Spring Cleaning for Deck
Photo: Kristine Larsen
The best way to keep a freshly cleaned deck from becoming gray is to give it a coat of a penetrating finish, such as the semitransparent stain shown above.
Q: Our 19-year-old cedar deck has no finish on it and is looking gray and dingy. Last summer, my wife managed to scrub off the dirt but not the gray. Now it's my turn. What should I do this year?

—Jeff Sherman, Woodbury, Conn.

A: Kevin O'Connor replies: According to Ed Burke, eastern regional representative for the Western Red Cedar Lumber Association, you'll have to clean it again, then sand it to get rid of the gray. He recommends doing your cleaning early in the spring when the weather is cool, because washing a deck in summer heat puts a lot of stress on the wood. "You may not want to be out there with a hose when it's cold, but that is absolutely the best time to clean a deck."

He recommends using an oxygenated-bleach cleaner; chlorine bleach, even when diluted with water, is too hard on the wood. He also cautions against using a power washer, for the same reason. A soft scrub brush works fine. Before you start, test the cleaner's strength in a small area first. It should kill the mildew and remove the dirt in 10 to 15 minutes. If it takes longer than 15 minutes, the mix is too weak; if it takes less than 10 minutes, the mix is too strong.

You can sand the cedar when it's dry. For this project, This Old House general contractor Tom Silva would rent a four-head random-orbit sander with 80-grit paper and use a handheld random-orbit sander along the edges. (Sanding pressure-treated wood requires taking special precautions; check the EPA guidelines.)

Before you start, make sure every exposed screw or nailhead is safely below the wood surface. Sand lightly, and stop as soon as the gray is gone. Vacuum up all the sanding dust, then apply a semitransparent stain, which should protect the wood for about three years, depending on sun exposure.
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