Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 63·4.25
Flue block chimney installation and support
Flue block chimneys must be installed with sealed joints according to manufacturer instructions, bends or offsets must use matching factory-made components, and unsupported blocks must be properly supported and restrained.
A flue block chimney should be installed with sealed joints in accordance with the flue block manufacturer's installation instructions. Where bends or offsets are required, these should be formed using matching factory-made components. Flue blocks, which are not intended to be bonded into surrounding masonry, should be supported and restrained in accordance with the manufacturer's installation instructions.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet L - Combustion Appliances and Fuel Storage Systems.pdf