How to get it right: Removing a chimney the right way (with video showing the wrong way...)

Blog Post
Picture of a chimney - LABC chimney removal

One of the most common internal alterations carried out is to remove an obsolete chimney breast at ground floor to create more floor space. Quite often the chimney is also removed at first floor level leaving just the roof void and external section of the chimney in place. Building Regulations apply to this work because it is a ‘material alteration’ to the structure ensuring the remaining part of the stack is properly supported.

If the entire chimney is removed it is essential to take professional advice to determine the structural implications. Planning permission may also be needed for its removal.

Care needs to be taken where this work also falls into work covered under the Party Wall etc Act 1996 and notice needs to be served on the adjacent property. This is so that shared flues and structural adequacy can be considered before work starts.

Removing a chimney

To remove a chimney breast at ground or first floor you must first support the chimney adequately. The stack must be properly supported and the gallows bracket illustrated below is a common method.

Gallows brackets for chimney support

Gallows brackets should only be used if...

  • The stack is not completely vertical (i.e. a gathered flue to a central stack).
  • The neighbours’ chimney breast on the other side of the party wall has not been removed (or partly removed). If it has then the whole of the chimney above the roof should be removed and the roof made good as there is a possibility that the party wall may only be 100mm thick above the ceiling line.
  • The party wall supporting the gallows bracket is a minimum of 215mm thick, in brickwork, and in sound condition.
  • The maximum width of the chimney breast is less than 1200mm. For wider chimney breasts a structural engineer should be consulted.
  • The chimney breast should project no more than 340mm into the room.
  • The chimney is no more than two storeys high plus roof space.
  • The relevant notices required under the Party Wall etc Act 1996 have been served on the adjoining owner (where the chimney is on a party wall).

Finding this interesting? Browse our How to get it right articles

Things you need to consider when removing a chimney

  • The bracket members should be 75mm x 75mm x 6mm mild steel angles with 6mm fillet shop welded joints with the angles pre-drilled to take a minimum of 2no M12 chemical or resin anchor bolts. (e.g. Chemfix or similar).
  • The bolts must be drilled into sound brickwork, not mortar joints. The condition of the brickwork is critical and there may be areas of the country where this option may not be acceptable to building control due to known problems.
  • A plate (e.g. 10mm steel plate) should be placed on the top of the brackets to prevent soot and debris falling from the remaining chimney.
  • The minimum height of the retained chimney breast below the roof line must be equal to or greater than the height of brickwork above the roofline. (See diagram below).
  • To ensure any rain or condensation passing into the flue will dry out by natural convection; the chimney pot should be capped with a ventilated cowl and insertion of an air brick at lower level.
  • Fireplace hearths at ground or first floor level should be removed. Additional timber joists must be installed and adequately supported by the existing timber floor trimming joists.

Diagram of chimney breast

Why is this important

One of our officers recently visited a site for unauthorised work after a phone call from concerned neighbours who could hear a cracking sound.

On arrival the completely unsupported chimney breast was being removed from the ground floor up through into the roof space and was already showing signs of severe stress. He instructed the ‘builder’ to get out of the property whilst trying to secure a structural engineer to design a solution.

Watch what happened:

The clip serves as a visual reminder of the significance of getting it wrong!

Fortunately everyone was out of the building but unfortunately too late to arrive at a solution to save the chimney.

Insertion of steel beam(s)

Where gallows brackets are unsuitable then the use of a structural steel beam or beam and posts may be required. This will involve the submission of structural calculations by your structural engineer to justify the design and size of the steelwork.

Fire protection

Any gallows brackets or steel beams used should be provided with a minimum of 30 minutes fire protection (unless they are fully within the roof above the ceiling). The easiest way to achieve 30 minutes fire resistance to steelwork in domestic properties is to use two layers of 9.5mm plasterboard with a skim coat or a single layer of 15mm Gypsum fireline or similar fire rated plasterboard. Plaster adhesive dabs is not an acceptable fixing method and mechanical fixing will be needed. You should speak to your local building control team for installation requirements.

Maintenance of the neighbours’ chimney

If the separation between flues is damaged during removal there is a possibility of carbon monoxide or dioxide leaking from the neighbour’s flues. All poor brickwork should be replaced and re-pointed and, if possible, a smoke test carried out on the neighbour’s flue to check for any leakage (flue test to be done by GasSafe registered engineer).

Finally you should not consider any of these...

  • Corbelled Brickwork – into existing brickwork should not be attempted as it will not be possible to gain a sufficiently strong bond between the new and existing brickwork.
  • Timber bearers onto the existing floor or ceiling joists – as the point load passed onto the floor or ceiling timbers will be significant and may lead to collapse.

If you are in doubt ask please just ask your local building control team.

Also read

How to get it right: Demolition
How to get it right: Working on or around a party wall
Chimneys and flues: Don't forget the neighbours!


Please Note: Every care was taken to ensure the information was correct at the time of publication. Any written guidance provided does not replace the user’s professional judgement. It is the responsibility of the dutyholder or person carrying out the work to ensure compliance with relevant building regulations or applicable technical standards.

This article was updated on 22 March 2022


(No subject)

Submitted 9 mis ago

I am a chartered structural engineer. Structurally this advice is safe as described. BUT the advice relies on the neighbour's remaining in place. I have recently been involved in a project where we discovered by chance that their neighbour had used gallows brackets. It cost thousands of pounds to provide a structure to make it safe to remove the chimney breast on the second side. There must be many projects where it is never discovered that gallows brackets have been used on the adjoining owners chimney. Therefore I consider that in the long-term the advice is not safe and that gallows brackets should NEVER be used on a party wall.

(No subject)

Submitted 5 mis ago

Dear Sir/Madam, I read your reply with great interest. Please can you explain to me why the use of gallows brackets on a adjoining Party Wall which has had the neighbour's chimney breast removed is not recommended? Many thanks, George

(No subject)

Submitted 1 flwyddyn 5 mis ago

The structure of a shared chimney is brickwork on both sides of the party wall often with just a single skin of bricks in line with the party wall.
When one side removes the structure of the stack on their side and installs brackets to support the stack above, they are relying on with remaining structure on the neighbours side of the wall to resist the forces generated by the brackets, both the static forces from the weight of the brickwork and the dynamic forces for example generated by wind, which can be not inconsiderable during a storm.
If both neighbours remove their sides of the structure, the entire weight of the chimney is now being supported by the central brick wall, which was only built to separate the sides of the chimney.
You need either steelwork to transfer the load down to the ground (or suitable intermediate load bearing point), or remove the chimney and make good the roof.
The problem with party walls is you don't know what has been done on the other side, possibly a many years ago by another owner.

thousands ?

Submitted 1 flwyddyn 3 mis ago

i would of suggested taking the chimney stacks off first. then the chimneys from the inside of the lofts, both sides. that would be safe and cost cutting.not the brackets can be used on a party wall as long as the brickwork is sound and 200mm thick IE, 2 course.

(No subject)

Submitted 9 mis ago

The one concern I have with this method is the condition of the brickwork when the flue or flues are removed the mortar having been subject to heat over a long period. Should the outside brackets be positioned a safe distance from the brickwork damaged by chopping out as no amount of making good is going to adequately strengthen the old work.

(No subject)

Submitted 9 mis ago

Do check that any masonry anchors are set into sound brickwork; the existing masonry is likely to be contaminated with soot and tar and not as strong as one would wish!

(No subject)

Submitted 9 mis ago

I am a bit unsure regarding the section your flue must not be completely vertical? Where I want to put my gallows brackets in the loft the remaining meter of the flue will be going straight up then through the roof

(No subject)

Submitted 9 mis ago

Hi - thanks for your message.

The note on our website seeks to avoid the support at a lower level of a completely vertical chimney breast.

You will need to ensure that the section of the breast that is remaining below the roofline is at least equal to the height of the stack above the roof.

The work you're proposing will require a Building Regulation application to be submitted.

You can search for your local council building control team's contact details using the postcode search at the top of this page, and they'll be happy to provide pre-application advice on your particular project.

John, LABC

Vertical chimney

Submitted 8 mis ago

Why can't gallows brackets be used on a vertical stack?


Submitted 8 mis ago

Hello - thanks for your comment.

It's a control on the height of the remaining chimney breast/stack that's to be supported.


John, LABC

Ychwanegu sylw newydd

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

Sign up to the building bulletin newsletter

Over 48,000 construction professionals have already signed up for the LABC Building Bulletin.

Join them and receive useful tips, practical technical information and industry news by email once every 6 weeks.

Subscribe to the Building Bulletin