There are a few sets of circumstances under which a chimney liner may need to be replaced. For example:
- the liner has warped or cracked
- there is a major problem with creosote accumulation
- the flue is the wrong size for the fireplace
These conditions, among other possible causes of necessary replacement, all call for a professional to come replace the liner.
Don’t Blame Yourself
Metal flues can be warped by excessive heat produced with fires built too high. Who has not kept adding logs to a warm fire on a brutally cold winter night to suddenly realize, oops, that is a really big fire? Even good quality flue tiles can crack when exposed to temperature extremes or shifted by settling foundations.
Creosote deposits can seep through cracks in mortar joints, getting behind the liner and making your clearances truly void. Re-heated and re-formed every time you use the fireplace, those easily ignited creosote deposits are no longer confined to the inside of the liner. Little sparks have access to the actual structure of your house, which is completely unacceptable.
Believe it or not, the flue can be the wrong size for the fireplace, just as a chimney can be the wrong height. That is a little mind-boggling, since one would expect all of that to have been considered when the fireplace system was first installed. Still, improperly sized or improperly installed flues are among the primary causes of an inadequate updraft.
Just Do The Right Thing
Whatever caused it, a warped or cracked chimney liner has to be replaced, and so does one with excess creosote buildup. If Stage 3 creosotes are present on the inside, their extremely difficult removal makes liner replacement preferable. If even less developed creosotes are on the outside of the liner, you can forget the liner you have got and start choosing another.