Make sure there is adequate and unobstructed air flow under the deck to prevent excessive water absorption. Improve drainage or grade flat areas where standing water may gather. For decks with limited ventilation, 6"" of clear ventilation is required.
If the gap between decking boards is less than 3/16"", organic debris such as leaves, seeds or pollen can settle on the deck and clog gaps. Water can pool, steeping organic debris that forms a “tea” or of tannin which may stain your deck. This organic debris is a strong food source for mold. Keeping the gap clean is the easiest way to keep the deck clean. If gapping becomes clogged, use a garden hose, a spatula, putty knife or similar tool to remove debris.
Clean your deck as often as needed, at least twice each year to remove pollen, organic debris, dirt or stains. Generally, a broom or a blower will work better than a hose for removing scattered organic materials like leaves. For general cleaning, use soap and water or mild household cleaners.
Dislodge accumulated dirt with a broom or by using soap and water and a non-metal scrub brush. Scrubbing in the direction of the grain is best. Thoroughly rinse off with a garden hose. Skilled professionals may use a pressure washer with wide fan tips, at low pressures under 1,500 psi and at safe distances, 12"" above deck. In the wrong hands, your composite deck can be damaged. Exercise extreme caution.
Speedy clean up is best. To clean grease and oil stains that soap and water cannot remove, some all purpose cleaners, such as Fantastik, will cut through grease and grime. Or use a commercial deck cleaner designed specifically for your type of decking. De-Solv-It Citrus Solution is effective in removing tar, asphalt, oil, grease and chewing gum. Be sure to follow the manufacturer’s recommendations and test in an inconspicuous area prior to cleaning the entire deck.