Decking for metal roof

Steve Decatur
Looking to replace storm damaged roof on a 26'x26' stand alone wood frame work shop building with 0.75"/12" pitch Plan to use R panel and caulk all over laps. I know its iffy doing metal on that low of pitch and would like some feed back on doing it with metal. Roof formally was done in roll roofing and has been replaced several times. Which leads me to the next question since the decking needs to be replaced and I would like to go with radiant barrier would it be best to go with 1/2" plywood or 19/32" OSB? I've read that plywood has better screw holding over OSB in one metal roof install manual (ie: on 24" centers 1/2" ply has 51 psf vs 19/32" OSB is only 38 psf. I've ruled out wood purlins for this project in favor of radiant barrier decking due to the heat issue I've had with this building, but what ever I do it needs to meet 120 mph wind requirements.
Todd Miller
Isaiah Industries, Inc.
In my experience, plywood is more reliable in the long run though both have similar fastener holding power initially. For that low of pitch, the only metal roof I can recommend is a mechanically seamed standing seam with concealed clips and screws. I can not even remotely condone anything else.

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