How to Deep Clean Mold and Mildew from Your Deck

Dampness is the inevitable enemy of any outdoor living space. Over time, that subtle green or black film creeping across your deck boards is more than just an aesthetic eyesore—it is active fungal growth feeding on trapped moisture and surface debris. Ignoring it doesn't just make the surface slippery; it invites rot that can compromise the structural integrity of your boards over several seasons. Restoring a deck isn't about harsh chemicals or aggressive power washing, which can often splinter wood or etch composite surfaces. The goal is to lift the biological growth safely, neutralize the spores, and restore the natural color of your decking material. With the right solution and a bit of elbow grease, you can reclaim your outdoor space in an afternoon.

  1. Clear the Deck First. Remove all furniture, planters, and decor from the deck surface. Use a stiff outdoor broom to sweep away loose leaves, dirt, and organic debris that acts as fuel for mold.
  2. Dampen Before You Attack. Lightly wet the entire deck surface with a garden hose. This prevents the cleaning solution from absorbing too quickly into dry, porous wood, allowing it to work on the surface mold instead.
  3. Spray the Solution On. Mix your oxygen-based deck cleaner according to the manufacturer's ratios in a plastic garden sprayer. Apply an even, wet coat over the affected sections, working in manageable 10-foot by 10-foot zones.
  4. Let Chemistry Work. Let the solution sit on the deck for 15 to 20 minutes. Do not allow the cleaner to dry out; if it starts to evaporate, mist it lightly with water to keep the surface active.
  5. Brush Out the Grime. Use a medium-to-stiff bristle synthetic brush to scrub the deck boards in the direction of the grain. Focus extra effort on the joints and grooves where mold spores tend to congregate.
  6. Wash Everything Away. Use a garden hose with a spray nozzle to rinse the deck from top to bottom. Ensure every bit of loosened residue and cleaner is washed away, as leftover chemicals can attract dirt.