Black mold is an unsightly fungus, and if you notice it growing on your deck, you might be looking for methods to remove black mold from your deck effectively.

Black mold is a fungus, usually greenish-black or solid black in color, with a distinct smell that thrives in dark, damp places with materials with high cellulose. It should be removed as soon as possible as can damage your deck and pose a health risk to people.


If you’re dealing with black mold on your deck, it’s crucial to immediately remove it as soon as you spot it and learn how to prevent regrowth.

With that in mind, read our article to know the relevant methods to safely and effectively remove black mold from your deck.

What Is Black Mold?

Stachybotrys chartarum (Stachybotrys atra), also referred to as black mold or toxic black mold, is a mold or micro fungus variety that produces non-motile fungus spores or conidia in slime heads. 

In general, the black mold is usually greenish-black or black to dark brown in color, but its appearance may vary depending on the mold species.

Black mold can often grow and be found on highly-cellulosic materials or highly organic matters, such as paper, fiberboard, and gypsum board. It also thrives in dark, damp places, such as showers, bathrooms, kitchens, toilets, basements, crawlspaces, and windows.

Some signs that mark the presence of a black mold in a particular place include an unpleasant or musty odor coming from the house’s walls or other surfaces (especially after rain) and visible moldy patches or growth on building materials, woodwork, ceilings, or walls.

Is Black Mold Dangerous?

Certain species of black mold produce mycotoxins or naturally occurring toxins that are airborne and can be released into the air. This toxic chemical commonly produced by mold or fungi is dangerous to human health, especially when inhaled or eaten.

Black mold exposure to a few spores can cause mild effects, including coughing, eye irritation, sneezing, stuffy nose, fever, chronic headaches, rashes, chronic fatigue, sore throat, and red or itchy eyes.

However, prolonged black mold exposure, especially to infants, people with allergies or preexisting health conditions, compromised immune systems, or people sensitive to mold spores, may experience stronger reactions and develop health problems. Severe symptoms include shortness of breath, vomiting, nausea, respiratory complications, and even bleeding in the nose and lungs.

Moreover, people with asthma may experience worsening asthma attacks and heightened breathing difficulty. Also, people with weakened immune systems are more likely to be susceptible to fungal infections.

Mold poisoning or mycotoxicosis is another health concern that may be dangerous to people exposed to black mold. It causes headaches, nosebleeds, memory loss, pains and aches, and mood changes.

Why Is Black Mold Forming On Your Deck?

A deck is commonly made from different materials, including wood, polyvinyl chloride (PVC), or metal. And just like any other building feature, it’s susceptible to problems like black mold growth.

Here are so several reasons why black mold is forming on your deck.

Improper Drainage

Improper drainage is a significant reason for mold growth under a deck as water is collecting on the deck, which can cause the mold to grow, especially if left unattended. Stagnant water or water pools may also cause water damage or water leaks that risk mold growth as it increases humidity, which is an factor for mold growth. Exposure to water within 24-48 hours may encourage the mold to take place and continue to grow, especially when accumulated moisture is present.

Not Getting Enough Sunlight.

The absence of direct sunlight or shaded decks may encourage mold growth as the moisture doesn’t evaporate, creating a perfect area for the mold spores to thrive. Shaded decks, especially when damp, also take longer to dry, fostering a breeding ground for mold and making them more prone to black mold growth.

Excess Humidity and Moisure. 

High humidity environments caused by changing seasons, cracks, leaks, and spills from the foundation can lead to black mold growth. A deck with poor ventilation may cause excess condensation, creating stagnant air and accumulating moisture that mold spores need to thrive.

Will Black Mold Damage Your Deck?

Black mold growth on your deck doesn’t only impact its appearances like discoloration and stains, but it can also damage your deck, especially when left unchecked. That’s why it’s essential to remedy and remove black mold on your deck, especially at its early stages, as quickly as possible.

Black mold can weaken and erode your deck structure over time, especially if the deck material is wood. It may cause wood rot, faded boards, and cracked and splintered deck boards when exposed for a long time.

Black mold growth on metal and composite decks may also result in rust, causing the deck to tarnish and its paint or finish to flake eventually.

How to Clean Black Mold Off Your Wood Deck?

Wear Protective Clothing. 

Before cleaning black mold off your wood deck, it’s important to take proper safety measures, such as putting on protective clothing to keep yourself safe, as prolonged exposure to mold can be dangerous to your health.

Examples of protective clothing include safety goggles, rubber gloves, an air mask, a long-sleeved shirt, and work pants. These will prevent mold spores from contacting your skin or inhaling it. It’s also good to wear old clothes or protective outerwear as chemicals may cause stains on your clothes.

Vacuum the Deck Area. 

Use a vacuum with a HEPA filter onto the deck area affected by mold to remove mold spores and other debris, dirt, or other organic matter that mold considers a food source. After vacuuming, empty the vacuum canister into a plastic bag and take it outside the house. Don’t forget to seal the plastic bag tightly to prevent the mold spores and other dirt from escaping before disposing of it.

If you don’t have vacuum, you may clean the deck area by sweeping it with a soft-bristled broom.

Wash and Scrub the Deck. 

Begin washing the deck surface area with a cleaning solution—a deck cleaner, liquid dishwashing detergent, and water solution or bleach solution. 

Apply the chosen cleaning solution to the entire area and scrub using a soft-bristled brush, gently going over the moldy area. It’s also good to remove excess water as you scrub and clean using a sponge.

Spritz the Deck with Vinegar. 

Using a vinegar solution in a spray bottle, spritzing the mold, and then letting the vinegar soak for an hour will also help kill the mold and its spores to prevent further spread. After that, wipe the deck area using a rag or clean, damp towel. Lastly, air-dry the deck to ensure any mold growth won’t occur.

Stain or Seal the Deck. 

If there are remaining mold stains, it’s best to sand the deck area before staining or sealing it. Use a proper sandpaper grit, working around the affected deck surface until there are no signs of mold.

After sanding, vacuum all the remaining dirt and then wipe using a rag. Lastly, stain or seal the deck to protect the deck surface from mold growth, penetration of mold spores, and future mold outbreak.

How to Remove Mold From Painted or Stained Wood?

Painted or stained wood won’t easily allow mold to grow on your deck, but old paint or stain may begin to break away, allowing black mold to take root. If this is the case, you can use a mild cleaning solution, such as dishwashing detergent with water or vinegar, to remove mold.

Apply the preferred solution and brush the entire area using a soft-bristled brush. You may also spritz the area with a spray bottle with vinegar to prevent mold growth and let it soak for an hour. After that, wipe the deck area using a clean, damp towel and inspect for any mold residue.

Remember that using bleach or a pressure washer isn’t a good option because it can strip the stain or paint off and cause discoloration or fading.

How to Remove Mold From Composite Deck?

Remember that household chemicals used for wood decking, like bleach, may have harsh chemicals that can damage the composite deck, including discoloration or fading. The recommended solution is a deck cleaning solution with Sodium Hypochlorite, a dishwashing solution, or a vinegar solution.

The first thing to do is pre-rinse the composite deck using a power wash or hose to remove as much mold growth as possible on the surface. Next, apply the chosen cleaning solution, preferably the vinegar solution, directly onto the mold and sprinkle baking soda. After that, soak the compound for 20 minutes, and then scrub using a gentle bristle brush to remove mold residue. After scrubbing, you can now rinse the area thoroughly.

How To Remove Black Mold Under Deck?

If mold growth appears under your deck, it means there is too much moisture present in that area. It may be because the deck was built too close to the ground, faulty grading, or improper drainage.

One method to remove mold under the deck is using a garden sprayer filled with a cleaning solution and then scrubbing the surface to remove the mold. You may also use a standard garden hose with a nozzle to spray to rinse the solution while removing any mold spore residue.

It’s also important to prevent moisture build-up under the deck by adding ventilation to allow the trapped moisture to escape. Installing a drainage system will also remove the trapped moisture, thus keeping your deck safe from mold growth.

How to Prevent Black Mold on Deck?

There are many reasons why mold is growing on your deck, and the two most prevalent causes are the ever-present moisture and nearby water sources near your deck.

Therefore, it’s crucial to always keep your deck dry as possible to discourage mold growth. Keep a lookout for puddles or stagnant water on your deck because these damp areas are where mold thrives. You can keep your deck dry by sweeping or mopping water pools on your dec, especially after it rains.

It’s also essential to frequently sweep your deck using a soft-bristled broom to remove any organic matter that mold loves, such as leaves, pollen, and dirt. It will also help clean any mold spores in your deck, if there are any, preventing mold growth on your deck.

Another important prevention method is to provide your deck with enough sunlight by clearing out objects like furniture or planters that may block sunlight from reaching your deck. 

In addition, you may catch excess water by storing potted plants in large sauces. If you have downspouts and gutters, it’s also important to regularly clean them, so they don’t overflow, as they can help redirect the flow of rainwater away from your deck. Then, remember to remove or sweep it away with a plastic shovel or broom when it’s snowing.

Staining or applying an all-weather sealant to your deck every 2 to 5 years will also help prevent mold from growing on your deck. In addition, adding ventilation to your deck will allow moisture to evaporate if it has enough space below.

If black mold is already starting to spread on your deck, the best way to stop the process from further progressing is by cleaning your deck with a deck cleaner and scrubbing it with a brush or soft-bristled broom. You may also apply your selected cleaning solution with a garden sprayer or hose nozzle, spraying the solution while scrubbing the entire surface.

After cleaning the deck, let your deck dry for about 48 hours, and then sand the deck’s entire surface. It’s also recommended to seal the whole deck.

Editorial Contributors
Matt Greenfield

Matt Greenfield

Matt Greenfield is an experienced writer specializing in home improvement topics. He has a passion for educating and empowering homeowners to make informed decisions about their properties. Matt's writing focuses on a range of topics, including windows, flooring, HVAC, and construction materials. With a background in construction and home renovation, Matt is well-versed in the latest trends and techniques in the industry. His articles offer practical advice and expert insights that help readers tackle their home improvement projects with confidence. Whether you're a DIY enthusiast or a seasoned professional, Matt's writing is sure to provide valuable guidance and inspiration.

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