Here is an informative article I found located here: http://www.scambusters.org/chimneyrepair.html
Chimney Repair and Cleaning Scams
Chimney repair and chimney cleaning scams are on the rise. Since most people know nothing about chimneys, this is a particularly easy way for scammers to cheat unsuspecting homeowners.
Here’s how chimney repair and cleaning scams work:
The scammer contacts you (via email, phone, etc.) and offers you a special on chimney cleaning for a ridiculously low price, such as $39.95. If you’ve just moved into a new home, they may say that the previous residents (and mention their names to add credibility) used their company.
Once they get to your home, they inspect your chimney and tell you that there is structural damage, or that you need new chimney caps (also known as spark arresters). They may even bring in dead birds or pieces of concrete that they claim fell down the chimney.
In my 20 years as a mason I have come across a bunch of people who have hired a chimney sweep. The VAST majority of these people’s experience has been the chimney sweep did clean their chimney, and they also STRONGLY advised they get a metal liner.
Metal liner’s are about $3,000.00 to start! There are some very good situations when a metal liner is very much needed. Pretty much anything that is gas and being vented up a masonry chimney needs a metal liner. Damage to a flue pipe in the furnace flue should really have a metal liner.
A metal liner may be of use in a fireplace flue, it may be appropriate in a damaged fireplace flue. BUT!~ if the chimney has damage to the structure of its insides, otherwise known as the throat, and smoke chamber, areas, then I would caution using a metal liner as an inexpensive way to circumvent a chimney repair or a masonry repair.
In this photo it isn’t shown , but the top half of the chimney has a distinct lean back to it. It was separated from the house over 2″ at the roof line. The only other evidence telling us of what is going on is a small mortar joint separation. If you look close this is not a settlement crack of the mortar joint. This little space in the bed joint is from the metal in the throat of the chimney expanding and as a result lifted the masonry up. Well, if there is a gap on the outside, then rest assured there is a gap on the inside where we cannot readily see.
My professional opinion is that a metal liner should not be used in this chimney, the front of the fireplace was cracked, the throat was cracked and this needed a chimney replacement.