WHY DO WE HAVE BLACK AND/OR GREEN SPOTS ON OUR MIDDLE-AGED ROOFS?

WHY DO WE HAVE BLACK AND/OR GREEN SPOTS ON OUR MIDDLE-AGED ROOFS?

When it was first installed, your new roof looked clean, fresh and sharp.  But over time, you’ve noticed something unsettling: dark stains, streaks, or maybe blobs of black or green fuzz seem to have been poured down from the peak of the roof to the gutters.  Suddenly, it seems, your home’s crowning glory looks old, tired and unattractive. What happened? 

Buildings on the shady side of the street and high humidity facing north develop black stains
from algae and fungi and in worst-case scenarios, green build-ups from moss and lichens. These organisms, which actually feed on the crushed limestone that is part of the shingle composition, travel on the wind to land on your home. The dirty appearance caused by the roof mold or roof algae can be eliminated by washing — preferably by professionals, to avoid personal injury and damage to the shingles. But if cleaning the streaks or stains becomes a regular maintenance issue, you might want to look for a more permanent answer. There is a cost-effective long-term solution: install copper or zinc strips at the peak of the roof.   As water interacts with the metals, it produces a chemical reaction that kills the uninvited guests.Though primarily a cosmetic measure, this simple solution will not only eliminate the unsightly stains, but protect the shingles, help them to reach their intended useful life, and increase curb appeal.