Most exterior sheet metal was 19ga or about .042
18 ga is around .048
19 ga is hard to find many suppliers simply dont carry it.
If you go to a metal supply store ask to mic the sheet as tolerances can be all over the place. You might run into a piece of 18 ga that is pretty close to 19 ga in thickness.
Very rarely will you find sheet metal on the high end of the tolerance, I would try to buy 19 but 18 if not found...Eric
