Remove any items from the deck and spray the wood thoroughly with a garden hose to rinse away any loose dirt or debris.
Fill a bucket with 1 gallon of hot water and add 1 cup of powdered oxygen bleach. Stir the solution with a spoon until the powder fully dissolves and let it sit for five minutes to activate.
Pour the oxygen bleach solution directly on the deck to saturate it, or pour it into a spray bottle and spray the deck thoroughly. You can also use a mop to apply the oxygen bleach to the deck. Mix more solution as needed to cover the whole deck. Allow it to sit for 15 minutes.
Scrub the deck with a long-handled scrub brush or push broom.
Rinse the deck thoroughly with a garden hose and allow it to air dry.