Abstract
Wood is one of the most versatile and widely used building materials. However, it is also biodegradable and may be attacked by decay fungi or insects when used in some applications or geographic locations. Uses that allow the wood to frequently become wet, such as embedded posts or other exposed wood members, are familiar examples of applications where wood will degrade. Although moisture is the key to deterioration of wood, in some geographic locations there are insects that will even attack dry wood used indoors. Because it is biodegradable, wood used in applications where it may be attacked by decay fungi or insects should be protected by pressure treatment with preservative chemicals. Wood preservatives are broadly classified as either water-based or oil-type, depending on the chemical composition of the preservative and the carrier used during the treating process. The most common oil-type preservatives are creosote, pentachlorophenol, and copper naphthenate. The oil-type preservatives are commonly used for applications such as posts, poles, piles, and glue-laminated members. They are not usually used for applications that involve frequent human skin contact or inside dwellings because they may be visually oily, oily to touch, or have a strong odor. Water-based preservatives have become more widely used in the recent years because the treated wood has a dry, paintable surface, and no odor. The most common of these preservatives has been chromated copper arsenate (CCA). CCA-treated wood, commonly called “green-treated” wood has dominated the residential market for several decades and is sold at lumberyards under a variety of trade names. CCA-treated wood has also been widely used in post-frame building applications. However, as the result of the voluntary label changes submitted by the CCA registrants, the EPA labeling of CCA will permit the product to be used primarily for industrial applications. The label change went into effect December 31, 2003, although suppliers were allowed to sell existing stocks of CCA-treated wood after that date. This recent development has raised questions about the availability of CCA- reated wood and the properties of alternative types of treatments.
Keywords
CCA,
wood preservatives,
treated wood
Citation
Lebow, Stan; Winandy, Jerrold; Bender, Donald. 2004. Treated wood in transition : a look at CCA and the candidates to replace it. Wood design focus. (Summer 2004): Pages 3-8
