Just because you used pressure-treated lumber doesn't mean your outdoor project has to stay green. Not only can you can stain treated wood, you should stain treated wood. Here are some tips.
Green-treated wood lasts a long time—and it's ugly. So, if you build, say, a deck out of green-treated wood, it'll be ugly for a long time. What can you do? Stain it.
Not only can you stain treated wood, staining is actually good for your new deck. Although the treated wood doesn't need to be protected against rot, staining it will help reduce surface cracking.
The kind of stain you put on your deck and when you apply it depend on the type and condition of your treated wood. There are three basic categories of green-treated, or Wolmanized, lumber. (Wolmanizing is a patented manufacturing process.)
Wet treated wood: The most common kind is still wet when you buy it. It'll be noticeably heavier than kiln-dried lumber. It may even “spit” at you when you nail it down. Let this lumber dry out (from a few weeks to six months, depending on the weather and the condition of the lumber) before applying any stain.
Treated wood containing water repellent: Manufacturers sometimes add a water repellent to their lumber. Look for a tag that says Thompsonized or ask the dealer if your lumber is this type. If you buy this type, make sure you use an oil-based exterior stain. A water-based stain won't adhere well, because of the repellent.
Kiln-dried after treatment: Dry treated wood is ideal because you can confidently stain it right away with either oil- or water-based exterior stains. To recognize it, look for a tag or stamp that says KDAT (kiln-dried after treatment) or ADAT (air-dried after treatment).
Use an oil-based, semi-transparent exterior stain if you can't determine how your lumber was treated or what its moisture content is.
If you're unsure of the type and condition of the wood, have its moisture content tested by the dealer (less than 12 percent is ideal) and use an oil-based, semi-transparent exterior stain. Solid-color stains and paints don't usually work as well on the deck floor, because they can peel and are difficult to maintain. You should be able to find stains specifically designed for treated wood decks at most home centers.