Q: We have a much-loved deck that's about 15 to 20 years old. On a sunny Friday four years ago, I cleaned it well and stained it with a Behr product, but the stain pooled and peeled, despite my best efforts. It didn't seem to absorb into the wood very well. Home Depot suggests using DeckOver, as do Behr's folks. Do I want to go that direction? I do prefer to see the grain.

Columbia, Md.

A: For years, the best advice was to finish a wooden deck with a water-repellent finish that doesn’t form a film, because a film is likely to peel when water gets underneath — as it is sure to do on horizontal surfaces exposed to the weather. But the more transparent the stain, the more frequently it needs to be reapplied, which has led many homeowners to opt for less transparent finishes. And as manufacturers have had to reduce the solvents in their products to meet air-quality regulations, the market has shifted to water-based products, which don’t penetrate into the wood like the old oil products did.

Consumer Reports, an advertising-free magazine with testing facilities, gives its highest ratings to solid-color wood stains, which are more like thinned paint than what most people think of as wood stains. The magazine rates Olympic Elite Advanced Stain and Sealant in One Solid in first place, with a score of 80; it’s $42.98 a gallon at Home Depot. The No. 2 product, with a score of 74, is Behr Deckplus Solid Color Waterproofing Wood Stain ($30.98). Both earned “excellent” ratings for their performance after one year and “very good” after two and three years. Other categories of deck finishes fared much worse. Among semitransparent wood stains, the top-rated Behr Premium Semi-Transparent Waterproofing Stain & Sealer, a water-based formula, scored only 65. An oil-based stain, Cabot Semi-Transparent Deck & Siding, rated second, but its score was just 46. Among clear sealer wood stains, the top score was just 28.

Consumer Reports hasn’t rated the super-thick deck paints advertised as “deck restoration” finishes. Behr’s Premium Advanced DeckOver ($35.98 a gallon at Home Depot) is in this category, as are Olympic’s Rescue It ($99.98 for three gallons) and Rust-Oleum’s RockSolid Deck Resurfacer ($37.16 a gallon). These finishes are thick enough to fill cracks, sometimes ones even one-fourth of an inch wide, and they make rough wood look so smooth and freshly colored that a casual viewer might think it is newly built from a plastic-wood composite. You see no wood grain or even much of its texture.

Some homeowners have reported great results with these finishes, but there are also many reports of peeling after two or three years. In March, Behr tweaked its DeckOver formula and added “Advanced” to the product name — a sure sign that there was a need for what the label touts as “even better adhesion + cracking resistance.” If you decide to use one of these products, be aware that they are best reserved for decks that are in such bad condition that your alternative is to replace the wood. From the pictures you sent, it’s not clear that your deck is that bad.

Olympic’s website, Olympic.com, has a tool called ProjectPro that walks people through a decision tree to select the best finish based on a deck’s condition. It recommends using the thick resurfacer on a deck that is very weathered with a lot of cracks and splintering. If the resurfacer becomes gritty, you can cover it with a solid color finish but nothing else. “Stripping a previously applied resurfacer is not recommended,” it says. “Applying a resurfacer on top of a previous resurfacer is also not recommended.”

If your deck isn’t yet super rough and splintering, you’re probably best off sticking with a more conventional deck finish, such as one of the top-rated solid-color stains. At least these can be stripped and redone. If your deck is beyond that, follow all of the instructions precisely, including using the recommended prep products and procedures. You might also want to invest in two tools that can make a big difference in whether the coating sticks and holds up over time.

Behr’s website says to use DeckOver only when air and surface temperatures are between 50 and 90 degrees, but a regular thermometer won’t tell you the surface temperature, and that is far more critical than the air temperature, said Adrian Hernandez, a customer service technician for Behr. To measure surface temperature, get a tool such as the Ultra Performance Non-Contact Infrared Thermometer ($17.45 at Home Depot).

Applying the correct amount of finish is also critical. The DeckOver label says one gallon covers 75 square feet in two coats (with two coats required). But how, exactly, do you figure out whether you are applying the right amount before you finish the gallon? Electronic meters cost a few hundred dollars, but for less than $10 you can get a nifty tool called a wet film thickness gauge. The Bon 82-479 Wet Film Gauge 1-80 Mil Scale ($6.97 at Amazon) is a thin piece of aluminum with fingers calibrated in mils, or thousandths of an inch, along its edges. You press an edge into paint you’ve just applied and see where the paint touches. Behr’s consumer-focused information doesn’t specify mil thickness, but the pro section of its website, Behr.com, does. Each coat of DeckOver should be 10.6 mils thick when wet, which should dry to 5.4 mils thick.

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