Of all the lead detailing around a chimney, the back gutter is probably the least visible and the most likely to be overlooked, largely because it sits on the upslope side of the stack, tucked against the roof and out of sight from the ground. That's exactly what makes problems with it so easy to miss until they've caused real damage.
A back gutter's job is to intercept rainwater running down the roof slope above a chimney and channel it around the stack rather than letting it pool against the brickwork or find its way behind the flashing. On wider chimneys, where a significant area of roof drains directly toward the upslope face of the stack, the back gutter is doing genuinely heavy lifting during periods of sustained rain.
Because it's hidden and largely out of sight, a back gutter that's split, corroded, or has become blocked with debris tends to fail quietly. Rather than an obvious, sudden leak, the result is often a slow, persistent damp problem in the roof space nearby, sometimes going unnoticed for a considerable time simply because nobody's looking in that specific spot. On the many pitched roofs across Bishopston where chimneys sit mid-slope rather than at the ridge, this hidden area is worth including whenever a chimney or roof inspection takes place.
Repairing a back gutter usually means accessing it from within the roof space or by lifting the roof covering around the chimney, since it typically sits beneath the tiles or slates rather than being visible on the surface. A properly formed replacement in new lead, correctly lapped with the surrounding roof covering, resolves the issue for the long term, rather than a surface patch that can't reach the actual point of failure underneath.
The size of the back gutter needed also scales with the width of the chimney it's serving. A narrow stack needs a comparatively modest gutter, while a wide chimney spanning much of a roof's width needs a correspondingly larger one to cope with the greater volume of water draining toward it, which is worth bearing in mind if a previous repair used an undersized replacement. If a property in Bishopston is already having its roof re-covered for another reason, that's a natural point to have the back gutter checked and renewed if needed, since the tiles or slates around the chimney are already being lifted anyway. Addressing it during other roof work avoids the extra cost and disruption of accessing it as a standalone job later. If you've had recurring damp near a chimney that previous repairs haven't fully resolved, it's worth specifically asking whether the back gutter has ever actually been checked, since it's easy for this hidden detail to be overlooked in favour of the more visible flashing and brickwork nearby.
If you've had a persistent, hard-to-pin-down leak near a chimney, particularly one that seems worse during heavy rain, a back gutter is worth ruling in or out. We inspect this detail as part of our free chimney assessments across Bishopston.
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