How to Remove Green Mold from Wood Deck?

Remove green mold from wood decks using a pressure washer or a long-handled broom and cleaning solution. Wet it, wash it, and scrub where necessary, and then rinse it thoroughly. Alternatively, try a mold-mildew-algae stain remover and let it do the work or one of the many homemade wood deck cleaners.

We will discuss what green mold is, whether it’s dangerous, what causes it, and how to remove it from a wooden deck. By the end of the article, you should understand how to remove green mold and protect your deck from damage.

What is green mold on wood?

Green mold growth occurs commonly on wood in shady or damp moist areas, or under debris that creates a shady, damp area. It often begins as dark spots or ‘shadows’ before becoming furry or fuzzy. Mold can appear in different colors depending on the type of mold, environmental factors, and sometimes on the content of the material, it is feeding on.

Is green mold dangerous?

Green mold on deck surfaces may be less worrisome than if it was growing in your basement or bathroom, but it is still a health hazard. Mold releases airborne spores that affect those with asthma, allergies, and other respiratory concerns. Decks are often located near homes, and mold spores can easily drift through screens and into homes to affect your family.

Mold can cause headaches, rashes, nervous-system disorders, and some types are linked to blood poisoning (sepsis) and even brain infections. It has also been linked to cognitive concerns like memory loss, depression and mood swings, dizziness, and fatigue. Green mold is toxic, and while it may not kill you, it can seriously affect your health.

What causes green mold?

Mold is a fungus and helps to decompose or break down organic material, like wood. Mold spores are present almost everywhere, and in the right conditions, they can settle in for a feast and thrive. Mold grows best in damp, shaded, or dark environments, like basements, attics, and bathrooms.

Wood decks are an organic material, which means mold will naturally be attracted to them, and if the conditions are right, it will thrive. Outdoor decks experience the full spectrum of climatic conditions and may spend weeks or even months being damp, especially if they haven’t been maintained and sealed or stained regularly. Anything that offers a shade that prevents sunlight from penetrating and drying the wood provides an ideal ‘home’ for mold to grow.

Leaves, planters, furniture, and even lattice screens provide shade and can keep wood from drying out. Trees and shrubs may also create seasonal shade, as can fall leaves left to decompose on the boards. Airflow over and under a deck helps dry the wood and prevent mold growth on the top and underside of the planks.

So, if you don’t want to remove green mold from deck surfaces every year, make sure air or sunlight can reach as much of the deck surfaces as possible.

How to eliminate green mold from the wood deck?

Green on wood deck boards would not be a good sign, especially if the wood didn’t start that color. The green tinge may be caused by mold, mildew, algae, or moss on deck surfaces. Regardless of what it is, you’ll want to clean it off before it can cause damage, expensive repairs, and health issues.

Many products for removing green mold from wood deck boards will also remove mildew, algae, and moss. Here are different ways to clean green growth off your deck.

• Pressure washer

On a small deck or one where the pressure washer isn’t practical, kindly use a scrub brush on a long handle and on a bucket of cleaning detergent mixed in water. Use a pressure washer with detergent on a large deck to clean the mold off. You can rent or borrow a washer if you don’t have one. Remove everything from the deck: chairs, planters, toys, everything, and then sweep it clear of any leaves, sticks, or debris.

Review the owner’s manual when adding a cleaning solution or detergent to the power washer. Use the nozzle recommended for dispensing soap. Apply the solution in a sweeping motion across the planks starting at the farthest side or corner. Wash the whole deck thoroughly. Use the scrub brush in awkward areas where mold is present.

• Mold, mildew and algae stain remover

Many products take algae and mildew from decks. There are fewer, though that does mold, mildew, and remove algae from wood deck boards. Some products are EPA certified for use around gardens, plants, and other landscape features. However, they shouldn’t be applied near water sources, rivers, or lakes. The concentrated formula is diluted following the manufacturer’s instructions.

For some products, one-gallon makes 6-gallons, so one part product to 5 parts water and the 6-gallons treats up to 1200 ft². It should be applied using an attachable hose spray bottle, pump-up sprayer, bucket and mop or broom, or a hand-held sprayer for small spots.

• Chlorine bleach

Mold and mildew are a fungus, which also means they are plants, not dirt. Mildew is a surface plant that eats across the surface. Mold isn’t only on the surface of the deck boards; it works its way into the cell structure and begins to decompose the wood. Just wiping them off the deck won’t get rid of mold and mildew.

Like poison ivy, they must be killed, including their ‘roots’ in the wood.

• Hydrogen peroxide

Hydrogen peroxide (3%) is an environmentally friendly choice for cleaning mold and mildew off a deck.

Mix the hydrogen peroxide with an equal amount of water in a spray bottle. Spray it on the mold and mildew and let it sit for 10 minutes. Wipe it off with a sponge for small areas, or rinse it off with fresh water on large areas. Make sure to keep away from clothing and fabrics as it acts like bleach.

• Baking soda

Baking Soda is not a harsh chemical but can be used to scour stains and blemishes off surfaces. Mix a cup of baking soda in a gallon of warm water and apply it with a scrub brush to remove green mold from the wood.

• Clean deck with vinegar

White vinegar is acidic and will seep into the wood and wipe out the mold at its roots. Mix the vinegar with an equal part of water and pour it into a spray bottle or plastic watering can. Apply it liberally to the whole deck as a cleaner, or only to the mold or mildew areas.

If the mold area is large, do a section at a time, so the vinegar solution doesn’t dry. Use a stiff-bristle scrub brush or broom to work it in and to remove the fungus. Rinse the wood thoroughly with clean water.