Flexible Chimney Flue Liner Guide

What is flue liner for?

Flue liner is used to line an existing chimney when installing a stove in a fireplace. It is not insulated and must not be used externally or through walls, for this you need twin wall flue.

Do I need flue liner?

Flue liner is super hard wearing, relatively cheap, easy to install, improves the efficiency of your system, prevents tar build up that can eat through your walls, helps prevent chimney fires and HETAS installers won’t install a stove without one. In the long term they will save you money and you won’t have to worry about cracks in your chimney and smoke leakage.

What diameter do I need?

You need to have a minimum diameter of the outlet of your stove. You can increase in diameter but never decrease and for that reason we do not sell reducers. The minimum diameter for a flue system is generally 6″ (150mm) unless your stove is DEFRA approved and then it can be reduced to 5″ (125mm).

How do I work out what length I need?

There are a few way to work this out:

  • Get on the roof and drop some weighted string down. When the sting reaches the floor, measure the string.
  • Measure floor to ceiling in each room and loft, then add on about 2 meters for the length of the chimney and space between floors. Then add at least 1 other meter to this to account for bends in the chimney.
  • Go outside and count the number of bricks from the floor up to the top of your chimney, measure 1 brick and multiple this by the number of bricks. Then add of about half a meter if you have a chimney pot on top of your chimney stack and another meter to account for bends in the chimney.
  • Ultimately it is always best to add a meter to your estimations as you can easily cut the liner down to length but you cannot join liner, it has to be in one continuous length.

What else do I need?

As well as the flue liner itself, you will need an installation kit which consists of a top fixings for either a chimney pot or a stack without a pot. We sell these kits complete with flue liner and all the fittings you need.

You will also need a stove pipe – the is the first piece of pipe that comes out of the stove and is black enamelled pipe. This can be found in our connecting stove pipe section. If you are coming out of the rear exit of the stove then you can use a 90 Tee and a length of pipe, if you are coming out the top outlet of your stove then you will just need a length of pipe.

You will need a register plate – this blocks your chimney off whilst allowing you stove pipe to pass through it. These can be cut to size and the stove pipe connects to the flue liner once it has passed through the register plate.

You will need some fire cement to seal all the joints and lastly you will need a CO alarm in the room where the stove is.

Need more help?

Our fully HETAS trained team are ready to help plan your system advice on all the building regulations and get your everything you need for a safe and compliant system. Call us on: 01376 315 760.

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