, How To Remove Green Algae From A Wood Deck

How To Remove Green Algae From A Wood Deck

Green algae is an unsightly yet common eyesore that can build up on your deck over time. If your deck is looking green after a long summer of humid weather or winter snowfall, read on to learn the best ways to clean it off and prevent regrowth. 

What Is Green Algae?


And how do you tell it apart from moss, mold, and mildew? 


Algae is a slimy, green film that grows on wood in wet, dark conditions. Moss is also green and grows in similar conditions, but is soft and fuzzy to the touch. Mold is a fungus that appears on wood as greenish-black streaks. Untreated, mold spores can pose a health risk to people and pets when inhaled.


While algae, moss, and mold are different, they are all equally harmful to your deck and should be treated right away. 

Why It’s Important to Remove Algae From Your Deck


Besides the fact that green algae isn’t a very pretty sight, it can also be hazardous. Moisture from the algae can seep into the wood, causing splinters and even structural damage if the problem is left unchecked. Algae is also extremely slippery – if your deck is covered with it, someone could easily get hurt, especially if it’s on your deck stairs. 


Algae is more difficult to remove than your average stain – it’ll regrow in just a few weeks if it isn’t properly cleaned. It also spreads quickly, so it’s important to remove any green spots you see right away. 

What Factors Aid Algae Growth?


Knowing what conditions cause algae to grow can help you prevent it from growing on your deck, patio, and wooden outdoor furniture.


Algae thrives in a dark, damp environment, but it doesn’t grow overnight. That means with proper maintenance, it’s relatively easy to prevent your wood deck from turning green. The two main factors you’ll need to be mindful of are debris and moisture. 


  • Debris: As leaves, pine needles, and other debris accumulate on your deck, they block sunlight from reaching the wood’s surface and create an ideal breeding ground for algae, mold, and mildew. Sweep or blow debris from your deck often.


  • Shade: If your deck is naturally shaded by trees or your home, sweeping alone may not be enough. You’ll need to do an annual deep clean of your deck to keep algae and moss at bay.


  • Moisture: When it rains, does water pool and sit on certain areas of your deck? While most decks have enough space between planks to allow for excess water to drain, your planks may be sealed or some may be uneven. In the winter, sweep snow off your deck to keep the surface as dry as possible. 

Cleaning Solutions that Remove Algae 


When it comes to removing algae from your wooden deck, you have quite a few options. The most common you’ll hear is bleach, but bleaching your deck can alter its color and even corrode the metal fasteners keeping your deck together. For these reasons and more, bleach is not recommended by the Occupational Safety and Health Administration for algae and mold removal. 


If you’re looking for alternative algae cleaning solutions, here are a few suggestions: 


  • Moss and algae removal products: There are quite a few different products on the market that are designed specifically to remove moss and algae from decks. Many of these products allow you to “wet it and forget it”, but tend to be more expensive than DIY cleaning solutions. 


  • Hydrogen peroxide: Another cleaner you probably already have in your home is hydrogen peroxide. However, it’s important to understand that hydrogen peroxide alone won’t kill algae growth – instead, it creates a foamy surface that helps lift the algae away from the surface, making it easier to scrub away.


  • White distilled vinegar: White vinegar is a popular natural cleaner that can be used both inside and outside. Simply combine one gallon of water with one cup of white vinegar and scrub the deck with the solution to remove algae, mold, and mildew.


  • Pressure washing: If you don’t want to use any products or chemicals on your deck, you can blast algae away with a pressure washer. Just be careful not to use too much pressure – if you’re not careful, you can damage the soft wood. 


How To Prevent Future Algae Growth


Unfortunately, there is no magic spell to cast on your deck to prevent algae growth, but there are some measures that can be taken to slow or prevent it. 


The first is cleaning annually or biannually. Algae spreads quickly, so the longer you allow it to build up, the more it grows. This is why it is important to have a regular cleaning schedule. It’s also a good idea to seal your deck with a quality water repellant. Algae needs moisture or standing water to grow, so keeping your deck dry is key.

If you have questions about deck maintenance, our knowledgeable and friendly team would love to hear from you – send us a message or call Decks & Docks Lumber Company at 866-528-9663.