Hello, ever since we had the new roof shingles installed, we started noticing that some of our light grey concrete windowsills are getting these black almost tar looking spots, that sometimes leak/bleed onto the wall below. The installer came and said it’s the mold/fungus from trees, which doesn’t explain why only those directly under the roof are effected, and some others, away from the roof are fine. I’ve seen the same issue on other houses, what do you think it is, and how can it be cleaned?
Thank you!!
