Open up a fireplace

quality build dundee renovation

Opening up an old fireplace is often top of a renovator’s to-do list — a great way to add character and value to a period property. In fact, few improvements are guaranteed to boost buyer appeal to the same extent.

With a bit of luck, opening up a fireplace could involve little more than prising off a sheet of old hardboard to reveal a hidden gem. But even if you don’t find a long-forgotten marble masterpiece behind, there’s still plenty you can do to create a captivating focal point.

It all depends on the age of the property and the overall style you’re aiming to create. A large inglenook might be perfect for a woodburning stove, for example.


Chimney breasts take up a fair amount of space. So in smaller houses with cramped layouts it can be tempting to remove a redundant chimney breast, perhaps towards the rear of the property in a kitchen or bathroom. However, where a previous owner has already taken out a chimney breast and you want to open up a fireplace, it should be possible to rebuild it without costs escalating (assuming the stack is still in place).


Do I Need Planning Permission to Open up a Fireplace?

When it comes to getting planning permission, unless the building is listed, you shouldn’t normally need to worry.

However, because of the potential risks from fire and toxic fumes, even if you’re only installing a stove in an existing fireplace or lining a flue, the work will need to comply with Building Regulations (Part J deals with combustion appliances). And, any structural alterations, such as removal of a chimney breast, will also need to comply.

How Much Will it Cost to Open Up a Fireplace?

This will very much depend on how your original fireplace was boarded up. Very occasionally part of the old surround or insert will remain. More commonly it will have been completely removed and the opening either boarded or bricked up.

If the opening is boarded up it will be easier, quicker and cheaper to reveal than one that has been bricked and plastered over.

As a rough guide, a new flue liner measuring six meters costs between £150-£250 depending on the quality and supplier. Usually on one or two are required.

Knocking out a fireplace will usually take around half to a full day, whilst sweeping and installing the lining could take another. The average day rate for a tradesperson to do this job would be around £150-£250.

How Do I Open up an Old Fireplace?

Before getting down to work it’s advisable to play safe and cover everything in sight because there is a potential that astounding volumes of soot and dust will be generated when opening up a fireplace — engulfing nearby furnishings, persons and pets in a thick, black miasma.

It’s also worth bearing in mind too that the vibration from builders’ Kango breakers can be very effective at rearranging the neighbour’s ornaments on the other side of a party wall. So a bolster and club hammer is probably a better option for localised demolition where old fireplaces have been bricked up. Having exposed the original ‘builder’s opening’, large deposits of accumulated soot and rubble will likely need to be removed before the chimney can be swept and the flue lined.

In most properties built in the 19th and early 20th centuries, the opening will be spanned by a load-bearing brick arch supported on a curved steel formerExposed brickwork can look very appealing, but if the size of the opening needs to be altered, a concrete lintel can be inserted and the masonry plastered over.

Whatever your taste in fires, once you have a clean opening and a freshly swept flue, the next job is normally to upgrade the hearth, traditionally made from concrete set flush into the floor void. To comply with Building Regulations this will need to be raised above floor level; it’s a simple job to form a new one directly on top from in-situ concrete, or you might opt for a marble or slate hearth.

The new fire surround will stand on top of the hearth, screwed to the wall via small side lugs which can be inset into the wall and plastered over. Finally, if your preference is for a traditional Victorian cast iron insert, this can now be positioned centrally, secured by a mass of weak concrete placed behind it.

Building Regulations When Opening Up a Fireplace

The provision of a sufficient amount of oxygen, both for occupants and for the combustion of fires or appliances is a key part of compliance with current Building Regulations. This might require vents to be fitted close to the fire.

n timber floors, vents can be inserted into the floorboards so that the fire draws air from under the floor (rather than creating a draught under the living room door), which has the beneficial side effect of enhancing subfloor ventilation. Alternatively, vents are sometimes placed on outside walls just above the skirting. Redundant flues also need to be ventilated to prevent staining to chimney breasts caused by moist air condensing within the flue.

If required, a new gas supply can be piped to the fireplace under a timber floor or via copper pipe (usually 22mm) run externally and clipped to the outside wall surface. But when it comes to the installation of gas appliances, by law this task must only be carried out by a Gas Safe-registered engineer.

As ‘competent persons’, approved installers can ‘self-certify’ that work has been carried out in compliance with Building Regulations and issue completion certificates. HETAS is the equivalent body for solid fuel-burning appliances.

How is a Flue Installed?

Enclosed by the chimney breast and stack masonry, flues are designed to safely disperse smoke and combustion gases. Often multiple flues are accommodated within a single chimney with thin internal partitions. Before a fire can be used, in most cases the flue will need to be lined. In older properties, flues were lime rendered internally (known as ‘parging’), but over the years this can come loose and mortar joints can erode, allowing smoke and fumes to emerge in an adjacent flue or room.

Lining typically involves inserting a flexible steel tube down from the top — a job which can require scaffolding, adding to the cost of the task. The type and diameter of the flue liner, and the cowl or terminal, are both specific to individual appliances and fires and are specified by the manufacturer and/or installer.

Opening Up a Fireplace: Troubleshooting

Does my Chimney Breast Have Damp?

If you spot damp patches and staining on your chimney breasts or the walls around your fireplaces you are looking at signs of underlying damp problems. The two main causes of damp (other than leaks at roof flashings) are rainwater coming down chimney pots and condensation.

Burning fuel produces water vapour which turns to moisture when it hits cold surfaces, especially if the stack is particularly tall or located on a cold outer wall. Fuels such as freshly cut timber are particularly wet and give off a lot of water vapour. Once mixed with soot the moisture can bleed through the plasterwork leaving ugly stains.

In older properties, the stack walls were built without a damp-proof course (DPC), and eroded mortar joints can allow damp to penetrate down through porous masonry. To prevent this, modern stacks have a DPC through the chimney at approximately 150mm above the roof and another near the head.

Condensation inside the stack can usually be resolved by installing a suitable flue liner. But this can sometimes lead to problems where pots and flues are exposed to rain, because rather than being absorbed into the masonry, the rainwater may be channelled straight down the ‘chute’ forming puddles in the fireplace.

To exclude the entry of rain there’s a wide variety of caps, cowls, and hoods available to protect pots and flues. Even if redundant fireplaces are sealed up and you don’t want to use them, there should be a flow of air to prevent condensation with pots hooded or capped, and airbricks inserted in the stack wall.

Where damp is seeping down through porous chimney masonry, repointing the brickwork joints can sometimes solve the problem, or new larger flashings can be fitted that extend higher up and deeper into the brickwork.

Why is my Fire Smoking?

You’ve opened up a fireplace only to find smoke doesn’t go up the chimney but instead blows into the room – or maybe you find that  the fire becomes choked and struggles to burn. What to do?

Fireplaces rely on the principle that warm air rises. A regularly used flue helps keep the escaping smoke warm, aiding its ascendance.

  • Some chimneys are simply too cold to draw well, particularly those on outside walls.
  • A stack that is too short or overshadowed by high buildings or trees can result in a downdraught with the smoke blowing back down.
  • Flues that are too large can cause smokiness because it takes a long time for them to get warm enough to help the smoke rise.
  • Flues that are too small can choke the fire.