What happens to the chimney when you re-roof?

1The junction is where new roofs fail first

Tiles and slates shed water easily across open slopes. A chimney breaks that flow, because water running down the roof meets a vertical wall of brick and must be steered round it. The task falls to a set of lead pieces: a front apron below the stack, stepped flashings up each side, and a back gutter on the uphill side that sends the flow sideways past the stack. Leadwork that was fine under the old covering often cannot be reused, because it was cut to a different thickness of tile or slate.

That is why a fresh roof around a stack is never completed by just laying the covering up against the brickwork. The old flashings are taken off, the new covering is laid, and new lead is dressed over it. Lead codes matter here: Leadworx calls code 4 the everyday choice for flashing, with heavier codes where the detail or exposure asks for them. A well-made lead flashing can last for well over 80 years, according to MyJobQuote.

2Repointing and brickwork while the scaffold is up

The stack stands in the open weather on all four faces, and it usually has the worst brickwork on the house. Mortar crumbles, bricks spall and the flaunching, which is the sloping mortar cap that seats the pots, cracks and lets rain reach the flue. With the scaffold already around the roof, it costs far less to put those right than to return for them later.

MyBuilder's guide (updated 21 August 2026) gives chimney repointing at around £750, in a typical UK range of £500 to £2,000, and it gives £2,000 to £10,000 or more for rebuilding a stack. MyJobQuote gives new leadwork for a whole chimney as £350 to £460 without scaffold and £700 to £920 with it. The gap between the last two figures shows what access adds, and that is the argument for doing it all at once.

The survey photographs show the stack from several angles, so you can see what needs doing before agreeing to it.

3Stacks that are no longer used

Many houses have chimneys that have not carried a fire for years. A redundant stack still needs weatherproofing, because rain falling into an open pot runs down the flue, damps the breast inside the house and can stain ceilings. The usual options are to cap the pots and fit ventilation so the flue can breathe, to take the stack down to roof level and tile over it, or to leave it fully repaired.

Lowering the stack removes a source of leaks and some weight, but it is not always allowed without a word to the planning team. In Old Shoreham and Kingston Buci conservation areas, Article 4 directions bring alterations to chimneys under planning control, and in the Warwick Gardens conservation area of Worthing the direction takes in building, changing or taking away a chimney. Adur & Worthing planning can tell you whether an address is affected.

An open flue in service is a different matter, and any work near a working flue should be discussed at the survey before it begins.

4Taking out a chimney breast and the neighbour

Removing the stack above the roof is one thing. Removing the chimney breast inside the house is a bigger one. According to the Planning Portal, a chimney breast is part of the structure, so removing one needs approval every time; a stack alone can be treated differently. Your building control body, the council team or a registered building control approver, can confirm.

In a semi-detached or terraced house the stack often sits on the party wall. Government guidance counts removing chimneys from a party wall as notifiable building work, giving the neighbour between two months and a year of notice before it starts, with silence never counting as consent. Ask the neighbour early, and keep the notice in writing. Silence from a neighbour cannot be taken as agreement. Our page on telling the neighbours about a re-roof covers the wider courtesies.

5Planning it into the job

The best time to decide about a chimney is before the roof is stripped, because the scaffold, the lead and any lowered brickwork all fit into one programme. At the survey, tell us whether the fireplaces are used, and whether you plan to take the breast out. We photograph the stack, note your answer and build it into the programme, so that lead, brickwork and any lowering of the stack happen in a sensible sequence under one scaffold.

If the loft is being cleared for the job, the chimney breast passes through it, and emptying your loft for a new roof says what to move around it. Gutters and fascias at the stack side can also be dealt with then, as replacing fascias and gutters with a new roof describes. Flat roofs below a stack have their own considerations, in roof replacement for flats. The wider picture of how we run a new roof is on the roof replacement page.