Metal over OSB and metal gauge

Riley Korchik
Planning on having built a 30' x 64' stick-built insulated garage with a workshop on one end. Roof will be 4/12 pitch; 45-5-5 loading with 14 foot walls. 2' x 4' trusses are 24" apart. My questions are, should metal roof sit on OSB and felt or just perlins? Besides cost, what are pros and cons of using 26 gauge steel for the roof and perhaps the side walls vs. 29 gauge. And finally, are stainless steel screws or powder coated screws to attach the metal prudent/worth the extra cost?
Todd Miller
Isaiah Industries, Inc.
Thank you. There are metal roofs that can be installed on purlins or decking, and metal roofs which can be installed on just one or the other. If you select a metal roof approve day its manufacturer for installation over solid decking, you do not need to add purlins. You are doing the right thing by using underlayment regardless. Thicker metal generally provides greater strength and life expectancy though some folks consider it to be "overkill" if you will. I would definitely use a painted screw. In your case, stainless steel may be less important but not a bad upgrade.

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