1/12 roof how tall a seam?

Laura Gossen
I have a 1/12 pitch roof that a contractor says we should use 24 gauge galvalume, double locking standing seam panels on. The seam will be 1.5" and the panels will be between 17 and 18 inch wide. The contractor says putting 30# felt under it would be sufficient instead of stormguard. He rolls his own panels so I can't really check with the manufacturer like you normally suggest. Here are my questions. 1. How high should the seam be for this low a pitch? 2. Is a double locking the same as a mechanically seamed roof? 3. are there different ways to mechanically seam it and are some of these ways better than others? 4. Are there polyethylene based underlayment that are as inexpensive and as water tight as the 30# felt? Thank you for your help!
David Stermer
Hi Laura, Thanks for the questions and your interest in metal roofing! I aggree that a 24 ga standing seam panel is the right way to go for a 1:12 slope. The rib height seems reasonable to me. Double-locking typically means mechanically seamed, but this is worth confirming for your roof panel. The typical standing seam panel only has a single mechanical seam. For those that have multiple mechanical seams, the more bends, the better the seam. I am not aware of synthetic underlayments that are as inexpensive as 30# felt. They certainly perform better. Regards, David Stermer
David Stermer
Jake, Every metal roofing manufacturer is a little different in their recommendationis of minimum roof slopes. However, there is a strong tendancy to only recommend standing seam panel systems for this flat of a roof. Also the building codes in the Roofing chapter (Section 1507.4.2 in IBC) restricts this flat of roofs to standing seam. Regards, David Stermer

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