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HeidelbergCement in the United Kingdom
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Clay flue liners

When considering the construction of a chimney for use with solid fuels, it is important to firstly establish the size of fireplace opening you require. From this the flue liner size can be specified.

The table below gives an indication as to the size of flue liner required, relative to the size of fireplace opening. Specifically, the internal cross-sectional area of the flue lining should be 15% of the cross-sectional area of the finished fireplace opening. The fireplace and flue system can then be constructed in accordance with approved Building Regulations.

Fireplace opening
Width (mm) 
Fireplace opening
Height (mm) 
Flue Size  Cross-sectional
area mm² of flue 
450 550  185 x 185mm int. square liners
210mm int. dia. circular liners  
500  550  200 x 200mm int. square liners
225mm int. dia. cicular liners
600  550  225 x 225mm int. square liners
250mm int. dia. cicular liners
700  600  250 x 250 int. square liners  62,500 
800  600  300mm int. dia. circular liners 70,686 
1000 600 300 x 300mm int. square liners 90,000

150mm int. dia. circular 185mm int. dia. circular  185 x 185mm int.square 
clay flue liner clay flue liner clay flue liner
210mm int. dia. circular  200 x 200mm int. square  225mm int. dia. circular 
clay flue liner clay flue liner clay flue liner
225 x 225mm int. square  250mm int. dia. circular  250 x 250mm int. square 
clay flue liner clay flue liner clay flue liner
300mm int. dia. circular  300 x 300mm int. square 
clay flue liner clay flue liner

Approved Document ‘J’ (ADJ)

Red Bank’s range of clay flue liners are manufactured in accordance with BS EN 1457 : 1999 ‘Chimneys - Clay/ Ceramic flue liners...’ as required under ADJ ‘Combustion Appliances and Fuel Storage Systems’. A chimney flue system correctly constructed using such components whether type A1 (see pages 4 to 14) or B2 (see page 16) will attain Building Regulations approval for appropriate usage.

Note that the industry recognised term Class 1 Flue Liner which refers to clay or concrete flue liners suitable for use in a masonry stack, should not be confused with the term Clay Type A1 Flue Liner which refers to those clay flue liners made to classification A1 of BS EN 1457 : 1999.