Chimneys are one of the more vulnerable points on any pitched roof, and in Brislington, where a good number of properties still have a working or capped chimney stack from when the houses were originally built, flashing failure is a recurring cause of leaks. The junction where a chimney meets the roof slope is complicated to weatherproof because it involves two different materials, brick and roof covering, moving slightly differently over time.
Traditional lead flashing works by being dressed into the brickwork joints and folded down over the roof covering to shed water away from the joint. Over many years, that lead can become fatigued from expansion and contraction through hot summers and cold winters, eventually cracking or lifting slightly at the edges. Once that happens, water can track down behind the flashing and into the roof space or even down inside the chimney breast itself, often showing up as a damp patch on a bedroom ceiling well away from the actual point of failure.
Older repairs are another common culprit. Many chimneys in Brislington have had flashing patched at some point with mortar fillets or bitumen-based products rather than proper lead work, and these repairs tend to have a much shorter lifespan than correctly installed flashing. Mortar fillets in particular are prone to hairline cracking as the roof and chimney move independently, and once cracked they let water in fairly readily.
Because chimney flashing sits at a junction rather than on an open roof slope, it's also more exposed to wind-driven rain from multiple directions, which puts extra strain on the seal compared with tiles or slates further down the roof. This is why chimney flashing often needs attention well before the rest of a roof covering is due for replacement, and why it's worth having it checked specifically rather than assuming a general roof inspection has covered it in detail.
The brickwork of the chimney itself is worth considering alongside the flashing, since a stack with eroding mortar joints or spalling brick gives the flashing a poor surface to key into in the first place, no matter how well the lead itself is installed. On older Brislington chimneys that are no longer in regular use, this kind of gradual deterioration can go unnoticed for years simply because nobody is checking the fireplace below or looking up at the stack from outside. Redundant chimneys still need to be weathered properly at both the flashing and the pot or cap, since an unused stack that's left to let water in can end up causing just as much internal damage as one that's still connected to a working fire.
When Brunel Roofing Bristol carries out a full re-roof in Brislington, chimney flashing is renewed properly in lead as a matter of course, giving one less weak point to worry about. If you've noticed damp near a chimney breast or simply want the flashing checked, a call to arrange a look is a good place to start.
Get a Free Quote for New Roof Installations in Brislington
Every roof is different — the fastest way to get an accurate answer is a quick chat with our team.