Cracked chimney crowns letting water into the flue
Why it happens here
Concrete crowns crack when water sits on them and freezes. In Voorhees Town Center, the winter swings above and below freezing dozens of times, so a hairline crack in November can be a quarter inch by March. Once water gets in, it runs down the inside of the flue.
Our approach
We chip out the failed crown, rebuild it with a slight slope so water sheds away from the flue, and seal the edges. We use a mix that handles freeze-thaw better than standard concrete. Most crown repairs take half a day and stop the leak immediately.