The chemical composition of Galvanized will 'self-heal' the cut or scratched area. Although the galvanized will be thinner in this area. That is why you should specify G-90 Galvanized. Which refers to .90 oz of total zinc applied to both sides combined. If you are being offered Galvalume you may experience some white rust on the cut edge. Usually this does not get worst.
All cutting needs to be done with shears or tin snips. The 'wiping' action of shears helps to heal the cut area. Abrasive saws will burn the coating back to a point where you can experience rusting prematurely.
The panel supplier should offer a neoprene closure to close the panel ends. If you elect to keep it open you need to provide an exhaust at the top of the panel.
Dick Bus
2013-01-26 23:30:03.000000
I have asked metal suppliers about the obvious issue of cutting metal panels and what to do about the exposed edge in order to avoid rust issues later that may streak down the surface of the roof. None of them have a reply and act like nobody has ever asked that before! I know the galvanization or treating process is better every year, but you have to believe that a freshly cut piece of metal will eventually rust on the exposed edge. Also, please make some suggestions on the tools and methods of cutting sheets.
On another note, what do you recommend to close the open areas that the ribs create near the gutter if using an ag-style panel? Would it be bad to block that off in regards to moisture buildup between the metal and roof or would it be better to have that air flow from the bottom to the top?. Thanks.
