Wood Deck Mildew Removal

mildew on wood
What You'll Need
Common garden sprayer
3 quarts of water
1 quart of oxygen bleach
1/4 cup of ammonia-free liquid dishwasher detergent
Water hose
Wooden deck sander
Oil-based wood sealer
Scrub brush
Rubber gloves
Face mask

It’s no secret that conditions like excess moisture, poor ventilation, and a lack of regular cleaning are what encourage mildew growth. However, when you have mildew growing on your wood deck, one of the additional causes is likely neglect. The presence of mildew in a place like a deck suggests that the wood has not been treated or cleaned in a long time.

In fact, it’s not uncommon for mold on a wood patio or deck to be accompanied by even bigger problems like graying, splintering, cracked boards, and in extreme cases, instances of wood rot.

Hopefully, if you’re ever unfortunate enough to encounter mildew on your wood decking, that will be the worst of things and you’ll still have time to react and save the deck from mold and rot.

If deck restoration is not yet needed, removing mildew is simple. However, it does require a number of tools and materials and a lot of scrubbing strength.

Step 1 – Choose a Hot Day

When removing mildew from your wooden deck, select a hot and sunny day to do the job. A hot sun does a great job of quickly drying the wood and makes killing the mold spores and removing mildew that much easier. Dryness doesn’t encourage spore growth and intense heat will aid in killing existing spores.

Step 2 – Wash the Deck

Wash the deck with a pressurized nozzle on your hose. Then let the area dry thoroughly under the hot sun. This should eliminate most of your mildew. If this doesn’t do the job or you see signs of lingering mildew stains on your deck, proceed to the next step.

Step 3 – Prepare the Treatment Solution

Prepare the wood deck treatment solution by mixing 3 quarts of water, 1 quart of oxygen bleach, and 1/4 cup of ammonia-free liquid dishwasher detergent. If you don’t have bleach, you can substitute vinegar. Vinegar acts like the bleach without the chemical composition.

WARNING: Make sure you have your face mask and gloves on firmly. These chemicals are harmful to your skin, lungs, and eyes, so it's important to make sure your body is covered and protected.

Step 4 – Apply the Solution

Spray or pour the chemicals on the mildew-infected areas. Allow the solution to sit for about 10 to 15 minutes. You need to give each of the chemicals time to do its individual job.

For example, the bleach in the solution will kill mildew spores on a wooden deck. The dishwasher detergent, on the other hand, will act as an emulsifier for the mildew and make it easier to remove. The bleach of vinegar will assist in both killing the mold spores, as well as lifting stains to the wood.

Thoroughly rinse all the residue off the deck once the chemicals have finished working their magic. If you still see any mildew present, repeat this step until you get results.

NOTE: If multiple washes still don’t make an impact, consider talking with an expert on wooden deck mold and mildew. There may be things happening that you aren’t aware of. In the worst case, your deck may need a full restoration.

Step 5 – Sand Down the Deck

Use a wooden deck sander to sand down the deck.

Step 6 – Treat the Deck

Treat the deck with an oil-based sealer. It’s possible that neglecting this bit of maintenance is what got you into trouble in the first place.

Treating your deck with the sealer every five years will help keep your wooden deck in good shape for a long period of time. A sealer will help repel moisture, the cause of mildew. If you’re especially worried about recurring mildew, find a wood deck sealant option with an added fungicide.