How to Prevent, Treat, and Remove Deck Mold

Source: iStock

Deck and patio season is one of the most anticipated seasons of the year. Unfortunately, just like you and your family, deck mold likes to come out during the spring and summer months, as well. Luckily, deck owners can prevent this common issue and remove their deck mold in three simple steps.

Locate the Source of the Mold

Even if you can’t freely see below the deck, that doesn’t mean mold is not present. Deck mold can occur on, around, or below your deck. As such, the source of each is quite different.

Mold Under the Deck

When mold appears below the deck, chances are, there is too much moisture, which, according to HomeAdvisor, is likely due to poor drainage near and around your deck. Adding ventilation will likely solve the problem as it can add an escape route for all that trapped moisture. If moisture is not the issue, then you will have to re-grade your landscaping so water does not accumulate under the deck.

Mold Above Deck

Most likely, if you have deck mold, it’s located above the deck. Like dirt on a tile floor or dust in the corner of your living room, the most likely cause is inattention.

As iterated in 5 Maintenance Items Deck Owners Must Know, your deck needs to be cleaned regularly. Whether you use a deck cleaner from your local hardware store or soap and a hose, your deck can’t go neglected.

Mold Around Your Deck

To make sure mold doesn’t grow anywhere near your deck, you should frequently:

  • Look for plumbing leaks in and outside the home.
  • Inspect your gutter system for proper alignment.
  • Check your eaves to see if they are correctly installed.
  • Examine the grading of your yard so water won’t collect at the home’s foundation. Look to see if your sprinkler system is in the right spot.
Source: iStock

Source: iStock

Clean Your Deck Regularly

If mold is apparent below your deck, you can add ventilation or re-grade your landscaping. For mold on the deck, you need to throw in some elbow grease. The steps are outlined below:

  • Spray your deck with a hose, removing any minor dirt.
  • Mix your deck cleaner (bleach first to kill the mold) with water and fully coat your deck.
  • Add your cleaning solution.
  • If your deck is near a flower bed, clean carefully to limit the amount of solution that gets on nearby plants.
  • Scrub your deck as your cleaning partner continues to spray with water. The dirt and algae should come right off.
  • If you have a wood deck, you should also sand down the deck and treat it with an oil-based wood sealer.

The same process can be used for composite decks, but make sure your cleaner has sodium hypochlorite in it.

If your deck has more serious issues than mold, like loose boards or rotting, you may want to contact a professional.

Seal Your Wood Deck

Most Americans go with a wood deck, so step three must involve sealing.Wooden decks need to be sealed at least once a year to protect against the climate change. The kind of deck you have in place can help determine which kind of sealant is best. Water-based sealants don’t last as long as oil-based sealants, but they are better for the environment. You can also choose to have pros come in who can change the color or hide any unwanted grain.


Preventing deck mold, both under and on your deck, is a relatively easy chore. As long as you regularly clean and inspect your deck, you can rest assured that no mold will ruin your deck season.

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