Removing a chimney breast sounds simple: take out the brickwork, put in a beam, redecorate. But a chimney breast is part of a column of masonry that can run from the ground floor to above the roof, and on many semi-detached and terraced houses it is shared with the house next door. Take out the wrong part in the wrong order and a great deal of brickwork is left with nothing holding it up.
This is general guidance on how chimney breasts are usually built and removed. It is not advice on your home: I have not seen your property, and every house is different.
Key Takeaways
- A chimney breast carries the weight of everything above it: any breast on the floor above, the stack in the loft, and the stack above the roof. Whatever stays has to be supported by something else once the breast below it goes.
- What needs supporting, and how, depends on which parts you remove and which you keep. That has to be designed before work starts.
- Many chimney stacks sit on or in a party wall shared with a neighbour. The Party Wall etc. Act 1996 will usually apply, and what your neighbour has already done on their side affects the design.
- Steel “gallows” brackets are increasingly rejected by Building Control. Where they are proposed, they have to be justified by calculation and testing.
- The retained masonry must never be left unsupported, even for a short time. The propping sequence should be specified before a builder starts, not worked out on the day.
- In England, removing a chimney breast is normally building work under the Building Regulations, because it alters the structure. When it is, it has to go through Building Control.
What a chimney breast is holding up
A chimney breast is not just decorative brickwork. It is a heavy column of masonry that carries the weight of everything built on top of it: the breast on the floor above if there is one, the stack as it passes through the loft, and the stack that sticks out above the roof. All of that weight comes down through the breast to the foundations.
When you take out a breast on a lower floor, the masonry above it does not become lighter. It still needs something to stand on. The job of the design is to give it a new, safe route down to the ground, or to remove it altogether.
Which parts come out changes what needs supporting
There is no single answer, because it depends on what you remove and what you keep. Broadly:
- One floor only. If you remove the breast on one floor and keep everything above it, the retained masonry above needs a new support, usually a beam or lintel designed to carry it, bearing onto walls that can take the load. Because the breast sticks out from the wall, its weight sits off-centre on the support, and the design has to allow for that.
- More than one floor, keeping the stack. If you remove the breasts on more than one floor but keep the stack in the loft and above the roof, that stack still has to be carried, usually on steel beams at loft floor level bearing into the walls. Ceiling joists are not built to carry it. Stacks in lofts are often corbelled (stepped out) or set over at an angle towards the ridge, so the weight may not sit directly above where the breast was, and the support has to allow for that. With nothing below it any more, the part above the roof still has to resist wind, so its condition and how it is held at loft level need checking too.
- The whole chimney. Taking the chimney out completely removes the load, but it has to come down from the top: the stack above the roof first, then the stack in the loft, then each breast in turn, working down. When the whole chimney is coming out, never take out a lower breast while masonry is still standing above it. The roof then needs making good, and checking: in many older houses a purlin or other roof timber bears on the stack or the wall beside it, and loses its support when the stack goes. If the stack is shared with your neighbour, you will usually need their agreement to take it down, because part of it is theirs and their flues may run through it. Without that, the stack may have to stay and be supported instead. Serving a party wall notice is not the same as having that agreement; a party wall surveyor can advise on both.
In each case, the walls that the new support bears onto have to be checked too. A beam is only as good as what it sits on.
The floors need checking as well. Floor joists are usually cut short around a chimney breast and carried on a timber trimmer, and in some houses the joists or the trimmer bear directly on the breast. They have to be given new support before the breast comes out, not after.
A note on gallows brackets
A common way of supporting a retained stack has been steel “gallows” brackets bolted to the wall below it. They are increasingly rejected by Building Control, because they depend entirely on the strength of old masonry that often cannot be checked, such as a thin party wall or a stone wall with a rubble core. Where they are proposed, they have to be justified by calculation and by testing how well the fixings hold in the wall. If Building Control does not accept them, the support may have to be redesigned. It is often better to design a beam from the start.
Shared stacks and party walls
On many semi-detached and terraced houses, the chimney stack sits on or within the wall you share with your neighbour. Two things follow.
First, the law. If the work affects a party wall or a shared stack, the Party Wall etc. Act 1996 will usually mean you must serve notice on the owner of the house next door (which may be a landlord rather than whoever lives there) before the work starts. A party wall surveyor can advise you on what is needed. Arranging this is the homeowner’s responsibility, and it is worth starting early.
Second, the design. Whether your neighbour has already removed their own chimney breast, and how, changes what the shared stack is sitting on. That needs to be known before the design is finalised, not discovered on the day.
Temporary support: the part that must be planned
The most dangerous moment is during the work. If a breast is taken out before the masonry above it has proper support, that masonry can move or drop without warning, onto whoever is working underneath.
The engineer’s design should set out the propping sequence before work starts: where the retained masonry needs propping, in what order each part comes out, and when the new permanent support must be fully in place and carrying load before any props are removed. Propping is usually done with adjustable steel props and short steel needles set into slots cut in the masonry above. Props must stand on something that can take the load: on a timber floor, that means spreading it and carrying it down through the floors below to solid ground. Nothing should be cut through a party wall into your neighbour’s side without the party wall process in place. Choosing the props, deciding what they stand on, and putting them in and taking them out is the builder’s job, but they should be following a written sequence, not improvising.
If you are getting quotes, ask each builder how they plan to support the chimney above while they work. Their answer will tell you a lot.
What the engineer will need to know
To design the supports, an engineer will usually need:
- Which breasts you want to remove, on which floors, and whether the stack above the roof is staying.
- Floor-to-ceiling heights, and the height of the stack in the loft and above the roof.
- What the breast and the walls around it are built from, and how thick they are.
- Which way the floor joists run, because that affects how the floor is supported around the opening.
- Whether the stack is shared, and whether your neighbour has removed their breast.
- Whether any breast in the house has already been removed in the past.
Some of this can come from drawings and photographs. Some, such as joist direction and what is hidden behind plaster, may need a visit.
Building Regulations and other things to check
In England, removing a chimney breast is normally building work under the Building Regulations, because it alters the structure. When it is, it has to go through Building Control before work starts, and once it is finished and signed off, you should receive a completion certificate (a final certificate if you used a private approver). Keep it: a buyer’s solicitor is likely to ask for it when you sell. Building Control will normally ask for structural calculations for the new supports.
Before any work, have any gas fire or appliance disconnected and the flue made safe by a Gas Safe registered engineer. In homes built or refurbished before 2000, some boards and old fireplace materials can contain asbestos, so have anything you are unsure about tested by a qualified asbestos surveyor. If your neighbour still uses a flue in the shared stack, or another fireplace or boiler in your own house does, that flue must not be damaged or blocked, including by rubble falling into it. A damaged flue can let fumes, including carbon monoxide, into either house, so it should be checked by a suitably registered engineer after the work.
If your house is listed, removing a chimney breast is likely to need listed building consent. If it is in a conservation area, check with the council’s planning department before taking down a stack that can be seen from outside.
If a breast was removed in the past
Many older houses have had a chimney breast removed at some point, sometimes with no paperwork. Start by comparing the floors. If a breast is missing on one floor but there is still a breast on the floor above, a stack in the loft, or a stack above the roof, something should be holding that masonry up. Often it is hidden above a ceiling, so you may not be able to see what it is. If you look in the loft, only do so if it is safe to get into, step only on boards or joists, never on the ceiling between them, and do not disturb loose insulation, which in older houses can contain asbestos. Signs that it may not be properly supported include cracking in the ceiling or walls around where the breast used to be, a sagging ceiling or floor near that spot, and a stack above the roof that leans or is cracked. Having no cracks does not prove the masonry is supported: old brick and stonework can hold itself up by arching for years before it moves. If a stack remains above a removed breast and you cannot confirm what supports it, an engineer should look at it, and the support may need putting right. Assessing a removal that has already happened needs a visit to the house; it cannot be done from photographs.
When it cannot wait
If, during or after chimney work, you see new cracks opening, a ceiling sagging, masonry moving, or the stack above the roof leaning, keep people away, stop any work, and do not try to prop or repair it yourself. Do not take out any props that are already in place. If collapse looks imminent or anyone is hurt, call 999. If anything could fall onto a road or path, contact your council’s Building Control dangerous structures service. Then get a structural engineer to look as soon as you can, and if a builder is working on the house, ask them to put in temporary support through their engineer straight away. If you smell gas, leave the building and call the National Gas Emergency Service on 0800 111 999.
When to call a structural engineer
Speak to a structural engineer before you remove any chimney breast. It matters most if the stack is shared, if you are removing breasts on more than one floor, if the stack above the roof is staying, if you think your neighbour’s breast may already be gone, or if a breast in your house was removed in the past without paperwork. Bring the engineer in early, let the party wall process run alongside the design, and make sure the propping sequence is written down before anyone starts.
Need expert eyes on your project?
I am a Chartered Structural Engineer (CEng, MIStructE) based in Huddersfield. The Beam Doctor offers homeowners and builders:
- Chimney breast removal calculations — for a planned removal: a design for the new supports, a calculation of the load from the masonry that stays and a check of the walls it bears on (or, where the whole chimney comes out, a check of the roof it leaves behind), and a written propping and needling sequence for your builder to follow. Site attendance, where it is needed, is charged separately. Not included: Building Control fees; party wall notices, surveying, and awards; and the builder’s propping and demolition. See the chimney breast fee bands →
- On-site attendance — a Chartered Engineer at your property, tiered by duration. A brief verbal summary on site, then site visit notes within 2 working days: photographs, annotated sketches, and anything still needed for the design. The notes are a record of the visit, not a report. See site visit fees →
Current fees for every service are listed on the services page.