Abstract: A system and method for supplying and distributing a viscous material onto a roof include a mobile vessel containing a supply of the material for location either on the roof or on the ground adjacent the building. A delivery conduit extends from a viscous material storage chamber in the vessel to a secondary vessel or to a material application tool on the roof. A heater is located on the vessel to heat the supply of material. A reversible pump and/or motor delivers the viscous material from the storage chamber through the conduit for subsequent application on the roof and pumps unused material through the conduit and into the storage chamber to maintain the temperature of the material and to prevent the material from hardening in the various conduits, supply lines and equipment. A bypass line extends between the conduit and storage chamber for return of the material by gravity to the chamber in the event of pump or motor failure.