I have heard people say that the black streaks on roofs are caused by everything from acorns cracking on the surface to tree sap or shingle degradation due to granule loss.  While these might be possibilities, the fact is that in most cases, the stains and streaks are a form of algae or moss.   

Roof algae, commonly known as Gloeocapsa Magma, is a type of algae that thrives in humid and warm climates and usually appears first on the North slope of the roof where shade is prevalent and moisture tends to accumulate.  The result is usually a black streaked roof.  Roof moss is a growth like what can be found on a tree or rock.  Roof algae and moss spores are carried by the wind until all roofs in the area are infested

Roof moss is very dangerous because it will grow underneath the shingle and act like a sponge soaking up water after a good rain.  Eventually the moss will cause roof leaks if not treated.  Roof moss also accumulates on the North side of the home or where shade is most prevalent.

Roof algae, once attached to a shingled roof, feeds on the dead organic matter used in the manufacturing process of the shingle.  As the fungus breaks down the asphalt shingle, the ceramic granules protecting the surface of the shingle are loosened and begin to fall off.  This causes the roof to deteriorate prematurely and diminishes the roof's abilities to reflect heat rays.  If not treated, the roof algae will reduce the life of your roof, diminish your home’s curb appeal and increase your home cooling expenses.

The initial removal of roof algae and moss is always more difficult then prevention.  A standard practice should be to clean your roof to remove staining and then apply a preventative every 12-18 months to keep the stains from returning. 

Many people spend countless hours and money cleaning their respective homes every year only to ignore one of the most visible and important parts of the home, the roof.  Adding a roof algae/moss prevention program to your annual spring cleaning chores will result in a beautiful home that looks fresh and clean! For additional information on roof cleaning and prevention contact us. We specialize in roof cleaning and prevention.