The black stains found on our roofs in Missouri is not mold, it’s actually a shingle eating bacteria called Gloeocapsa Magma (a.k.a. blue-green algae).  Washing your roof with bleach only keeps it at bay for a 12 -18 months; conversely, washing it off every year will lead to early shingle replacement because the shingles cannot handle strong chemical baths on a repeated basis.  Left untreated the algae can cause roof replacement in as little as 15 years, not what you expected when you bought a 30 year rated shingle.

If you are reading this you probably already have black streaking in a few spots.  You’re most likely wondering why now, it’s been 7 years or more with no streaks and it’s everywhere.  Most shingles in our area include an algae resistant technology; to easily explain it, they simply add copper.  Once the copper wears away your protection is gone.  Over time the entire roof will turn black.  The trick is to catch it early, clean a few small areas, and then set up a maintenance plan to have the roof treated just as you would pest control for the rest of your home.

Unfortunately the algae is transported through the air, and it’s contagious, so if your neighbors have it you will too.  To quote an article sent to us by Owens Corning “Shingle manufacturers estimate that approximately 80 percent of all roof replacements are caused by this pest.  Gloeocapsa can end up costing homeowners thousands of dollars they may not need to spend”.  Roof Doctor strongly suggests a community effort to battle the shingle eating bug.  After your roof is washed educate your neighbors about the dangers of algae, you are not only doing your neighbors a favor you are also helping yourself by cutting down on the risk of re-infestation.