All chimneys shall be built of brick, cinder
blocks, stone or reinforced concrete, the walls of which shall not
be less than 3 3/4 inches thick and shall have terra cotta flue linings.
Chimneys shall extend at least two feet above the highest ridge. Chimneys
shall be built upon concrete or solid masonry foundations. The footing
for an exterior chimney shall start below the frost line. Listed factory-built
chimneys shall be installed in accordance with the term of their listings
and the manufacturer's instructions.