Deck treatments that retain their appearance the longest are the ones that are the most like paint. Widely advertised clear finishes don’t provide long-term protection.

Lumber, like skin, doesn’t fare well when it’s left unprotected. The sun’s ultraviolet rays are always on the attack. Rain and sun alternately swell and dry wood, eventually causing it to crack and split. Moisture promotes the growth of mold and mildew. Even redwood, cedar, and pressure-treated wood can benefit from a protective coat. Our tests show that many clear deck treatments usually don’t offer more than a year of protection before their appearance has visibly degraded.

WHAT'S AVAILABLE

Major brands include Ace, Behr, Benjamin Moore, Cabot, Flood, Glidden, Olympic, Sherwin-Williams, Sikkens, Thompson’s, and Wolman. There are also many smaller, specialized brands.

Clear finishes are generally water-repellent, but they don’t provide protection from ultraviolet and visible light. They let the wood’s natural grain show through but allow the wood to turn gray. Semitransparent finishes contain some pigment but still allow the wood grain to show. Opaque stains completely mask wood grain and are also known as solid finishes. Price range: $10 to just over $50 per gallon.

IMPORTANT FEATURES

Deck treatments may be alkyd-based (solvent) or latex-based (water). Most alkyd-based products require cleanup with mineral spirits, but a few can be cleaned with water. Latex-based products clean up with water. Linseed oil and tung oil, once common binders in wood coatings, have largely been replaced by synthetic resins. These new formulations are described as preservatives, protectors, stabilizers, repellents, sealers, cleaners, restorers, or rejuvenators.

HOW TO CHOOSE

Make an opaque treatment your first choice, as it retains its appearance the longest. And because an opaque deck treatment should last for two to three years, it’s also more economical in the long run. After several coatings, however, an opaque finish can build up a film layer that may require more extensive preparation--such as scraping or sanding--for subsequent coats. Special precautions, such as the use of goggles, gloves, and respirators, are necessary when scraping or sanding pressure-treated wood due to the presence of toxic substances. Consider a semitransparent treatment if you want the wood grain to show. Be aware that if you choose a clear deck treatment, you’ll likely be doing the job over again within a year.

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