We have a flat roof on our 34X20 family room that is only three years old. The contractor treated the roof with a rubber coating that is now deteriorating. We need to reapply a reliable material used for flat roofs. We are do-it-yourself homeowners. The contractor has not answered our requests to reapply the material nor make the application good. Can you recommend a material that can be applied without special equipment and where can we purchase the material? We live in the mid-west USA and are subject to extreme temp. changes. We also use the flat roof for a extended patio. Thank you.