19 Nonmetallic building materials for roofing, namely, screws, underlayments, artificial stone composed primarily of plastic, balustrades, chimneys, chimney flues, chimney cowls, chimney pots, chimney shafts, cladding, ducts for ventilating and air conditioning installations, gutters, moldings, piping, flashing, slates and tiles, shingles, stones, and lumber