Typically this system is installed over a structural metal roof system where the existing roof system becomes the metal deck for the new roof system.
Roof repair gap in tin.
Cover the base coat with a piece of glass membrane fabric.
Cut the fabric to size with.
Repairing a metal roof seam with turbo poly seal is simple and it is a do it yourself p.
I am not a professional roofer but.
Smaller nail holes will be permanently fixed by this method standard roofing nails would be either 3 8 inch or 1 2 inch making a hole.
Both mesh and purlins reduce summertime heat penetration to the interior somewhat but i believe the significant advantage of the more effective ventilation gap provided by purlins is the reduction of the summertime temperature of the metal roofing itself.
Apply uniform layer of metal roofing base coat 6 inches each way of the gap at the overlap with a paintbrush.