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corrugated asphalt roofing panels

SCBO1

SCBO1

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Had a question in regards to corrugated asphalt roofing panels and if you can re-roof over the same product. Install instructions for the brand I looked up indicated you can cover shingles but no indication you can cover up the same product. Also looked up the ES report with no answer. The product I looked up was made in Virginia, the state for lovers!
 
When I built my house I installed 90lb rolled roofing because I new it would take a couple of years before I would be ready for the metal roofing to be installed. I was advised to install a layer of 15lb before installing the metal. The reason was the expansion and contraction of the metal directly on top of the granular 90lb would scratch the paint on the bottom side of the metal and condensation would cause the metal to rust on the bottom side where the paint was scratched off.

Don't know if it would be true or not but 15lb was cheap and I did not want to replace the metal roof in my lifetime so I installed the 15lb between the metal and the granular 90lb roof.
 
I had to tell the contractor that I could not find any information that allows the same asphalt corrugated shingling material to be installed over the same product. However it can be installed over a standard 3-tab shingle and attached to sheeting with felt paper and or cleats. So it looks like it's a tear-off and re-roof.
 
The instruction guide said it can be installed over purlins spaced no more than 24" O.C. It might be possible to install hat channels over the present roofing, then attach the new layer to the hat channels. The problems would be figuring how thick a hat channel would be necessary for the screws to develop the necessary uplift resistance, and how to seal the edges. Tear-off might be simpler.
 
space or solid sheathing? with 90 lbs with 15lbs with corrigated metal over ='s 3 layers, what about weight?
 
mtlog, thanks for the reassurance, that's how how interpreted the information as well.

I was told by the manufactures home office that the individual roofing panel weighs approximately 18 lbs.
 
Corrugated asphalt roofing is designed for easy handling and installation for any size roofing project. Lightweight and easy to trim. This helps keep your building cooler on sunny days and quieter during storms.
 
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