How to get rid of mold and mildew on a deck

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Introduction

If your deck looks dark, slippery, or smells musty, it’s time to learn how to get rid of mold and mildew on a deck. These unwanted growths thrive in damp, shaded environments and not only make your deck look unattractive but can also damage the wood and create safety hazards. Fortunately, with the right cleaning techniques and preventative care, you can restore your deck’s appearance while protecting it from future outbreaks.

Why Mold and Mildew Removal Matters for Your Deck

Mold and mildew aren’t just cosmetic issues—they impact the safety and longevity of your deck. Proper cleaning ensures:

  • Safety: Mold and mildew create slippery surfaces that can cause accidents.
  • Durability: Trapped moisture weakens wood fibers, leading to rot and costly repairs.
  • Health: Mold spores can trigger allergies and respiratory issues.
  • Aesthetics: Removing growth restores the natural beauty of your deck and boosts curb appeal.

Ignoring mold and mildew allows them to spread quickly, so tackling the problem early is always the best approach.

Step-by-Step Guide to Removing Mold and Mildew from a Deck

1. Gather Supplies

You’ll need:

  • A broom or leaf blower
  • A bucket and garden hose with spray nozzle
  • A stiff-bristle deck brush
  • Protective gloves, mask, and safety glasses
  • Cleaning solution (oxygen bleach, white vinegar, or commercial deck cleaner)

2. Clear the Deck

Remove furniture, rugs, planters, and any items sitting on the surface. Sweep or blow away dirt, leaves, and loose debris. Mold thrives in trapped organic matter, so start with a clean slate.

3. Inspect the Deck

Look for green, black, or white patches—signs of mold and mildew. Also check for areas with soft or rotting wood that may require repair before or after cleaning.

4. Choose a Cleaning Solution

  • Oxygen Bleach (Recommended): Mix according to directions; safe for wood and plants.
  • White Vinegar: Mix equal parts vinegar and warm water for a natural option.
  • Commercial Deck Cleaners: Stronger formulas for heavy growth; follow manufacturer instructions.
    Avoid chlorine bleach—it can strip color, damage wood fibers, and harm surrounding landscaping.

5. Pre-Wet the Deck

Lightly spray the deck with water before applying any cleaner. Pre-wetting helps prevent the wood from absorbing too much cleaning solution too quickly.

6. Apply Cleaner

Pour or spray the cleaning solution onto the mold- and mildew-affected areas. Work in sections for best results. Allow the solution to sit for 10–15 minutes (longer for vinegar).

7. Scrub Thoroughly

Using a stiff-bristle brush, scrub the deck boards along the wood grain. Apply firm pressure on mold patches, focusing on cracks, corners, and shaded areas where growth is worst.

8. Rinse the Deck

Once scrubbed, rinse thoroughly with a garden hose. Use enough water to flush away mold, mildew, and cleaner residue. If necessary, repeat the process on stubborn areas.

9. Optional: Use a Pressure Washer (Carefully)

If growth persists, you can use a pressure washer set under 1,500 PSI with a wide spray nozzle. Hold the wand 12–18 inches away and keep it moving to avoid damaging the wood.

10. Allow to Dry

Let the deck dry completely—24 to 48 hours depending on weather—before returning furniture or applying sealant. Drying ensures moisture doesn’t get trapped, which could encourage new mold growth.

11. Seal the Deck for Protection

Once dry, apply a water-repellent stain or sealer to protect the deck from moisture and sun damage. This step reduces the risk of mold and mildew returning.

Common Mistakes to Avoid

  1. Mistake: Using Chlorine Bleach
    It damages wood and surrounding plants.
    Solution: Use oxygen bleach or vinegar instead.
  2. Mistake: Ignoring Safety Gear
    Mold spores can irritate eyes, lungs, and skin.
    Solution: Always wear gloves, a mask, and safety glasses.
  3. Mistake: Spraying with High Pressure
    Too much PSI splinters wood and strips finishes.
    Solution: Keep PSI below 1,500 and use a wide nozzle.
  4. Mistake: Not Rinsing Properly
    Residue attracts dirt and weakens sealers.
    Solution: Rinse thoroughly with fresh water.
  5. Mistake: Skipping Sealant
    Unsealed wood absorbs moisture, inviting mold back.
    Solution: Apply a protective sealer after cleaning.

Extra Patio & Deck Tips & Hacks

  • Clean your deck at least once a year, ideally in spring or early summer.
  • Improve airflow by trimming shrubs and trees near the deck—sunlight naturally deters mold.
  • Move planters and rugs regularly to avoid trapped moisture.
  • Sprinkle baking soda in corners and shaded areas to raise pH levels and discourage growth.

Want to keep your deck looking brand-new? See our guide on how to clean a wooden deck without damaging it.

Conclusion

Learning how to get rid of mold and mildew on a deck is essential for safety, aesthetics, and durability. By scrubbing with the right solutions, rinsing thoroughly, and sealing for protection, you’ll restore your deck’s beauty and prevent future growth.

Pro tip: Regular maintenance is the best defense—don’t wait until mold takes over. A seasonal cleaning schedule will keep your deck safe, strong, and inviting year-round.