A1 Flue Liners - (Class One)


Dunbrik A1 concrete flue liners systems for domestic chimneys
Flue liners are UKCA marked.

System details and design guidance
The Dunbrik A1 Concrete Flue Liner Systems are used in the construction of domestic chimneys suitable for all types of domestic fires. A domestic chimney is a structure made with a minimum of 100mm thick masonry lined with purpose made flue liners.
Householders can burn any domestic fuel including coal and properly seasoned wood or install any domestic gas fire including flame effect fires.

Dunbrik A1 concrete flue liners outperform clay liners, are available for delivery to site within 3 working days and cost typically half the price

Flue Liners:
Dunbrik concrete liners are made with tongue and socket joints for accurate location and tight jointing. They are manufactured from kiln burnt aggregate and Portland cement and are designed to withstand repeated temperature fluctuations. Flue liners should be joined with Dunseal fire proof mortar paste. Allow approximately 3 joints per cartridge for 200mm liners, 2 joints for 250 & 300mm liners and 1 joint for 450mm liners. Any void between flue liners and masonry surround should be filled with Dunfil insulating infill.

Liner Standards:
British Standard BS EN 1857:2003 established performance standards for concrete flue liners for domestic chimneys. Dunbrik liners have been tested by BSRIA and achieved the highest categories in each class as follows:

Dunbrik Type A1 - T600 N1 G D 3

T600 Temperature nominal operating temperature 600oC
Gas tightness
negative pressure test at 40 Pascal
Sootfire resistance
heat shock tested to 1,000oC for 30 minutes
Condensate resistance
for dry flue conditions
Corrosion resistance
for all domestic fuels (new scrub test for durability)

Flue Liner Ranges:
Dunbrik flue liners are available in the following round and square sizes to allow for the indicated fireplace opening sizes for burning domestic fuels.

flue size

Flue cross
1000 sq mm

lintel span


recess area
1000 sq mm

Typical recess
width & height

200id 31 600 375 265 500 x 550
300id 71 800 475 471 800 x 585
450id 159 1,100 625 1,060 1,100 x 960
250sq 62 800 425 417 700 x 595
300sq 90 800 475 600 800 x 750

For details of lintel span see the product guides & installation page and the prices & costings page for sample costings.

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