Abstract: A fastening assembly for mechanically attaching a waterproof flexible membrane to a roof construction at spaced apart intervals, comprising a post member that is mounted over an insulation member and that receives the flexible membrane in overlying relation thereon, a flexible circular member being forced into overlying relation on said flexible membrane as located over the post member to cause said flexible membrane to encircle said post member in tight fitting relation thereon, wherein the flexible membrane is sandwiched between the post member and the flexible circular member for mechanically fixing the flexible membrane on the roof construction.