Chimneys can sometimes leak. There are a few common places where leaks happen. The most common area of leaking is the connection where the chimney and the roof meet at the roof line, if the area surrounding the chimney isn’t properly flashed or the flashing is damaged- rainwater will funnel inside the house during a rainfall instead of being wicked off the side of the house.
The second most common cause of a roof leak is no rain cap. At the top of the chimney there should be a rain cover that covers the majority of the chimney stack opening from above to prevent rainfall from entering inside the chimney. Water will wear away the mortar inside a brick chimney over time, also aging these chimneys more rapidly. Prevent rainwater from entering the chimney by installing a rain cap.
A great way to spot if you have a water leak or not, is to look for the tell tale waterstain, usually above on the cieling. For water that has been leaking on brick, it creates a white powder substance afterwards that is called “efflorescense”. When you see this, it is a indicator to have your chimney inspected.