This discoloration on your roof is actually blue green algae named Gloeocapsa Magma. This is an air born algae that can easily move from roof top to roof top and quickly cover any neighborhood. Like any algae, best conditions for spreading are wet, humid and shaded areas. Growth normally begins on the north side of structures. These areas generally get more shade and take longer to dry out from nightly dew and rain.
Shingle manufacturers began to change the makeup of their products in the 70’s and 80’s. Their new composition consists of crushed limestone which is an excellent food source for the algae, and when combined with warm and humid weather, gives it the perfect environment to thrive in. This algae can hold water on your roof and act like a magnafying glass raising you roofs temperature and eventually increasing your cooling costs. If left to worsen, this growth will also cause granule loss and ultimately shorten the life span of your roof.
Are you concerned with damages to your roof or landscaping? Take a few moments to watch a safe Low Pressure Roof Cleaning in progress.
Roof algae will eventually return to a roof, some sooner than others. Just as before, it will start very small and unnoticed. The more ground it covers, the faster it will begin to spread. The recommended prevention is a quicker, lower priced maintenance cleaning every 1-3 years. This can vary from home to home depending on shade, humidity, and moisture levels through the year.