What’s Growing on My Roof & How Do I Get Rid of It?
A Guide to Roof Growth in Wisconsin
When it comes to roof growth the stains and discoloration from moss, mold, mildew, algae or lichens are not only unsightly, they can actually cause roof materials to break down and rot. This can leave your roof and your home extremely vulnerable.
What Causes It?
Roof moss, mold, mildew, algae and lichens are typically caused by overhanging trees, clogged gutters, flat roofs with poor drainage, and/or ample shade. Around here, we typically see these kind of roof problems crop up in spring and summer when there’s lots of rain and humidity.
What’s the Difference?
Moss: Moss commonly grows on wood or shake shingles, as well as asphalt shingles. Because of how thick moss is, it holds more moisture than mold, mildew or algae. Its ability to retain lots of moisture means roof materials begin to break down and rot quickly, leaving the structural integrity of your roof vulnerable.
Mold: Mold looks fuzzy or slimy and often manifests as black, brown or green. Black mold is the most dangerous and weakens the structure of your roof quickly. If it’s allowed to spread, it can easily make its way into your home, causing even more problems, including health problems for your family and pets. The good news is that Wisconsin has one of the lowest mold rates in the US.
Mildew: Mildew is more powdery in nature. It’s often found on roofs with poor drainage or places where trees hang over the house. Green, black, red & pink mildew are quick to spread!
Algae: Algae is typically blue-green or black-green in color. It often shows up on wood or shake shingles, as well as asphalt shingles that don’t get very much sun. Algae is also common in gutters and downspouts. Wisconsin is especially susceptible to algae roof stains since we’re in a high algae growth region.
Lichens: Lichens are organisms that develop from algae and fungus. They can manifest in a variety of colors, sizes and forms. Lichens are extremely hardy, and can grow in nearly any environment and on nearly any surface, including rocks and trees. Lichens also spread very easily – usually through the wind.
What Should I Do About It?
If you have roof stains or notice that your roof is growing moss, there are several things you can do.
- Trim back overhanging tree branches
- Wash your roof with a chemical cleaner, such as Wet & Forget or Moss Out (never use a power washer!)
- Replace roof shingles with algae-resistant shingles, which are mixed with copper granules that help mitigate algae growth
- Install strips of copper or zinc coated sheet metal along each side of the roof
- Schedule bi-annual roof inspections