Chimney Repair & Repointing in London

Standard repointing on a two-storey house with scaffold access typically sits at £600–£1,200. Swap in lime mortar for a Victorian or Edwardian stack — usually the correct approach rather than cement — and the figure moves to £700–£1,400. Flaunching repair or renewal alone is £200–£550, a pot or cowl replacement with re-flaunching is £200–£650, lead flashing renewal at the roof junction is £450–£1,600 depending on stack width and pitch, a partial rebuild of the top courses is £900–£2,800, and a full rebuild from roofline up matching brick and lime pointing is £2,500–£6,000 or more. Scaffold access, usually £400–£1,400, is very often the single largest line item and is normally priced separately from the brickwork itself. VAT applies to labour and materials on most residential work.

Repointing means raking out and replacing the mortar joints between sound bricks — it doesn't touch the pot, the flaunching or the brick itself, and it's the right fix where mortar has simply eroded back far enough that you can pick it out with a fingernail or find sandy debris on the roof below after wind. Flaunching is the sloped mortar collar around the base of the pot; it's usually the first thing to fail, and once cracked it lets water straight down the flue even if the pointing elsewhere looks fine. A rebuild, partial or full, is needed when the brick itself is spalling, the stack has genuine structural movement, or enough courses have deteriorated that repointing alone won't hold. Most stacks we survey need a mix — repointing on the sound sections, re-flaunching at the pot, and only rebuilding the courses that have actually failed, rather than a full rebuild by default.

Like-for-like repointing and flaunching repair generally doesn't trigger Building Control involvement — it's maintenance. A partial or full rebuild is different: taking the stack down and rebuilding it engages Building Regulations Approved Document A for structure and Approved Document C for weatherproofing, including the metal tray damp-proof course at the flashing junction, so sign-off via a full plans submission or a building notice is expected. If a flue remains in use or is being capped, Approved Document J on combustion appliances and fuel storage systems applies too, covering flue lining, ventilation, and correctly ventilating any flue you're decommissioning rather than just sealing it. We flag which category a job falls into at survey stage so there are no surprises once scaffold is up.

It applies whenever the stack sits on or over a party wall shared with the terrace or semi-detached property next door, which describes most Victorian and Edwardian chimney stacks in London. A straightforward repoint of your own visible section generally doesn't require notice. But rebuilding a section, raising the stack, or any work that could affect the shared flue or the structure the neighbour also relies on does require serving notice under the Act, with statutory notice periods, before work starts. We check this at survey stage rather than assuming it doesn't apply, and handle the notice process as part of the job rather than leaving it for the homeowner to sort out separately.

Lime, in almost every case. Solid-wall Victorian and Edwardian stacks were built and originally pointed with lime mortar, which is softer than the surrounding brick and lets moisture that gets into the brickwork evaporate back out and move with normal seasonal expansion and contraction. Cement pointing is harder than the original brick, so instead of moving with the wall it traps water inside the softer original brick, which then freezes and expands over winter and accelerates frost damage and spalling — often within a handful of winters. This is exactly why we see so many stacks where a previous cement repoint has made the brick condition worse rather than better. On period stock we specify a lime-based mix matched to the original, even though it costs more in materials and labour than a straight cement repoint.

A visible lean — checked by sighting the stack against a true vertical nearby, such as a drainpipe or window reveal, or comparing it with old photographs — is a structural question first, not just a pointing job, and it's worth having looked at properly rather than left. Common causes include long-term mortar decay softening the joints, corroded wall ties no longer tying the stack back to the roof structure, or settlement affecting the supporting brickwork below. A leaning stack that turns out to be sound once inspected is usually a repointing or partial rebuild job, £700–£2,800; if the lean is structural, the repair cost depends entirely on the engineer's findings, which is why we won't quote a leaning chimney stack repair cost in London until that's established. We get a structural engineer's opinion on the cause before proposing a fix, because a stack that's still moving needs the movement stopped first — rebuilding or repointing over it without knowing why it moved just buys a few years before the same crack reopens, at a higher cost than sorting the cause now.

Yes. A flue that's been capped off without ventilation, often done during a loft conversion or when a chimney breast was removed downstairs, traps condensation inside the flue with nowhere to go, and that's a very common cause of black mould or damp patches at chimney breast level in rooms where the roof itself is completely sound. The fix isn't removing the cap, it's fitting a vented cap or bird guard at the top combined with a register plate or ventilated grille at the base, so air can still move through the flue even though it's no longer used for a fire. This is Approved Document J territory and it's one of the most common things we find when called out to damp that turns out to have nothing to do with the roof covering.

These are different jobs solving different problems. Stack repair (repointing, re-flaunching, flashing, rebuilding) keeps the external chimney standing and weatherproof, and is usually needed regardless of what happens inside the house. Internal chimney breast removal, which we cover separately, is about taking out the breast inside a room — typically £1,500–£5,000 for a single storey or £3,000–£7,000+ for a full stack — using a steel beam or gallows brackets to support what remains above. If the stack above roof level is staying in place after a breast removal, which is common, it still needs to be sound and weatherproof, so the two jobs often go together rather than replacing each other.

A straightforward repointing or re-flaunching job with scaffold or tower access already up typically takes one to three days once access is in place. A partial rebuild of the top courses usually takes two to five days, and a full rebuild from roofline up can run a week or more, largely dictated by lime mortar curing time and weather windows rather than bricklaying speed — lime mortar and lead flashing work both need reasonably dry, above-freezing conditions to go in properly. Scaffold erection and, where relevant, a council scaffold licence or Party Wall notice period, usually add more calendar time to the project than the physical building work does.

It depends on the freehold and lease structure, but the practical issue we see most often is that a single stack serves multiple flues from different flats or converted units, and a defect in one flue's lining or capping can affect the others even if only one owner reports a problem. Before quoting, we establish which sections of the stack are actually in dispute, whether it needs coordinated agreement across the affected flats or the freeholder/managing agent, and whether the Party Wall Act applies between the affected properties — rather than assuming it's a straightforward single-owner repair when it isn't.

Flaunching is the sloped mortar collar around the base of each chimney pot, angled so rainwater runs off rather than pooling around the pot. It's a relatively thin, exposed piece of mortar sitting at the very top of the stack, taking the worst of the weather, so it's usually the first thing to crack and crumble, often years before the main brickwork joints show real wear. Once flaunching goes, water runs straight down inside the flue lining rather than off the stack, so it's worth checking and renewing on its own even if the rest of the stack looks sound — renewal alone runs roughly £200–£550.