Pressure-Treated Wood Key Terms

Investigate pressure-treated wood key terms before you buy

By Steven A. Ottem

Concern about pressure-treated wood stems from environmental and health issues. Consumers worry about how the chemicals used to treat the lumber affect their health. They want to know whether the chemicals will permeate their home if this type of wood is used to build a deck, or whether a playhouse made of treated lumber will be safe. You will also want to know how effective the pressure-treatment will be and how long you can expect the pressure-treated lumber to last. Being familiar with the pressure-treated wood key terms will be a big help as you research, buy and install the materials for your project.

CCA

Chromated copper arsenate (CCA) is the big name in pressure-treated wood. Manufacturers still use the chemical to treat wood used for power poles, bridge pilings and other outdoor products not used in close proximity to people. The chemical is toxic to humans, because chromium can adversely affect breathing passages and lungs, and arsenic is a deadly poison.
Try: New York State Department of Environmental Conservation is one of many sources that discusses the toxicity of CCA, its uses and its restrictions.

ACQ

Alkaline copper quat (ACQ) replaces CCA as a pressure treatment for preserving wood that will be near living environments. Quat stands for quaternary ammonium compound. Most oversight agencies consider ACQ safe for use in residences or playground equipment.
Try: US Forest Service lists safe alternatives to CCA as a method of pressure-treating wood, including ACQ. The text features variations, uses and compatibility of ACQ.

ANSI

The American National Standards Institute sets voluntary standards for products manufactured in America to make American companies competitive in the global marketplace. ANSI accredits other institutions, such as the American Wood Protection Association, which sets standards for pressure-treating wood products for the purpose of preserving and protecting structures from damage from insects or weather.
Try: Go to American National Standards Institute to find out more about how the institution operates. Techstreet provides a link to AWPA and explains its association with ANSI.

Retention level

Retention level refers to the amount of preservative treatment that stays in the wood after the completion of the treatment process. Manufacturers indicate this amount in weight per cubic feet. Harsher conditions require a higher retention level. Retention level varies for each product used to pressure-treat wood.
Try: For a good explanation of retention level, go to Simpson Strong-Tie. There you'll also find the different types of chemicals used to treat wood and the types of wood used for pressure treating.

Incising

Incising refers to a method of improving the penetration of preservatives in pressure-treated wood. It involves cutting slots in the surface of the timber prior to placing it in the pressure-treating chamber.
Try: The USDA provides a link to a PDF file of an article that explains the effects of incising on pressure-treated wood.

Hot-dipped galvanized

Any discussion of pressure-treated wood will include the term hot-dipped galvanized and stainless steel, because these are two metals recommended when using fasteners in contact with pressure-treated wood. Other metals will react with the ingredients of the preserving process and deteriorate and fail over time. Regular galvanizing provides some protection, but will also fail sooner than the hot-dipped method.
Try: Voigt & Schweitzer describes the process of hot-dip galvanizing and includes a video illustrating the process. For a list of recommended fastener materials, see Universal Forest Products.