Adding a metal porch roof to an existing metal house roof

Ray Owens
10/24/2015
We plan to add a front porch to our 1960's ranch house. The house is roofed with exposed fastener "R" style metal panels over one layer of asphalt shingles. (I think "R style" is the right term, the panels are not the standing seam style panels). The house roof pitch is 4:12. We are planning a shed style porch roof of metal roofing panels to match the house roof. We plan to tie the porch roof into the house roof 6 feet up from the front eave of the house roof. The porch will extend 6 feet out in front of the house, so the porch roof will be 12 feet, front to back. If I am calculating correctly, the pitch of the porch roof will be 2:12. The metal house roof is in very good condition, and I would like to avoid removing it, if possible. But I know that the top edge of the porch roof should be under the bottom edge of the house roof, so that rainwater will flow from the house roof onto the porch roof. I have seen how flashing and pitch transition materials are used when the porch roof and the house roof are installed at the same time. But I have not found information on how to tie in a new metal porch roof to an existing metal house roof. Your advice will be appreciated. Thanks. (By the way, this house is not located in an area of heavy rainfall, it never snows here, and there is very little ice accumulation, so I am not concerned about the low pitch of the roof as far as leaks are concerned. The roof has never leaked). Thanks very much for your help.
Todd Miller
Isaiah Industries, Inc.
10/24/2015
That all makes sense. I would not do this without removing the existing roof panels in the affected area, shortening them, and re-installing with a pitch change flashing and the new roof.
Ray Owens
10/24/2015
OK. Thanks for the reply and the advice.

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