The uphill side of a chimney, where the roof slope meets the back of the stack, is one of the most exposed and hardest-working parts of any roof, and it is a detail that is very easy to underestimate when simply looking up from ground level. Rainwater running down the tiles above the chimney has nowhere to go but around the stack, and on wider chimneys of the type found on a number of older Henbury houses, this can mean a genuinely significant volume of water needs to be directed safely to either side during heavier downpours through the autumn and winter months.
A saddle, sometimes called a back gutter, is the raised timber and lead structure built behind the chimney specifically to split this water flow and channel it around the stack rather than letting it dam up against the brickwork above roof level. Without one, water can pool behind the chimney during heavy or prolonged rain, which over time leads to damp patches appearing inside the loft space or, during colder spells, frost damage working its way steadily into the mortar joints from repeated cycles of freezing and thawing.
Whether a saddle is genuinely needed, and how large it should be built, depends on the width of the chimney relative to the overall roof and the pitch of the roof itself. A narrow stack on a steep roof may only need a fairly simple lead tray behind it, while a wide chimney on a shallower slope, more common on some of Henbury's post-war housing, usually needs a proper timber-framed saddle covered in lead to cope safely with the amount of water flowing off the roof above it in any given storm.
This is a detail that often gets missed on quick patch repairs, since building a saddle from scratch takes considerably more time and material than simply pushing the old flashing back into place and hoping it holds for another season. A full roof replacement is the natural point at which to put this right, because the tiles and battens around the chimney are already exposed and the extra structure can be built in properly from the start, rather than added as an afterthought once the rest of the roof is otherwise finished and the scaffolding is due to come down.
If your Henbury home has a wider chimney stack, or you have noticed damp patches in the loft close to the chimney breast, it is well worth having the back gutter looked at specifically rather than simply assumed to be fine because nothing has visibly leaked yet. Brunel Roofing Bristol checks this exact detail on every re-roof quote in Henbury and can advise honestly on whether a saddle needs building or rebuilding as part of the wider job, with the cost set out clearly upfront.
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