The common problems with a chimney and its liner – Part 7

The common problems with a chimney and its liner – Part 7

Retro fitting!

This is a continuation and final installment of a 7-part article on chimneys and their liner – giving a brief history of chimneys, their liners and the associated problems that can arise from them.  If you have any queries on your chimney or liner or should you wish to know more about any of these issues, get in contact with your certified chimney sweep, who will be delighted to advise you on this topic.

In this final part we look at the retro fitting of a liner and the relining of older flues that really aren’t up to the job of serving a modern stove.  I say stove, because the relining of a flue is an expensive process when talking of a 6” diameter flue as needed by a stove.  You can line for an open fire, as long as it is a small one.  There are sectional rigid liners and you probably can get them for a large open fire, but the cost will be significantly higher as soon as you go over the 10” diameter liner.  Plus, a fireplace of any size, when served correctly with a wide bore flue will rip the warm air out of your house 24/7, so what is the point?

So you wish to reline an open fire.  What are the sensible liner options?

Well there are pumped liners.  Oddly I have found that if you ask for a CCTV scan of the flue two weeks after lining, with the understanding that if the liner shows bald spots or cracks they will ream it out and reline at no extra charge, people lose interest for no apparent reason.  We will therefore focus on a rigid liner.  These are basically the self-same terracotta tubes that modern chimneys are lined with, and very good they are.  There are also ceramic and pumice versions, and the pumice ones are the very best of all.  Not surprisingly, they are also the most expensive liner.  Now who would have expected that?

Holes are cut in the chimney and the sections fitted into place.  If done correctly these are the Rolls Royce of re-linings.

The remaining type of liner is the flexible stainless steel tube.  These are made of two strips of stainless steel wound around each other.  They are lowered down the chimney and connected to the pot at the top and the stove at the bottom, secured at each end with specific adaptors that close off the ends of the tube, stopping the tapes from unravelling.  A bit like hemming the end of a knitted sleeve.

The only down side to this liner is that they are a high tech material and must be handled and treated with respect.  If during installation they are bent too savagely, the internal tape will ‘frill up’, reducing the efficiency of the gas flow and providing a soot trap in the liner that can grow into a point of corrosion.

Another point of concern with a liner is overheating.  No chimney likes chimney fires, and all are damaged to a greater or lesser extent.  Mild damage shows up as rainbow patterns on the surface of the liner, but a serious chimney fire will push the liner out of its comfort zone and over the edge. Stainless steel is basically an alloy of steel and chromium or vanadium, both of which prevent the acids in the flue gases from eating holes in what would otherwise just be thin steel sheet.  When the heat gets to extreme, the vanadium and chromium migrate away from the hot spots, leaving raw steel to face the flue gasses.

Unsurprisingly, these chromium free zones will rot through in record time allowing condensation, tars and fumes to escape into the chimney void, necessitating a re-reline.  So, it makes good sense to get your chimney swept annually, and swept well each year.  That will also keep your guarantee valid.  A chimney fire that may be linked to poor maintenance of your chimney will invalidate your guarantee, so do get the chimney swept each year by a certified chimney sweep who will issue you with a certificate, which should be kept in a safe place for insurance purposes.

To recap.

  1. There are rigid sectional liners for open fires
  2. For stoves, the recommended liner is the twin wall, flexible stainless steel liner
  3. This liner needs careful and correct installation
  4. Regular maintenance of these liners is essential
  5. Get your chimney swept each year by a certified chimney sweep who will issue you with a certificate of sweeping.
  6. Keep the certificates in a safe place.
  7. That’s all folks.

 

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