Build a little, learn a little about building materials. Screwing on the roof took two of us about four hours. It’s made of Galvalume, which was recommended by (and gotten at a bit of a deal from) a friend working in construction. I looked it up. Galvanized steel is made by dipping steel in molten zinc. The two metals bond on a chemical level, resulting in pure zinc on the outside, a mix of zinc and steel as you go in, and a center of pure steel, making for a highly corrosion-resistant final sheet metal product. Fascinating! Galvalume is an advanced galvanized steel, with a zinc-aluminum fusion going on. Well, well!