Flat Metal roof on zero pitch

There really is no do it yourself metal product suitable for a flat roof. If it had some pitch you could go to a mechanically seamed standing seam which also isn't a DIY product, With it being flat about the only thing I can think of would be a flat lock copper roof with soldered seams, not a DIY project typically.

Hello, We just brought a fixer-upper house in Florida, and theres an extention on the back of the house 17x42 feet. This extension is a flat roof installed in 2007, We think it was the rubber membrain system. The entire roof was rot through, it was falling in the plywood and the rafters were black, the rafters were totally rot through. We had to take it all down. We have just installed the new rafters, but there is zero pitch, there was no way we could make a pitch to it...So now its completely flat. We do not want to put another rubber glue down roof I think thats what is was, it's the standard roofing material for flat roofs. We think a metal roof will at least stop the water from getting in and the sun will try if off. Florida has extensive rain full during the summer months. We know are there is some complex alternative roofing materials for flat roofs, but budget is an issue and we would install the metal ourselves. Can you recommend the gage metal we should use and any other tips. Thank you so much for your help. Geri