A vertical corner joint for joining a first shower wall panel having a J-shaped channel integrally formed on an edge thereof and second shower wall panel having a resilient, elongate wedge member attached to the back side and along an edge thereof. The edge with the wedge is inserted into the channel of the first panel, thus compressing the wedge and forming a tight corner joint or seam. A multi-piece shower enclosure may include one or more such joints. A four-piece enclosure may include a shower base or bathtub, a back wall with channels on both vertical edges, and two side walls, each with an edge with a wedge for insertion into a respective channel. The channel may form a nailing flange. A sealing strip may be included between the front side of the second panel and the short side of the channel.