When might I need a liner?
The current code for chimneys states that every chimney flue shall be lined. This is a safety concern to protect the chimney exhaust from getting into the house. A chimney liner (be it metal or terra cotta clay) should not have holes in it. A hole in the liner is like a hole in your vacuum cleaner hose. It makes the chimney not function well, and will allow toxic gasses to enter the living space.
A new chimney liner is called for when either the chimney was built without a liner (usually before 1900), or the existing (terra cotta) liner has developed cracks or holes. We can determine that with a thorough inspection.