Anybody know what the best way is to clean a metal roof that is under a tree where there appears to be mold on top of the roof? Is cleaning even recommended using a high pressure washer? I'd be wondering if it'll make the roof leak. And how heavy can a person be and safely walk on a metal roof? If it can be pressure washed, is there any spray on treatment (like a clear coating of some kind) that would make the metal roof resistant to allowing mold to again grow on it in the future?