Chimney Lining

Chimney Lining  using a flexible stainless steel liner

If you are considering fitting a gas fire into an existing fire place with an old flue you will have to line the chimney flue. The combusted gases produced are very dangerous and if they escape into a room can have severe consequences. Old chimneys may have small gaps and cracks where gas can escape. Fitting a liner will ensure all the gasses are extracted to the open air.

Make sure you have safe access to the chimney by using a scaffold tower.

chimney lining

typical chimney arrangement

A variety of Chimney Lining are available, from traditional to new and everything in between. Flexible Stainless Steel chimney lining & Twin Wall flues have been available for some time but more recently advanced systems providing for installation of the chimney linings without needing to reopen the wall to replace the ductwork have arrived

Chimney lining has been used in chimney construction for decades, but are absent in historic structures where the masonry has not been updated. Chimney lining help prevent flue gases escaping through the sides. They separate combustible construction materials from the worst of the heat, and prevent by-products of combustion from leaking through the porous construction materials

Typical Chimney Lining Arrangement

Line your Own Chimney

New chimney lining must comply with the Building Regulations. The relevant regulations are contained in Document J of the Building Regulations 2000 updated in October 2010. Fitting a new stove or liner now falls within the ambit of Building Control. The Building Control Department of your local council will advise.

New chimney lining must be of the flexible type, and must be installed in one continuous length with no joints. Do not use coring balls on any metal flue system. No mention is made in the regulations of insulating the chimney lining but we recommend it so as to protect the outer structure from the effects of extreme heat. All of the necessary parts and accessories and chimney lining pipe are readily available on the Internet.

chimney lining

Installing a liner

Installing a chimney lining is a two person DIY job. One person goes on the roof and the other stays at the fireplace. We strongly recommend that the person on the roof secures himself to a solid part of the roof structure. The person waiting at the fireplace needs goggles, a dust mask and suitable clothing as protection from the dust or even lumps that may come down the chimney. The edges of a chimney lining are very sharp so it’s advisable to wear gloves.  The person on the roof and the person at the other end need to be able to communicate either by shouting up the chimney or by using a mobile phone

Basic Tools required are:

At least one length of rope, (but for safety sake several others), sand, cement, buckets, unibond, integral waterproofer, cold chisel, hammer, adjustable spanner, metal snips, pliers, trowel, Phillips screwdriver, and a paintbrush.


Chimneys should always be swept before trying to install a new chimney lining

  • Remove the chimney pot and associated mortar.
  • Have the raw plugs ready for any register to be fixed into place once the chimney lining is down.
  • Take the chimney lining and all the parts up to the roof

Fitting the Chimney Lining

  • Feed a weighted rope at least 5 metres longer than the distance to the fire place down the chimney. If it gets stuck raise and lower it to dislodge any obstruction. Person 2 should advise when it reaches the fireplace at which point it should be secured on the roof.
  • Check that the chimney lining is the right way up. The arrows on the side should be pointing upward and if you rub your hands up and down it, it should feel smooth on the way down and rough on the way up. For the rest of the process you should wear gloves.
  • If it’s a straight chimney and the chimney lining goes down easily it’s possible to attach the flex adaptor first and attach the rope to the three lengths of wire wrapped around the self tappers. But if the chimney lining is a light fit or there are difficulties with bends we suggest attaching the rope to a nose cone. The closing plate goes on the top end of the chimney lining with the Top Fixing Clamp above it. If you’re using insulation wrap it around the chimney lining

    chimney lining

    Connecting wires for pulling through

Chimney lining adaptor wires allowing for rope attachment

  • Feed the chimney lining down the chimney. It is helpful if the person at the other end has a torch to see what’s happening and to identify any obstructions but he should beware of dislodged material falling to his end. The chimney lining itself can be used to dislodge obstructions.
  • If a serious blockage occurs use the known length of the rope to work out where it is and open the chimney inside the house. It should also be possible to hear through the wall where the blockage is located. Remove the obstruction and close the hole.

    chimney lining

    Sealing plate

  • When the chimney lining goes as far as it needs to, move the fixing clamp down the chimney  lining until it rests on the top of the chimney and can support the weight of the chimney lining. Pull the chimney lining up slightly before tightening the fixing clamp.  Notch the chimney itself so the fixing clamp legs sit flush with the stack and with the closing plate sitting above the clamp. Remember that the closing plate itself is not a support device. If the chimney opening is too big reduce it with some pieces of slate or something else suitable.

Leca Backfill

  • If a leca backfill is involved tie the chimney lining off while fixing the register plate. Having screwed the register plate into place seal the outside edge of the plate where it meets the masonry wall by putting a fillet of mortar up the flue hole. Draw the adaptor through the hole in the register plate and tighten the clamp around it making it ready for the leca backfill. Pull the chimney lining up as you backfill to keep it straight and fill the chimney with the leca

    chimney lining

    Leca fill. available in bags

Next Step

  • Remove excess chimney lining length using a hacksaw or snips reducing it to half the height of the chimney pot. Remember that the edges of the flexible chimney lining will be very sharp. To prevent water running down the outside of the chimney lining fill the space between the pot and the chimney lining with mortar. If need be cut the chimney lining off shorter. You are then ready can fit the closing plate and fixing clamp.

Closing plate bedded in mortar with gap between stack and chimney lining closed 

  • Work (more thoroughly than usual) 5 parts sand to 1 part cement and integral water proofer. Establish a good key for the mortar by wetting the top of the chimney, pot, closing plate, chimney-lining end etc with a water/Unibond mix. Put the mix around the chimney lining and push the pot into the mortar bed ensuring the pot is straight by using a spirit level. Try to create an overhang to keep water drips away from the stack and create a sloped and smooth finish on the mortar around the pot.
  • Make sure you fit the correct gas terminal pot this stops water going down the liner but will allow the gasses to excape.

    chimney lining

    Typical Gas terminal

  • Wipe the chimney pot with a wet sponge to remove cement etc. If there is a chance of any downdraft fit a cowl or a rain top
  • At the stove end, use a rigid flue to connect to the chimney line adaptor and then to the stove.
  • Allow at least 24 hours before light the stove. 36 may be better to allow for two full days of day temperatures

KCS will be returning to the subjects of stoves and chimney lining of all types in the future including more advanced modern systems. We would be happy to hear form any readers who would like us to feature any particular types.

Types of chimney lining, flexible stainless steel, 2010 chimney lining regulations. Chimney lining apparatus and tools needed for DIY Installation. Clearing obstructions. Leca Backfill. Safety . Insulation