What Causes Black Roof Streaks?

Gambril Roof Cleaning - Before And After

The main bacteria causing these “black-streaks” on roofs is called Gloeocapsa Magma, this bacteria as well as other bacteria, algae, molds, fungus and lichen are one of the main causes of roofing material breakdown and decomposition. The lichen has a filament root system that will grow down into an asphalt shingle to feed and ultimately pull the aggregate granule layer off exposing the asphalt layer therefore starting a rapid deterioration. The algae can form where moisture tends to dwell on roof surfaces. Gleocapsa Magma protects itself from damaging ultraviolet rays by producing a dark pigmented sheath. The algae discoloration typically begins as small spots then quickly transforms into streaks on the roof plane. By the time the algae is visible, it likely has been present for several months or longer.

Regular cleaning and maintenance can preserve your roof’s integrity. Keeping your roof clean and free from destructive things like algae, moss, mold and debris helps prevent serious damage. Although many roofs come with warranties, most roof manufacturers suggest regular cleaning to keep your roof in ideal condition and extend its life.


  • 1 out of every 3 residential roofs are replaced prematurely due to the appearance of the shingles rather than the functionality of the roof itself.

  • The algae that grows on roofs feeds on the limestone filler in shingles causing them to breakdown and deteriorate.

  • Keeping your roof clean can save you on your ELECTRIC BILL! Darkening of shingles from the mold and algae causes your roof to get hotter costing you more.

  • Keeping your roof clean of algae, mold and fungus free can dramatically extend the life of your roof and restore curb appeal