Disclosed is a bath wall assembly. The bath wall assembly includes a first back wall panel and a second back wall panel. Each of the back wall panels are configured to be mounted to a structural wall of a bathroom. The first back wall panel includes a flange that extends at least partially along an edge of the first back wall panel. The second back wall panel includes a channel configured to receive a portion of the flange therein. The channel is configured to prevent relative movement between the first back wall panel and the second back wall panel in a vertical direction. Together, the flange and the channel form a substantially water-tight seam between the first back wall panel and the second back wall panel.