Different types of finish have varying lifespans
Q: I have a treated wood deck about 10 years old and I am tired of messing with it every year or so to keep it looking good. Can I paint it to get a lasting finish? What other choices do I have?
— P. Collins
A: You should be able to paint it, but paint isn’t considered a good finish for treated- wood decks and is seldom used. In many cases, paint results in more maintenance issues than you might already have, though you don’t mention what finish it is ( that finish would have to be completely removed before painting).
If you have done any exterior painting, you probably know that paint is subject to mildew and mould, that it can peel, flake and chip and that it can wear away rather quickly in traffic areas. I have some treated- wood steps that are painted with top- quality porch- and- deck paint, but have to be repainted every few years. The vast majority of wood decks are finished with one of four finishes: Solid- colour stain ( also called opaque stain), semitransparent stains, toner ( a lightly tinted stain) or a clear sealer. All of these finishes provide some protection against water penetration into the wood, which can lead to cracking, mould and other problems.
Solid- colour stains usually hold up longest, typically about eight years if a high- quality stain is properly applied and maintained, but these stains are much like paint and are subject to the same problems. Solid- colour stains completely hide the wood grain but let the texture show through; since they have the most pigment to screen out ultraviolet rays of the sun, they can protect wood better from surface damage than other types of stains. Semitransparent stains, with less pigment, give some UV protection but won’t last as long, typically two to four years. Many deck owners prefer semi- transparents because they let the wood grain show through and are less likely to peel because they penetrate the wood better. These stains are sometimes recommended by experts as the best finish for treated wood.
Toners have little pigment and provide little UV protection; the wood is clearly visible through the stain and the lifespan is sometimes no more than a couple of years. Some pricier clear sealers have additives to give UV protection, but these finishes usually have the shortest life of any deck finish, sometimes only a year or two, although some manufactures might promise more. Finally, some deck owners don’t use any finish at all, leaving the wood bare. This is usually a mistake, since the wood is subject to all types of damage from sun and water.