new metal roof to existing shingle roof interface

Old 06-07-16, 09:31 AM
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Join Date: Jun 2016
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new metal roof to existing shingle roof interface

I have a new porch roof that I am laying out for my backyard. My wife would like the new porch roof to be of metal roof construction, and not very steep. However, at the ends where the new roof will mate up to the existing roof at the house, it will overlay an existing asphalt shingle roof.

The new metal roof will be approximately 2 vertical to 12 horizontal slope. The existing asphalt shingle roof is approximately 9 vertical to 12 horizontal slope.

Is it practical to have a new metal deck roof that at its high point interfaces to an existing roof, with that roof be asphalt shingles? Can that work?

If so, what details and or precautions need to be taken? If you have reference to any details or illustrations or photos that would be greatly appreciated.

What details or precautions also need to be taken with concerns towards replacing the shingles on the older roof in say 5 to 7 years?

Old 06-07-16, 10:01 AM
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Yes a metal roof can intersect a shingled one. It's rather simple and anyone who has shingled up to a chimney should be able to do it.

You touched on the big problem/question. What about your shingled roof in the future??? When it needs to be re-shingled the shingles under the metal roof will not be accessible. You'll have to decide whether or not you replace those shingles or let them be. replacing them will likely require the metal roof to be removed.

Another issue is what to do with the narrow space between the metal roof and your existing? Will it be boxed in or left open? If left open it's a great spots for wasp and bird nests.

Also since you are at the coast make sure you get a permit for the work and comply will all the hold down requirements. The codes have qotten very particular about it in the past 10+ years.

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