New roof over spray-foamed attic
Hello,
My asphalt shingle roof is 30 years old and may have a leak. It seems time to replace.
House is an 1850s farmhouse in coastal Maine. I had the attic walls, ceiling and rafters spray foamed some years ago for added insulation.
Are there any special considerations I should keep in mind, given this attic situation, when talking to contractors about the new roof? I was wondering about venting, especially, since the old vents are now covered with spray foam, and I saw roof vents when I was looking at roofing materials. However, any advice would be appreciated. I just want to make sure I’m making the overall situation better in every way I can.
Thanks for your help,
Ilmari
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Replies
Make sure the rioters know about the spray foam. Spray foam greatly complicates replacing any sheathing that the roofers may need to do. Aside from that, I can’t think of any issues.
Bill
Thanks Bill.
Am I right in thinking 30 years is the outside life for asphalt shingles? A friend just said they can last 40+ years.
Thanks again!
The heavier weight modern shingles can have warranted life of 40 or 50 years. Some even have a "lifetime" warranty, though of course there are caveats. Depending on location, these warranted lifespans are reasonable expectations of life.
My caveat: None of these 40 year+ shingles have been on the market for more than 15-20 years, so nobody really knows how long they are going to last. Some of the 30 year shingles had big problems in the 1990's and failed 10-15 years in. That was a manufacturing issue that the shingle companies fixed, and there are 30 year shingles in service in my area (around NJ) that have been installed for 30+ years and are still doing OK, though ready for replacement. We will all see whether the 40 year+shingles are still around in another 20 years or so.
FWIW, I'm seeing more pockmarks in the 40 years shingles at the 20 year mark than I am comfortable with. I'm watching to see if they continue to grow over time, and whether any start to leak over the next 5-10 years.
Another note: I see you also asked a question about venting. If you spray foamed the entire attic interior, you have an unvented attic. No roof vents of any kind would be appropriate.
"Vent until you can't." When can't you vent? When you can't create a vent chute either topside or bottomside of the structural sheathing. Or your roof is less than 3:12 pitch. Or the roof is crazy complicated with hips and valleys and dormers all over the place.
But if you are taking off the shingles on an unvented cathedral roof assembly, you COULD vent topside it just means adding sleepers/furring strips and a nailbase sheathing for your shingles.
Is it worth it? Depends on y0ur exposure level: I would say coastal Maine qualifies as worth it.
Peter
>" I had the attic walls, ceiling and rafters spray foamed some years ago for added insulation."
Open cell or closed cell?
How thick?