You might have a chimney built before 1965. Or, have a stove burning a different fuel from before. You might even have changed the capacity of your stove. Any of these reasons and more can mean you need a new chimney flue liner.
But how much do they cost in the UK?
Flue liner installation costs vary depending on manufacturing material, size, and fuel type. But, on average:
- Purchase costs vary between £15 and £40/m.
- Installation times vary between 4 hours and 3 days.
- A typical installation needs two people.
- And, a tradesperson charges from £150 to £250/day.
Labour charges vary depending on whereabouts you live in the country, with average rates in London and the Southeast being 20% higher than elsewhere in the country.
In this article, we will discuss:
- What is a chimney flue liner?
- How it works, and what are its benefits?
- How much does it cost for a chimney flue installation?
- What types of chimney liners are available in the UK market?
- What regulations and compliances do you need to maintain adequate ventilation and fire safety?
How Much Does Chimney Lining Installation Cost?
The following table contains details of chimney liner kits made from different materials.
We compiled the figures for each liner from various online sources. By all means, use them as a guide. But, if you intend fitting a flue liner, make sure you ask a qualified flue installer for a detailed quotation. All chimneys are different, and the professional might encounter problems when working on your chimney. So, it’s essential to have a site inspection before you receive a quote. And, you’ll make sure to have a liner to suit your appliance and chimney.
|Chimney flue liner||Chimney size||Estimated cost per typical chimney||Duration|
|Stainless steel flexible liner||100cm to 125cm||£350 to £700||4 to 8 hours|
|Clay liner||140cm to 205cm||£750 to £1000||2 to 3 days|
|Ceramic liner||215cm to 255cm||£850 to £1500 minimum||2 to 3 days|
Stainless Steel Liners
Stainless steel flexible liners mould to the inside of a flue and accommodate bends and kinks. You can also feed them down from the chimney pot to the hearth or vice versa in one piece. Usually, the best way to install a flexible liner is to have one person on the roof and one in the house. Tie a rope to the liner, drop the rope down the chimney. Then, pull the liner from top to bottom.
If you have a gas appliance, probably, you should use a single–skin liner as the exhaust fumes from gas aren‘t very hot and don‘t transfer much heat. However, a solid–fuel appliance needs a double–skin liner, to keep the heat inside.
Stainless steel liners come in various standard diameters to suit the appliance and chimney flue size:
- 5″ (125mm).
- 6″ (150mm.
- 7″ (175mm).
- 8″ (200mm).
They also come in two grades:
- 316 stainless steel, with a lifetime guarantee of 15 years.
- 904 stainless steel. With a lifetime guarantee of 30 years
Additionally, there is another type known as W3G. It is a double–core 904–grade steel liner, designed for highly efficient Ecodesign stoves with lower temperature flue gases. Lower temperatures mean that there is more chance of condensation and subsequent corrosion. So, the W3G liner is the solution to this problem.
If you use coal or smokeless fuel, then the steel grade should be 904. However, this grade liner is suitable for use with all HETAS approved fuels.
Lastly, a double-skin 316–grade steel liner is only suitable for log burner flue installations, wood–fuelled stoves, gas appliances, and light use. In comparison, only use a single–skin 316–grade steel liner with a gas appliance.
All liners are cut to length during installation to suit the length of your chimney.
Clay, concrete and pumice liners
All these materials can withstand high temperatures. When used as a liner, they help to insulate the heat from the surrounding chimney. However, only use these liners in chimneys that don‘t suffer from condensation.
Pumice liners have air pockets giving a lightweight liner section with built-in flue liner insulation. However, for best results, use the three materials in conjunction with granulated insulation to fill the chimney void.
It isn‘t easy to install these liners. They require a skilled bricklayer or mason to cut access ports into the chimney, insert the liner lengths, and make-good the holes afterwards. Alternatively, the bricklayer installs the liner sections inside a new–build chimney during construction. Typically, these liners last around 50 years.
Ceramic liners (Thermocrete™)
Thermocrete™ is a proprietory ceramic chimney lining method that provides a stable duct for waste gases to escape and strengthens the chimney.
The installer inserts a rubber former for a diameter suitable for the appliance through the chimney’s entire length. The former adapts to curves and kinks within the chimney and stays centralised at all times. Then, the installer pumps Thermocrete™ slurry from the roof level into the void between the chimney and former. The slurry fills all voids, cracks, and damaged parts of the chimney. And, uses ceramic fibres to strengthen the slurry after it sets hard. Thermocrete™ also provides efficient flue liner insulation. Depending on the height of your chimney, the total height is split into manageable sections and poured independently. Finally, the installation engineer deflates the rubber former and removes it, leaving a perfectly smooth cylindrical flue duct. However, only a registered Thermocrete™ installation company can give a detailed and accurate quotation.
For flues that suffer from poor updraught, there is the chimney fan. This is a mechanical device that boosts a heating appliance’s performance by forcing the waste gases up the flue. It also eliminates excess smoke and increases the airflow to the appliance or fireplace.
Many chimney fan models differ in specifications from each other. Therefore, you should ensure you buy the one matched to your appliance, chimney type, and fuel. Usually, to install one of these costs between £400 and £850, depending on the size and complexity of your chimney system. Typically, the lifespan of a chimney fan is at least 10 years.
Gas flue block system
These have a narrow flue, designed explicitly for gas fireplaces, and attach to nearby brickwork. Under no circumstances must you use gas flue block systems with any other fuel except gas. Otherwise, the temperatures rise too high. A qualified installation engineer can install one of these systems for between £300 to £700, depending on your fireplace’s complexity and size. Finally, you can expect a typical lifespan of around 15 to 25 years.
A flue terminal is what you might expect from the name. It fits on the end of a flue. A terminal has many other names in everyday use; chimney ‘caps’ and ‘cowls’ are only two. A terminal’s purpose is to improve the draught in a chimney by rotating its exit hole to leeward, that is, so it’s not facing the wind. No matter which flue type you use, draught improving terminals are always recommended and are easy to install onto the chimney pot.
You‘ll find that labour rates range from about £150 to £250 per day. A skilled flue installer knows the approximate duration to do the work on your chimney. So, you might receive a set price for the job, rather than a day rate. Depending on the liner type, you might have to hire scaffolding for access to the chimney stack. Don‘t worry, your quotation should include this extra cost. Irrespective of what type of liner you choose, most installers work in teams of two persons.
Labour charges vary depending on whereabouts you live in the country. London and the Southeast of England charge up to 20% more than the remainder of the country.
Types of Chimneys
Traditional Chimneys (Class 1)
Generally, we find a traditional chimney on older properties. Usually, they are made from brick, but sometimes from block or stone, with a covering of render. If it‘s older than 1965, it probably served an open fire and removed the fire‘s waste fumes and smoke.
A Class 1 flue has a diameter of at least 180mm ( 7“). It is suitable for all types of solid fuel, gas fires with a high heat output, and any less efficient fire than usual. A Class 1 flue disperses the heat from these and produces a good updraught. You can also use this flue liner in chimneys with corrosion, low-quality mortar, and those that seep fumes through the walls into the house.
Prefabricated Flues (Class 2)
We often find Class 2 flues in old and new properties with a steel flue liner retrofitted or built-in.
The flue consists of interlocking, standard lengths. Usually, it terminates at the chimney with either a fixed or rotating metal cowl.
Don‘t use Class 2 prefabricated flues with solid–fuel appliances or fireplaces. Instead, use them with a gas or an electric fireplace.
Usually, a Class 2 flue has a diameter of 5“ or 125mm.
Usually, we find a pre-cast flue in a new property. The flue terminates on the roof using a small ridge vent. However, they can only accommodate Class 2 fires, namely gas or electric appliances.
Just because a property doesn‘t have a chimney doesn‘t mean that it can‘t have a fireplace. There are other options you can use:
- Electric fires. These don‘t have any waste gases, so they don‘t need a flue of any kind.
- Flueless Gas Fires contain a built–in catalytic converter to remove toxic fumes. However, the UK Building Regulations require certain restrictions: an external airbrick of a size to match the combustion of the appliance; the room needs an external opening window to adjust room temperature; must not be the only form of heating; the room must have a volume of more than 40m3. There are other restrictions, so check with your local Building Control Department.
- A Balanced Flue appliance has two concentric pipes, one to remove waste gases and one to introduce fresh air. The appliance installation must allow the pipes to go through a hole in an external wall.
- A Power Flue Gas Fire has a fan that helps to remove waste gases. They must be fitted to an external wall and have a power supply.
Why have a chimney flue liner?
Before we start, let‘s say what the difference is between a chimney and a flue. Strictly speaking, the flue refers to the inside duct that carries the smoke away. While, the chimney refers to the entire structure, both inside and out. However, in practice, many people disregard the difference and use the terms interchangeably. Furthermore, in case you didn’t know. The chimney stack is the piece that protrudes from the roof. The chimney pot is a tubular extension of the flue that sits on top of the stack. And, the chimney cowl (sometimes called a ‘terminal’) sits on the pot to ensure the inside of the flue remains dry. The cowl also helps prevent smoke from blowing back into the flue.
Waste gases, smoke and fumes from any fire, are toxic for us to breathe, and reduce a fire’s heating efficiency. So, we need a chimney to remove them from the fire. Oxygen laden air then takes its place in the fireplace and allows combustion. However, over time, the mortar between a chimney’s bricks chemically reacts with the acidic fumes. They become porous and start to crumble, allowing the acidic fumes to further damage the chimney mortar.
So, we need some way to preserve the chimney and prevent the fumes from damaging the mortar. A chimney flue liner does the job well. And, when lining a chimney, it prevents the toxic fumes from seeping into the house.
What does a flue liner do?
The flue lining has a few different functions. But, each one is essential to the proper operation of the heating appliance or fire.
- The heat should remain in the chimney to ensure the hot air draws the smoke up the flue and away.
- Many flue liners come with insulation to prevent excess heat from seeping into the building‘s structure.
- Modern heating appliances use gas, oil, or solid fuel. Each appliance needs a flue with the correct cross–sectional area, to ensure there‘s enough ventilation for the waste gas to escape. Thus, allowing fresh air to take its place. Using the wrong size liner limits the airflow causing a build-up of toxic gases. You should also use a chimney lining for an open fire, as this produces waste gases too.
- Flue gases contain acidic fumes such as sulphur dioxide, that combine with water from rain or condensation, to form strong acids. Over time, this corrodes the inside of the chimney flue and destroys the brick and mortar. Not only does this reduce your building‘s lifespan, but it also roughens the inner surface, causing the flue gases to slow down by friction. A flue liner protects the chimney structure from damage and ensures the waste gases don‘t lose velocity.
Due to changes in the UK Building Regulations, houses built after 1965 generally had clay flue liners installed. However, this material might not be the best for modern appliances and fuels. So, get expert advice before deciding whether you need a liner or not.
Not a DIY project
Fitting a chimney liner isn’t suitable for an amateur’s DIY project. Highly skilled flue installers need to know how to work with all types of chimney linings, connect the flue liner to a stovepipe, or install a fireplace liner. A person’s health and life might depend on correctly installing a chimney lining. This is why local authorities regulate fitting a flue liner using the Building Regulations. And, you can expect to pay a premium for expert labour costs.
So, to summarise: a flue liner protects the chimney from acidic corrosion; ensures there is enough updraught to provide a steady flow of oxygen-rich air; prevents a build-up of carbon monoxide; and allows the appliance to operate at maximum efficiency.
Chimney Lining Installation Process
Installing a chimney flue liner is a difficult job that requires compliance with many regulations. So, it‘s one you should leave to the professional. Most homes need a replacement flue or one newly installed at some time. And, it‘s essential to understand the installation process to calculate the budget. Without an expert‘s knowledge and experience, a poorly fitted flue might make your home liable to chimney fires and a general all–round fire hazard with poor ventilation.
1. Clean the chimney
Before having a flue installed, get the chimney cleaned by a professional HETAS approved chimney sweep, who also advises on your chimney’s condition. You can find one local to you by using the search tool on the HETAS website. You’ll then know if you need remedial work on the chimney before having a flue liner installation.
2. Inspect the job
You should use a HETAS approved flue installer to inspect your chimney, heating appliance, or fireplace if the appliance uses solid fuel. Otherwise, use a GasSafe Engineer if the appliance runs on gas. A professional installer inspects the job, measures the chimney cavity, and advises on flue type, size, and material.
3. Feeding the flue down the chimney
A flexible stainless steel flue liner is the easiest to fit. And, for this exercise, we can assume that this is the one suitable for your circumstances.
The installation engineer feeds the liner from the roof down through the chimney cavity until it reaches the “thimble”. Here is the place where the chimney opens out into the fireplace.
4. Fix the liner in place
Depending on the type of appliance or fireplace, you must fix the flue to be immovable and ensure that the waste gases don’t leak or transfer into the chimney void outside the liner. There are various fittings and attachments to fix this end to the appliance. The HETAS or GasSafe installer knows which ones to use.
5. Cut the liner to length
Once more on the roof, the installer connects the flue liner to the ‘top plate‘. The top plate protects the chimney cavity and prevents rainwater and snow from entering. Seal all gaps around the top plate using silicon sealant before cutting the liner to length.
6. Fitting a register plate
Alternatively, if the stove vents directly into the chimney. And, the chimney is sound and has no separate flue liner (it might have a Thermocrete™ flue or similar); the installer fits a register plate. The metal register plate seals the fireplace’s chimney cavity. But, it has a hole suitably sized for the stove pipe to go through. It ensures that the airflow in the chimney goes from the appliance to the chimney pot and prevents waste gases from escaping into the room.
7. Protect the flue from rain
Next, the fitter installs the rain cap, strengthening the liner and protecting it from rain, birds, and their nests.
8. Signing off the work
Finally, the HETAS or GaSSafe engineer approves the appliance’s connections and issues an appropriate certificate to the householder. For the purposes of the Building Regulations, they are competent persons and able to self-certify their work. They notify the local Building Control Department that they connected and tested the flue liner and appliance while complying with the Building Regulations.
Signs that your chimney requires lining
Just because you have a chimney does not necessarily mean that you need a liner. Whether you need one or not depends entirely on what type of chimney you have, its condition, and the type of heating appliance.
For example, if you have a gas fire that doesn’t produce much heat, the chimney won’t be damaged and won’t need protection. But, if you have a coal or wood–burning stove, the fuel produces high-temperature acidic gases, soot, and tarry deposits. These waste products damage and corrode masonry surfaces.
It is complicated to identify problems with a damaged chimney or flue liner. But, there are certain things you can look out for:
- Can you smell soot in upstairs rooms that join onto the chimney? If so, it means that the fumes are seeping through crumbling mortar or cracks in the masonry.
- Look up inside the chimney. If you can see cracks, then the chimney needs lining and might need strengthening.
- Can you see or hear debris falling down the chimney or flue? If so, the inside of the chimney might be in poor condition.
- Is the flue liner nearing the end of its lifespan? Stainless steel flue liners typically last between 15 and 30 years depending on the steel grade; Clay and pumice last about 50 years.
Probably, the best way to ensure you keep on top of this is to have the chimney regularly swept by a HETAS registered chimney sweep. They give you a certificate to prove the chimney is clean. And, perhaps more importantly, point out any problems with the chimney and liner.
UK Building Regulation & Planning Permission
Installing a flue liner usually comes under the category of a ‘permitted development’. Therefore, it doesn’t need Planning Permission as long as the installation complies with certain restrictions. Check with your local Planning Department for the restrictions in your area.
For work to a chimney or flue liner, you need to take into account fire safety, general safety and ventilation. Furthermore, for any work on a solid-fuel appliance and flue, you need a HETAS registered installer. Whereas, for a gas appliance and flue, you need one registered with GaasSafe.
The appropriate engineer installs the appliance, fits and connects the appropriate flue liner according to the manufacturer’s instructions. All work must comply with the UK Building Regulations. The manufacture of the liner and appliance and their fitting instructions already comply with various British Standards and the Building Regulations. But, you also need someone qualified to do the work, and registered with the UK Government as a competent person to comply with the flue liner regulations.
On completion of the job, the registered installer will self certify the work, issue a certificate and notify the local Building Control Office of the installation. If the work is for a rental or commercial property, you must, by law, safely keep the certificate. If the property is a private dwelling, you don‘t need to keep the certificate. But, it‘s a good idea to ask for one and keep it safe. This is because your home insurance company might require proof that a competent person did the work in case of a house fire or similar.
Typically, a HETAS installation and certificate costs between £120 and £300.
Chimney Liner FAQ
Can you fit a flue liner yourself?
The simple answer is no. Not only can the installation itself be dangerous for an amateur (crawling around on a roof is dangerous at the best of times). But, if you install it incorrectly and exhaust fumes leak into the house, people can become seriously ill or die. Also, an incorrect installation might be a fire hazard too.
Only a qualified person, registered as a ‘competent person‘ should work on chimneys, install flue liners and connect heating appliances.
Even though the installation procedure sounds very straightforward, only a trained person can inspect the chimney, determine if anything needs repair, and install the appliance correctly. So, leave it to the expert.
Do you really need a chimney liner?
Suppose you intend installing a wood–burning stove, gas fire or open fire in a new build property. The installation must comply with Document J of the Building Regulations. If you have an older property, you might or might not need a liner, depending on the condition of the existing chimney. Only a HETAS engineer can determine if the chimney is satisfactory or if you need a liner.
Are unlined chimneys safe?
This question depends on the appliance you intend using, its fuel and the condition of the chimney. Consult a registered HETAS (solid fuel) or GasSafe (gas fuel) engineer to determine whether you need a liner. However, most experts recommend a flue liner because they are safer than an unlined chimney.
Can chimney liners catch fire?
Yes. However, the severity of the fire depends on a few points.
You need to maintain a hot chimney to help expel waste gases from the appliance. But, if a properly installed liner has non-flammable insulation, the heat should be confined to the liner. Thus, preventing tar products condensing onto the liner wall. And, the subsequent adhesion of soot, which are the leading causes of chimney fires.
So, to prevent chimney fires:
- Make sure a HETAS registered chimney sweep cleans the flue regularly to remove soot and condensate.
- Ensure the registered installer fitted the correct liner, with insulation if appropriate. This keeps the flue hot and prevents condensation.
- Only use HETAS approved fuels, that don‘t produce excessive soot and tar.
Do I need to line my chimney for a Woodburner?
If you intend to install a Woodburner, the law states that you must install a flue liner complying with Document J of the Building Regulations.
Can you join a flexible flue liner?
Yes. Although not ideal, you can buy joints to connect two lengths of the flexible flue liner. Generally, all flue liners must be one continuous length. However, if the chimney height exceeds the maximum liner length, you can join other flexible liners with purpose–made connectors. First, push–fit both liners together into either side of the connector. Then, use self–tapping stainless steel screws to hold the liners in place.
How do you size a chimney liner?
The best way to size a chimney liner is to measure the exhaust outlet of the appliance. As a rule of thumb, the liner must not have an area smaller than the exhaust outlet. And, must not have an area larger than three times the exhaust outlet.
In practice, the HETAS installer chooses the correct sized liner depending on these and other factors.
What grade flue liner do I need?
The grade depends on the fuel you intend to burn.
Generally, there are two grades of stainless steel used for flexible liners.
- 316 grade is the cheaper of the two. And, should be used for burning seasoned wood only.
- 904 grade is the more expensive of the two. Use this grade if you intend burning coal or unseasoned wood.
Get Installation Quotes
If you intend installing a new heating appliance in your fireplace, or if your existing chimney is unsafe, its time to fit a flue liner. But, don‘t even consider doing it yourself.
Installing a flue liner must be done by a registered HETAS or GasSafe engineer (depending on the fuel) to comply with the UK Building Regulations.
Suppose you are serious about having the work done. And you‘re not sure of the cost of lining a chimney, complete the form on this page. Then, you‘ll receive 3 or 4 quotes from registered installation engineers local to you.