How to Prevent Mold and Mildew on Your Deck

Surface with Mold - Preventing Deck Mold and Mildew
Kevin Marshall
October 2, 2020

Most property owners want to prolong their deck’s life, but they don’t know the best way to do it. In this article, we will show you how to prevent mold and mildew on your deck.

Discouraging Mold Growth

To discourage mold growth, keep your deck as dry as possible. While you cannot keep an outdoor deck dry all the time, make sure to mop or sweep up any pools of water that accumulate so that mold does not get a chance to get started.

Any potted plans on your deck should sit in saucers that will catch any excess moisture from watering your plants. Make sure that gutters and downspouts direct water away from your deck. Make sure your gutters stay clean so that they do not overflow. Fix any leaks that drip on your deck. If too much snow falls to sweep away with a broom, use a plastic shovel to remove the excess snow, as a metal shovel might damage your deck.

Remove items that block sunlight from shining on your deck. This means moving your patio furniture and planters periodically so that all of your deck gets sunlight. Shady areas are more likely to incur mold.

If you like the look of an outdoor rug on your deck, use one made of plastic. Carpets made of natural fibers such as jute do not dry out as quickly after a rain and are therefore more likely to encourage mold growth, both on the rug and the decking underneath.

Reduce Moisture Under Your Deck

If your deck is low to the ground, consider installing ventilation underneath to help keep it dry. You should also install drainage ditches to move water away from the underside of your deck as well. You can also fix leaks with these tips: quick fixes for a leaky deck.

Have a landscaper grade the area under your deck if it continues to pool water. They can also install the drainage trenches for you if you do not feel up to the task.

How to Prevent Mold and Mildew on Deck - Do Not Use a Pressure Washer!

You may read elsewhere that you should just pressure wash your deck, and the mold or mildew will just go away, which is not valid. While pressure-washing is a great way to prepare a deck for sealing, this is not recommended on decks with mold or mildew. The reasoning behind this is because the pressure washer will drive the mold and mildew spores deep into the wood where they will continue to grow, even if you cannot see them.

Once your deck has signs of mold or mildew, that growth must be killed with commercial cleaners so that it will not recur after resealing the deck.

Cleaning and Sealing Your Deck

Commercial cleaners designed to kill mold and mildew on the wood, hydrogen oxide bleach, and sunlight will all do wonders for getting rid of mold and mildew on your deck. Make sure that you have killed all of the molds before resealing your deck. Mold will continue to grow and cause your stain or sealant to fail prematurely, as well as cause rotting beneath your deck's surface, which can be dangerous.

If you are going to reseal your deck after cleaning, you should sand it smooth first. After that, you should restain and reseal your deck every 2-5 years based on how much use your deck sees each season.