Abstract: A prefabricated polymer bathroom wall apparatus has a unitary molded wall section formed of a waterproof polymer and having a gridwork of interconnected molded frame portions forming a plurality of hollow cells therebetween and having a plurality of edges with one or more insets in the edges. Some of the molded frame portions are formed with elongated passageways therein to form prefabricated pipes in the wall section opening at the wall insets. Coupling members are attached to the ends of the passageways within the wall section edge insets whereby a lightweight prefabricated wall section can be attached to a wall for coupling to a building's plumbing and to plumbing fixtures.