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Peeling and Flaking Deck Sealers

Peeling and Flaking Deck Sealers

Peeling and Flaking Deck Sealers | The steps, railing, and boat dock are cleaned and sealed. The top walkway is ready for the sealer. The penetrating sealer I used is below. It should NEVER peel.  This column was SO GOOD that I shared with the 31,000 subscribers who read my July 5, 2020 newsletter. Copyright 2020 Tim Carter

Deck Sealers That Peel & Flake

DEAR TIM: I’m so frustrated and at my wits end. Before I clean and seal my outdoor deck, I need your advice. It’s a tremendous amount of work and I’m discovering I need to do it every three years. I scream each spring when I see the expensive sealer I’ve used start to peel and flake. Surely there’s a better way. If you could wave a magic wand how would you clean and seal your outdoor wood so maintaining it is not so much work? What are the do's and don’ts to cleaning outdoor wood? Gina H., Cilleyville, NH

Do you suffer the same agony each spring as does Gina? I can tell you for a fact it’s getting worse and I’m hearing more and more complaints about deck sealing products that peel and flake.

Are Deck Sealers Made to Peel?

After writing my Roofing Ripoff book about how asphalt shingles are failing far faster than the predecessors did I used to use early in my career, it’s easy for me to be a cynic when it comes to outdoor wood sealers. While I have no evidence to support this, I can tell you it wouldn’t surprise me if sealer manufacturers made products that failed fast and in a dramatic way so you end up buying more before you really need to. That’s what my research showed with some asphalt shingles, but I digress.

Are Penetrating Stains Better?

Let’s talk about wood stains for a moment. If you’ve ever stained interior wood you might have used a colored liquid that’s the consistency of water. These stains typically soak immediately into the wood fibers and nothing is really left on the surface of the wood but some microscopic pigment particles.

Years ago many outdoor wood stains and sealers were made the same way. They penetrated into the wood. That said, there were outdoor sealers you could buy that behaved more like urethanes or varnishes. These are film-forming products that deposit a resin or coating on top of the wood. When they fail, and they all do, they peel and flake. It seems many of today’s deck sealers are film formers.

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Why Do Deck Sealers Peel?

The failure of the outdoor deck sealers is predictable. The sun’s harsh ultraviolet (UV) rays blast apart the film-forming sealers with little effort. Add to this the fact that wood is also a hygroscopic material. This is a fancy word describing how wood swells and shrinks as it absorbs and releases water. I recorded a dramatic video of this happening in recent months. You can watch it on my AsktheBuilder.com website by typing “treated lumber cracking” into my search engine.

What Deck Stain Do You Use, Tim?

I just started testing a penetrating wood sealer stain this past spring. I used it to seal my boat dock panels and the stairs leading down to the dock. I have a combination of treated lumber and cedarwood. I could tell it penetrated into the wood fibers and if it left a resin on the surface, it’s very light. The product description says it’s a penetrating sealer.

boat dock sealer stain

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Does it Have Natural Oils?

The only thing I didn’t like about it is it’s a combination of three oils: linseed, tung, and long-oil alkyds. These are scrumptious food for mold and mildew. I’m sure the manufacturer added chemical additives to prevent the growth of these things. So far after one month, I’ve not seen any trace of mold or mildew growth. Water beads up wonderfully on the wood surfaces so it’s doing a good job of protecting the wood.

Are Dark Sealers Better Than Clear Ones?

You get the best protection from a sealer when you choose one that’s got lots of dark pigment. The pigment acts like sunscreen you use on your skin to prevent sunburn. The pigment sacrifices itself to the UV rays and slows the destruction of the wood fibers. You can see the UV damage caused by the sun after cleaning the wood. Have you seen the peach fuzz after the wood dries? Those are sun-damaged wood fibers just hanging on.

How Do You Clean the Deck?

You may wonder how I clean my outdoor wood. Here’s what I don’t do. I don’t use a pressure or power-washing machine. These are highly destructive to wood. The high-pressure water erodes the lighter-colored spring wood from between the darker bands of denser summer-wood. Use a pressure washer a number of times and soon your new wood will look like a decades-old fishing pier.

I’ve had the best luck using certified organic oxygen bleach cleaners that you dissolve in water for cleaning. I apply mine in the shade to dry wood so the solution soaks deep into the fibers to help clean the wood. Don’t use chlorine bleach as it’s so harsh it will remove the natural color from the wood and it destroys the lignin that holds the wood fibers together. Any product that has sodium hypochlorite on the label is chlorine bleach.

Oxygen Bleach

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When Should I Re-Seal My Deck?

I feel the best way to minimize work with maintaining outdoor wood is to re-coat the wood before it completely fails. If you use a penetrating sealer as I did a month ago, you may discover that in two years you should apply a thin maintenance coat. By then you may just have to do a mild washing of the wood much like you wash your car using liquid dish soap and water.

How Can I Check for Color Fade?

I did a little experiment this year to be able to gauge the wear of the sealer. I had to rebuild a few of my dock panels and had a few pieces of scrap cedar leftover. I decided to seal those too and I put them in my garage up on a shelf out of the sun and weather. Next spring I’ll take them out and put them on the dock to see how much the sealer suffered. As soon as I see significant wear, I’m going to do a maintenance coat.

Related Column: Deck Sealer - Epoxy Fortified

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