How to Clean Mildew Stains Off Outdoor Wood

Removing mildew stains from outdoor wood restores its natural beauty.

Mildew stains on outdoor wood can turn beauty into a beast. Mildew attaches itself to outdoor wood furniture and decks and stains them with black splotches, making the wood look old and used. Fortunately, removing mildew stains from outdoor wood can be done with a few household and hardware store items, and without the damage that power sprayers cause. Forget expensive cleaning and renovation; instead, just gather a few cleaners and get started.

Things You'll Need

• 1 quart oxygen bleach
• 1/4 cup ammonia-free liquid dish washing detergent
• Spray canister
• 1 cup chlorine bleach
• 8 to 10 tbsp. washing soda or trisodium phosphate
• Gloves
• 3 tbsp. oxalic acid
• Water
• Soft-Bristle Brush
• Measuring Cup

Instructions

1. Sweep wood decks thoroughly to remove loose mildew spores. Mix 3 quarts of water, 1 quart of oxygen bleach and 1/4 cup of non-ammonia liquid dish washing detergent in a spray canister. Liquid detergent is better than regular or laundry because it breaks down the mildew more efficiently. Spray the mixture evenly and liberally. Leave the mixture on for 10 to 15 minutes. Rinse with water.

2. Mix 8 to 10 tbsp. of washing soda or trisodium phosphate with 1 gallon of water for outdoor wood furniture. Dip a soft-bristle brush in the mixture and scrub the mildew stains. Rinse with clear water. Allow the wood to dry and then paint it with a mildew-resistant paint.

3. Remove the paint on mildew-stained painted wood. Scrub the bare wood with a mixture of 8 to 10 tbsp. of trisodium phosphate,1 cup of chlorine bleach and 1 gallon of water. Rinse and allow the surface to dry completely before repainting.

4. Scrub stubborn stains on outdoor wood furniture with a mixture of 3 tbsp. of oxalic acid and1 pint of water. Rinse the wood thoroughly with water, and allow it to dry before painting or staining.

Tips & Warnings

• Always wear gloves when working with oxalic acid mixtures.

References

• Western Red Cedar Lumber Association: Prepare Your Deck for Winter and Take the Hard Work Out of Spring Cleaning
• Ask the Builder: How to Clean a Deck
• UGA College of Family and Consumer Sciences: Mildew Prevention and Removal