I found a product several years ago called "Peel And Seal". I had a flat roof that I was having repaired every couple of years and got tired of putting the money out. I put Peal And Seal on almost 10 years ago and haven't had a leak out of it since. It comes in aluminum and white in a 36" wide roll to cover 100 sq.ft. It is available at most roofing distributors.