Abstract: A shower pan which forms a base of a shower stall has a one piece drain surface and is capable of being built in various sloping configurations. The shower pan is constructed of a top drain panel supported by graduated shims and perimeter strips which are in turn mounted on a planar foundation. Perimeter strips and graduated shims are secured to the foundation, concentrically spaced apart surrounding a variably located drain opening. The top drain panel is cut to the same contour and size as the foundation and has a rear member, side members, and threshold members to provide lateral water barriers. Kerfed break lines in the top drain panel permit the panel to bend to form a basin like drain surface. The kerfed relief lines are in the form of at least two concentric, straight lined, polygonal cuts which are substantially identical in shape and have their corresponding vertices connected by radial relief lines.