Expert Answers: Fix a Failing Deck Finish

How do you get a failing deck finish to last longer and look better? HANDY has the answer.

Q: I built a deck of green-treated wood and stained it with a gray-tinted decking stain, which peels and has to be reapplied every year. How can I get a finish to last longer? - Handyman Club member Hal Matheson, Selkirk, Manitoba, Canada

A: Although finishing a deck is considered an elementary DIY project, many factors can lead to failure. A peeling finish is one of the most common disappointments homeowners encounter — despite their sincere efforts to properly preserve and maintain their decks. For a lasting remedy, first identify the cause of your deck's peeling problem. Here are some possible culprits:

Moisture content — New wood naturally contains some moisture, but pressure-treated wood (which has been saturated in a preservative) is often still quite wet when sold. If you apply a finish to the wood before it is dry, the trapped moisture eventually pushes its way through, causing the finish to peel. Recommended wood-drying times vary, ranging from "Stain it immediately" to "Wait until next year." The correct answer is, "It depends." What has the weather been doing? Is the deck in the sun or shade most of the day? Has it been pressure-washed? (This can drive water deep into the wood cells, especially if the pressure was too high or the sprayer was too close to the wood.) Check the wood's dryness with a moisture meter, aiming for a reading below 15 percent. Or you can use a less scientific approach: Drizzle water on the wood; if it absorbs quickly, the wood is dry.

"Polished" wood — New wood often has a mill glaze (or sheen) from the machining process, which impairs stain absorption. You can open the pores by rough-sanding the surface with 60-grit sandpaper or by cleaning the wood with a deck cleaner and then applying a deck brightener to neutralize it.

Stain choices — As always, the type of stain and its quality make a big difference to the outcome. Use only decking stain (not siding stain); it's formulated to endure foot traffic, moisture and direct sun exposure. Although pigments aid in UV protection, you should stick with a lower-pigment (transparent or semitransparent) stain, which doesn't create a film on the wood's surface.

Unfortunately, the peeling base that remains will continue to peel. For long-term ease of maintenance, you'll need to remove the peeling finish by sanding with coarse-grit sandpaper or by applying a deck-stripping product. Make sure the wood is dry before sealing it with a high-quality deck stain. You'll still have to clean and stain your deck every couple of years, but the process will be easier and the results more satisfying. - HANDY