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Chimney sweep information hub > All about chimney lining



All about chimney lining



James the Sweep does not line chimneys but I can advise you on chimney liners and costs involved. I can also inspect, measure and sweep your chimney and perform a smoke soundness test.

 

I have observed both professional and amateur/dangerous work during my career. I can now recommend certain companies within your area – contact me for more details.

 

So, why line a chimney? A stove only works well if connected to a sound chimney and correctly sized flue. A chimney ideally serves to remove combustion products (gases) from the interior to the outside without causing danger. It works on the ‘hot air rises’ principle so the flue must be well insulated to be productive.

To clarify the terms:-

 

FLUE - The flue is the passageway through which the combustion products travel to the outside from the stove.

 

CHIMNEY - This is the structure surrounding the flue/flues.

 

FLUE LINER - The material used to form the flue.

 

STOVE PIPE - The appliance connecting from the appliance to the flue within the chimney.

 

Factors such as operating a stove at a low setting for long periods, or cool air leaking into the flue; will cool the gases down and affect the performance of the chimney. To keep the flue gases warm, consider the insulation value of the lining within the chimney itself.

 

Most houses built prior to 1965 (before a change in the building regulations) were built without liners. Flues were usually ‘parged’ (rendered) on the inside with lime mortar. This parging will have suffered attacks in time from corrosive elements within the flue gases, resulting in erosion and leakage. A sign of that happening is sand-like material (old lime mortar) falling down the chimney. Also, the mortar between the bricks will have deteriorated in the same way.

 

Houses built after 1966 should have lined flues usually done with clay liners. However, this type of lining may not suit an efficient wood or multi-fuel stove.

 

Chimneys are often built on the outside of the house and are subjected to the elements. Combine that point with the fact that insulation around liners is generally excluded – and you get a cold flue.

 

Please remember that stoves are efficient heating appliances and will produce anything up to 85 per cent of heat from the fuel burnt into the room, unlike an open fire that can lose up to 95 per cent. It becomes essential to maintain a reasonable flue gas temperature to get a natural rise in gas.

 

A lined and well-insulated flue will make for an efficient and safe appliance. Unlined flues can result in costly building work.

 

What are the reasons for lining a chimney?


There are a number of reasons why an old chimney may need lining.

 

  1. The flue is leaking smoke and fumes into other rooms or parts of the building.
  2. Condensation or tar are seeping through the chimney walls causing staining either outside or inside the building.
  3. The flue is much too large for the appliance being used.
  4. The flue is too cold, particularly if on the outside wall and consequently not drawing properly.
  5. If the chimney was built from 1965 onwards, with liners installed the wrong way up, tar and condensation leakage may occur. This is quite a common occurrence and I have found many chimneys in this condition, especially in the Brighton and Eastbourne areas.
  6. The old flue surface is eroded - causing leakage, chilling and poor up-draught. 

 

What is the appropriate chimney liner for your appliance?

 

There are two types of chimney liner: Class 1 (for wood and solid fuel) and Class 2 (for gas).

 

Class 1 liners

 

All wood and multi-fuel stoves must be lined with Class 1 flue liners. There are different types:

 

All wood and multi-fuel stoves must be lined with Class 1 flue liners. There are different types:

 

  • Rigid 316 grade stainless steel
  • Flexible 316 grade stainless steel
  • Pumped refractory concrete (thermocrete)
  • Rigid pumice

 

The Class 1 Flexible 316 grade stainless steel liners are the most cost effective means of lining an existing chimney. The work can generally be carried out in one day with minimum upheaval and little mess. If the liner is installed correctly, it will last many years and also carries a long guarantee. This liner type is often recommended by chimney lining companies since it is reliable.

 

All chimneys need to be swept prior to fitting a liner for reasons including:-

  • To keep the mess to a minimum on the day of lining the chimney
  • To check the flue way is clear of blockages and birds’ nests. It makes no sense to install a chimney liner against a dirty chimney and run the risk of a chimney fire.
  • Most liner manufacturers give a ten year guarantee and having your chimney swept prior to installing the liner is one of the conditions.

 

Class 2 liners

 

The Class 2 Flexible Flue Liner could be mistake for a Class 1 type. You can tell the difference as it is inexpensive, lightweight and rough on the inside. All gas stoves should be lined with a Class 2 liner to meet safety regulations.

 

FuranFlex Chimney Liners

 

FuranFlex is a glass fibre reinforced, thermosetting resin which is as strong as steel when set. The beauty of FuranFlex is that, unlike steel liners, it gives better corrosion resistance and also comes with a 25 year guarantee.

 

FuranFlex chimney liners really stand out as great liners on long or bendy chimneys, such as found in some Victorian houses. I have seen many flexible steel liners get stuck on the bends in flues during installation, and extra holes were made to guide the liner down the chimney. This wouldn’t have happened if FuranFlex had been used.

 

I remember sweeping a chimney/liner in Tunbridge Wells for a customer. They told me a nightmare story about a company that had to break three holes in the bends of their chimney to guide the liner down the structure. FuranFlex would have been an ideal choice for this chimney.

 

When the FuranFled liner is delivered it is bendable (like a fireman’s hose). The chimney will be swept first to remove tar, creosote and loose parging (old lime mortar). After sweeping the chimney, a CCTV survey will be carried out.

 

The new FuranFlex liner can be pulled up a chimney or down from the top of the flue, which makes for easy instalment. All adaptors and fittings are then secured to the FuranFlex.

 

The FuranFlex chimney liner is pushed into the exact shape of the flue by filling it with air. Because the liner can follow the whole route of the flue, bends and all, horrors such as the aforementioned Tunbridge Wells installation can be avoided!

 

The next step of installation sees the FuranFlex chimney liner being connected to a steam generator and steamed so that it can be set into a fixed shape. The steaming process takes between one and three hours, eventually resulting in the liner setting completely.

 

The end result should be the chimney now has 3mm of gas tight liner with no joints whatsoever.

 

If you live locally and I am sweeping your chimney (Tunbridge Wells, Sevenoaks, Tonbridge, Brighton & Hove etc) and you are curious about this kind of liner -please remember to ask me to show you a sample, as I carry an offcut in my van.

 

 

 

 

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