Abstract: A molded exterior decorative unit for securement to a structural facing comprises a molded unit with front and back surfaces and side edges. The front surface has decorative features, while a channel is molded in the back surface into which a compressible, expandable, flexible sealing member is partially secured. Preferably, a groove is formed in the floor of the channel so as to provide a labyrinth path for air or moisture. Upon securement of the molded decorative unit to a facing, the compressible, expandable, flexible sealing member forms a seal adjacent the periphery of the molded unit. In one embodiment, weep holes or slots are provided at the back adjacent a bottom surface of the molded exterior decorative unit. In another embodiment, where the unit is adapted for securement in a recess in the structural facing, the channel is formed in the side edge of the molded unit, and the compressible, expandable, flexible sealing member forms a seal between the side edge and a surrounding wall forming the recess.