After checking various sources, we bought our metal roofing from Mueller, Inc.
Rockytopper pegged them, on-line at
http://www.muellerinc.com/roofing/index.php.Some 12 years ago we bought some lighter weight roofing tin from Home Depot for a small guest house and it has shown its age already. It must have been 28 or 30 Gauge and it showed dents from the hail storm plus the galvanizing has not held up well. I won't go less than 26 Gauge now.
