Is this a question you've wondered about from time to time? Whether it was happening on your roof or someone else's? Well, ask no more. Here's what our friendly neighborhood home inspector, Jim Schwarz of Center Grove Real Estate Inspections had to say:
Dark streaks on your roof are algae growth. This typically shows on the North or East exposures of the roof surface that stay cooler and more damp than the sun exposed surfaces.
These streaks are also an indication that the roof is beginning to approach its latter stages of useful life. As the algae grows, it begins to harden the shingle, making it brittle and more susceptible to damage.
This damage will show up as granule loss, which will then expose the mat of the shingle to more heat and weather. Over time, the degradation of the roof will accelerate.
Roofs like this should be monitored bi-annually to find necessary repairs and to best determine the point of eventual replacement.
Great insight...thanks Jim!
This information was originally posted at: www.iShopGreenwood.com