Shared chimney stacks: dealing with repairs

In terraces and semis, chimneys are often built in pairs on the wall that divides two houses. The flues run side by side inside one block of masonry, with a single set of pots on top. In other houses each home has its own flues, but they share the brickwork above the roofline, so one set of failing joints puts both at risk.

You may also meet a stack that rises from one house's gable and serves the house next door. The legal position depends on your deeds and the property boundaries, which is a matter for your solicitor, not a roofer. What we can say is practical: whoever owns the stack on paper, weather does not stop at the boundary. Water entering a stack on one side can damp the breast in the other house, and a loose pot falls onto whichever roof is beneath it.

Old stone terraces in Stroud's valleys often have stacks of this kind, with several pots in a row and flashing that crosses from one roof to the next.

Check your title documents and, if the stack is a common feature, any shared maintenance obligation they mention. A roofer cannot read the deeds for you, but we can describe the stack in terms a solicitor can use.

Most disagreements start from surprise. A note through the door that says "your side of the stack is crumbling" lands badly. A better opening is to show what you can see and ask what they have noticed. Useful steps:

• photograph the stack from your garden, and from the loft where it can be reached safely
• write down any damp, soot or staining you have seen on your side
• ask the neighbour whether they have seen the same, or have had work done before
• suggest a single survey that covers both sides, so there is one set of findings
• offer to share the report and the quote

Sharing a survey means nobody has to take a roofer's word through a third party. Pictures of the pots, flaunching, joints and lead on both sides give each household the same facts. They are also useful if the house is later sold, or if an insurer asks what was done and when.

Before any work begins, put the following in writing, even if it is a short email both of you reply to:

• the repair agreed, in the words of the itemised quote
• how the cost is divided, whether equally, by the share of the stack each home uses, or otherwise
• who pays the scaffold, and whether it is one scaffold serving both roofs
• when the work is likely to happen, and what notice each household gets
• who lets the roofer in, if any part of the work is from inside a loft

Access tends to be the biggest single cost, so one shared platform saves both parties money. MyBuilder's 2026 chimney guide puts repointing at about £750 on average, in a range of £500 to £2,000, and a stack rebuild at £2,000 to £10,000 or more, as national figures. Dividing even a modest bill is easier when both sides have seen the same breakdown. Where a repair goes ahead under the Party Wall etc. Act 1996, the Act divides the cost having regard to the use each owner makes of the structure and to responsibility for the defect. If a stack is also due for repointing, our guide to chimney repointing explains what the quote will contain.

Sometimes the other household is absent, a landlord, or simply unwilling. A leak into your own home does not wait for them. We can make a leaking roof safe first, and temporary measures on your own side may be possible without touching their property. A permanent repair to a shared stack involves their roof, their loft or their share of the masonry, so it needs either their written agreement or the formal route under the Party Wall etc. Act 1996. The Act lets an owner repair or rebuild a party structure where defect or want of repair makes it necessary, after serving a party structure notice at least two months before work begins. If the neighbour does not consent within 14 days, a dispute is treated as having arisen, and it is settled by surveyors under the Act.

If talking has failed, take legal advice, because the rights of each owner depend on the deeds and on the circumstances. A party wall surveyor or a solicitor can tell you what notice to give and what happens if the neighbour does not respond. Meanwhile, keep a written record of what you have seen and asked for. Photographs with dates are persuasive, and a roofer's survey report is better still.

Do not climb onto a shared roof to carry out your own repair. Aside from the risk of a fall, working on someone else's roof without agreement creates a dispute you did not have before.

Where a tenant lives next door, the landlord or managing agent is the person to write to. Give them the same photographs, set a reasonable date to reply, and keep a copy of what you send.

Once agreed, the repair is planned as one job. Pots and flaunching on the whole stack are checked together, and both sides of the lead are inspected, because a back gutter or flashing that spans the boundary protects both roofs. Our answer on the chimney back gutter explains why that part matters so much on a shared stack. If the stack is also being treated against water, read whether chimney waterproofing works before agreeing to a coating.

Work is done in a sensible order, with both households told when the scaffold arrives. When it is finished, the waste goes with us and the 10-year workmanship guarantee comes in writing. Our chimney repairs page describes the rest of our work on stacks. If you are the one raising it, a handful of photographs is enough to start a conversation with us.