JOE NATALI
8/21/2013
I'm looking at having a new metal roof installed over my existing asphalt shingle roof. I have six different peaks. One point brought up is when the roofing is cut for the valleys there will be an unpainted edge that will rust because of exposed bare steel. If this is correct what procedures are recommended to insure that rusting doesn't happen and what does warranty cover ? Thanks Joe
Todd Miller
Classic Products, Inc.
8/21/2013
Warranty information would come from the individual product manufacturer but generally speaking I doubt you will find coverage for cut edge protection. Cut edge performance has so much to do with the care taken in cutting the metal. It also has a lot to do with the environment and how aggressive it is. Salt coast environments of course would be very bad as well as areas prone to very low pH (acid) rain I will be referencing steel products here rather than non-ferrous products like aluminum which will not be as prone to edge issues. Cuts in the steel need to be made with a crisp clean shearing action. They should not be saw cut. You want to expose as little of the edge as possible. The steels used in roofing have anti-corrosive coatings of zinc and/or aluminum on both sides of the core steel, and underneath any paint that is applied to the product. Much of the corrosion protection comes from those zinc and aluminum coatings. When it rains, ions from the exposed zinc and aluminum on the cut edge will go into solution, combining with Hydrogen molecules, They then "coat" the cut edge of the core steel, providing corrosion protection to it as well. I regularly see steel applications 30+ years old that show no cut edge problems, due to this phenomena.
Info @windowsonwashington.net
An informed customer is our best customer.
8/21/2013
+1 Check with the specific supplier but we rarely see issues with them if at all. Some companies have specific protocols for cutting as well as edge primers.

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