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 |
34,225
34,640 |
| 500 |
550 |
200 x 200mm int. square liners
225mm int. dia. cicular liners |
40,000
39,761 |
| 600 |
550 |
225 x 225mm int. square liners
250mm int. dia. cicular liners |
50,625
49,095 |
| 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 |
 |
 |
 |
| 210mm int. dia. circular |
200 x 200mm int. square |
225mm int. dia. circular |
 |
 |
|
| 225 x 225mm int. square |
250mm int. dia. circular |
250 x 250mm int. square |
 |
 |
 |
| 300mm int. dia. circular |
300 x 300mm int. square |
 |
 |
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.