You might ask, “Why is the metal rusting, isn’t it galvanized?” Yes, it was – electroplate galvanized. This is also called zinc coating, applied in a cold electrolytic bath rather than a molten zinc bath as in the hot-dipped process. Traditionally the plating/coatings are thinner than hot-dipped and not suitable for extended outdoor exposure. Why aren’t we using hot-dipped flashings? Good question, but electroplate galvanized metal is all I’ve ever seen at the roof supply houses.
Over the years I’ve noticed that the drip-edge on flat roofs will rust after 10 years or so, particularly at the areas where the roof drains. The zinc is literally being washed off. For a long time I advised my roof replacement clients to paint their flashings after we were finished. To my chagrin, over the years, I noticed my advice was often not heeded as I began to see rusted metal on some of my old flat roof projects. About five years ago we started including factory painted metal flashings on all of our roofing projects. Considering it costs about $30 more on an average home in Miami Springs for this upgrade, why don’t all roofing contractors do this? You’ll need to ask them . . .
First we removed the old drip-edge and 10 inches of the old roof to accommodate new Gafglas #75 base sheet and a 9” strip of Ruberoid Torch Smooth. All rotten fascia was replaced and painted and the new drip-edge installed over the Smooth and primed. This is a Code feature which “sandwiches” the metal in rubber once an 18” sheet of Ruberoid Torch Granule is torched as the final cap.
All in all, a fairly simple flat roof repair but instructive regarding a foolproof low-slope perimeter
Insulated Flat Roof Repair in Miami Lakes