Section 36(b) in The Haryana New Mandi Townships Building Rules, 1967
(b)a chimney or two chimneys built back to back may be reckoned as a pier if:(i)the least horizontal sectional areas of solid material in the jambs and in the chimney breast or breasts added together are not less than the area required for the pier;(ii)the thickness of the back of the fire place opening or the back common to two fire place openings built to back is not less than 22.86 centimetres (9 inches).
