Rot-resistant wood update

by Rob Yagid

More choices for durable decks

In FHB #186, contributing editor Scott Gibson reported on new preservative treatments for rot-resistant lumber. Before the ink had a chance to dry, three wood-treatment manufacturers unveiled some even newer rot-resistant wood products at the 2007 Deck Expo trade show. These new preservative treatments are more environmentally benign than chromated copper arsenate (CCA), which was banned by the EPA in 2004, and less corrosive than its replacements, alkaline copper quat and copper azole (ACQ and CA). In fact, they’re all OK to use with standard joist hangers and aluminum flashings.

The most widely available treatment, MicroPro (developed by Osmose, but used in several products), uses copper as its preservative, but in fine particles that make treated wood no more corrosive than CCA. Arch Wood Protection introduced Wolmanized L³ Outdoor Wood, which uses a combination of fungicides, insecticides, and water-repellents rather than copper compounds as its preservative, so corrosion isn’t a concern. And according to the manufacturer, the durability of L³ is similar to traditional copper-based treatments (based on seven years of testing).

PureWood, developed by Bay Tree Technologies, protects wood through a heating and steaming process. Ron Long, the president of Bay Tree, says this process changes the composition of the sugars in wood into a nonedible substance that mold, fungus, and insects otherwise would feed on.

While PureWood meets European structural standards and has a 10-year track record, it’s still in the process of being recognized by the ICC. Bay Tree’s distribution in the United States is limited.