Light plastic foam construction element for making shower stalls, bathroom stalls and the like

A lightweight construction element forming an upright wall for a bathroom shower incorporating plumbing fixtures, said construction element comprising

• a plastic foam core having an inner working surface and an outer surface with at least one outer, fiber-reinforced mortar layer, wherein the inner working surface has a groove that has two or more steps and that narrows going into the foam core from the inner working surface;
• a wall component of material more rigid than the foam core that is positioned in the narrower or narrowest step of the channel to support plumbing that projects through the inner working surface;
• and
• a foam filler element in the form of a plastic foam board that is positioned in a step of the channel at the inner surface, seals the channel, and has openings through which plumbing projects,
• wherein the wall component is of a waterproof plastic and wherein the groove is in the form of a channel cut with a mirror-symmetrical stepped cross-section that narrows toward the inner side, whereby the groove has opposing steps and at least the filler element rests against the opposing steps, thereby hiding the wall component.