(1)  Flue liners in the same chimney shall be separated by not less than 70 mm of masonry or concrete exclusive of liners where clay liners are used, or 90 mm of firebrick where firebrick liners are used.

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(2)  Flue liners referred to in Sentence (1) shall be installed to prevent significant lateral movement.

Article 9.21.4.9. Ontario Regulation 332/12 Building Code,   Information published by oncodes.ca for educational purposes only.