If you’ve ever wondered why some chimney flaunching lasts for years while other repairs crack, fail or let water in after a winter or two, the answer often starts with the mix.
On a recent chimney repointing and flaunching repair in Wollerton, Nottinghamshire, I took a few spare minutes on site to explain the flaunching mix I use in my day-to-day chimney repairs, why I mix it the way I do, and how small details can make a big difference when you’re working at height.
If you’d like to watch the full video first (well worth it, even if only to see me trying not to overthink a bucket of mortar), you can watch it here:
👉https://youtu.be/4fY6Q5lui98
This ties into a lot of the repair principles I use in my wider DJI High Access Services work, whether carrying out DJI High Access Services style chimney maintenance and repair, tackling roof repairs, or using specialist cherry picker access to reach awkward stacks safely.
Why Chimney Flaunching Fails So Often
A lot of failed chimney repairs aren’t because the tradesman didn’t care often it’s poor mix design, too much water, weak mortar, or rushed application.
And yes… sometimes dreadful workmanship.
I see plenty of flaunching done with overly sandy mixes, no bond additive, or far too much water. It may look fine when you leave site.
Then the first freeze gets hold of it.
That’s where problems begin.
For me, good chimney flaunching is not just about shaping mortar around chimney pots it’s about shedding water, resisting movement, and giving the top of the stack long-term protection.
The Chimney Flaunching Mix I Use
My Standard Flaunching Mortar Mix
My preferred flaunching mix is simple:
- 3 parts sharp sand
- 1 part cement
- SBR bond in the gauging water (around 10%)
- Polypropylene fibres for crack resistance
Nothing exotic.
Just a practical site mix that works.
I typically mix:
- 1½ bags of sharp sand
- ½ bag cement
That sits nicely in a mixing bucket and gives enough for most chimney flaunching jobs.
Why I Use SBR Bond in the Mix
I often get asked why I use SBR in chimney repairs.
For me, it helps with:
- adhesion
- water resistance
- flexibility
- durability
But, and this matters more is not always better.
Too much can make a mix overly polymer-rich and potentially affect performance.
Like many things in roofing, a little judgement matters.
(Which is a polite way of saying don’t pour half a bottle in and hope for the best.)
Why I Mix With a Paddle – Not by Hand
I always use a mixing paddle where possible.
Consistency matters.
That’s one reason I often carry equipment specifically for these kinds of repairs, just as I do for specialist access work and some of the high-level repairs covered on my roof repairs page.
A paddle mix gives:
- better consistency
- fewer dry pockets
- more even fibre distribution
- easier trowelling
I’ve put together the mixing kit and tools I use here if you want a look:
🛠️ Mixing Tools I Use:
https://www.amazon.co.uk/shop/danthecherrypickerman/list/1VPMZBK4HV87E?ref_=aipsflist
The Real Secret: Water Content
Honestly?
This is where good flaunching is won or lost.
Not the sand.
Not the cement.
The water.
Wet winter sand behaves differently from dry summer sand.
That means no rigid formula ever works perfectly.
You have to judge it.
My rule:
Always start drier than you think.
Add water slowly.
Much easier to loosen a mix than rescue soup.
Too wet:
- shrinkage cracking
- weak mortar
- poor durability
Too dry:
- poor adhesion
- difficult finishing
- hard to compact properly
Getting that balance right is one of those “boring but critical” things experience teaches.
Why I Add Fibres to Flaunching Mortar
This is something I’ve come to value more over time.
I add polypropylene fibres to help reduce shrinkage cracking as the mortar cures, particularly on warm days.
I mention the fibres in the video and linked the ones I use because they disperse far better than some of the chunkier stuff I’ve tried.
They’re here:
https://amzn.eu/d/06iE5JJa
Worth a look.
Especially if you’ve ever trowelled over giant hairy mortar strands and regretted your life choices.
Working at Height Changes How You Think About Repairs
One thing people don’t always appreciate about working at height is how much efficiency matters.
When I’m on a chimney using specialist cherry picker access, I’m thinking about:
- materials behaving predictably
- mixes that trowel well first time
- minimising return visits
- doing repairs that last
Because access is often the biggest cost component.
That’s true whether it’s chimney work, awkward gutter repairs and gutter clearance, or other high-access maintenance.
Good preparation saves headaches.
Lessons Learned From Real Chimney Repairs
If I’ve learned anything from years of chimney work, it’s this:
Simple done well beats complicated done badly.
A sound mix.
Good consistency.
Careful shaping.
Proper falls to shed water.
That gets you most of the way there.
The full video shows the mix and process in more detail, so do give it a watch and come back to continue reading:
👉 https://youtu.be/4fY6Q5lui98
Final Thoughts on Chimney Flaunching
There are plenty of ways to mix flaunching.
This is simply the method I trust in real-world chimney repairs.
Could others do it differently?
Absolutely.
But it’s served me well.
And if you’ve got your own preferred mix, I’d genuinely be interested to hear it.
Trades learn from trades.
That’s how standards improve.
If you need help with chimney defects, leaking stacks or broader chimney maintenance and repair, or even related issues like moss-related water problems covered in my roof cleaning services, feel free to explore the site.
Frequently Asked Questions
How do you stop chimney flaunching from cracking?
Using the right mortar consistency is key. Too much water often causes shrinkage cracks. I also use fibres and SBR bond to help improve durability and reduce cracking in chimney repairs.
What is the best mix for chimney flaunching?
A common traditional mix is 3 parts sharp sand to 1 part cement. For my own chimney repair work, I also add SBR and reinforcing fibres.
What causes chimney flaunching to fail?
Common causes include weak mixes, too much water, frost damage, poor falls that hold water, and poor workmanship. Failed flaunching often leads to bigger chimney repairs if ignored.
Can SBR be used in flaunching mortar?
Yes used sensibly. SBR can improve adhesion and water resistance in mortar mixes. The key is not overdoing it.
Can a cherry picker reach awkward chimney stacks?
Often yes, specialist cherry picker access can make many difficult chimney and roof repairs safer and more efficient than traditional methods.
How much does chimney repair cost in the UK?
It varies hugely depending on access, defect severity and repair type. Minor repairs differ significantly from major repointing or rebuilding, which is why proper diagnosis matters.
Watch the Full Video
If you haven’t already, do watch the full video and let me know in the comments what mix you use:
👉 https://youtu.be/4fY6Q5lui98
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