Chimney fire damage
A chimney fire can reach temperatures well above a thousand degrees inside a structure that was never designed to be heated that hard. The fire itself is over quickly. What it did to the masonry usually is not obvious for months.
If a chimney fire is happening now: call 999. Do not attempt to deal with it yourself. Close doors to the room, move anything flammable away from the fireplace, and get everyone out. This page is about what to do afterwards.
Why the aftermath matters
People often assume that once the fire is out and the flue has been swept, the matter is closed. It frequently is not. The sudden, extreme and uneven heating of a masonry structure does real damage:
- Thermal shock cracking. The inner face of the flue heats violently while the outside stays cold. That differential cracks masonry and mortar.
- Liner failure. Clay liners crack or shatter; older stacks may have no liner at all, meaning the fire was directly against the brickwork.
- Mortar degradation. Lime and cement mortars both lose strength when heated hard, and the joints in the flue may effectively be cooked.
- Loss of separation between flues. On a shared or multi-flue stack, cracking can open a path between flues — which means combustion gases from one property's appliance can enter another's. This is a carbon monoxide risk, not just a repair issue.
- Spalling and displaced brickwork where the heat has driven moisture out of saturated masonry rapidly.
- Damage to flaunching and pots from heat and from the force of the fire.
- Heat transfer to adjacent timber — joists and rafters built into or near the stack, which is how chimney fires become house fires later.
The single most important point: a chimney that has had a fire should not be used again until it has been inspected and, if necessary, repaired. That applies even if it looks fine from the outside. Most of the damage is inside the flue and inside the masonry.
Which trade does what
Chimney fire aftermath crosses more than one discipline, and it is worth being clear about who does which part — including where our work stops.
| Task | Who |
|---|---|
| Extinguishing the fire | Fire and Rescue Service — 999 |
| Sweeping and internal flue inspection (CCTV) | A registered chimney sweep |
| Flue integrity testing (smoke test) | Registered sweep or HETAS installer |
| Relining the flue | HETAS registered installer (solid fuel); Gas Safe registered engineer (gas) |
| Appliance safety check and recommissioning | HETAS installer or Gas Safe engineer |
| Structural masonry: cracked brickwork, failed joints, rebuild | Us |
| Flaunching, pots, flashing, weathertightness | Us |
| Internal plaster and decoration | Plasterer / decorator |
We do the masonry and the weathertightness. We are not sweeps and we do not line flues — if you need those, you need someone registered to do them, and we will say so rather than improvise.
What to check after a chimney fire
Outside, from the ground
- Cracks in the stack that were not there before, particularly horizontal ones
- Displaced, bulging or dropped brickwork
- Broken, cracked or shifted pots
- Flaunching cracked or blown apart
- Debris on the roof or in the gutters
- Staining or scorching on the brickwork near the top
Inside and in the loft
- Cracks appearing on the chimney breast
- Scorching or charring on timbers where they meet the stack — check the loft carefully
- A smell of smoke in rooms that do not have the fireplace
- Smoke staining appearing on walls in adjoining rooms or a neighbour's property, which suggests a breach between flues
- New damp patches, where the fire has damaged the flue's ability to keep water out
Over the following months
Some damage only reveals itself with weather. Cracks opened by thermal shock take water in, and the first hard frost afterwards can break masonry apart that looked sound in the autumn. A stack that has had a fire is worth looking at again after its first winter.
Insurance
Chimney fires are usually a covered peril under buildings insurance, as sudden and accidental damage — unlike gradual deterioration. Some practical points:
- Report it to your insurer promptly. Most policies require it.
- Keep the Fire and Rescue Service's incident record if they attended. It is useful evidence of date and cause.
- Photograph everything before repairs.
- Be aware of the maintenance question. Insurers may ask when the chimney was last swept. Where a fire is attributable to a flue that had not been swept for years, cover can be disputed — a genuine reason to keep sweeping records.
- Get the damage documented properly, separating fire damage from pre-existing condition. Insurers pay for the former, not the latter.
Preventing the next one
Chimney fires are caused by ignition of deposits in the flue — principally creosote from burning wood, especially wet wood or slow smouldering burns. The prevention is not roofing work: sweep regularly, burn only properly dried wood, and run the appliance hot enough to avoid heavy deposit build-up. A registered sweep will advise on frequency for your appliance and fuel.
What we can contribute is keeping the structure sound and weathertight, so the flue is not additionally compromised by water getting into it.
Had a chimney fire?
Once the flue has been inspected by a sweep, we can assess the masonry — the stack, the flaunching, the pots and the flashing — and tell you what the fire actually did to it.
After-the-fire questions
The fire brigade said it was fine. Do I still need it looked at?
The Fire and Rescue Service's job is to make the situation safe on the day, not to survey the structure. They will often say exactly that. A proper assessment of the flue and the masonry is a separate exercise and is worth doing before the chimney is used again.
Can I use the fireplace again?
Not until the flue has been inspected and confirmed sound. A cracked flue or a breach between flues can put combustion gases, including carbon monoxide, into living space. That check is for a registered sweep or HETAS installer.
The stack looks completely fine from outside. Is that reassuring?
Only partly. Most chimney fire damage happens inside the flue and within the masonry, where you cannot see it. Visible external damage tells you the fire was severe; the absence of it does not tell you the stack is undamaged.
Do you do the flue lining as well?
No. Flue lining is for a HETAS registered installer for solid fuel, or a Gas Safe registered engineer for gas. We handle the masonry, flaunching, pots and flashing, and are happy to coordinate so the structural work and the lining happen in a sensible order — masonry repairs generally need to come first.