Fitting flexible liner

Fitting a flexible liner

If you are installing a liner in an existing chimney, be sure to get the chimney cleaned first as this will ensure there is no residual soot or other obstructions that could create difficulties on installation.

Once installed , it is important to remember that all such work must be visually inspected as per the UK Building Regulations, Document J . This check ensures that all flue liners are properly installed; that they are the right size for the appliance requirements and that they are completely free of obstructions.

You can install your flexible liner either from the top or bottom of the brick chimney stack. Whichever way you choose to install the liner, please ensure that you have sufficient clearance around the outside of the liner to ensure the least amount of friction, or possibility of catching any bricks within the chimney stack, does not occur.

Unpack your flexible liner and, attaching a drawstring to the nose cone, (making sure it is long enough to reach the bottom of the stack), connect the nose cone to the end of the liner using gaffer tape. Ensure the arrows marked on the liner are facing an upward direction (representing the direction of flue gases). 


You will need two people to install your liner successfully, one at either end of the chimney stack. From the top of the roof, start to push the liner, nose cone first, down the stack. The person at the bottom of the stack should hold the string and take up the slack. Work in tandem to feed the liner down the chimney stack, ensuring you leave enough liner at the bottom to secure your adaptor and enough at the top to secure the top fixings. (See “Completed install” diagram).

Flexible liners are relatively easy and clean to install. They are usually drawn down the chimney by rope from the top and will pass round most bends without opening up the flue. Support is provided by “hanging” the liner from a clamp or plate mounted at the top of the chimney. It should also be firmly clamped at the base before forming the connection to the appliance or flue pipe. Unlike rigid pipe, expansion and contraction will be taken up by the flexible construction of the pipe itself. The solid fuel liner can be left with an air space as insulation. This may be satisfactory for open fires with relatively high flue gas speeds and temperature which will reduce the likelihood of condensation. A better solution is to back fill around the liner with a loose fireproof insulation material such as Perlite, Vermiculite or Leca granules. Some systems offer an insulation wrap, well suited to the large voids found in inglenook situations where back filling would be impractical. (Fibreglass insulation should not be used). Insulation is essential with wood burning stoves due to the high incidence of condensation problems. In all cases a small ventilation hole (usually 15mm) should be provided at the top of the chimney stack to allow any residual moisture to escape. Always follow the manufacturers installation instructions carefully.

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