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Forest Products Extension

New wood-protection treatments

Wood products that are used outside are exposed to a variety of hazards that can greatly reduce their service life. This is especially true in Tennessee , where wood-eating termites are prevalent and the mild climate is favorable to the wood-rotting fungi.

Preservative chemicals are often added to wood products to deter wood-destroying organisms and thus increase the usefulness of wood products. To achieve the highest levels of protection, the chemicals are forced deep into the wood using a pressure treatment cycle. Southern pine poles and structural lumber are very well suited to this purpose, because they have large amounts of easy-to-penetrate sapwood. Creosote and pentachlorophenol are two effective preservatives that are used to protect utility poles and railroad crossties. Unfortunately, these chemicals are carried in an oil solvent that makes the treated wood unsuitable for applications such as residential decking and fence boards, where people frequently come into contact with the wood.

Chromated copper arsenate (CCA) is a clean, waterborne wood protection system that has a long history of excellent performance. The copper, chromium and arsenic components of this system bind to the wood chemically, ensuring that the treatment stays in the wood. The result is treated-wood products that remain protected after many years in service and are safe for human contact.

Many people are familiar with CCA-treated wood. It is the relatively inexpensive, green-colored wood that has been a popular choice for building decks and fences over the past twenty years. Recently however, amid general concern over the presence of arsenic in the environment, the manufacturers of wood preservatives voluntarily withdrew CCA from use for residential treated-wood products (i.e. decking and fencing). A variety of other waterborne chemicals have been introduced to take the place of CCA. These products are also green in color and contain copper, but they do not contain arsenic. The new formulations do not yet have the proven history of CCA, but they should provide years of safe and effective performance.

Forintek and the Canadian Wood Council have an informative site about wood treatments. Click here for more...

Adam M. Taylor
Tennessee Forest Products Center
2506 Jacob Drive
Knoxville, Tennessee 37996

Phone: 865-946-1125
Fax: 865-946-1109

Adam Taylor's email