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Useful Flue Facts from Gary the Chimney Sweep

Lining your flue

There is a vast number of flue liner types that you can choose from to line your chimney with. Each kind is suited for a different type of stove or fireplace, and knowing which one is the right one for your chimney is more than half the battle in keeping it well maintained and in avoiding needless expense and hassle at a later date.

It is important to note that a poorly installed or upkept liner can cause all manner of problems as a result of leaking, such as:

  • Risk of fire
  • In worst case scenarios, risk of carbon monoxide poisoning
  • Poor up draught
  • The smell of smoke indoors

In my time working in Brighton, Hove, Tunbridge Wells and the surrounding areas, I have come across several examples of poorly lined chimneys that needn’t have caused their buyers trouble if only they’d had the correct information available to them at the time of buying.  I am hoping that this guide will help towards reducing the number of flue related issues that you the customer will have the head ache of experiencing.

FlueTypes and Their Properties

FuranFlex Liners

Suitable for:  Gas fires, oil heating chimneys, condensing boiler flues and solid fuel burning fires.


  • Furan flex flue liners have been developed to fit chimneys of all shapes and sizes – they mould to the shape of the flue and can be installed in chimneys of any diameter or height.
  • These liners are joint-less, so they are gas-tight so that leakages of any kind are extremely unlikely.
  • They are just as strong as any steel liners.
  • You don’t have to demolish or alter the structure of a building at all to install Furan Flex liners.
  • Liners are long-lasting, generally coming with a 25 year guarantee from good providers.

Installation:These liners are fairly straight forward and mess-free to install.  The liner is placed inside the chimney, and is then inflated so that it moulds to fit the shape of the flue.  A steam generator is then used to heat the material, which hardens into place as it cools.

If you are interested in Furanflex lining Gary the chimney sweep can give you the details of a local firm based in Tunbridge Wells.

Thermocrete Liners

Suitable for: Gas and solid fuel burners.


  • Perfect for repairing the damage caused to chimneys by weather (erosion of inner render and mortar joints – this has the effect of increasing leakages and weakening the chimney).
  • By patching up holes and faults in the chimney, thermocrete liners strengthen the structure, and prevent further damage in future.
  • Installation is usually pretty straight forward and can be completed in one day.
  • Fills all gaps, cracks and damaged joints.

Installation:A cylindrical former or mould is fed into the chimney, and the base is sealed off. Thermocrete is then pumped into the gap at the base between the former and the wall. Once the liner is set, your newly lined chimney flue should be smooth, safe and fully working once more.

Eldfast Liner

Suitablefor:  Stoves, open fires, concrete block, brick and clay chimneys.


  • Eldfast liners are resistant to several things such as:
    • soot fires
    • acid condensation
    • frequent and continuous exposure to very high temperature (as doesn’t contain lime or concrete)
  • Even with this coating on top of the chimney’s width, minimum flue measurements can still be maintained with it on.

Installation:The professional responsible for applying the lining should first carry out a thorough sweep of your chimney (and if not, you can get a chimney sweep like myself in to carry out this initial sweep before the installation) in order to remove any lingering soot or debris.

At the time of installation, at the end of a winch, a plug is initially positioned at the base of the chimney, forming a seal.  The lining is then continuously poured down the chimney as the winch is slowly raised up the structure, coating the walls as it goes.  The coating can also be poured into the chimney’s connecting pipes in some cases.  The liner is then left to dry, which, dependent on conditions such as draught and temperature in the flue, can take anywhere between 1 and 48 hours.

Flexible Stainless Steel Liners

Suitable for:  wood burning stoves, multifuel stoves, open solid fuel fires, boiler flues, large gas fires.


  • Suitable for an array of fireplace types and chimneys.
  • Several kinds of stainless steel types available for different types of heating appliances (e.g single skinned for oil burners or double skinned for class 1 gas fires).
  • Long lasting.

Installation: As this kind of flue liner has to be cut to the right size before it is installed, as it doesn’t mould to the chimney’s shape like the previous few liner types mentioned. This kind of installation is best left to the professionals.  Installation methods can vary and can be dangerous if attempted by an untrained person.

If you need any advice at all regarding liners, especially if you live in Seaford, Lewes, Hurstpierpoint, Henfield, Portslade or any other areas I cover, then please feel free to give me a call or submit an enquiry form.  Don’t be shy!  As a chimney sweep, it’s my job to lend a hand in all matters chimney sweeping related!