Avoid Annual Deck Cleaning

Cleaning pressure treated lumber is not rocket science. Just use common sense.

DEAR TIM: My husband and I have a problem with our condominium deck. Last summer, I pressure washed the cedar wood because it had turned gray. Although the wood was rough after the washing, it looked superb after we applied a sealer. But this spring the sealer has started to peel. I fully expected the sealer to last at least two years possibly three. What went wrong? Is there a way to avoid the annual deck cleaning/sealing ritual? Marge G. Oaklawn, IL

DEAR MARGE: Welcome to the club! There are tens of thousands, perhaps hundreds of thousands, of people just like you who get very frustrated each spring. Just like you, they worked their fingers to the bone cleaning and sealing wood decks, playsets, boat docks, fishing piers, etc. and achieved spectacular short term results. But Mother Nature, and her good friend Old Man Winter, flexed their muscles and over a period of just a few months wreaked havoc. The good news is that there are deck cleaning and care products that will allow you to take a year or two off.

Your deck sealer is peeling because you unfortunately selected a film forming product. Not all deck sealers or water repellents are created equal. Film forming deck finishes contain clear resins that soak into the wood but they also lay at the surface. A film on any horizontal wood deck or railing is the kiss of death. Penetrating water repellents are a better choice. They soak deeply into wood and stop water penetration.

Intense ultraviolet (UV) rays in sunlight blast away at horizontal deck surfaces during the mid part of the day. These same rays glance off vertical railing pickets. This is why your flat surfaces always look worse than the railings. Add to this the fact that rain and snow puddle and stand on the horizontal decking and hand rail tops. The UV rays and water vigorously attack the film finish. The net result is that the weakened film finish peels off rapidly and readily.

To add insult to injury, you made another mistake using a pressure washer. These devices work great to get paint off of metal, but I have seen hundreds of decks ruined by these devices. The light colored wood bands in any piece of lumber are the growth rings created each spring and early summer. This wood is not as dense as the dark colored grain bands that grow as the tree hardens off for the upcoming winter. Power washers can easily erode the soft spring wood leaving your deck looking like a 30 year old fishing pier.

Unfortunately, you are going to have to strip off the film forming finish you applied last year. The elements will continue to do it for you if you wish to wait, but that is not a good idea. Decks that are neglected suffer continued UV damage and water seeps into unprotected wood. This water causes continued expansion and contraction as the wood swells when it gets wet and then shrinks as the water dries out. This movement creates small cracks or checks. These cracks allow the next rainfall to penetrate even deeper into the wood.

Once the wood finish is stripped off, use oxygen bleach to safely clean the wood. Avoid deck cleaning products that contain sodium hypochlorite. This is the primary ingredient in household chlorine bleach. Chlorine bleach is toxic to nearby vegetation, it removes the color from wood, it destroys the lignin that holds wood fibers together, and it accelerates corrosion of the metal deck nails and hardware. Oxygen bleach does none of these things. It simply forms a froth on the deck and the millions of oxygen bubbles deep clean the wood while you watch.

Once the deck is clean, purchase a penetrating water repellent that is made with synthetic resins. Many of the common deck sealers you see are made with natural oils and waxes. These products are the very food that mildew and algae love to eat. The manufacturers add mildewcides and fungicides to the sealers in an attempt to keep your deck from turning black and green, but these chemicals are often dissolved quickly by rain and snow. Synthetic resin water repellents are not mildew and algae food.

Purchase a synthetic resin water repellent that has colored pigments in it. The pigments help to block damage from UV rays. These rays turn the wood gray. If you apply the water repellent according to instructions, there is a good chance you will get two and possibly three years of protection. These same products work as long as five to seven years on log cabins or any other vertical wood surface.

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