Pressure-Washing Your Deck

Get tips for maintaining your deck, and learn how to pressure-wash your outdoor space.
Deck Pressure Treated Wood Close Up

Deck Pressure Treated Wood Close Up

By: Peter Walsh

All decks need maintenance at some point, and this is especially true for wood decks. Because of their natural properties, wood decks are prime targets for surface mold, mildew and discoloration over time. Decks built in a shady backyard or in very humid climates are especially prone to mold and mildew buildup because they rarely dry completely after a rainstorm. If your deck suffers from mold or mildew, there are several ways to restore it to nearly new.

Gas or Electric Power Washer

When using this method care must be taken when using these. They produce a blast of water that can scar the boards, raise the wood fibers or splinter the wood if used improperly.

First, sweep the deck free of any leaves and debris, then, using a thin tool such as a putty knife, remove any debris caught between the boards. Set the machine on a weak to medium power spray and remove the surface debris in layers, repeating the process until the surface is clean.

Starting at the house and going with the grain or the length of the boards, sweep the deck with the pressurized water, overlapping as you go along to help prevent streaks. Raise the nozzle of the power washer several feet off the surface of the deck and maintain this height to prevent gouging the wood surfaces. This method is slower and requires more strokes as you clean the deck, but it does the job. Be sure to also clean the railings, posts and stairs.

Using a Deck Cleaning Product

Another method is to use a deck-cleaning product. There are many to choose from, so ask at the store which product is best for the type of deck you have. For wood decks, most contain a bleaching agent that will help loosen debris and lighten the color of the wood.

They are applied using a synthetic bristle brush attached to a long handle. To reach tighter areas of the deck such as under thresholds and in the corners, get a smaller hand-held brush. Always wear protective clothing, such as long pants, closed shoes and rubber gloves. Eye protection is also recommended and, as always, follow the directions on the container to the letter.

In most cases, you apply the product to a wet deck, let it sit on the boards for about 15 minutes so it penetrates the surface, scrubbing out stubborn stains, then hose it off completely using a common garden hose and nozzle. Let the deck dry for at least 24 hours before replacing your deck furniture or container plants.

If you have a deck made of plastic or composite materials, the deck can still benefit from a thorough cleaning at least once a year. Composite decks can still harbor mold and mildew because the material is made of wood fibers and plastic. A gentle power washing will help clean it up, but resist using a strong setting on the machine, as you'll likely cause the wood fibers to pill.

Purchase a product specifically made for those materials. Most contain a detergent that will effectively clean the deck and lift off surface stains easily. Using the wrong product can discolor synthetic deck boards. Always follow the directions on the container for the best results.

Next Up

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Get tips on how to find the right materials for your deck.

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