The 5 YO roof on my Coleman is starting to show black across the trusses, which is the coating wearing off. Last fall when I washed and protected the roof I tried scrubbing to see if it was on top or ...
I have shringled roof and I have no idea about this but it can be very complicated. I think you must seek professional advice from home remodeling professionals. Go here and ask your query, may be this will help.