1. A cracked crown
The crown is the top layer of a masonry chimney, and it sheds water away from the bricks and flue. Cracks here can let water straight into the structure.
2. Crumbling mortar
Mortar joints wear out over time. If mortar is sandy, missing, or falling out, tuckpointing can often restore the joints before the damage spreads.
3. Flaking or broken bricks
When water soaks into a brick and freezes, it expands and can break the face of the brick off. Pieces of brick on the roof or ground are a clear warning.
4. White staining
White, powdery stains on brick usually mean water has been moving through the masonry and leaving minerals behind. The stain itself is harmless, but the water is not.
5. A leaning chimney
A chimney that looks like it is leaning may have a serious structural problem. Avoid using the fireplace and have it looked at soon.
Why early repair helps
Freeze-thaw cycles keep working on any opening they find, so small problems tend to grow. Repairing early can help you avoid a much larger chimney rebuild.