Remove everything from the deck floor. Sweep the deck with a broom to remove loose dirt and debris. Hose down the deck with water from the garden hose. Set the hose on a high pressure setting to effectively loosen dirt and grime.
Fill a bucket with 1 gallon of water. Add 1 cup of chlorine bleach.
Scrub the deck with a stiff, long-handled scrub brush and the bleach mixture. Let the bleach sit on the deck floor for 15 minutes.
Rinse the deck with water from the garden hose to remove all of the bleach. Treat the deck floor again with the bleach solution if necessary.