I'm considering a new metal roof on the house(it currently has shingles) and notice that the latest trend is to nail or screw the roof in the flat instead of the ridge. I don't think this makes sense if you plan to keep the roof as long as the metal will last. I asked a roofer to explain why the flat is the best he gave some reason that I don't remember. I asked what happens when the rubber washer rots from around the screw and he said, "Well, it will probably be time for a new roof." I thought, are you kidding? There is no time for a "new" metal roof unless it is damaged. We have metal roofs on our barns that have been there for 50 years, all nailed in the ridge. All they need is a coat of paint about every 8-10 years. For some unknown reason, there are a few random nails in the flats, and those are the places that give leak problems. My theory is this: Nailing in the flat is quicker and, therefore, better for the installer. For support, some idea has been developed as to why screwing in the flat is better, but i don't buy it. It might be possible that it will last as long as people will "want" the roof. I realize that people these days replace things long before they "need" replacing just because they want something different. But, if I want the roof as long as the metal will last, which will be years and years, wouldn't putting screws in the ridge make more sense?