Black Streaking, or Algae Removal


If you live in Northeast Wisconsin, you’ve probably seen unsightly dark streaks on asphalt shingle roofs. Though often attributed to an accumulation of dirt, defective shingles, mold, or mildew; the most common culprit is actually a blue-green algae known as Gloeocapsa Magma that is spread by airborne spores.
Roof algae (black streaking), or Gloeocapsa Magma, is a type of algae that thrives in humid and warm climates (much like our summers), and usually appears first on the North slope of the roof where shade is prevalent and moisture tends to accumulate.

To keep the algae (black streaking) from coming back, I can insert a 4-inch-wide strips of zinc or copper under the row of shingling closest to the roof peak, leaving an inch or two of the lower edge exposed to the weather. That way whenever it rains, some of the metal molecules will wash down the roof and kill any algae trying to regain a foothold on your shingles. Another great, maybe better alternative is a stain blocker I can apply to your roof immediately after the cleaning is completed. there of course is an addition charge for these services, but they are a great way to keep black streaking, algae, moss, or lichen from coming back for several years longer than the cleaning alone.  For more on this, go to: preventing roof damage. It is a page on this site.