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Alternatives to CCA-Treated Lumber Raise Corrosion Concerns

Manufacturers voluntarily reached an agreement with the EPA to phase out by the end of this year CCA-treated lumber for such residential applications as fences, decks, sill plates and playground equipment. The biggest fear was that small children could be exposed to arsenic poisoning on playground equipment constructed of CCA-treated lumber, although no link between the two has been discovered to date.

Several alternatives to CCA have been used in other countries for a number of years, including ACQ (ammoniacal copper quat), CBA and CA (copper azole) and SBX (borate oxide). Builders will recognize lumber treated with these alternatives in such product lines as NatureWood, Wolmanized Natural Select, AdvanceGuard and SmartGuard.

While corrosion of connectors and fasteners used with pressure-treated lumber, including CCA, has always been a concern, laboratory tests have found higher corrosion rates for lumber treated with ACQ, CBA and CA.

Part of the problem is that fasteners and connectors are being used with treated lumber other than products made of stainless steel or hot-dipped (not electroplated) galvanized steel, contrary to the recommendations of manufacturers.

Although it is expensive, stainless steel is effective in combating corrosion from ACQ, CBA and CA. If galvanized steel is used, thicker coatings will probably be needed.

How much more these alternative chemicals will increase the corrosion of galvanized steel connectors and fasteners is not fully known because many factors are involved, including the thickness of the galvanizing, the species and moisture content of the wood, the chemical treatment used and the exposure of the materials.

The American Wood-Preservers' Association (AWPA); the International Staple, Nail and Tool Association (ISANTA); and members of those two groups are researching this issue and working to develop improved fastener and connector products. Standards for these products are also being reviewed and updated for their use with the chemical treatments that are replacing CCA.

NAHB staff is currently evaluating guidance on this issue for builders, and the information will be made available to all NAHB members when the evaluation is completed.

Until then, builders who are using lumber treated with alternative chemicals should check with the connector or fastener manufacturer for guidance.

For further information, e-mail Jeff Inks or call him at 800-368-5242 x8547.

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