Building materials, pipes and flexible tubes, all the aforesaid goods not of metal, in particular gutter pipes, drainpipes, water conduits, grilles not being for ventilation and heating purposes, shafts, non-metal manhole covers; drain traps being water-pipe valves, not of metal or plastic, for drainpipes and water conduits; geotextiles; ducts, not of metal, for ventilating and air-conditioning installations