Run off Stains on roof

Building a home with the option for metal rook canopy over the garages and bay windows. There is a home in the neighborhood already built with run off stains on their metal roof. How do I prevent this from happening on my home?		Guest User 11/3/2016	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/21625/find/
I really do not understand what that stain is on the neighboring house. If anything, if that area is staying damp, I might expect to see some dirt and possibly fungal growth but not the whitish stain. I wonder if much could be related to the downspout ... by the way, that is a lot of water from that downspout dropping onto one standing seam panel. That bothers me a bit from a technical standpoint.		Todd Miller Isaiah Industries, Inc. 11/3/2016	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/21626/find/

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