Much ado about nailing Corrosion

and the neYv treatments

By Huck DeVenzio Arch Treatment Technologies

lat ONTRACTORS. manufactu rers. \-rand even consumer media have expressed confusion and concern over the proper fasteners to use with "next generation" types of preserved lumber. The hubbub has reinforced two points that are commonly known but also commonly overlooked:

1. Change often brings confusion, whether warranted or not.

2. Follow recommendations and you'll avoid problems.

The copper-based preservativescopper azole and alkaline copper quaternary-protect wood effectively, but the treated wood is somewhat more corrosive to hardware than is CCAtreated wood. After 30 years and countless installations, contractors have come to know well the characteristics of CCA-treated wood and to recognize applications where they could get satisfactory results using inexpensive hardware. The introduction of the newer products erased historical expe- rience and, as change often does, brought doubts and questions.

An article in Rural Builder noted. "The jury seems to be out on the kinds of nails you need to be using with treated lumber." However, this article appeared in January of 1987. It reported on the preservative switch from CCA salts to CCA oxides, and noted that different hardware was necessary for each. Similar statements probably accompanied previous preservative changes, so it is not unusual that corrosion concerns are being heard now.

Most concerns are covered in published hardware recommendations. While responsible preservative producers are reluctant to endorse specific fasteners, since preservative companies do not monitor hardware production, and responsible hardware manufacturers do not endorse brands of lumber, since they do not monitor treating processes, both groups know their own products and have provided information to guide contractors.

For example, the producers of Wolmanized Natural Select wood say in literature and on their Web site: "Use hot-dipped galvanized fasteners (meeting ASTM A 153) and connectors (ASTM A 653 Class GI85 sheet), or better, for protection against the effects of moisture often present where treated wood is used."

They go on to advise against contact with aluminum ("When using aluminum, a protective physical barcier should be used to separate the aluminum from the wood.") and suggest stainless steel for certain applications ("For Permanent Wood Foundations, use 304 or 316 stainless steel hardware.") In corrosive environments, such as areas with saltwater spray, stainless steel may be advisable.

Licensors of other next generation brands have recommendations that are virtually identical. As does Fine Homebuilding: "Perhaps the most important point to keep in mind relating to copper-based wood treatments and galvanic corrosion is to avoid aluminum flashings altogether. Aluminum corrodes quickly in the presence (Please turn to page 50)