Q: How long do I need to wait before painting or staining pressure-treated wood?
Let’s talk. Though pressure-treated wood has existed commercially since the 1940s, a lot of us don’t know precisely what it is. To start with, pressure-treated wood is a kind of softwood lumber that’s been chemically treated to resist damage from insects, rot, and decay—making it ideal for outdoor use. But given that it has been saturated with chemicals, it’s also a fairly “wet” wood. That means that, for all its benefits, pressure-treated wood happens to be resistant to paint, and you have to approach painting it much differently than you would other kinds of lumber.
The first step is good-sense prep work: clean the wood with a stiff-bristle brush and soapy water, then rinse the wood and let it dry thoroughly. When we say “let it dry thoroughly,” be patient: the drying of pressure-treated wood can be a protracted process, in the vicinity of several weeks or even a month. You’ll know it’s ready when the wood not only feels dry to the touch, but when you can sprinkle a little water on it and watch it soak in. If the water beads on the wood, though, you’ll have to hold off on painting.
Once the wood is dry, the primer goes on. Make sure the manufacturer’s label approves your chosen primer for pressure-treated wood, and be advised that the primer shouldn’t take more than a day to dry. You can then move on to the topcoats (very likely two of them), and if you can use latex paint here, you’ll thank yourself, as oil-based paint is far less effective on pressure-treated wood.
Should you instead want to stain your pressure-treated wood, your safest bet will be an oil-based, semi-transparent exterior stain. Color stains also work, but they’re more likely to peel. The process of cleaning and prepping the surface is similar to painting; just remember to stain in the direction of the wood grain. Generally speaking, pressure-treated wood doesn’t really require staining, as the chemical treatment is explicitly meant to provide protection against the elements. Still, whether you’re painting or staining, a nice topcoat can add a lot of character, panache, and sleekness to your outdoor wood.