Someone Already Removed the Chimney Breast. Is It Safe?

There is a particular sinking feeling that comes with lifting a floorboard, or pulling back a bit of plasterboard in a house you have just bought, and realising the chimney breast stops. Not at the roof. Halfway up the wall, with a good deal of brickwork still sitting above it. An unsupported chimney breast is one of the more common things we are called out to look at, and it is almost never the current owner who created it.

The good news is that it is usually fixable. The less good news is that it needs sorting out properly, and it has a habit of surfacing at the worst possible moment — usually during a sale.

Why it happens so often

Chimney breasts eat floor space. In a small bedroom a breast can swallow the best part of a square metre, and once the fireplace has been out of use for thirty years it starts to look like dead weight.

Removing the section in one room is a day’s work for two people with a bolster and a skip. It feels like demolition rather than construction, which is precisely why it so often happens without anybody involving an engineer or telling Building Control.

The part that gets missed is that the breast was not just sitting in the room. It was carrying the breast in the room above, and the stack above that, all the way to the chimney pot.

What actually goes wrong

Remove a mid-height section of a chimney and you have not removed the load. You have removed the route that load was taking to the foundation.

Everything above now has to be picked up and carried across to the walls either side. If nothing is put in to do that, the remaining brickwork is spanning on nothing more than the bond of its own mortar joints — which is not a structural system, it is a slow-motion problem.

Old lime mortar makes this worse. It was never intended to work in tension, and a hundred years of chimney use will have left the brickwork in indifferent condition anyway.

What proper support looks like

There are two established ways to do it, and the right one depends on how much weight is left above.

The first is a pair of gallows brackets — steel brackets bolted into the chimney wall either side of the removed section, carrying a support beneath the retained breast. They are neat, relatively cheap, and they work well within their limits.

The important word there is limits. Gallows brackets rely entirely on the wall they are bolted into. If that wall is soft brick, if the mortar is poor, if the bolts land in a perpend rather than a brick, or if the weight above is greater than the brackets were ever intended to take, they are not adequate. Some local authority building control departments have become noticeably more reluctant to accept them without calculations, and that reluctance is well founded.

The second approach is a beam — typically steel, spanning between the flank walls and picking up the retained brickwork on a plate. It costs more and involves more disruption. It is also the answer whenever the loads are anything other than modest.

Deciding between the two is not a matter of taste. It is a calculation.

How to tell whether yours was done properly

From inside the room, often you cannot. That is rather the point. But there are signs worth looking for.

• Cracking above the old breast line, particularly stepped cracks following the mortar joints, or a horizontal crack where the remaining brickwork meets what is supporting it.
• Sloping or springy floors in the room above, which can indicate the retained breast has settled slightly.
• Nothing visible at all where the breast used to be. If there is no beam, no bracket and no obvious means of support, something is holding it up and you want to know what.
• No paperwork. Ask for the Building Regulations completion certificate. If the work was done properly there will be one.
• A neighbour’s breast in a terrace or semi. Shared stacks mean one side being removed can affect the other.

The sale problem

This is where most people first hear about it.

Structural alterations without Building Regulations approval show up during conveyancing. A buyer’s solicitor asks for the certificate, there isn’t one, and the sale stalls while everybody works out whose problem it is.

Regularising it after the fact is possible — a retrospective application supported by a structural engineer’s assessment — but it is slower and more expensive than doing it correctly at the time, and it happens under time pressure with a buyer waiting.

Indemnity insurance is sometimes offered as a shortcut. It is worth understanding what that actually does: it protects against enforcement action by the council. It does not make the structure adequate, and it does not help you if the thing moves.

What we do about it

An assessment usually starts with establishing what is genuinely up there. That means looking in the roof space to see whether the stack was removed at high level or is still standing, checking the room above, and establishing what — if anything — is currently supporting the retained brickwork.

From there it is a calculation of the actual load and a design for the support it needs, whether that is brackets, a beam, or occasionally the conclusion that taking the rest of the stack out is simpler and cheaper than holding up what remains.

We then produce the drawings and calculations for a Building Regulations application, including a retrospective one where the work has already happened.

Frequently asked questions

Is an unsupported chimney breast dangerous?

It ranges from a paperwork problem to a genuine structural risk, depending on how much weight is above and what condition the brickwork is in. It should not be left unassessed, but it is rarely an emergency.

Are gallows brackets still acceptable?

Sometimes. They can be entirely appropriate for modest loads on sound brickwork. Increasingly, building control will want calculations demonstrating that rather than accepting them as a default.

Can I just leave it?

You can, but it will resurface when you sell. It is considerably cheaper to deal with on your own timetable than during a chain.

Do I need Building Regulations approval retrospectively?

Yes, and it is worth doing. A regularisation certificate resolves the conveyancing issue permanently, which indemnity insurance does not.

How long does an assessment take?

Usually a single visit, with the report following within a few days. If the roof space cannot be accessed or the support is fully concealed, some opening up may be needed.

Not sure what’s holding yours up?

If you have found an unsupported chimney breast in a property you own or are buying, the useful first step is establishing what is above it and what is currently carrying that weight — before anyone quotes for remedial work. We are a chartered structural engineering practice with offices in Peterborough and Borehamwood, covering the East of England, Hertfordshire and Greater London, fully insured to £5 million professional indemnity.

Send us a photo of the breast, the room above it and the roof space if you can get to it, and we will tell you honestly what you are dealing with.