Abstract: The present invention relates to a roofing underlayment system comprising two layers of a coated structural article which comprises a substrate having an ionic charge coated with a coating having essentially the same ionic charge or one layer of such coated structural article in combination with one layer of felt material. The coating of the coated structural article consists essentially of a filler material and a binder material wherein the binder material bonds the filler material together and to the substrate and wherein the coating does not bleed through the substrate. The roofing underlayment system of the present invention can impart a Class B or better (Class A) fire rating to a roof assembly.