There’s also the case of the roof rusting. If you have metal roof tiles or roof shingles, this may also be a possibility. Damaged roofing materials can also cause your roof to look discolored, so watch out for that as well. Your roofing company should either repair these or replace missing patches of shingles in your roof.
And in the case of contamination, rarely is it avoidable— so don’t stress out! Mold, mildew, and algae growth are common because of moisture in your roof. And it’s the most common cause of bad cases of discoloration. To combat this, a correct method of pressure washing is done by professional roofers in order to remove the colony off of your roof shingles.