If you think about it, your chimney is the only thing on your house that is not protected by your roof. This makes it vulnerable to water entry at many levels. For example failing roof flashing will typically cause the wood & drywall around a chimney to soften, discolor, & eventually deteriorate. Many micro cracks or even a single, credit-card-thick crack within your brick, stucco, or stone chimney can introduce a significant amount of water into the chimney resulting in smells or water staining on walls and even floors.
Chimney tops – or “crowns” as we call them – are very critical in preserving a chimney. The design and integrity of the materials will either lengthen or decrease the life of a chimney. When water enters here it damages everything below it such as your flue (the tube where the smoke goes out) and the masonry structure. Meanwhile most people don’t know it’s happening until it’s too late!