A. Tim Uhler, a lead framer for Pioneer Builders in Port Orchard, Wash., responds: Unlike the CCA (chromated copper arsenate) material they've replaced, the new pressure-treating chemical compounds — ACQ (alkaline copper quat), ACZA (ammoniacal copper zinc arsenate), CA (copper azole), and CC (ammoniacal copper citrate) — are very corrosive. Since conventional fasteners aren't compatible with this current crop of pressure-treated lumber, you'll need to use either hot-dipped galvanized or stainless steel fasteners.
Because my crew frames new homes, this issue affects how we fasten joists, rims, and sheathing to treated mudsills. Our initial response was to switch to hot-dipped galvanized stick nails when we were working with mudsills (stainless steel fasteners are just too expensive), but it's a big hassle to change fasteners every time you want to nail...
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