A one-piece shower base includes a pitched bottom surface, a plurality of vertical flanges extending upward from a plurality of outer edges of the one-piece shower base, a drain integrated within the one-piece shower base, and a pitched foam support base having an upper surface and a lower surface. The pitched bottom surface is pitched downward in at least one direction toward the drain. The upper surface of the pitched foam support base is adhered to an underside of the pitched bottom surface. The pitched foam support base fills in a hollow space below the underside of the pitched bottom surface created by the pitch of the pitched bottom surface.