Reconsidering Rot-Resistant Framing Material
Copper- and borate-based preservative treatments have proven effectiveness, but structural plastics are more durable.
Synopsis: When copper chromated arsenate (CCA) was eased off the market at the end of 2003 due to fears about its toxicity, builders needed to find new sources for rot-resistant structural lumber. As contributing editor Scott Gibson has discovered, the industry has responded by developing three new types of rot-resistant framing materials. The new materials include lumber treated with alkaline copper quaternary (ACQ) or copper azole (CA); wood treated with borate, a naturally occurring mineral salt; or fiberglass-reinforced plastic lumber (FRPL), made from recycled plastics. The article includes a sidebar about new compounds and organic treatments in development.
For 60 years or so, a compound called chromated copper arsenate (CCA) successfully protected structural lumber from the harmful effects of weather, bugs, and microbes. Eased off the consumer market at the end of 2003 due to concerns about its toxicity, CCA was replaced by two other compounds also rich in copper but…