TOPIC: I Have An Existing Metal Roof and Have A Question
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I'm hoping for some recommendations regarding apparently non-compatible fasteners used on a galvalume roof. Roof system is only 10 years old, and directly around many of the field panel fasteners red rust is forming. This doesn't appear to be happening to the lap screws. The screws used for each detail look to have visibly different finishes, based on the color/shine of the heads.
Attached are example photos of this issue.
At the ridge & end lap joints there are spots were various coatings have been applied and the encapsulation of the screw heads seems to have caused rapid corrosion. So much so that the panels completely lifted off the screw heads in some places.
Am I correct in my initial analysis? Is it possible to replace the field fasteners with compatible ones? Should the red rust rings be coated with some sort of galvanized paint or is there another way to inhibit the rust from spreading? We plan on trimming the panels upslope of the end laps and installing replacement panels making 2 new end lap seams, but also getting rid of the severe corrosion.
Any help or insight would be much appreciated!
Savoy - Field vs Rib Fastener Examples.pdf
Let's see what some others think but I would replaced the rusted screws with a larger diameter and better screw. And yes I'd suggest cleaning up the rust and using a good rust-inhibiting paint on the screw holes. You might want to go ahead and then cover the screw heads with a quality sealant.
The process that Todd states should be good, but one concern that may be present is an incompatibility issue between the sub-straight and the screw. It looks like some form of reaction has occurred, either between the screw and panel or from the structure. Without finding out if this is the case, replacing the screw with a similar material may only repeat the problem.
In my experience, these rust marks are typically a result of the shards of metal not being cleaned off properly after installation and the shards themselves have burnt into the metal giving the appearance of rust. These can typically be primed and then treated with a rust inhibitor.
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