Ground Contact use in residential applications. CA is widely available under the brand name Preserve® from 84 Lumber and independent dealers across North America.

          Continue reading scientific studies at this link.

        • Does Preserve ACQ protect against powderpost beetles?

          This question comes from a homeowner in Washington state.

          Based on a study performed by the International Research Group on Wood Preserveation, ACQ is effective in protecting wood against the Powderpost beetle.

          Michael Merchant, Ph.D., Professor and Extension Urban Entomologist, with Texas AgriLife Extension Service states, "The most commonly infested woods include ash, oak, hickory and walnut." He also explains in an article on the Texas A& M website, that powderpost beetles pose little threat to the structural integrity of most homes because they are framed with softwood lumber, and thus not susceptible to attack. Removing infested wood and replacing it with treated wood will eliminate the problem in most cases.

          Aaron Sooter, Technical Services Representative

          Aaron Sooter