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Hello, I have been reading prior threads and becoming confused. I have a 70 year-old, one story house in Mechanicsville, VA. The attic has eave vents and no obvious moisture issues. There is no insulation under the house and the crawl space is vented. The walls of the living space have blown-in insulation (I do not remember R-value.) I am tearing off leaking shingles to install white metal roof on south facing roof with full length porch (~1200sqft). I expect to replace some of the sheathing due to the leaks. I want insulation and water barrier over the entire roof (a small investment for the life of the roof.)
Is there a best way to proceed?
What is the order, layer by layer from the rafters up?
Thank you for your patience, Erin
Proper Installation from the rafters up
10/7/2019
Or copy this URL: https://www.metalroofing.com/spirit/comment/24502/find/Normal construction, and the safest, would consist of the following:
Drywall
Vapor barrier
Insulation
Attic vented per code
Solid decking
Underlayment per code
Metal roofing
If there are any components of that which cannot be met, let's discuss alternatives.
Isaiah Industries, Inc.
10/7/2019
Or copy this URL: https://www.metalroofing.com/spirit/comment/24503/find/Thank you. Just to make sure I understand. All the insulation is immediately over the conditioned living space. No insulation to reduce heat gain into the attic. And no purlins under the metal to allow air flow. The water barrier is not required where I live inland, but the installer said they put high heat barrier over entire roofs at the beach. Does that sound right?
Proper Installation from the rafters up
10/7/2019
Or copy this URL: https://www.metalroofing.com/spirit/comment/24504/find/So, you do not have a vented attic space, correct? I would definitely want underlayment to be down beneath the metal roof, purlins or no purlins. Where are you located? Do you know if there is a vapor barrier such as polyethylene behind the drywall on your ceilings? My concern is how big of a risk there is in your area for condensation? If there's no vapor barrier and you're in an area prone to condensation, then the purlins / battens may be wise.
Isaiah Industries, Inc.
10/7/2019
Or copy this URL: https://www.metalroofing.com/spirit/comment/24505/find/