Common Practice for a 1/12 pitch is to use a 2" high single or double locking standing seam with concealed clips. At 70' long the clips need to allow for expansion and contraction.
Your leaks may come from an improper flashed chimney.
Dick Bus
2013-02-08 18:16:23.000000
I have a R-panel roof with above dimensions with three over-lapping seams to fit the 70' length. It leaks along the upper seam located 2 feet below the chimney protrusion. I've put sealant above the chimney and along the seam which works for a period and then leaks again, especially in colder weather. I'm frustrated to the point of replacing the roof even if it is 8 years old. Suggestions?