Is there such as an acceptable product called sealant for shingle roofs to keep off algae, black stains, etc.
Here's my story:
My current house (moved in 2.5 years ago) has "black stains" (3 ft strips) running along the sides of 2nd floor dormers. We assume they are roof parcels shadowed by the dormers (blocking the sun) which permitts wetness, and therefore, spores to form. The home inspector said it is cosmetic, but worthwhile to clean off at some point. Fast forward 2.5 years to present, and my wife, who is ruled by design & looks, bumped into a contractor who was roof cleaning a neighborhood house, and guess what, asks him to clean our roof. The contractor says he uses biodegradeable cleaner & spore killer which won't harm our close-in plantings. My wife is pleased with the result -- basically, the roof is uniformed color again, and not too painful to the wallet ($400), and getting rid of organic matter from the roof (we think, basic quality installed 9 years ago to sell the house) is a good thing.
Yesterday, my wife calls at my workplace in the afternoon and says the contractor descfribed to her a process of adding a clear "sealant" to the roof shingles that would keep algae, moss, black stains (whatever) from attaching for a period of years for $X,YYY. I said, what ?? Let me think about it. Wife said, too late, work was done . . . . check written out. She's no dummy, but wants what she wants, and sometimes in an instant, and previously heard about roof sealant from others so her scam alarms didn't ring.
So I Google roof sealant and that's not much out . . . there're products claiming to seal gaps & minor water leaks, but almost nothing about keeping out spores (but learned about copper strips, interesting). I'm not concern of getting overcharged, but does this stuff work ?
The receipt for the work has no description of the applied sealant.