Chimney flaunching, pots & cowls
In short
The flaunching is the mortar fillet on top of the stack that holds the pots and sheds water off the head. It is the most exposed mortar on the whole building, and when it cracks, water runs straight down inside the stack and comes out on the chimney breast below.
Also called: Chimney flaunching cracked · Chimney pot loose · Chimney cap · Chimney cowl
Signs you need this
- Visible cracks in the mortar around the base of the pots
- A pot leaning, rocking or visibly out of upright
- Mortar debris in the gutter or on the ground below the stack
- Damp on the chimney breast with no obvious flashing fault
- Vegetation growing out of the head of the stack
- A capped flue with no visible ventilation
Look at the top of any chimney and there is a sloping mortar bed around the base of the pots. That is the flaunching, and it does two jobs: it holds the pots upright and it throws water off the head of the stack rather than letting it soak in. It is a comparatively thin layer of mortar in the single most weather-beaten position on the house.
So it cracks, and everything follows from that. A crack lets water into the head of the stack, where it runs down inside the masonry and emerges as damp on the chimney breast — often a floor or two below, which is why the cause gets missed. It also loosens the pot, and a pot that is rocking on a failed flaunching is a serious falling hazard from the highest point of the building.
Renewing it is a contained job: the old flaunching is cut out, the pots are checked and reseated or replaced, and a new fillet is formed with a good weathered slope and a drip so water leaves the stack cleanly rather than running back down the face. Where the mortar has been mixed too strong, it cracks again quickly — a slightly softer, well-graded mix with a proper fall lasts considerably longer than a rich, hard one that shrinks as it cures.
Pots and cowls are worth thinking about at the same time, because the flaunching has to come off to change them anyway. A cracked pot gets replaced. A stack with a live fire needs the right terminal for the appliance. And a stack that is no longer used should be capped — but capped with a ventilated cap, never sealed solid.
That last point catches a lot of people out. A flue that has been sealed at the top with no ventilation cannot dry out: moisture from the masonry and from the house condenses inside it and comes out on the breast as damp, which then gets diagnosed as a roof leak and expensively chased. A vented cap at the top and an air brick at the bottom keeps a gentle airflow through the flue and the problem disappears.
Access is the constraint. A flaunching sits at the very top of the stack, which means a scaffold with a proper working platform at chimney height in nearly all cases — and on a town-centre terrace built against the pavement that scaffold stands on the highway and needs a licence from Cheshire East. It is a small job with a considerable amount of arrangement round it, which is why it makes sense to do everything on the stack at once while access is up.
What the job covers
- Old flaunching cut out and the stack head made good
- Pots inspected, reseated or replaced as needed
- New flaunching formed with proper fall and a drip
- Vented caps fitted to disused flues rather than sealing them
- Cowls fitted where downdraught or rain ingress is an issue
- Pointing and flashings checked while the access is up
What it costs
We don't publish a price for this yet, because a number pulled out of the air is worse than no number at all — your roofer has to honour it. On roofing it would also be close to meaningless: access is often the biggest single factor, and it varies enormously house to house. You'll get a firm price for your actual job when they ring you back, before any work starts. The quote itself is free and there's no obligation either way.
Common questions
What actually is flaunching?
The sloping mortar bed on top of the chimney stack that holds the pots and sheds water off the head. It is a thin layer of mortar in the most exposed position on the building, which is why it is usually the first thing on a chimney to fail — and why so many chimney-related damp problems start there.
My chimney is not used. Should I take the pot off and seal it?
Cap it, but never seal it solid. A sealed flue cannot dry out, so moisture condenses inside it and comes out as damp on the chimney breast — a problem people then spend a lot of money chasing on the roof. A ventilated cap at the top and an air brick at the bottom keeps air moving and keeps the stack dry.
Is a leaning pot urgent?
If it is above a path, a doorway or where cars park, yes — that is a falling-object risk from the highest point of the building and it gets made safe immediately. Above a garden nobody walks in, it is important rather than an emergency, and it will be described that way rather than talked up.
Can this be done from a ladder?
Realistically no. The work is at the very top of the stack, takes time and needs both hands, which under the Work at Height Regulations means a proper working platform. Since the scaffold is the expensive part, it is worth doing the pointing and the flashings at the same visit rather than paying for access twice.
Need this doing in Macclesfield?
Tell us the job and it goes straight to our local roofer — one call back, usually the same day. Free quote, no obligation.