metal underlayment on ashpalt shingles

Ray Pethtel
12/10/2011
I have an old house with ashphalt shingles. A contractor recommended "white metal roofing" directly over the shingles. I understand there should be an underlayment of some kind. Are underlayment always necessary? What underlayments are suitable?
Todd Miller
Classic Products, Inc.
12/10/2011
You will want to inquire both with the roofing manufacturer and check local building codes for the answer to this question, However, in most cases a layer of 30 pound felt, perhaps combined with a slip sheet OR simply a layer of a new synthetic underlayment will suffice. Also, ice and watershield is likely required on the roof perimeter and valleys in your area, per building code.
Info @windowsonwashington.net
An informed customer is our best customer.
12/12/2011
Is your current roof leaking? Did the contractor indicate why he wants to go overtop of the existing roof? While it is permissible, I always think that the investment in a metal roof deserves looking carefully at the roof deck. Most manufacturers will require some sort of slip layer if you are going directly over top. If you are going on battens you can usually do without. Check with the metal manufacturer for their specific guidelines and code as Todd mentioned.

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