I completed this gutter project last week on Yahara Place, in Madison, WI. Bob wanted the downspout moved from the end of the gutter to the center. The configuration of the new gutter and downspout channel water on the lawn, a permeable surface, instead of his concrete driveway. This subtle adjustment to his gutter system was an effective way to help protect the Madison area watershed from runoff, and helped prevent dangerous ice patches from forming on the driveway. I fabricated a downspout tray to channel water from the upper lever gutter into a scupper that I made from 6” gutter. I favor the use of trays instead of running downspout across shingles. Running downspout across a shingle roof looks a little tacky to me – I think trays are a less conspicuous option, especially when color matched to the shingles instead of the gutter system. Guttersmiths fastens them with neoprene washer screws, and sealant is applied to both the screw head and the bottom of the tray to prevent water infiltration.
I’ve seen many gutter installers in Madison simply elbow the water onto the shingles of a lower level roof. This will eventually cause premature aging of those shingles, and the runoff will have more of an opportunity to pick up nasty asphalt shingle grit and spread it into your garden, or rain barrel system, and/or a local body of water.