Opening up a fireplace for a log burner
Plenty of houses have a chimney hiding behind a gas fire, a fire surround or a plastered-over wall. Opening it back up to the original builder’s opening gives a stove a proper recess to sit in. The building work usually costs £300 to £1,200 before the stove and liner go in, depending on how much has to come out and how much making good is needed.
Typically £300 to £1,200
Get a quoteSigns there is a fireplace to open
- A chimney breast with nothing in it. A projecting breast in the room and a stack on the roof above usually mean a flue that has been closed off.
- A gas or electric fire on the breast. Behind the fire there is often a small opening that can be enlarged to the original size.
- An air brick or vent on the breast. Left there to ventilate a sealed flue.
- A pot on the roof that matches the room. Counting pots and fireplaces tells you which flue serves which room.
What opening up costs
| Item | What it covers | Typical cost |
|---|---|---|
| Small job | Removing a surround and blocking, little making good | £300 to £500 |
| Full opening | Enlarging to the builder’s opening, new lintel, rendering the recess | £800 to £1,200 |
| Stove, liner and fitting | After opening up, with a mid-range stove | £1,700 to £3,200 |
| Sweep and smoke test | Before anything is fitted | £70 to £100 |
Typical UK ranges including VAT, from national price guides read November 2026. Estimate your own job.
Gas fire or blocked opening? A fitter can look at the breast and tell you what is behind it.
Get a quoteWhat opening up involves
Opening a fireplace is mostly building work: careful demolition, checking what holds the chimney up, and finishing the recess so it can take heat. It is messy and dusty, so expect sheets and a vacuum, and plan for a day or two of disruption.
Taking out a gas fire
A gas fire or back boiler must be disconnected and the supply capped by a Gas Safe registered engineer before anyone starts. Back boilers also mean altering the heating pipework. Some stove fitters are Gas Safe registered; many arrange it separately.
The lintel
Above the opening, a lintel or arch carries the brickwork of the breast. Older houses may have a timber lintel, cracked concrete or nothing much at all. A stove gets hot enough that a timber lintel near it is not acceptable, and enlarging the opening may need a new steel or concrete lintel. If a chimney breast has been removed in the room above, the support there needs checking too.
How big the recess needs to be
The stove maker states the clearance needed round the stove for air to move and heat to escape, often 50 to 150 mm at the sides and more above. Approved Document J also sets thicknesses for the walls of a fireplace recess. A common mistake is choosing a stove from a showroom and finding it does not fit the opening, or that it would need the opening enlarged further than the lintel allows. Measure first, then choose.
Making good
Once opened, the inside of the recess is usually rendered with a lime or heat-resistant mix, or lined with fire board, and the old hearth is checked. A cracked or crumbly back wall can be repaired at the same time. Ordinary gypsum plaster near a stove will crack and blow, so it should not be used inside the recess.
Then the chimney
An opened-up flue that has been sealed for decades is swept and smoke tested before a stove goes in. Most will need a liner; see chimney liner installation.
Sources we used
- GOV.UK: Approved Document J, combustion appliances and fuel storage systems (2010 edition incorporating 2022 amendments)
- HETAS: Find a registered installer and check a certificate
Prices are typical ranges from national UK price guides for homeowners, read November 2026, including VAT. Rules are summarised in our own words as general information.
How it gets done
Opening up and fitting can be done by one firm in one visit of two to three days, or by a builder first and the stove fitter after.
Make safe
Gas capped by a Gas Safe engineer; the breast checked and the floor protected.
Open up
Fire, surround and blocking removed; the opening enlarged if needed.
Support and finish
Lintel checked or replaced, recess rendered or boarded, hearth checked.
Sweep and fit
The flue is swept and tested, then lined and the stove fitted.
Common questions about stoves
How much does it cost to open up a fireplace for a log burner?
- Usually £300 to £1,200 for the building work, depending on what is there now and whether a new lintel is needed. The stove, liner and fitting are on top.
Do I need a new lintel?
- Often, if the opening is enlarged or the existing lintel is timber, cracked or missing. A fitter or builder checks once the blocking is out.
Can I open up a fireplace myself?
- You can do the demolition, but gas must be capped by a Gas Safe engineer, and any change to the structure needs care. The stove fitting is notifiable under Part J.
What if the chimney breast has been removed upstairs?
- Then the stack above must be properly supported, usually on steel beams or brackets. Have that checked before using the flue.
How do I know which pot is my fireplace?
- A smoke pellet lit in the fireplace shows which pot it comes out of. Fitters do this as part of the smoke test.
More on stoves and flues
- Chimney liner installation
The next step once the fireplace is open.
- Hearths for log burners
What the stove stands on in the recess.
- Log burner installation cost
Add opening up to your estimate.
Get a quote for your stove
Start with a postcode. A few details about the room and the chimney (or the lack of one) let a fitter give you a sensible first figure before they visit.
Free to use. We tell you which registered installer we have in mind before anyone else sees your details.
Thank you. Here is what happens next.
- We look for a HETAS-registered stove installer who works in your area and fits stoves in homes like yours.
- We get in touch by email or phone to say who they are. Nothing is passed on until you tell us that is fine.
- With your go-ahead, they arrange a visit to look at the chimney or flue route, then send you a written price. No marketing follows.