Systems for new construction and for refurbishing, renovating, and modernizing existing bathtubs, bathtub enclosures, shower enclosures and shower bases and floors, bathroom walls, waterproofing interior and exterior walls of buildings, tunnels, train stations, stairwells, hospitals, subway stations and lobbies, water sprinkler, steam pipe and other plumbing fixture soffits and other public spaces, using bathtubs, showers, bathtub liners and parts thereof, shower bases and parts thereof, and various shaped wall panels, enclosures, and assemblies for bathrooms and parts thereof, made of steel with a fired-on porcelain enamel coating