If you want your roof to outlast you make it from two layers of 1/2 inch ply layer 90 degrees overlap glue and screw , then 1/8 torch on. For metal roof use a method called standing double seam with 11 inch pans and one continuous length. You might want to not have apex roof, if you have off set roof you can use Windows at top for lighting and ventilation. Basically instead of meeting at apex the one roof is 18 inches lower allowing for Windows. Aim south for warm north for cooler
