Pots and cowls
Can a cracked chimney pot be replaced, and should you fit a cowl?
A cracked pot can be changed without touching the rest of the stack. Whether a cowl goes on top turns on what the flue serves, so settle that first.
The short answer
Yes, a cracked pot can be replaced on its own, and the mortar bed it sits in is checked while it is off. Whether to fit a cowl turns on the use of the flue beneath: an open fire, a stove or boiler, or nothing at all. A cowl that suits one flue can be wrong for another, so settle that before buying one.
4 min read · Part of Chimney repairs
Replacing a cracked or loose pot
A chimney pot is the clay or concrete outlet at the top of the stack. A crack through it, a piece missing from the rim or a pot that moves when touched is a reason to replace it. The pot cannot be mended in place with a coat of mortar, because the crack is part of the pot itself.
Replacing one is a short job once we can reach the stack safely. We:
- lift the old pot clear and check the flue opening below it
- look at the mortar bed round its base, which is called the flaunching
- choose a replacement of the right size, shape and colour
- bed the new pot in fresh mortar and shape the flaunching to shed the rain
If the flaunching is cracked as well, it is renewed with the pot, because there is no sense in fitting a new pot into a failing bed. Our page on chimney flaunching explains what it does. Matching a pot on a terrace or a period house is a matter of looking at the neighbours' pots and bringing a photograph, and the survey allows for that.
Cowls, caps and what the flue serves
A cowl sits over the top of the pot and keeps weather and birds out of the flue, while a cap closes off a flue that has been left out of use. The right choice follows what is below it.
| What the flue serves | What to settle first |
|---|---|
| An open fire in use | A cowl must not choke the draw: ask the sweep or fitter |
| A stove or boiler | Ask the engineer who services the appliance |
| A flue left out of use | A cap, and a decision about the flue below |
| A flue with birds nesting | Wait until the nest is empty |
For a live flue we fit the cowl the engineer specifies, because the type is theirs to choose. Where birds are already nesting, the work waits until the nest is empty, since a nest in use or being built is protected by law. A cowl is no substitute for a sound pot: if the pot is cracked, replace it and fit the cowl to the new one, so the two are bedded together and checked in one visit.
Planning, listed homes and conservation areas
Swapping a pot like for like is small work, but the planning rules say something about chimneys. Class C, the permitted development rule for roof alterations, excludes any alteration that involves a chimney being altered or replaced. Whether a new pot of the same kind counts is a question for your council's planning team, so ask before you order anything out of the ordinary.
If the house is listed, listed building consent is needed for works in any manner which would affect its character. A change of pot style or height can do that, so the council is asked first. In a conservation area, an Article 4 direction can take further permitted development rights away; the council can tell you whether your street has one.
The survey note gives you the pot's size, material and fixing, with a photograph, so that your planning team can answer from facts. See chimney in a conservation area for how to find which council and which map apply. When the stack itself is in trouble, our page on chimney repairs shows the options.
Access, licence and the written price
A pot is the highest thing on the house, and getting to it safely sets how the job is done. The survey decides whether it needs scaffold or another safe working platform, and the written price covers whichever is chosen. Scaffolding that stands on the pavement is licensed by the county highway authority.
- Kent County Council licenses scaffolding on the highway at £52 per week for 2026 to 2027, and its page says the scaffolding company should submit the application; we arrange it with our scaffolder.
- In East Sussex, scaffolding on the highway needs a licence from East Sussex Highways (£127 for 28 days on its fee table); we arrange it with our scaffolder. Check the current fee.
The two fees run for different periods, so they are not directly comparable. Our page on scaffolding for chimney repairs sets out the licence rules in more detail.
Following the survey you are given one written total price. If the pot is replaced along with other stack work, the scaffold serves both jobs, so the sensible time to change a pot is while the stack is already being worked on.
More questions
How can I tell from the ground that a pot is cracked?
Zoom in with binoculars or a phone camera and look for a line running down the pot, a missing piece at the rim or a pot that sits at a tilt. Photograph it from the same spot. A pot that looks sound from below can still have a crack on its far side, which is why the survey looks from the roof.
Does a cowl change how a fire draws?
It can, because a cowl sits across the outlet of the flue. That is a question for the sweep or the engineer who services the appliance, and it should be settled before the cowl is bought. We fit the cowl they specify. A cowl on a flue that is no longer used is a simpler matter.
More on chimney repairs
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