Clean a composite deck by sweeping it or using a leaf blower to remove loose debris. Clean any materials caught in the grain of the decking with a soft scrub brush and a mild detergent solution. If necessary, use a pressure washer with a fan tip to clean the deck, but consult the manufacturer's literature and avoid exceeding its maximum recommended pressure.
When cleaning a deck made from wood containing composite materials, tannins in the decking can cause water stains, just as with solid wood decking. Wait about three months after the stains appear and use an oxalic acid-based deck brightener to remove them.
Clean fresh oil stains from the deck using a high-quality degreasing dish detergent and hot water. If you discover the stains after they set into the materials, choose a cleaner the manufacturer specifically makes for this type of removal.
If mold is growing on the deck, use a bleach-based mold cleaner for decking. The cleaner can temporarily cause the material to appear lighter in color. After removing the mold, apply a mold inhibitor to prevent it from coming back.
Clean ice or snow from the deck using a plastic shovel. Apply rock salt or calcium chloride to melt the frozen materials so they are easier to remove.