A door jamb assembly for an entryway has a wooden jamb plate to which an extruded plastic brick mold and stop member is attached. The brick mold and stop member forms the raised stop of the jamb assembly also may form the brick mold thereof. The extruded plastic brick mold and stop member has a core made of economical cellular PVC plastic at least partially encased in a stabilizing layer of a plastic material, such as SAN, having a heat distortion temperature greater than that of the PVC plastic of the core. The stabilizing layer holds the core material in place and restrains it against distortion and shrinkage due to extreme temperatures, such as those found between a storm door and a door exposed to direct sunlight.