July 2, 2013
I think this will depend on your individual circumstances. If you have trees overhanging your deck, you will probably have to clean more often, as leaves leach pigment into wood. Also, shady areas trap more humidity and stay moist longer, which breeds algae and mildew. Application in sunny areas will probably look clean longer, as the sun naturally bleaches wood. About a month ago, I cleaned my deck, which gets early morning sun and is shaded all afternoon, with trees nearby but not directly overhanging. I had nine years of algae, mildew, and dirt on weathered, untreated wood. Currently, it still looks like I just cleaned it. My wood really looks brand new at this point, but when the leaves come down this fall, I would expect they will begin to stain the wood with those pretty orange, red, and yellow pigments, so I plan to apply a stain. Behr has indicated that their stains self seal, so there's no need to apply a separate sealer after staining. The Behr Deckover product is another option that will even seal cracks but it covers the wood grain, so if you like to see the beauty of the grain, you can stain. Another option is to clean your wood and simply apply a clear polyurethane wood sealer so you can keep that clean look longer. I have asked Beher several questions via their website and they have responded to my questions very quickly. I've been impressed by their helpful advice and I love, love, love their deck cleaner product.
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