Wood decks add to the beauty of your home and help you appreciate the outdoors. With their natural, warm appearance, they just feel good.
But these decks take a lot of abuse, particularly from continual exposure to the elements. Without proper care, they can quickly become weathered and uninviting.
Fortunately, most wood deck surface problems are cosmetic–not structural. That’s because natural wood decking is built from durable materials, such as redwood, cedar or pressure-treated pine. Redwood and cedar heartwoods have a natural resistance to termites and decay, while pressure-treated pine is infused with chemical preservatives to protect the wood.
Even so, the sun’s UV radiation will inevitably break down your deck’s surface fibers and natural organic polymers (called “lignins”). This causes erosion and oxidation, which results in the gray, weathered appearance. And exposure to moisture encourages mildew and stains, particularly in damp or humid climates where surfaces never completely dry out.
But regardless of the type of wood, the process for restoring your deck’s good looks is fairly simple and straightforward:
- Diagnose and treat discolorations
- Apply a durable finish
How to Clean Your Wood Deck
First, sweep all debris off the deck’s surface. Use a putty knife to remove debris from between deck boards. Now you’re ready to wash. Choose a cloudy day when the decking is cool and the sun won’t evaporate the cleaner.
If your deck is relatively small, you can clean it with a scrub brush and commercial deck cleaner. The best cleaners contain sodium percarbonate, which removes mildew, oxidation and dirt. Mix the deck cleaner following the label directions, and be sure to wear rubber gloves and safety glasses.
Using your stiff brush, thoroughly scrub the surface along the wood grain. Work in small areas and rinse frequently with clear water. Then allow to dry. This may be all it takes to restore much of the wood’s natural tone.
For a larger deck, you may want to use a power washer, adjusted to 600 to 800 psi. Wearing safety goggles, hold the nozzle about six inches above the deck’s surface. Spray slowly and steadily along the wood grain, overlapping your path.
Power washers can be tricky. Be careful not to get the nozzle too close to the wood or stay in one place too long. If you do, you’ll soon find that the powerful spray can erode soft wood grain. When you’ve finished washing, you’ll need to let your deck dry for several days before applying any type of finish.
How to Diagnose and Treat Discolorations
When it comes to removing stains and discoloration from your wood deck, remember: Bleach-based products remove mold and mildew, while acid-based products remove oxidation and other stains.
If you’re unsure what kind of stains you have, test for mildew. Here’s how: Apply a drop of undiluted liquid household bleach to a small, black spot. If the spot disappears after a minute or two, it’s mildew.
Treating Algae, Mold and Mildew
If your redwood or cedar decking has an issue with algae, mold or mildew, chlorine bleach-based cleaners are best. These cleaners remove mold and mildew while they lighten the wood. Treat the stains with a solution of one part household liquid bleach to four parts water. Then rinse with clear water.
Algae or mildew stains on pressure-treated pine can be removed using non-chlorine oxygenated bleach (such as Stain Solver or OxyClean). These products are non-toxic, biodegradable, and environmentally friendly. They will also clean and brighten the pine. (However, they will darken redwood or cedar, and so are not recommended for these woods.)
Acid-based products remove oxidized (i.e., grayed) surface fibers, as well as the dark tannin stains that can occur on redwood and cedar decks.
Oxalic acid deck cleaners can be bought pre-mixed or in crystal form from any hardware store or home improvement center. When using the crystals, mix four ounces of product to one quart of water in a non-metallic container.
Be sure to wear rubber gloves, eye protection, and old clothes. Apply the acid solution with a rag, one board at a time, and scrub with a soft brush. Allow to dry, then rinse with clear water. Allow to dry again (completely) before applying any finish.
How to Finish Your Wood Deck
Once your wood deck is thoroughly dry, it’s ready for finishing or sealing.
Be sure to select the finish best suited to the lumber used to build your deck. You may wish to consult with a paint supplier or other expert. The finish you choose should contain either oil or paraffin to keep moisture from soaking in. It should also contain UV blockers or pigment to keep the sun from oxidizing the wood. (Unless, of course, weathered gray is the look you’re going for.)
If your home is subject to termites and other wood-eating bugs, the deck finish should also contain some sort of insecticide.
Types of available finishes include semi-transparent stain, opaque stain, clear sealer, and paint. Bear in mind that the best finishes will soak into the wood. On the other hand, films that only coat the surface (such as paint) tend to peel and show wear patterns more readily. They’ll require more frequent re-coating.
An oil-based finish or seal protects best, but water-based finishes are easier to apply and clean up.
Some experts recommend that you lightly sand the deck first, to remove any fuzziness caused by washing. The easiest way to sand your deck is to use a pole sander equipped with 80-grit paper.
After sanding and thoroughly sweeping, you’re ready to apply the sealer. Use a roller, pad or brush to apply the finish along the wood grain, covering three or four boards at a time, working their entire length.
Be careful not to spill or overlap onto adjacent boards; this will cause splotches that are hard to conceal. And don’t apply it too thickly. Two thin coats are better than one thick one.
Wood decks are exposed to regular abuse—harsh sun, foot traffic, rain, snow and ice. So be sure to make deck maintenance a routine affair, such as once a year.
Annual deck maintenance will not only protect your investment and boost your enjoyment of your outdoor space, it’ll also prevent costly repairs. Your wood deck must withstand the elements all year round, so it’s a good idea to establish a maintenance routine to protect it.
For instance, late spring is the ideal time for washing and sealing your deck, to keep mold and mildew at bay. Midsummer, when the weather is warm and dry, is the time to inspect and repair your deck. The following video shows how:
Of course, you’ll want to consult a professional carpenter or builder for large repairs.
And early fall presents another opportunity to wash and seal the deck, if you were unable to do so in the spring, as long as temperatures are still mild.
With proper maintenance and a little TLC, your wood deck will stay beautiful longer and provide you with years of outdoor enjoyment.