If you've never done torch down modified bitumen, I would not suggest trying it. Burning down a building would be no fun. You would need a cover board to install over the substrate, perhaps a 1/2" high density fiberboard. Then a base sheet of some kind, usually a 33# fiberglass or 43# organic. Base sheet can be doubled up for higher system rating. A smooth modified bitumen can be installed for a 10 year system, or 12 year if coated. Or a granulated cap can be installed for a 15 year system. Granulated requires more work, imbedding the seams and penetrations, forget to imbed and it will fail. If smooth and granulated are used together, it will be a 20 year rated roof.
Why not try something easier and safer like EPDM or TPO?
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