Streaks and dark spots on your roof can be caused by several different things. But the major reason for dark spots on a roof is algae.
What is black algae?
While often called “black algae,” the organism Gloeocapsa magma is technically a cyanobacterium. Modern asphalt shingles use crushed limestone as a filler material, which provides an abundant food source for the algae. To protect themselves from damaging ultraviolet (UV) rays, these microscopic organisms develop a dark, pigmented outer sheath. As the colony expands, these sheaths merge, creating the long, vertical black streaks commonly seen on roof surfaces.
The lightweight spores easily detach and are carried by the wind, birds, or wildlife, which is why an entire neighborhood can develop streaking once a few roofs are infected.
Do black algae spores damage roofs?
While the Asphalt Roofing Manufacturers Association notes that algae doesn’t directly eat the structural components of the roof, the colonies themselves hold moisture, which can encourage the growth of destructive moss and lichen. The dark areas also absorb more heat, increasing attic temperatures and causing your air conditioning to work harder.
Black algae spores spread by wind from place to place, just like dandelion seeds. When algae land on a “friendly” roof – one that’s warm and moist with asphalt shingles containing crushed limestone, an excellent food source – they begin actively growing.
When the roof dries out, the algae go dormant and discolor. Unsightly dark stains remain that can detract from your home’s curb appeal. If left unchecked, algae problems can even cause the shingles to deteriorate and leak.
Algae stains and dark spots on a roof
Most shingles now have algae-resistant products on them, but they only last 10-12 years. So as a roof ages, it becomes more and more discolored as the algae takes over the roof. This is not only a sign that your roof may need replacing, but also might be a sign that you have other issues, like trees overhanging the roof, or a major shaded area from another structure blocking the sunlight. Or simply a worn-out roof.
Algae-resistant shingles to the rescue
Muth & Company offers algae-resistant shingles from GAF in a variety of colors to complement your home. The concept behind algae-resistant shingles is quite simple. Copper or zinc, one of the main ingredients in this type of shingle, poisons algae so it’s unable to survive on the roof surface. The metals present in algae-resistant shingles are further activated by rain, which distributes the poison along the roof’s surface.
These shingles do cost a bit extra, but are well worth the money. Especially if you find dark spots on a roof and algae staining bothersome, this can save you time and money on frequent cleanings.
For more information about algae-resistant shingles and to schedule a FREE estimate with roofing contractors in Columbus, call Muth & Company Roofing today at (614) 882-0900.