Installing Flexible Flue Liner

Installing a flexible flue liner may seem like a daunting task, however if you follow this step-by-step guide, you can get this job done with relative ease.

First of all get the equipment for the task:

  • A length of rope twice as long as your flue and some string
  • An angle grinder
  • Dust mask
  • Gloves
  • Safety goggles
  • Old clothing or overalls
  • Someone else to help you
  • Ladders to get onto your roof
  • Cement and mortar

With everything ready you can begin.


Step One:

Clean your chimney/flue. This is the first thing that has to be done otherwise you will find the task incredibly difficult and very messy. Get a professional chimney sweeper to do this for you. After this remove the stove attached to the flue/chimney.

With a clean flue/chimney and the stove removed, you can begin actually fitting the liner. Take the rope, go up to the top of the chimney/flue and tie one end into a knot. Insert the rope down the chimney/flue until it reaches the bottom (this is when you may need someone to check for you). Then, taking the other end of the rope, tie it around the chimney pot/flue exit. This will stop the rope disappearing down the chimney/flue.

Step Two:

Measure the distance between the bottom of the rope and where it is attached to the chimney pot/flue exit by marking the latter with some string. This will be the length of the flue liner. Now measure the width and length of the flue exit/chimney stack. This is to determine the size of the closing plate which should overlap the inside edge of the stack/pipe by about 25mm leaving 75mm the stack/pipe exposed all the way round.

Step Three:

Cut the flue liner down to size or purchase one that is the right length. After this is done, remove the chimney pot/flue exit and place it somewhere safe whilst also removing the rope. Taking one end of the liner the rope, turn this end of the liner back on itself in a ‘U’ shape and tie the rope around this until secure. Drop the other end of the rope down the chimney/flue.

Step Four:

Now feed this folded end of the liner down the chimney/flute with someone else at the bottom carefully pulling on the rope to bring the liner down.
When you are happy the flue liner is all the way down and the top is level with the top of the chimney/flue without its stack/exit, cut off any excess at the bottom to size so that it is exactly the length of your chimney/flue.

Step Five:

Fit the closing plate at the top of the flue liner with cement/mortar to secure it and replace the stack/flue exit. Use a spirit level here to make sure the closing plate is flat and square with the stack/exit.
When the stack/exit is safely replaced and the cement/mortar has fully set, reattach the stove to the flue. Then start a small fire to check the smoke flows out of the chimney/flue properly and then you’re done!