What is the best alternative to re covering or covering over an old tar flat roof that leaks and is no longer flat enough to cover with tar. It leaks really bad and has uneven sinks in the roof. Some have suggested trusses with a regular pitch roof over the flat roof, graduated slope to the back by adding new sheet metal roofing sloping to the rear of the building. Any ideas or technique that has worked for you. I hate flat roofs!!!