Treating Pressure-Treated Lumber
Q: If I cut through pressure-treated lumber, should I treat the exposed wood?
When I cut through treated lumber, should I be putting something on the freshly exposed wood?
—Frank Scott, Vienna, VA.
Tom Silva replies: Field treating, as it's called, is a good idea because the treatment doesn't always penetrate completely. Some manufacturers even require field treating to maintain the product warranty, so check with your lumberyard when you buy it.
Coatings for field treating, available at home centers, should contain at least 1 percent copper naphthenate, although some manufacturers specify a 2 percent minimum for their lumber. Brush or dip all cut edges, as well as any holes larger than about ¾ inches in diameter. This extra step will go a long way to protecting your projects from decay.