Why is my house turning green?

“The yellow pollen I understand, but why is my house turning GREEN?” We hear this from so many customers!  Don’t worry, its not just yours! The reality is, regardless of the type of siding on your house—or whether your home is in the sun or the shade, in open air or tucked into a wooded lot—your house is almost certain to go green from time to time. 

Let’s take a look at why, and what you can do about it.

 “Why is my house turning green?” Here’s why…

That green muck visible on your siding, deck or roof is a result of excess moisture lingering on the surface. It might be algae; it might be mold or mildew.

The only way to know for certain which you have is to send the material off for testing. As a rule of thumb, green on the sunny side of your house is often algae. Green on the shaded side is more likely to be mold or mildew. 

Algae, mold and mildew are generally present just about everywhere, and moist surfaces promote their growth. The number one place we see green on a house is on the North Side. This is of course the shadiest side and a breeding ground for unwanted green film. Other common culprits include:

  • clogged or loose gutters, that may be spilling over onto the side of the house;
  • shrubs and vines against the house;
  • or, if there’s been a long damp spell, condensation dripping steadily from siding, shutters, eaves or sills may be the cause.

Siding that is close to the ground will have higher exposure to moisture, giving mold mildew and algae a food source to grow. Sometimes, as in the image here, it’s found right under the eaves.

We have seen a lot of precipitation this season in Raleigh, NC so homeowners in the Triangle area are likely to see a lot of green this Spring. The good news is that removing it requires the same approach, so it’s not always necessary to figure out which you have in order to remove it!

How do I get rid of that green film on my house?

If you’re seeing green, you DO need to take quick action to remove it. Most homeowners agree that green growth is not a good look for your home. But many don’t realize that it can lead to faster spread, and other problems (like damage to wood)—and if left unchecked, may result in fines from the HOA! Furthermore, on some surfaces, like decks and brick paths, it’s a slippery safety hazard.

Unfortunately, you can’t just spray it away. These are living things that stubbornly cling to surfaces in a life-or-death battle. Simple cleansers don’t remove them either. 

At Dr. Detail Pro we’ve found the most effective approach to remove this nasty and invasive organism, is to use a blend of sodium hypochlorite (the same active ingredient you would find in bleach) and detergent. We call this a “soft wash” for siding. This combination provides a 1-2 punch that knocks out molds and algae!

While we are soft washing the house, it is critical to protect plants and flowers that skirt the home. We recommend removing potted plants back away from the home. Before we get started, we lubricate all the foliage thoroughly with water. This creates a protective buffer for the plants so that the cleaning solution slips off and away. (Check out our short video that explains it further.)

Also, I would caution all homeowners never to use high pressure on the side of their house. I have seen this method strip paint from many homes. Even the weaker pressure washers that you might find at Lowes Home Improvement or Home Depot can do damage when used incorrectly. The force is so great that it can even loosen siding.

What are some ways to help prevent my home from turning green?

  • Ensure your gutters are clear and secured. 
  • Trim back shrubs, trees and foundation plantings, and remove any climbing vines. We want air to circulate and light to reach your siding.
  • Be sure your sprinklers are not adding to the moisture—redirect so water focuses on the soil or base of plants, not the siding or wood surfaces.
  • Check that you’re not seeing a build up of green around dryer vents (which often spew moist heat), and remove it promptly if any begins to show.
  • Get your home’s exterior cleaned regularly to remove spores and budding growth. 
  • We recommend washing your house twice a year for most homes in North Carolina because of our specific climate. Early Spring and late fall are usually the ideal times for routine washings.


And, if you’re a new homeowner, NCSU has some other really helpful tips on keeping your North Carolina home well maintained.  

Hopefully that helps answer your question “why is my house turning green?” and provides some strategies to help you reclaim your home and decks’ beautiful look. We’d love to help you prevent any future algae, mold or mildew issues. Also, we are happy to provide a free customized maintenance schedule for your home!