Disclosed is a retrofit shower corner shelf assembly kit including a shelf adapted for retrofitting into an existing shower corner; an adhesive composition for securing the shelf into the existing shower corner; and optionally a decorative composition for concealing edges of the shelf directly adjacent to the existing shower corner. Disclosed is a shelf adapted for retrofitting into an existing shower corner, the shelf includes two flat edges configured for securing the shelf directly on top of a surface and a third flat, free edge, wherein the shelf includes an upper layer, a middle layer attached to the upper layer, a lower layer attached to the middle layer, and the third flat, free edges conceals middle and lower layers of the shelf.