Remove Old Peeling Sealer From Deck

By James Dulley

August 15, 2019 4 min read

Dear James: I used a dark deck sealer several years ago. It looked good for the first year or two, but now it is peeling off in areas. What is the best way to fix the bare areas and stop further peeling? — Roger M.

Dear Roger: The attractive dark sealer you applied a couple of years ago functions more like a coat of paint than a sealing stain. No matter how well you prepare the deck surface and apply it, this type of sealer will eventually start to peel, as paint would on the surface.

Unfortunately, the only good solution to this peeling problem is to totally remove all the old sealer and start again with a more durable sealer. If you were successful restaining those peeling areas, it would not match the rest of the deck, and each year, you would find peeling in new areas.

What you used on your deck was a film-forming sealer. These are easy to apply and look great when first applied. The film relies on surface adhesion to keep it tightly connected to the surface of the deck. Once there is a small break in the film, or if moisture comes up from below, it begins to lose its adhesive strength and starts to peel.

What you should have used is a penetrating sealer. This will not have as attractive a surface appearance, but its finish looks more natural. Because it penetrates down into the pores of the wood, it provides more protection, and there is no surface film to peel off over time.

The easiest method to remove all the old deck sealer is using a chemical stripper made specifically for decks. You should be able to find it at your home center or paint store. It is best to do this project on an overcast day or early in the evening, when the sun is less intense and it is cooler outdoors.

You will find several types of chemical deck strippers from which to choose. The ones that are the strongest and strip the quickest often have a higher toxicity level and require more careful usage. Strippers that contain methylene chloride fall into this category. Carefully read all the safety precautions.

Another type of chemical stripper contains sodium hydroxide, which works slower than methylene chloride. Sodium hydroxide is an alkaline compound that can burn your skin if you're not careful. More mild strippers use chemicals such as NMP, d-Limonene and citric acid derivatives.

You will likely need a large container of the stripper to do the entire deck, but purchase a small container of one of the milder strippers first. Test it in a couple of spots to see how well it works. If it doen't work well, keep testing the next-strongest stripper until you find one that's effective.

If you have trouble finding these strippers at your local home center store, contact these manufacturers: Napier Environmental Technologies Biowash, "Stripex" — sodium hydroxide base; Rustoleum, "Wolman Deck Brightener" — mild chemicals; MFG Sealants, "Clean & Brite" — sodium hydroxide base; Savogran Co., "Super Strip" — methylene chloride base; and SaverSystems, "Stain Stripper" — sodium hydroxide base.

Once you have the deck surface stripped, spray it off with a pressure washer. Allow the deck to dry thoroughly for a day or two, and then treat it with a synthetic-based penetrating sealer.

Send your questions to Here's How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com. To find out more about James Dulley and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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