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Strip old film sealer off of wood deck
Dear Ms. Builder: I stained my deck two years ago with a sealer that is almost opaque and it looked great. Now it is starting to peel off in spots. What can I do to stop more peeling and repair the bad spots? - Sylvia H.
Dear Sylvia: I hope that you enjoyed treating your deck two years ago because treating the entire deck is about your only option. If it started to peel in a few spots, by next season there will probably be many more unsightly areas. Even if you could repair the finish on those spots, they would not match the color of the remainder of the deck.
The problem that you are having is most likely due to the selection of the improper type of deck sealer last time. It sounds like you used a film-forming type of sealer instead of a penetrating sealer.
Film-forming sealers look great when first applied, like a finish on furniture, but they rely on surface adhesion to keep them fixed to the decking. With very careful preparation of the deck before application, these film-forming sealers can be effective. In real life though, there will be spots where it does not adhere adequately.
You will have to remove all of the film from the wood decking and start over again, this time with a penetrating type of deck sealer. Chemical stripping chemicals, made specifically for decks, are your best choice. Choose a fairly cool, overcast day to strip the deck. It is not only more comfortable for you, but the stripper will work better too.
There are several classes of strippers that will work well for your deck. They have varying degrees of strength and toxicity. The strongest chemical strippers typically contain a compound called methylene chloride. These strippers will work the fastest of all types, but care must be used.
Stripping chemicals that contain sodium hydroxide (you may also see alkaline on the label) have a lesser level of toxicity and work slightly slower. The mildest strippers use NMP, d-Limonene, or other milder chemicals. The labels of these chemicals may mention citric acid derivatives.
Buy the smallest package of one of the mildest strippers first and try it in a small, inconspicuous spot. Give it some time to work. If it is effective, buy a larger container of it and get to work. If not, move up to the next stronger stripper and give it a try too.
If you have trouble finding these strippers at your local home center store, here are some manufacturers to contact: Biowash (800-858-5011) - "Stripex" - sodium hydroxide base, Wolman (800-556-7737) - "Deck Brightener" - mild chemicals, MFG Distributing (800-297-7325) - "Clean & Brite" - sodium hydroxide base, SaverSystems (800-860-6327), Savogran Co. (800-225-9872) - "Super Strip" - methylene chloride base, and WM Barr (800-235-3546) - "Citri-Strip" - mild critic acid base.
Once you have all of the old film-forming sealer stripped from the decking, you must clean the deck surface. Avoid all cleaners that have the word "bleach" in them, specifically chlorine bleach, that can damage the wood surface. A good, pressure washing, not at the highest pressure setting, will clean it effectively and remove deteriorated wood fibers from the surface.
Now all you have to do is reseal the deck. A lightly tinted, penetrating type of sealer will be most effective. It actually penetrates down into the wood fibers on the surface so that there is no chance that it can peel. Since you cleaned the deck too, the natural graining will show through for an attractive appearance.
You will have two basic types of penetrating sealers to choose from: organic and synthetic. Organic sealers are less expensive and look good when first applied. The main problem is that the organic oils can support the growth of various molds and fungi that create dark spots. Synthetic sealers will not support this growth.
Send your questions to Ms. Builder, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com/msbuilder.