Green stains on a wooden deck are generally caused from moss, algae or mildew. These stains occur over time due to the decks exposure to the elements. An otherwise beautiful deck may appear dirty or unclean if green stains are covering it. Removing green stains from a wooden deck will restore its original appearance. It is important to clean deck stains at first sight before they set in and are more difficult to remove. Ideally, the entire deck should be cleaned, not just the stained area, to provide an even appearance.
Remove any objects or furniture from the deck. Furniture, grills and plants should all be removed from the deck to make cleaning easier. If you choose to just clean the stained area, remove any objects in close proximity to the stain.
Sweep away any loose dirt and debris from the deck using a broom. Plants below the deck should be covered with plastic sheets to protect them from the cleaning solution. Cover electrical sockets with duct tape.
Mix a solution of oxygen bleach and hot water into a bucket. The exact ratio of oxygen bleach to water will vary depending on the concentration of sodium percarbonate in the product you are using. Generally, use about 177ml for every gallon of water. Refer to the label instructions for specific directions for mixing.
Spray down the deck with plain water from a garden hose. If you are only cleaning the stained area of the deck, you need only wet that area.
Pour the oxygen bleach mixture directly onto the deck. Work in small sections if you are cleaning the entire deck. This will prevent the cleaning solution from drying before you can scrub it. To apply the cleaner to railings and posts, pour some of the mixture into a garden sprayer. Allow the cleaning solution to soak into each section for about 15 minutes.
Scrub the deck, and particularly the green stained areas, with a stiff brush or broom. A long-handled brush or broom is ideal for the floor of the deck. Use a hand-held scrub brush to scrub railings and posts.
Rinse the cleaned portion of the deck with plain water from the garden hose. Continue rinsing until no more suds appear from the oxygen bleach mixture.
Allow the deck to dry completely. Inspect the deck to see if the green stains have been completely removed. Repeat the process if the stains remain.