Wood Treatment

Because wood is an organic material it is subject to decomposition which destroys its integrity. This is not important on the inside of a home because the atmosphere is, for the most part, sealed off from the elements. On the outside, however, where moisture can collect on wood and get between the cracks, a treatment has be applied to preserve the wood.

There are three basic methods of wood treatment carried out in today’s market: pentachlorophenol pressure-treatment, creosote pressure-treatment and inorganic arsenical pressure-treatment.

The most popular treating is chromated copper arsenate (CCA). Despite the “arsenic” in its name the chemicals in the wood are inert but still offer great protection from water and decay. As with many pressure-treated products the ends should be dipped in the solution when cut. Since copper is the main insecticide and fungus killer the EPA is putting cautionary labels on this preservative and deems it unsuitable for inside the home.

Research into less toxic have found that the use of boron (borax) derivatives offer protection from insects and have fire retarding abilities. Full-scale commercial introduction of borates in the U.S. awaits resolution of the leaching problem of borates. The downside is that borates are water soluble and can leech out in wet areas. Ammoniacal copper quatenary (ACQ) is another new wood preservative. The preservative components are listed as “General Use” pesticides.

If you are building a deck you can use borate treated wood and even apply it yourself. However it’s good to use a deck stain or a water seal after the solution has dried in the wood.