Arizona warehouse roof corrosion failure

The worst carbon-steel corrosion rate Tom has ever seen (40–80 mil/year). Diurnal wet-dry cycling between vapor barrier and roof decking created a sauna in the ceiling cavity that destroyed galvanized steel hangers within a year.

Let me first tell you the worst corrosion rate I ever saw of carbon steel was in Arizona. It was about a one- or two-acre distributing warehouse, right there on the interstate from California — all the semis would come in here and they'd store things for a few days or a few weeks. They were building this warehouse, and in Arizona you don't usually worry about rain when you're doing construction. But it does rain in Arizona every now and then — when it rains it pours. They were building this warehouse, and they had put in a moisture barrier, because that's how you design roofs. They hadn't put the top roof on yet. They had some galvanized steel that was going through the moisture barrier — but it wasn't a perfect moisture barrier. In any case, the rains came while the roof wasn't complete.