Chimney flashing does an unglamorous but essential job: sealing the join between the stack and the roof slope so that water running off both ends up where it should, on the tiles, rather than finding its way into the loft space beneath. It is also one of the more common sources of a chimney-related leak once it starts to fail. It rarely announces its failure loudly, which is part of why so many flashing problems go unnoticed until water has already found its way inside.
Proper flashing on most chimneys is made up of several parts rather than a single sheet of lead — an apron or step flashing dressed along the visible edges of the stack, individual soakers tucked under each course of roof tiles to route water past the joints one at a time, and often a back gutter behind the chimney to handle the larger flow of water coming down the roof slope above it. Each part has a specific job, and a failure in any one of them can cause a leak even if the rest of the leadwork is sound, which is exactly why a proper repair needs to check the whole system rather than the most obvious section alone.
Failure tends to happen gradually rather than suddenly. Lead is a durable material, but decades of thermal movement, general weathering, and the mortar joint it is dressed into eroding over time can all cause it to lift, crack, or pull loose from where it was originally fitted. On older properties around Fishponds, it is also fairly common to find a previous repair that used sealant rather than proper leadwork — an understandable shortcut that tends not to last, since sealant perishes and cracks in a way lead genuinely does not, and a repair relying on it tends to need doing again within a year or two, often on the same section of the stack.
A proper repair involves re-dressing the lead where it can be salvaged, or replacing sections that have degraded beyond that point, then re-securing everything into a freshly cut mortar joint rather than simply resting it against the brickwork. It is a job that benefits from being done thoroughly the first time — a flashing repair that has not been dressed and sealed correctly tends to fail again fairly quickly, which costs more overall than getting it right initially.
If you have noticed damp near a chimney breast, or you can see lifted or cracked flashing when looking up at the stack, it is worth having it assessed before the next heavy rain rather than after.
Brunel Roofing Bristol carries out proper flashing repairs across Fishponds, backed by our 15-year guarantee — contact us for a free, no-obligation inspection before the problem has a chance to spread any further.
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