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Do I Need a Flue Liner for an Open Fireplace?

Do I Need a Flue Liner for an Open Fireplace?

Whether you’re renovating an old open fireplace, or building a new one, you may be wondering whether it’s necessary to use a flue liner with it. Keep reading and the Trade Price Flues team will tell you the answer…

Is it a legal requirement to use a flue liner with an open fireplace?

The first thing you may be wondering is where the law stands on the issue of using flue liners (or not) with open fireplaces.

The answer is fairly straightforward and will only vary depending on the age of your property.

If you live in a newly built home and you’re creating an open fireplace, you are legally obligated to use a chimney flue liner. This requirement is set out in Document J of the Building Regulations; this is a government document that lays out rules for the safe installation and usage of heating appliances, fireplaces, stoves and more.

If you live in an older house, then the rules are slightly different.

Should you be renovating an old open fireplace and bringing it back into use, then Document J states that:

‘Where it is proposed to bring a flue in an existing chimney back into use or to re-use a flue with a different type or rating of appliance, the flue and the chimney should be checked and, if necessary, altered to ensure that they satisfy the requirements for the proposed use’.

In other words, it’s possible to bring an open fireplace back into use without a chimney liner, provided that it is still able to handle the job of venting away the smoke and combustibles from an open fire.

If you want to do this, then it is highly recommended that you have a CCTV inspection of your chimney carried out by a chimney professional. This can generally be done as part of a level 2 chimney inspection and sweep.

A level 2 chimney inspection and sweep will involve a smoke leakage test, a full pressure test, an exterior inspection of the chimney, and a CCTV inspection of the interior of the chimney.

The majority of chimney sweeps who carry out level 2 inspections will be able to provide you with a written report on the state of the chimney - as well as the video footage of the inside of the chimney.

This evidence can be used in the event a local building inspector takes issue with your open fireplace.

Tip - whilst it is technically possible to use an older open fireplace without a chimney liner (provided it is fit for purpose as per Document J of the Building Regulations), we would strongly recommend using a flexible chimney flue liner anyway. 

Why you should use a chimney liner with an open fireplace

As we mentioned above, we strongly recommend that you use a chimney liner with an open fireplace - even if you aren’t legally obligated to use one.


Because, there are a whole host of benefits that come from using a chimney liner with an open fireplace.


First and foremost, using a flue liner with an open fireplace will improve the safety of your chimney.

As you use an open fireplace, you’ll find that over time your chimney begins to accumulate combustible materials such as creosote and soot.

If you allow your chimney to build up an excessive amount of creosote, then it can lead to blockages, which in turn can lead to a chimney fire.

Chimney flue liners offer protection against this happening, as they very effectively funnel combustible materials up and out of your chimney - preventing any dangerous build up from occurring.


Related to the point above concerning safety, the use of a quality flue liner will also protect your chimney.

This is especially important if you have an older class 1 chimney that’s unlined (i.e. simply bricks and mortar), or an older clay lined chimney.

Combustion by-products such as creosote are caustic, and as such can cause damage to, and corrode, both bricks and mortar. Over time, continued exposure to flue gases can cause mortar joints to fail - leading to leaks from your chimney.

These leaks will not only impair the function of your chimney, but can lead to smoke leaking into your living space - or that of your next door neighbour!

By using a chimney flue liner, you will be preventing flue gases and caustic combustible by-products from coming into contact with the chimney itself, thereby prolonging the life of your chimney considerably.


The use of flexible metal flue liners has the benefit of keeping your chimney clean and free of combustible materials and condensation - both of which can lead to problems.

In particular, a metal flue liner can help prevent the build up of condensation as it will keep the flue gases warm as they travel up and out your chimney. Metal flue liners also expand and contract as they heat up and cool down - which can prevent creosote build up.


Adding a flue liner to your chimney will make your fireplace far more efficient.

The key to creating a well-functioning fireplace is to ensure that you have sufficient ‘draw’ through the fireplace and up the chimney. When burning, your open fireplace should naturally ‘pull in’ air from the room it is situated in, with the resulting smoke and combustibles then being naturally drawn up the chimney.

However, in order to achieve a proper draw, it’s vital that your chimney is sufficiently ventilated.

Unfortunately, many older chimneys are NOT well ventilated, meaning they are cold. This can result in the smoke and combustibles from the fire cooling down too much before they reach the top of the chimney.

Not only can this result in a poor draw, and thus a poorly burning fire, but in the worst cases can result in the draw almost failing completely with the smoke and combustibles drifting back down the chimney and out into your living room.

That’s hardly ideal!

High-quality chimney flue liners remedy this situation by creating a well-ventilated passage for the smoke and combustibles from your fire to travel up.

The result is that your fire will have a much better draw.

This will not only mean your fires burn better and be more fuel efficient, but they will also be easier to light and start, will be less smokey, and are less likely to gutter and suffer from issues like chimney downdraft.

What type of chimney flue liner do I need for an open fireplace?

If we’ve convinced you that you need to get a flue liner for your open fireplace, you may now be wondering what type of liner is best.

When it comes to selecting the best flue liner for your fireplace’s chimney, there are few things to consider:

> Flue liner material.

> Flue liner diameter.

> Flue liner length.

What material or grade flue liner for an open fireplace?

First of all, you need to make sure you select a flue liner which is made of the correct material.

904 grade stainless steel

For an open fireplace which is burning coal, you’ll require a flue liner which is made from 904 grade steel.

As it incorporates molybdenum, 904 grade stainless steel is highly resistant to corrosion. Thanks to its high alloying content, it is also resistant to stress corrosion cracking.

This means that a liner made from 904 grade steel will provide a long-service life and will be able to withstand the caustic, combustible by-products given off by a coal fire.

The 904 grade flue liners that we sell here at Trade Price Flues are manufactured with two treated skins of 904 grade stainless steel, making them extremely durable. They are ideal for those of you who do not wish to replace a chimney liner for as long a period as possible.

We’ve manufactured our 904 grade flue liners to such a high standard that we are proud to offer a 30-year warranty on them.

316 grade stainless steel

316 grade stainless steel is a lighter form of steel that should only be used with open fireplaces that are burning seasoned wood.

Like 904 grade stainless steel, 316 grade steel contains molybdenum making it resistant to corrosion and able to provide a long-service life.

We believe that the 316 grade flue liners that we sell here at Trade Price Flues are of such robust construction and quality, that we offer a 15-year, no quibble warranty on every one.

Tip - if you think that you’ll be burning both seasoned firewood and coal on your open fireplace, then we’d recommend erring on the side of caution and buying a 904 grade flue liner.

What diameter flue liner for an open fireplace?

For an open fireplace you should use a chimney flue liner that is at least 200mm (eight inches) in diameter. This is as per the Building Regulations.

Here at Trade Price Flues we stock both individual flue liners that are suitable for open fireplaces, as well as open fireplace flue liner fitting kits which not only include the flue liner, but also a pot hanger rain cap (which is used to ‘hang’ the liner from your chimney pot).

What length flue liner for an open fireplace?

When it comes to selecting the correct length flue liner for your open fireplace, this is very much dependent on the height of your chimney.

The installation of a flexible flue liner usually involves the liner being drawn down the chimney by rope from the top. An individual standing on the roof will then affix the top of the liner to the top of the chimney. In the majority of cases, the liner will be fixed to the top of the chimney using a pot hanger.

Because of this installation process, it’s vital that you buy a flue liner which is sufficiently long enough. We recommend that you err on the side of caution and buy a liner which is longer than you need.

Flue liners can always be cut down to size. Whereas, it is against the Building Regulations to stick two separate liners together.

Here at Trade Price Flues, we make it easy to select the exact length of your chimney flue liner. Simply go to your chosen liner and on the right hand side in the product description, you’ll find a drop down menu where you can select how many metres of liner you require.

In summary - as long as you pay attention to the diameter, length and material/grade of a flue liner, you’ll end up with one that is perfect for your open fireplace.

Note - if you are not sure which flue liner is best for your individual circumstances, feel free to contact our friendly expert team who will be happy to help. You can reach them on 0161 7300 969 or via our contact form.

How to look after an open fireplace chimney flue liner

Once you’ve bought and installed a flue liner for the chimney of your open fireplace, it’s important that you maintain it - particularly if you want it to last a long time.

The most important thing you can do to prolong the life of your flue liner, is to have it swept on a regular basis. If you are regularly burning wood and/or coal in your fireplace, then it’s recommended that you have your flue liner inspected and swept on a quarterly basis (e.g. four times per year).

It’s important that the correct tools are used when sweeping a metal flue liner. Ball-topped polypropylene brushes of the right diameter should be used. Failure to use these kinds of brushes can result in damage to the liner.

We recommend that you always use the services of a qualified and experienced chimney sweep.

Guide - for more information on chimney sweeping and inspections, read our complete guide.

Best chimney liners for open fireplaces

If you’re looking for a chimney liner that’s suitable for an open fireplace that burns either seasoned wood or coal, then check out the flue liners and flue liner kits below.

8” 904/904 Super Flex Chimney Flue Liner

Shop Now - 8” 904/904 Super Flex Chimney Flue Liner

Designed and manufactured to be the highest quality chimney flue liner you can buy, the 8” 904/904 Super Flex liner from Trade Price Flues is a double skinned, 904 grade liner which is suitable for open fireplaces burning coal or seasoned firewood.

Manufactured here in the UK, we are so confident that our 8” 904/904 Super Flex flue liner is the best on the market that it comes with a 30-year no quibble guarantee.

Thanks to its strong yet flexible design, the 8” 904/904 Super Flex chimney flue liner is easy to install - even if your chimney isn’t perfectly vertical.

If you want to buy a chimney liner for your open fireplace that’s going to last a lifetime, then buy this one.

8” 904/904 Super Flex Chimney Flue Liner Basic Fitting Kit

Shop Now - 8” 904/904 Super Flex Chimney Flue Liner Basic Fitting Kit

If you’re looking for a flue liner for your open fireplace that also includes the essentials you need for installation, then choose our 8” 904/904 Super Flex Chimney Flue Liner Basic Fitting Kit.

In addition to the 8” 904/904 liner (which is detailed above), the kit also comes complete with a stove pipe to Super Flex adapter (if you are going to be using a wood-burning stove), as well as a Pot Hanger Rain Cap - which is essential for the correct installation of the flue liner.

It’s the job of the Pot Hanger Rain Cap to provide an ‘anchor’ at the top of your chimney. As its name suggests, the Pot Hanger Rain Cap attaches to the chimney pot, with the liner then suspended down the chimney from it.

Fireplace chimney gather

Shop Now - 8” Gather 230mm x 600mm

In addition to the flue liner itself (and components such as a pot hanger), you may also require a fireplace chimney gather.

Chimney gather hoods are used at the base of the chimney stack and, as their name suggests, help to ‘gather’ the smoke and combustibles from your fire and funnel them up into the chimney flue liner with minimal resistance.

In addition to this practical function, gathers can also play an aesthetic function, helping to tidy up and close up the base of the chimney stack into a neat funnel.

Here at Trade Price Flues we offer a range of different fireplace chimney gathers covering a range of different flue liner diameters and fireplace sizes and dimensions.

We manufacture our gathers from 316 grade steel, making them suitable for use with all types of open fireplaces. Our gathers are also designed to fit seamlessly with our Super Flex flue liners - making them easy to install for professionals and DIYers alike.

Essential open fireplace accessories

If you’re fitting your open fireplace with a new chimney flue liner, then it’s a good idea to make sure you have the other required essentials too.

Fire Angel Digital Carbon Monoxide Detector

Shop Now - Fire Angel Digital Carbon Monoxide Detector

A carbon monoxide detector is an absolutely essential fireplace accessory. In fact, under proposed new regulations, whenever a new fixed combustion appliance is installed (such as a fireplace), then a carbon monoxide alarm will be required by law.

Whilst these regulations have not yet come into law, we’d strongly recommend getting ahead of these changes by buying a CO2 alarm now.

The Fire Angel Digital Carbon Monoxide Detector is a high-quality detector that’s perfect for homes of all kinds. Thanks to its sealed lithium battery, it’ll function for at least 7 years. What’s more, it also includes a handy room thermometer function, so you can keep a track of how much heat your fireplace is emitting.

Wood Moisture Meter

Shop Now - Wood Moisture Meter

An important part of keeping your fire functioning well and preventing the build up of creosote in your chimney, is to make sure you are only burning properly seasoned firewood.

The best way to check that your wood is sufficiently seasoned is to use a wood moisture meter.

This particular wood moisture meter is easy to use and provides both a minimum and maximum moisture reading. The meter’s large LCD display makes it easy to see the reading in even low-light environments.

800W 15 Litre Ash Vacuum

Shop Now - 800W 15 Litre Ash Vacuum

Another important accessory to have at hand is an ash vacuum. An ash vacuum makes the job of cleaning ash from your open fireplace easier and cleaner.

Our 800W 15 Litre Ash Vacuum is designed to suck up cold ash from your fireplace, whilst simultaneously using its filter system to capture the finest ash particles, preventing them from circulating around your room.

This ash vacuum also features a flexible metal end cap and a 2.5 metre power lead.

Flue liners, accessories and more…

Whether you’re looking for a new flue liner for your open fireplace or you need to pick up some fireplace essentials, Trade Price Flues has got you covered.

With same day and next day delivery available and a huge range of items kept continually in stock, make Trade Price Flues your first and last stop for chimney flue liners, accessories and more.

Shop chimney flue liners at Trade Price Flues now

For more chimney and flue advice, read the Trade Price Flues blog

Why You Should Insulate Your Chimney Flue | What Sort of Air Vents Do I Need for My Stove or Fireplace? | How to Stop Birds Nesting In Your Chimney 

1st Aug 2022 Trade Price Flues

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