19 Building materials (non-metallic), non-metallic rigid pipes for building; glass used in building, including tiles; glass plaques; buildings (non-metallic); flooring, not of metal; safety glass; floors, not of metal; walkable glass; insulating glass building; mosaics for building; wainscoting, not of metal; non-metallic partitions; stair-treads (steps), not of metal; facings, not of metal, for building