Why is my chimney leaking?

Chimney Academy · Solve a symptom · Updated October 2026

Where the water can come from

• The cap or lack of one. Without a cap, rain can enter the flue directly. A cap that is damaged or loose can also let water in.
• The crown. The crown is meant to shed water away from the flue and masonry. Cracks in it let water into the chimney below.
• The masonry. Worn mortar joints and damaged brick absorb water, and freezing and thawing make the damage worse over time.
• The flashing. Where the chimney meets the roof, failed or gapped flashing lets water run in beside the chimney.
• Elsewhere on the roof. Sometimes the water is not coming from the chimney at all but from a nearby roof or gutter problem that shows up near it.

The signs are similar for all of these, which is why a stain on a ceiling or a damp patch near the fireplace does not by itself tell you which part has failed.

What to note and photograph

• When it happens: during any rain, only in wind-driven rain, or after snow melts.
• Where you see it: in the firebox, on the wall or ceiling near the chimney, in the attic.
• Photos of stains, dampness and anything that has fallen into the firebox.

This helps whoever inspects the chimney narrow down the source.

What not to do

• Do not climb onto the roof or the chimney to look.
• Do not seal or coat the first spot you can reach without knowing the source. A coating applied over the wrong spot can hide the problem and, in some cases, hold moisture in the masonry.
• Do not light a fire in a fireplace that is visibly wet or shedding debris until it has been looked at.

How leaks are fixed

The repair follows the source. It may be a new cap, a crown that is resurfaced or replaced, repointing of mortar joints, or new flashing. You can read how these are handled on our chimney repair page, and see a real example in our Montclair crown repair project.

When to call

Call when you see water staining or dampness near the chimney, or when pieces of mortar or tile start appearing in the firebox. If a fire or carbon monoxide alarm sounds, leave the building and call emergency services first.