my house has two levels of roofing, and the shingles above the garage (lower level roof) have some moss. The shingles are also somewhat discoloured. this roof receives a lot of runoff from the upper roof because there is no upper level eavcestrough. How can I assess the potential damage to this lower roof? is the fact that the moss is there a cause for concern? Should I put troughs on the upper level?
Answer:
You'll probably have to replace the shingles because they usually don't support moss unless they are kept wet for extended periods of time. Your shingles appear to have suffered enough abuse to have turned into absorbing sponges rather than water shedding shingles. Wait for a real dry eay and turn the garden hose on them to see how long they stay wet. They should shed water immediately.
