The short answer
Rebuilding a chimney stack is normally a short job on site, measured in days rather than weeks for a single plain stack. A tall, shared or stone stack takes longer, as do lead flashings, lime mortar that has to cure, and wet or frosty weather. Scaffold, ordering matched bricks or stone and any hidden damage inside the stack can add time before work begins.
What a rebuild involves
In a rebuild the stack is dismantled to sound masonry and then built up again. That is different from repointing or patching, which leave the existing stack in place. The stack is dismantled course by course, usually down to the roof line or a little below, and the bricks or stones are sorted. Sound ones are cleaned and kept, and damaged ones are set aside to be replaced.
New work is then built up with fresh mortar, the flue linings and pots are refitted, and a flaunching, the mortar slope at the pot bases that sheds rain, is formed at the top. At the base, the lead that seals the stack to the roof is laid so that water runs over the joint and away. Only then is the job complete.
Each of those steps has to happen in order, and several of them depend on materials drying or setting. That is why the timescale is shaped less by how fast anyone works and more by how the job has to be sequenced. For a stage-by-stage account of the work, read our guide to chimney rebuild goes through it stage by stage.
Why there is no single number
We give a programme only after we have seen the stack. Two stacks that look alike from the street can differ a great deal once you are up close.
A short, brick stack on a low roof with good access is a compact job. A tall stack with several pots on a steep roof is not. More masonry means more to take down, carry and rebuild, and more care is needed because the work is higher and more exposed to wind.
Stone stacks take longer than brick. Stones are larger, vary in shape and have to be fitted rather than simply laid in a regular pattern. On Bath stone stacks, where stones are cut to match, the dressing and fitting of each piece adds to the day count.
Shared stacks that serve a neighbouring house add a further layer. Work to a party stack affects both sides, so access and timing have to be arranged. Our page on a shared chimney stack covers how that works.
Scaffold, materials and lead time
Work on site is only part of the picture. Before any bricks come down, scaffold has to be erected, and beyond a small patch it makes up a noticeable share of the price. MyBuilder's 2026 chimney guide notes that scaffold is a significant cost driver and that a simple patch repair costs noticeably more with it than without. On a rebuild it is simply required.
Matching materials can add time at the start. Where a stack is built from a particular brick or a cut stone, the replacement has to be sourced to suit. Reclaimed bricks that match an older stack are found rather than ordered off a shelf, and cut stone is shaped to fit. We prefer to hold the work until the right material arrives rather than rebuild a stack in something that does not belong on the house.
Lead is the last item. Flashings are formed to suit the stack once it is built, because the finished size decides the pieces. Lead work is skilled, careful work and not something to hurry. For more on that part of the job, see our page on chimney waterproofing, which also explains what sprays can and cannot do.
Lime mortar and the weather
Lime mortar sets slowly and by reacting with the air. It cannot be rushed with additives the way a cement mix can, and fresh lime is vulnerable. Hard frost damages it, heavy rain washes it out, and strong sun dries it too quickly so that it cracks. A good lime job is protected with hessian or sheeting while it cures.
For that reason a rebuild in a poor spell of weather is often paused, and a stack that is half built is covered and left until conditions improve. This is a sensible delay and not a fault. The winter months need particular care; our note on chimney repairs in winter explains what can go ahead and what is better left.
Wind is the other limit. Working at the top of a tall stack in gusts is unsafe, and it is not a risk we take to keep to a date.
Things found once the stack is down
Some of the work cannot be seen until the stack is opened. Taking the masonry apart may show that the flue liner has cracked, that the brickwork below the roof line is as poor as the part above, or that the timbers around the stack have been soaked by years of leaking. A stack that has been leaking at the base can have rotted rafters or a wet ceiling nearby.
When this happens we stop, photograph what is exposed and explain it before going further. Where it changes the scope, the price and the timing are agreed with you in writing before the extra work starts. We would rather tell you what we have found than build a new stack on a weak base.
If the stack is leaning or cracked from the start, much of this is predictable. Our page on a leaning chimney explains the signs that point to a rebuild and what causes them.
Planning a rebuild around your household
Most of the disruption is outside the house: scaffold, noise from taking masonry down, and dust. Inside, a rebuild of the stack above the roof leaves rooms largely untouched, though chimney breasts and flues in use should not be lit until the work is finished and the mortar has cured.
Tell us if you rely on a fire or stove, if the stack serves a neighbour, or if the property has listed status or lies in a conservation area. Altering the stack of a listed building requires consent from B&NES, and we would sort that out before booking the work. There is no charge for the survey. It comes with photographs of the stack, then a written price and the order of work.
MyBuilder's 2026 guide puts a typical UK stack rebuild at £2,000 to £10,000 or more. If the fire or stove will be out of use during the rebuild, plan it for late spring or summer, and ask whether the flue liner needs replacing while the stack is down.
Our chimney repairs service page covers the rest of what we do on stacks.
