News & Resources

Algae on roofs

Algae Roof Stains

Roof discoloration from algae or fungus growth made its way to the Cincinnati area about 10 years ago. It originated in the coastal areas of the southeastern United States and traveled north. The name of the algae is Gloeocapsa Magma. The algae is transported through the air and collects upon roofing structures. It produces a natural pigment that will discolor most roofs. The roof stains are dark brown in color and are easily seen on lighter-colored shingles.

Shingles that were manufactured in the 1990’s are most susceptible to algae growth and discoloration. During this time period the shingles were not resistant to this type of algae. Small amounts of copper (or Zinc Oxide) were added to the shingle granules in 1999 to make them algae resistant. Each time it rains, the roof is cleaned with the copper solution and algae growth is eliminated. Algae growth on the surface of the shingles will not cause roof leaks and is not a health hazard.

Algae on roofs

Roofs with algae problems can be difficult to clean. The effects of the algae can be significantly lightened by applying a solution of bleach, trisodium phosphate, and water. The roof should be gently rinsed off with a garden hose shortly after the solution is applied. Asphalt shingles should never be pressure washed.

Algae cleanings are usually a short-term solution for roof discolorations. Strips of Zinc or Copper can be installed in a continuous manner near the ridge of the roof to prevent future algae growth. These products distribute a metallic solution on the roof that eliminates any algae that is present. The strips offer a long-term solution but the results may not be noticed for a couple of years. A combination of algae cleaning with zinc or copper strip installation is recommended.

When installing a new roof on your home, be certain that the roofing company is using algae-resistant (AR) shingles. The AR warranties and products vary greatly among shingle manufacturers. Shingles that have smaller amounts of copper granules are less expensive but have very limited algae warranties – beware! Deer Park Roofing began installing Owens Corning AR shingles in 1999 (as soon as they became available in Cincinnati). They cost a fraction more than non AR shingles but are well worth it. At the time of this writing, DPR has not had a single algae warranty claim from the entire family of Owens Corning Shingles.

The photos above demonstrate the effectiveness of algae-resistant shingles. The photo on the left was taken after Deer Park Roofing repaired this roof after the (Hurricane Ike) windstorm. New AR shingles were applied and were identical in color to the original roof minus the algae stains. When we came back one year later to replace this customer’s roof, the AR shingles had already begun to clean the older shingles below.

Email Us for more information about AR shingles or roof cleanings or call 513-891-9151.

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