How to Remove Mold from Your Wood Deck

Mold on a deck is more than just a visual eyesore; it is a symptom of trapped moisture that will eventually compromise the structural integrity of the wood. If your boards feel slippery when wet or show patches of black, gray, or green spots, the fungus has likely taken root in the grain. Cleaning it properly requires breaking the bond between the mold spores and the wood fibers without stripping the finish or damaging the wood itself. By using the right chemical agents and a bit of elbow grease, you can restore your deck's appearance and prevent rot from setting in before the next season.

1. Clear the Deck First. Remove all furniture, planters, and grills from the deck surface. Sweep away loose leaves, dirt, and debris to provide a clean workspace for the cleaning solution.
2. Activate Your Cleaner. Combine one part oxygen bleach powder with four parts warm water in a plastic bucket. Stir until the powder is fully dissolved and the solution is active.
3. Let Chemistry Do the Work. Pour the solution onto the deck or use a garden sprayer to coat the surface evenly. Let the mixture sit for 15 to 20 minutes, ensuring it stays wet and does not dry out.
4. Scrub With the Grain. Use a stiff-bristle deck brush to scrub the wood in the direction of the grain. Focus on heavily infested areas, applying firm pressure to lift the mold from the wood pores.
5. Wash Away the Evidence. Rinse the entire deck with a garden hose or a pressure washer set to a low-pressure, wide-fan nozzle. Ensure all cleaning solution and loosened mold is washed off the surface.
6. Patience Wins This Round. Allow the deck to air dry completely for at least 48 hours. Inspect the boards once dry to ensure no mold remains before deciding if a sealant or stain is needed.