I'm not familiar with the term "eyebrow" as it relates to a building, but I'm assuming you're talking about an overhang over the door? If that's correct, there's no reason that that would make the siding rust if it's installed correctly. Depending on the roof pitch and how far out you want to go the best option may be to extend the roof further out over the door. If that's not an option for some reason, you can bring an overhand out from underneath the existing eave. We need more information.My concerns are I may cause the metal building sheeting to rust.
Ideally, I'd like it come out 36" total with a 6" overhang so the framing would come out 32" if it is to match the current overhang.I don't understand your concern about rust. Just don't expose cut edges or treat those that are. Zee flashing below eve,simple shed above door and diagonal 2x brace on both sides of door and you have it covered.
How far out do you want cover to extend?
You shouldn't be mounting things like that to the surface of the siding. The siding should come off, build the overhang and then siding put back on around it with the proper trim, J-channel etc. You use the term "metal building". Hard to tell from your picture. Does this structure have a metal frame as well, or is it wood framed?Ideally, I'd like it come out 36" total with a 6" overhang so the framing would come out 32" if it is to match the current overhang.
My concern with rust is if the eyebrow structure materials and the metal building's siding move/expand at differing rates will moisture and dust/grit get between the siding and the eyebrow and cause rust.
Its got metal framing too.You shouldn't be mounting things like that to the surface of the siding. The siding should come off, build the overhang and then siding put back on around it with the proper trim, J-channel etc. You use the term "metal building". Hard to tell from your picture. Does this structure have a metal frame as well, or is it wood framed?
I see. No way to say exactly how to build this without seeing interior framing, but either way, it should not be fastened on top of the siding.Its got metal framing too.