The mortar fillet at the top of a chimney stack, known as flaunching, is one of the least glamorous parts of a roof but one of the most important. It slopes away from the pots to shed rainwater, and it holds the pots themselves firmly in place. On older buildings in Old Market, where stacks have often stood exposed to decades of weather, flaunching is frequently found to be cracked, crumbling, or missing in places by the time anyone actually gets up to inspect it closely and properly. Because it sits at the very top of the stack, it is also one of the last things a homeowner is ever likely to check without professional help.
Once flaunching starts to fail, water can seep down around the base of the pots and into the brickwork of the stack itself, rather than being shed cleanly away as intended. This is a slow, largely invisible process from ground level, which is part of why chimney tops are one of the more commonly neglected parts of a roof, simply because the damage does not tend to announce itself until it has been developing for quite some time already. By the time staining appears on a chimney breast indoors, the flaunching may have been compromised for a year or more.
Pots themselves take a battering over the years too, particularly on older properties where original pots may be many decades old. Cracking, chipping, and general erosion are common, and a pot in poor condition can let water track down its inner surface even if the flaunching around its base is still reasonably sound. Leaning pots are usually a sign that the flaunching has already failed enough to lose its grip on the base entirely, and a pot in this state should really be treated as a priority rather than something to monitor.
Repairing flaunching properly means removing the old, failed mortar around the base of the pots and reforming a fresh fillet, sloped correctly to shed water away rather than towards the stack below. Where pots are cracked or badly worn, replacing them at the same time makes sense, since redoing the flaunching around a failing pot is a false economy that just means revisiting the job again before long.
This work sits right at the top of the chimney, generally the highest and most exposed point of the whole roof, so scaffold access is standard practice rather than an optional extra, both for the safety of anyone working up there and to allow the flaunching to be formed properly rather than rushed through in a single pass.
If the top of your chimney in Old Market has not been checked in some years, it is worth having it inspected, since flaunching problems are cheap to fix early and considerably more disruptive once they have let water into the stack below. Brunel Roofing Bristol offers free inspections and quotes for this kind of work across the area.
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