Q&A / 

Deck Stain Test Photos

DEAR TIM: I've got a wood deck that needs to be sealed again. I say again, because every other year I'm having to clean and seal it. It looks great for several months, then the wood starts to look black, green and some of the sealers I've used start to peel. I'm trying to find the best deck sealer, but am running out of patience. I'm thinking of doing my own test. What's involved and do you think it's worth it? Heather S., Bismark, ND

DEAR HEATHER: Virtually every homeowner that cares for a wood deck suffers like you do. I own a wood dock and lament myself every few years about the care it needs. It's a solid two-day project to clean and seal my boat dock, and the set of steps leading down to it.

Like you, I'm on a quest to discover the Holy Grail of deck stains and sealers. I'm looking for one that doesn't peel and looks good for at least three years or more. So far, I've not found it, but I'm getting closer.

I have to admit that it's a significant challenge to produce a product that can stand up to all of Mother Nature's weapons. The ultraviolet rays in her sunlight can wreak havoc with pigment molecules as well as the sealer and stain resin that soaks into the wood. Oxygen can break down other ingredients in the deck stains and sealers. Water, ice, and snow also work to break down the wood preservatives.

All the boards were treated with the exact same deck stain. Two of the boards were left out all year in the weather and the other two were kept in a sealed box. You can tell the difference! Photo Credit: Tim Carter

Most people want the wood to look great, but you need to realize that it's very important to keep the wood sealed to minimize water penetration. Water that soaks into outdoor wood causes it to swell. When it dries, it shrinks. This back and forth movement eventually creates tiny checking cracks. Water that gets in these cracks penetrates even deeper into the wood creating larger and larger cracks.

Keep in mind that when you go to clean your deck, beware of power or pressure washers. The extreme pressure and concentrated stream of water will erode the lighter bands of spring wood in the decking. Your deck can look like a 50-year-old fishing pier in no time. It's better to use oxygen bleach to clean a wood deck.

If you want to do a test of deck sealers, be prepared to spend lots of time and money. You'll have to buy new lumber and possibly different types. You absolutely want to match the wood you currently have on your deck, as some decking lumber is much denser than others. The denser lumber requires a different sealer to prevent peeling.

To conduct a proper test, in my opinion, you need to get new decking lumber and cut it into short lengths, perhaps 8 inches long. This lumber needs to be clean and dry. It could take a season to dry it, as some lumber that comes into the lumber yards is not always dry.

You'll then need to purchase probably twenty-five or even thirty-five brands of deck stains and sealers. Some manufacturers have multiple brands and types of outdoor wood sealers. This can get prohibitively expensive to purchase all this material when you just need about two ounces of each for the test.

You'll then need to purchase as many small cheap disposable brushes as you have sealers in the test. You can't compromise the test by cross contaminating the sealers. They all need to be applied with a new or clean brush. You may discover it costs less money to buy a new brush than clean the same one after applying each stain.

I would cut two pieces of each type of lumber you intend to test. All the pieces of decking get stained the same way at the same time. Mark the underside with a permanent marker as to the brand of stain used on the decking board. Use a letter code as well and record this on a document you save.

Once the decking pieces are dry, box up one set to keep them out of the sun and weather. Put them in your garage or attic. Place the other set outdoors where they'll get the worst Mother Nature can serve up. See who wins a year later when you compare the two sets!

To save you the trouble, I did such a test over the past year. I was stunned at the difference between some of the sealers. The sealer I thought would lose the test actually won. I almost fell over.

You can see dramatic before and after photos and a list of the deck sealer products I used in my year-long deck sealer test at this web page:

Deck Stain 2013

Pay attention to how many of the decking boards have mold and mildew on them, but surprisingly many of the same wood species do not. It makes a big difference as to the type of lumber I'll be purchasing for my next wood deck!

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