Joints in Chimney Liners

(1)  Joints of chimney liners shall be sealed to provide a barrier to the passage of flue gases and condensate into the cavity between the liner and the surrounding masonry.

(2)  Joints of clay, concrete or firebrick chimney liners shall be struck flush to provide a straight, smooth, aligned chimney flue.

Article 9.21.3.2. Ontario Regulation 332/12 Building Code,   Information published by oncodes.ca for educational purposes only.