Flaunching is one of those chimney components that most homeowners have never heard named, despite it doing a genuinely important job. It is the mortar fillet moulded around the base of the pots at the very top of the stack, sloped to shed water away from the flue opening while also holding the pots firmly in position. It is a small amount of material doing a job that affects the entire stack beneath it, which is why its condition deserves more attention than its modest size might otherwise suggest.
Because it sits at the highest, most exposed point of the entire chimney, flaunching takes more weathering than almost any other part of the structure. Rain, frost, and years of temperature swings gradually crack and erode it, and once cracks appear, water starts getting in behind the pot rather than running off as intended. This is one of the more common early-stage chimney problems we see, and it is often the underlying cause behind a pot that has started to look loose or lean out of true, which is why a wobbly pot should prompt a look at the flaunching rather than just the pot itself.
The signs are not always easy to spot from the ground, since flaunching sits above eye level even on a single-storey extension chimney and is genuinely difficult to inspect properly without getting up close. A pot that looks slightly off-kilter, visible mortar debris on the roof below the stack, or a chimney leak that traces back to the very top of the stack rather than the base, are all reasonable indicators worth having checked, even if none of them look especially dramatic on their own or seem worth the trouble of a call-out at first glance, even though each one can develop into a larger repair if left long enough.
Repairing flaunching properly means removing the old, cracked material entirely rather than simply patching over the cracks, then applying a fresh mortar fillet correctly sloped and moulded around the base of each pot. It is a fairly quick job once access to the top of the stack has been arranged, but it needs proper preparation to bond well and last — a rushed repair applied over failing material underneath tends to crack again within a season or two.
Because flaunching failure often shows up alongside other top-of-stack issues — a loose pot, a missing or damaged cowl — it is generally sensible to have the whole top of the stack looked at together rather than treating flaunching in isolation.
If you suspect flaunching may be behind a leak or a loose-looking pot on your Fishponds chimney, Brunel Roofing Bristol can inspect and repair it properly, with a free assessment to confirm exactly what is needed before any work begins.
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