Installing Metal Roofing

I am thinking of putting galvalume metal roofing on my shed. So far I've cleaned off the old composite roofing down to the bare plywood and put down roofing paper. The shed is 10' wide by 16' long with gables on the 10' ends. Including the overhang I will need at least 16' 10'' along eaves. From the ridge to either eave is 67".

Questions:
1. As far as I can find out, the Galvalume only comes in 3' widths. The metal is 5 ridged, with 9" between ridges. Would it be ok to overlap two ridges instead of one, or will I have to cut one of the panels longways?

2. Since I have a good plywood base, do I need to use purlins?

Thanks, David Sherer

 

You will have to cut the metal longways but if you are using rake it will cover the cut end. Being that is just a shed it is okay to screw it directly to the decking.
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American Roofing Company

 

Thanks for your help. David