Possible causes
- Cracked or lifted lead flashing
- Perished mortar joints or flaunching
- Damaged or uncapped chimney pots letting rain down the flue
- Porous brickwork
Warning signs
- Damp patches on the chimney breast inside
- Stains on the ceiling next to the stack
- Loose or missing mortar visible on the stack
Typical solutions
- Renewing step and apron flashings in lead
- Repointing and re-flaunching the stack
- Fitting caps or cowls to redundant flues