Application of Steel Roofing
The choice in roofing falls logically to sheet steel roofing manufactured in panels and cut to length for you by the manufacturer. Requiring no roof sheathing for our application (since it does not need to be insulated and can be applied directly on the horizontal purlins), the application of metal roofing directly over the roof frame saves weight, while outlasting shingles and almost all other normal roofing. The diagrams earlier in this book portray a roof frame with only two rows of purlins on each side of the ridge board, as this would be sufficient should you use standard roof sheathing (ply deck) and asphalt shingles.
If you go this route you need to apply 3/8″ or 7/16″ plywood sheathing first over the entire roof framework, then apply your choice of shingles. This type of roofing will be much heavier than the steel panels, and I would not advise it.