A roofing membrane was recently patented comprising an upper layer of modified bituminous material. The material is modified with a modifier selected from a group including: Atactic PolyPropylene (APP), Amorphous Poly Alpha Olefin (APOA), Thermoplastic PolyOlefin (TPO), Styrene-Butadiene-Styrene (SBS), Styrene-Ethylene-Butadiene-Styrene (SEBS) and synthetic rubber. The upper layer has a longitudinally extending side lap and a lower layer of self-adhesive bituminous material is comprised of asphalt, filler and tackifier. The lower layer has an exposed lower surface that is adhesive-based. The material of the lower layer is different from the material comprising the upper layer. There is a reinforcing layer between the lower and upper layers, and a coating of factory-applied adhesive is present on the side lap. The coating is comprised of an adhesive selected from the group consisting of: tackifying resin, pressure sensitive adhesive and Poly Vinyl Butyral (PVB). A release film covers the coating of factory-applied adhesive, and a release liner covers the lower layer. Adjacent and successive overlapping membranes may be connected by the factory-applied adhesive to form a seal and a permanent bond upon the application of pressure, such as by a roller.