Roof stains… not only are they ugly and impact your property’s curb appeal, but they also can cause severe damage to your shingles!  If you’ve ever wondered where the stains come from, the simple answer is from a living “plant” called Gloeocapsa magma, a genus of cyanobacteria. This algae is feeding on the limestone filler used to add weight to asphalt shingles. The reason it is more prominent on the north side and shaded areas of your roof is because these areas get the least amount of sunlight which causes that area of the roof to stay wetter longer. Lack of sunlight means moisture from morning dew and rain remain on these areas longer, creating the perfect environment for maximum growth. Once the colony gets established it creates a petri-dish effect on your roof, allowing dozens of different hazards to thrive, such as lichen, mold, mildew, moss, and even ferns!


Did You Know?

Some insurance companies are canceling homeowner insurance policies due to dirty roofs? Don’t let this happen to you! Call Radiance Exteriors, we can safely and effectively remove algae, mildew, lichen and contaminants from your roof. Watch this video!



Should you be concerned about it? Yes, besides being an eyesore, this algae has a root system and over time it will shorten the life of your shingles by dislodging the granules that protect and give your shingles color. The plant life that is growing on your roof is holding moisture 24/7, keeping the shingles constantly damp. Continual exposure to moisture can cause your singles to prematurely fail.

Additionally, all roofing material, whether masonry (tile) shingles or metal, has certain reflective properties. A layer of algae will impact your roof’s natural reflectivity and cause the surface to become hotter than a clean roof, thereby impacting your home’s energy efficiency.



We clean roof shingles using a “no pressure” approach. The shingle’s granules are its protection. The worst thing to do is to use pressure to clean them because it will blow the granules off of the shingle, severely shortening the life of the shingle.

Our “soft washing” method uses a combination of cleaners, algae-cides and soaps to kill the algae at its roots. Our custom solutions are based on the Asphalt Roofing Manufacturers Association’s Technical Bulletin which can be found here