We get a lot of questions and concerns about possible cracks or earthquake damage inside a chimney. For the most part chimneys are very well secured and most chimney fires are self contained. Chimney fires become a problem when you have cracks inside the chimney. Cracks inside the fireplace are very common and dangerous. The back wall typically has cracks in it and must be sealed. There are several areas inside the firebox and on top of the chimney that are essential to keep crack free.
Cracks on the top of a chimney above the roof are bad because of the ability for water or moisture to get inside different areas. Again moisture causes cracks and cracks allow chimney fires to become house fires. Every chimney cleaning includes an inspection of these areas. The price to repair these areas varies but is usually around $100 per area.