Painting treated lumber
About six months ago I built a porch from pressure-treated lumber. I would like to know the best way to prime and paint—not stain—the treated wood.
Kenneth Finney, Pittsburgh, PA
Bill Feist of the Forest Products Laboratory at Madison, Wisconsin, replies: Generally, treated wood (usually CCA, which stands for chromated copper arsenate—the green stuff) can be finished just like untreated wood. The only requirements are that the wood be clean and dry. It isn’t normally necessary to let the wood weather for six months or a year, as is often heard; treated wood just needs to be thoroughly dry for painting.
Because your treated wood has weathered for so long, I suggest you give the wood a good scrubbing with a stiff-bristle brush, detergent and water. Be sure to rinse thoroughly and then let the wood dry for two days.
For the handrails and spindles of your porch, I suggest a stain-blocking acrylic latex primer followed by two coats of acrylic latex semi-gloss house paint. For the porch floor, I suggest the stain-blocking acrylic latex primer followed by two coats of an acrylic latex semi-gloss porch and deck enamel.
It’s important to know that the woods that are CCA-treated (for example, southern pine) don’t have very good paint-holding characteristics, even before they are treated. Research has shown that the all-acrylic latex paint systems give much better performance on woods that don’t hold paint well because acrylic paints stay flexible and do not get brittle as do the oil-based or alkyd paints.