Cleaning a Wood Deck


A natural wood deck is a good-looking and utilitarian addition to any home, extending the living space into the yard and providing a stage for outdoor activities. But the wood used for decks can have drawbacks. Over time, it can become discolored or mildewed from exposure to moisture. And the sun’s ultraviolet radiation can break down the wood’s fibers, graying and weathering the surface.

Fortunately, reviving a discolored, weathered wood deck is a relatively easy project you can do during a weekend, using only a handful of tools and materials. The process involves cleaning the surface, dealing with discoloration, and protecting the wood.

You’ll need:

• Plastic drop cloths

• Garden hose with nozzle

• Putty knife

• Long-handled stiff nylon fiber brush

• Plastic bucket

• Laundry detergent (non-ammonia) or TSP

• Oxygenated bleach (or acid-based wood brightener for redwood)

• Rubber gloves and safety glasses

• Paint roller and roller tray

• Deck finish

Wash first
Wash the deck first before applying a chemical cleaner. Use a garden hose with a powerful nozzle to blast away the debris between decking boards, and then go after stubborn deposits with a putty knife. Next, use a long-handled, stiff-bristle brush to scrub the surface with a sudsy mixture of water and laundry detergent. Rinse with clear water, and then repeat.

To reduce your labor, you can wash a large deck with a pressure washer set at 800 to 1,000 psi with a spray nozzle that fans an arc of 30–40 degrees. Do not allow the powerful spray to erode soft wood grain! For more about pressure washing, check out this video.

Deck cleaners
Once the deck is clean, you’re ready to rejuvenate the wood. To remove mildew, stains, and graying on decking other than new redwood, buy an oxygen bleach-based wood cleaner. Note: You want oxygen bleach, not household chlorine bleach. If the ingredients on the label include sodium hypochloride, the product contains chlorine bleach, which kills vegetation, accelerates corrosion of metal fasteners and breaks down the wood, aging the surface. Oxygen bleach is nontoxic to humans and plants.

Regardless of the brand you choose, mix the wood cleaner according to label directions. In most cases, you’ll have about five hours to work before the cleaner becomes inactive. Avoid working in direct sunlight, because the solution will dry too quickly. After wetting the deck with a garden hose, pour the fully dissolved cleaner into a garden sprayer, and then apply liberally, allowing it to sit for about 15 minutes and keeping the surface wet. Work the cleaner into the deck with a stiff nylon brush. Repeat a second time, and then rinse the surface clean with water.

For a redwood deck, use an oxalic acid–based wood brightener to eliminate graying and reddish-brown stains (oxygen bleach can darken some redwood). You can also make your own wood brightener by mixing 16 ounces of oxalic acid crystals with 1 gallon of warm water in a plastic bucket. Apply with a pump-up garden sprayer, allow it to sit for 10 minutes, and then rinse with water.

Application tips
When applying deck-cleaning products, wear rubber gloves, safety glasses and old clothes — and follow the label directions. Scrubbing is usually best done in the direction of the wood grain using a long-handled, stiff-bristle nylon brush, working in 4-by-4-foot sections. Most products recommend thoroughly rinsing the surface after application. Protect nearby flowers and plantings — and the area beneath a raised deck — with plastic drop cloths. Always test the solution beforehand in an inconspicuous spot to be sure it produces the results you want.

Finishing the job
Once the deck is completely dry, apply a sealer or protective deck finish with a roller. Consult your paint dealer for the best type of finish to use in your region. A penetrating, semitransparent, water-based wood stain, applied in two coats about 20 minutes apart, is often the best choice. Apply according to label directions.

Last, but not least, enjoy your beautiful deck!