Why is my chimney leaking?
The most common cause is the flashing, the lead that seals the joint between the stack and the roof tiles. Next come porous or cracked mortar joints in the stack, cracked flaunching (the mortar around the pots) and rain falling straight down a disused, uncapped flue.
- Flashing that has split, lifted or lost the mortar holding it into the brickwork.
- Mortar joints that have eroded and need repointing.
- Flaunching on top of the stack that has cracked and lets water into the brickwork.
- Open pots on chimneys no longer in use.
If the leak is away from the chimney, see roof repairs instead.
How much do chimney repairs cost?
Checkatrade's chimney repair guide (April 2026) says most chimney repairs cost between £180 and £1,000, with scaffolding or other access often the biggest variable. These are general ranges, not quotes:
| Job | General range |
|---|---|
| Flashing repair | £250–£1,000 |
| Repointing the stack | £300–£1,000 |
| Chimney cap fitted | £180–£520 |
| Up to five roof tiles around the stack | £170–£500 |
Ask whether the quote includes scaffolding, and get it in writing.
Is a damaged chimney dangerous?
It can be in high winds, if the stack is tall, leaning or has loose bricks or pots. The Met Office suggests moving beds away from areas directly below tall chimney stacks in poor condition when a storm is forecast.
If bricks or pots have already come down, keep people clear of the area below and don't go up to look. A roofer can make it safe once the wind drops.
Should a chimney be capped or removed?
If you don't use the fireplace, a cap or cowl stops rain and birds getting in while keeping some ventilation. Taking the stack down is a bigger job; on a listed building or in a conservation area, check with your council's conservation officer first, as Historic England advises.
When should a chimney be checked?
If your house has a chimney, it's worth asking for it to be looked at whenever the roof is being checked, because the access is already there. For leaks elsewhere, there's a Crawley roofer on the same number.