How to Refinish a Wood Deck

If the water soaks in and darkens the wood, the inner fibers of the wood are getting soaked like a sponge every time it rains. When the sun finally comes back out, the wood dries again, and that “soak-dry-soak-dry” cycle means that the wood expands and contracts constantly. Eventually cracks will appear, harboring mold, mildew, algae, and all sorts of destructive organisms. When that soaked-in water freezes and thaws in a cold winter, the damage can be even worse.

It all starts with a good cleaning. You wouldn’t paint your car without removing all of the debris on the surface, would you? Think of your wood deck the same way. You’ll first need to remove all of the stains from dirt, mildew, mold, and algae, along with any residual deck stain or waterproofer to make sure that the new waterproofer will be able to do its job right.

Luckily, cleaning your wood deck is not the labor-intensive project it was 20 years ago. These days, we’ve got plenty of help in the form of off-the-shelf cleaners and waterproofers formulated to kill biological contaminants while cleaning off dirt and old coatings.

Wood Deck Cleaner Options

• Deck Wash: A standard deck wash is great for cleaning off basic dirt and grime. It will also help to remove mold, mildew, and algae stains and kill the spores that cause them.
• Heavy Duty Deck Cleaner: One step up from Deck Wash is Heavy Duty Deck Cleaner. This cleaner will take up stains from dirt, mildew, mold, and algae, as well as remove residual clear waterproofers.
• Deck Stripper: Have some semi-transparent or solid stain left over on your deck? A deck stripper will take it all off -- dirt, mold, mildew, algae, and residual semi-transparent or solid deck stain.
• Deck Brightener: Cedar, redwood, and other high-tannin woods tend to turn gray in the weather or when exposed to standard deck cleaners. By using a Deck Brightener, you can restore the rich color of cedar or redwood deck boards before you apply a new coating.

How to Clean a Wood Deck

Once you choose the right cleaner, the steps for cleaning your wood deck are simple. Use a plastic, pump-up garden sprayer and a stiff-bristled plastic brush (put the brush on a pole to save your back) to do most of the work. Quick Tip: Make sure to use plastic sprayers and brushes, since the cleaners will react with metal.

1. Spray and Drape: Make sure to spray down all plants in the area with water before you start. Cover any other surfaces you don’t want to treat -- especially other painted surfaces -- with plastic to avoid any overspray.
2. Apply the Cleaner: Pour the cleaner into your plastic pump-up garden sprayer and spray the cleaner onto the wood deck boards. Soak an area about 10’-0" x 10’-0" and let the cleaner sit for about 10-15 minutes on the wood. The cleaner is working, loosening dirt and grime, and killing mold and mildew spores.
3. Use a Little Elbow Grease: Using your stiff-bristled plastic brush on the pole, work the cleaner into the wood to make sure it gets into every nook and cranny. If your cleaner is getting a little dry, lightly mist the area with water and scrub again.
4. Rinse: Using a strong spray from a garden hose or a pressure washer, rinse the area well. Remove the plastic draping from plants and rinse them with water as well.

Depending on the type of coating you’re going to use, you’ll need to let the deck dry from a few hours to a few days before applying the waterproofer. With a standard clear or tinted wood protector as well as an oil-based semi-transparent or solid stain, the wood deck will need at least 48 hours to dry before the waterproofer is applied. Newer formulas, like Thompson’s Water Seal Advanced Wood Protector, can be applied to damp wood, so your deck will only need to dry for 3-4 hours before applying them. Just make sure to read the manufacturer’s directions for the waterproofer you select.

Many people think they need to use a pressure washer when they clean their deck. Unless you’re very careful with a pressure washer, it’s easy to do more harm than good. Too much pressure will damage the top layer of wood fibers, allowing water beneath the surface and biological contaminants to thrive. Using a pressure washer alone, without a pre-packaged cleaner, will leave invisible mold, mildew, and algae spores behind, which can interfere with the new waterproofer.

An electric pressure washer might be a good, middle-of-the-road alternative. With a lower pressure you can get out tough stains, but be sure that you don’t accidentally damage the wood deck boards. Electric pressure washers also require much less maintenance than gas pressure washers and are far less expensive to purchase.

How to Waterproof a Wood Deck

Now it’s time to apply your waterproofer. Generally speaking, whether you choose an oil-based or latex waterproofer, the more pigment in a coating, the longer you can wait between recoating. This is due to the fact that the pigment reflects harmful UV rays, protecting the wood (and the coating) from fading due to sunlight. Here’s a quick breakdown of waterproofers:

• Clear Wood Protector: Allows all of the wood color and grain to show through -- expect 1-2 years before recoating, depending on your climate and use.
• Tinted Wood Protector: Allows the grain to show through while adding color -- expect 2-3 years before recoating, depending on your climate and use.
• Semi-Transparent Deck and House Stain: Allows some wood grain to show through while adding more intense color -- expect 3-5 years before recoating, depending on your climate and use.
• Solid Deck and House Stain: Completely covers the wood grain while adding intense color -- expect 5 years or more before recoating, depending on your climate and use.

Use a paint pad and pole to apply most wood protectors and stains. Usually, one coat will give you the protection you need. Check the label on the waterproofer you use to learn the proper temperature for application and drying -- usually you’ll want dry weather over 50°F and no rain or freezing for 24 hours after application.

Hey, you’ve done it! You’ve made your deck look like new again while protecting it from the elements. Take a break, sit down, and enjoy the view. Maintaining your deck means you’re protecting your investment and making your outdoor space beautiful at the same time.