Looking for advice on metal roof installation

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Old 12-18-10, 01:31 PM
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Looking for advice on metal roof installation

I'm looking to have a metal roof installed on my home here in southern Maine (built in 1964). Rather than tear off the old layer of shingles, the previous owners installed asphalt shingles over an already existing layer of shingles, so there are now two layers of shingles up there. My potential metal roof installer, a friend of the family's, is insistent that I should just install the new metal roof right over the two layers of shingles. However, I'd prefer to completely tear off ALL the shingles, inspect the sheathing and replace if needed, add new underlayment (possibly ice and water shield), and then install the metal roof. First, I don't want to put a long-lasting roof over old, worn-out, (and possibly rotting) shingles. Second, I think it's important to ensure the sheathing boards have no rot and are suitable to continue using. Third, I've been told it MAY be a violation of city code to have more than two layers of roofing, although I haven't been able to confirm this yet. My question is, why would my roofer be so insistent that I DON'T remove the existing roofing? He says leaving it on will be more layers of protection, but I'm questioning why "more layers" are necessary if metal is supposed to be such an effective and long-term roofing material. How would stripping the roof bare before installation be any different than installing a metal roof on a newly constructed home? Incidentally, I've already indicated to him that I would be willing to do the tear-off and underlayment work myself. Thank you for any advice anyone can offer me!
 
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Old 12-18-10, 03:28 PM
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I'd go with (1) (2) and (3). Without removing the shingles you don't know what the substrate looks like. Applying 30# builder's felt, then your strapping, then your roofing will give long life and allow for ventilation. You didn't say whether your family friend was planning on strapping across the shingles or not. Laying the steel directly on the shingles is like laying it on sandpaper.....first the finish, then rust, then further decay, then leaks. No.
Your roofer is insistent, because it is an easier job for him to put the steel on without all the additional work, dump fees, etc. Deduct demo from your original estimate, as the job done right would have demanded its removal.
 
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Old 12-18-10, 05:23 PM
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I agree with everything chandler says, but where I am we rarely use the strips and we put a 15# slip sheet on over our 30# as we do the roof to keep the nails and tin tabs from touching the underside of the metal.
 
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Old 12-18-10, 06:07 PM
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Originally Posted by chandler View Post
Your roofer is insistent, because it is an easier job for him to put the steel on without all the additional work, dump fees, etc. Deduct demo from your original estimate, as the job done right would have demanded its removal.
That's what my assessment would have been, but as I mentioned in my original post- "I've already indicated to him that I would be willing to do the tear-off and underlayment work myself."
 
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Old 12-21-10, 12:06 PM
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I think he wants the old roof there because it's easier to get 29 gauge metal to look good over old shingles than over sheathing. I wouldn,t use any metal thinner than 26 gauge, (pref. 24 gauge). Kynar 500 coated. All metal roofs are not created equal. Jim
 
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