Q&A / 

Strip Finishes Off Decks

DEAR TIM: I really made a mistake. I applied a wood deck sealant several years ago that seemed great at the time, but it is now peeling! How can I remove this mess? What steps do I have to take to clean my deck? Should I powerwash the stripper off the wood? Is there a product that will not peel but provide protection and beauty? Pam T., Hamlet, NC

DEAR PAM: Ouch! The pain isn't over yet as you now have to strip off the offending film former from your wood deck. The good news is that once removed and a penetrating synthetic water repellent is applied, your wood deck care problems will be minimal in the future.

Deck sealant products are available in two major groupings: film forming products and penetrating finishes. Film formers tend to look fantastic when applied. Some resemble highly polished furniture finishes. These products try to grab tenaciously to the surface of the deck lumber, but the sun's ultraviolet (UV) rays and repeated expansion and contraction of the wood caused by moisture gain and loss eventually cause the films to break down and peel.

Penetrating water repellents are finishes that deliver wood protecting resins and pigments into the top layers of the wood's cellular structure. Many of these finishes surround the wood fibers at the surface and do a decent job of repelling water and sunlight for several years. The best synthetic resin water repellents can provide protection and beauty for up to 3 years on horizontal wood surfaces.

To remove your existing film former deck product, you will need to use a stripper. Some wood deck strippers contain a chemical called methylene chloride. These are super powerful and should only be used with care. You need to protect all skin surfaces and avoid breathing the product's fumes. You may find other strippers that contain caustic chemicals like sodium or ammonium hydroxide or sodium metasilicate.

Oxygen bleach (see link below) is deep cleaning this wood deck. The bad film forming finish was previously removed with a stripper.

Never mix these products with any other solution, chemical or chlorine bleach. You must neutralize the wood surface after using caustic strippers. Do this with lots of clear water or a 50/50 mixture of vinegar and water. The least toxic deck strippers are NMP or d-Limonene based products. These are not too toxic, but can sometimes be slow acting.

Deck stripping can take time. It is best to start in a small area to see what methods and products work best. Avoid working with the products on hot, sunny, windy days. An overcast, cool day with a temperature near 75F would be my choice. You will achieve the finest results if you follow the directions on the label of the product. Do not use a pressure washer on wood decks. The powerful stream of water that comes from these professional tools can easily erode the soft light colored spring wood that lies between the dark colored summer wood grain bands in your wood.

Once the deck is free of the film former, you should clean it with oxygen bleach. This non-toxic powdered product mixes with water and cleans decks that have been coated with penetrating finishes or even unprotected wood. The foaming oxygen ions aggressively attack mildew, algae and dirt buildup on the deck, but do not harm the wood deck, metal connectors or vegetation surrounding your deck. You simply mop on a solution of oxygen bleach, let it sit for 15 minutes, lightly scrub it with a brush, and rinse with a garden hose.

Do not use chlorine bleach (sodium hypochlorite) or any product that contains chlorine bleach to clean your deck! Chlorine bleach blasts apart the lignin or glue that holds together wood fibers, it removes the natural wood color, it kills vegetation, and it can corrode metal deck components.

If you apply a semi-transparent synthetic water repellent on your wood deck, you will be very satisfied. These products contain synthetic resins that are not food for mildew and algae. Many common and highly advertised deck sealants are made using natural oils such as animal fat, tung, vegetable and other oils that are food for mildew and algae. I have used a synthetic water repellent on my own wood front porch for the past 4 years and it looks superb. I know your deck will look the same!

Message from Tim:

Years ago while researching a column about cleaning decks, I discovered the wonders of Oxygen Bleach. It is perhaps the 'greenest' cleaner I know of as it uses oxygen ions to break apart stains, dirt and odor molecules. There are no harsh chemicals, and it works on just about anything that is water washable.

I decided to create my own special blend using ingredients made in the USA. In fact, the raw materials in the active ingredient are food-grade quality registered with the FDA. I call my product Stain Solver. I urge you to use it to help clean your deck. You will be amazed at the results!

Companion Articles:  Wood Deck StrippersOxygen Bleach & Synthetic Water Repellents

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