TOPIC: I Have An Existing Metal Roof and Have A Question
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I have from bottom to top - acoustical galvanized coil coated decking, plastic covered insulation in the low points, 5/8" treated plywood screwed down with SS screws, rubber membrane flashing, standing seam metal roof.
I am getting white rust from the acoustical holes on hot muggy days.
This sounds like condensation which is the result of warm moist air originating inside the building trying to drive its way out and encountering a cooler surface along the way.
It is an outside pavilion. And I was told there should be no white rust. Just trying to figure out where the mistake in design may be.
Can you send me a photo of what you're seeing please? [email protected]
Thanks. I have a better understanding now. Have you talked to the manufacturer of the acoustical panel? My best guess is water vapor is passing through it and condensing someplace in the assembly and the corrosion is occurring. I'd ask the panel manufacturer if they can come do a site inspection.
Yes, they have done evrything according to specs.
We believe it could be the 1000 holes they drilled in it that once drilled it created a exposed galvanizing. But simply, that it holds too much condensation and the design should have a rubber barrier between the decking and wood, and there should have been 2 inches of insulation to help control the condensation.
Simply: decking supplied per specs, deck installation per specs, wood installation per specs, standing seam roof supplied and installed per specs.
Everybody is at a loss.
I agree that I was leading toward it coming from moisture dripping down against the perfed holes and then causing corrosion around the holes. This is an unusual application and normal dynamics don't come into play which would protect the exposed steel edges.
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