Flue systems for gas fires
Dunbrik Mini Clearflow Gas Flue Block System
This is a neat efficient method of providing a flue in a new domestic dwelling. Gas fires suitable for “pre-cast flues” may be fitted. The outlet depends upon the house design. It is usually through twinwall flue pipe in the roof space to a ridge vent or to a gas terminal at eaves or through the roof slope.
The gas flue blocks are built and bonded into the inner leaf blockwork of an external wall, into a party wall or partition wall.
The gas flue blocks are designed for ease of installation. The tongue and socket detail provide a tight concrete-to-concrete internal joint and an external compressive seal using special heat resistant sealant. The bonding nib has a 10mm cut-out for mortar jointing with the adjacent blockwork – this assists coursing.
Dunbrik Triple 7
Gas flue block fittings for timber framed houses. The Triple 7 Panel fittings have been designed to allow the Mini Clearflow gas flue block system to be installed within the inner leaf of a Timber Frame construction by using specially designed flanking blocks and fixing channels. The system is also suitable for other forms of modular build.
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 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 250mm & 300mm liners and 1 joint for 450mm liners. Any void between flue liners and masonry surround should be filled with Dunfil insulating infill.
British Standard BS EN 1857 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 600°C
- N1 – Gas tightness negative pressure test at 40 Pascal
- G – Sootfire resistance heat shock tested to 1,000°C for 30 minutes
- D – Condensate resistance for dry flue conditions
- 3 – Corrosion resistance for all domestic fuels (scrub test for durability)
UK Building Regulations ADJ
Dunbrik A1 Concrete Flue Liners meet the minimum standards set in approved document J (ADJ) and exceed the requirements for temperature and gas tightness.