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What Size Flue Do I Need for a Wood Stove?

What Size Flue Do I Need for a Wood Stove?

If you’ve just bought a wood burning stove, then you’re probably wondering what size flue you’ll need to connect it to. There are a huge number of different flues with different sizes, grades and materials available. If you’re finding all that choice overwhelming, keep reading to find out what size flue you need for a wood stove.

Do I Need a Flue Liner?

Firstly, you might be wondering if you even need a flue liner at all. At Trade Price Flues our answer is a firm YES.

Flue liners are not mandatory, but any installer worth their salt will recommend that you use one. Using a flue liner has a number of benefits, such as improving the safety of your stove, being cleaner than not using a flue liner and improving the efficiency of your stove.

This last point is an important one. Nearly all wood burning stoves perform better with a flue liner. With a flue liner connected, you’ll experience fewer issues with lighting your fire and keeping it burning. A flue works under negative pressure, drawing the product of combustion from the stove and out the chimney.

(Pictured: The Lowry 5 stove).

Achieving a successful ‘chimney draw’ will depend on the following factors:

> The difference in air pressure between the appliance and the top of the chimney (this difference is created by the height of the chimney).

> The difference in temperature between the stove’s exhaust gas and the outside temperature.

> The quality of insulation along the length of the chimney.

> The route of the chimney (the straight and more vertical your chimney, the better).

A suitable flue liner will help you achieve all of these factors, significantly improving the draw and performance of your stove.

There is an additional point to consider. You should make sure you have a suitable chimney in place. It’s a very obvious point, but a flue liner cannot be used without a chimney.

Will I Need to Re-line my Chimney?

As well as buying a flue liner for your new wood burning stove, it’s also important to check the condition of your chimney.

If your property was built after 1964, then the chimney will have a concrete or clay inner liner. If this is the case with your property, then you should have your chimney tested for any blockages or leakages. 

If your property was built before 1964 then the inside of the chimney will usually just be exposed brickwork. It’s not a legal requirement to have it lined (unless it is leaking), but there are many benefits in doing so, such as increased draw and reduced risk of fire.

Can I Fit A Flue Liner To My Wood Stove Myself?

Yes, however if you’re fitting a new stove and a new flue liner this can be quite a big job. The installation of the new flue liner will usually require scaffolding and working at height. We would recommend using a HETAS qualified instructor. Not only are they trained and experienced professionals, but they are able to sign off their work and provide you with a certificate.

If you complete the work yourself you will need to inform the Building Control department of your local authority and arrange for them to inspect your work.

Any work done to chimneys and flues is covered by UK Building Regulations in conjunction with the relevant European and British Standards. So, any work completed has to meet these standards. These Regulations and Standards dictate the minimum criteria which it is necessary to apply if the chimney and/or flue are to function safely and correctly. These Regulations are set out in The Building Regulations 2010, Combustion appliances and fuel storage systems, Approved Document J.

Do I Need Planning Permission?

You don’t normally need Planning Permission to install a new stove and flue liner. However, there are two general exceptions; If your property is a listed building, you may need to seek special permission. Likewise, if you intend your new flue pipe work to run up the outside of your property, you will need to contact your local planning department.

What Size Flues Are Available?

Before considering what size flue you’ll need for your wood burning stove, it’s important to understand a little more about what sizes are available.

Flue liner sizes are typically given in inches. This number refers to the internal diameter of the flue liner (or in other words, the size of the hole rather than the entire size of the liner). This is the part of the flue liner through which combustibles and smoke will travel.

(Pictured: the 6” 904/904 Super Flex Chimney Flue Liner).

So, onto the sizes themselves…

You will find various sized flue liners available including 5 inch, 6 inch, 7 inch, 8 inch and 9 inch. However, the vast majority of stove installations involve 5 inch or 6 inch flue liners.

Usually, you will want to use a size of flue liner that matches the size of the stove pipe coming out of your stove. However, we’ll go into more detail about flue liner sizing later in this article.

Understanding Different Grades Of Flue Liner

As well as making sure you buy the correct size flue liner for your stove, you will also need to ensure you buy the correct gradeflue liner.

What grade flue liner you require will depend on what fuel you’ll be burning and how you’ll be using your stove.

There are two main grades of flue liner on the market:

> 316 grade. This is generally the cheaper grade flue liner, however it’s only suitable if you’ll be burning seasoned wood.

> 904 grade. This is the more expensive, but more durable grade flue liner. This is suitable for stoves that’ll be using fuels that burn at a higher temperature than seasoned wood.

Picking The Right Size Flue For Your Wood Stove

As we’ve already mentioned, you will generally want a flue liner that matches the corresponding outlet on your stove. For example, if your stove’s stove pipe has a diameter of 6 inches, then you should buy a 6 inch flue liner.

But, there are a few other things you need to know.

Most solid fuel appliances in the UK have either a 5 inch (127mm) or 6 inch (152mm) flue outlet on either the top or the rear of the stove. You will normally connect a stove pipe to this outlet which runs up into your chimney.

The stove pipe is the visible part of your flue system that connects your stove to your flue, so you will want to make sure you buy a stove pipe that you like the look of. It’ll be continually visible! At Trade Price Flues we have a great range of stove pipes available in matt black vitreous enamel or stainless steel.

(Pictured: 5” Stainless Steel Stove Flue Pipe With Door L500).

Make sure you make a note of the diameter of your stove pipe so that you can select the correct flue liner.

Selecting Your Flue Liner

With your stove pipe selected, it’s time to select your flue liner.

Building Regulations in the UK stipulate that the minimum flue liner you may use is 6 inches.

However, you may use a 5 inch flue liner in the following instance:

> You have a DEFRA approved stove and the manufacturer states that your stove is compatible with a 5 inch flue liner.

It’s really important that you use the recommended size flue liner for your stove. Never use a smaller flue liner than required, as this can create a serious safety hazard. Your stove manual will generally provide you with the manufacturer’s recommendation for flue liner size.

If you find that your stove pipe is a different diameter to your flue liner (for example, if your stove pipe is 5 inches in diameter and your flue liner is 6 inches) you should buy an adapter.

You should also ensure that the flue liner you select is certified to BS EN1856-2. You’ll find this information in the specifications of the liner.

Another important point to remember is the lengthof your flue liner.

You need to make sure that the flue liner you buy is long enough to reach from the top to the bottom of your chimney. Sticking two separate flue liners together is not only against Building Regulations, but dangerous too. If in doubt, err on the side of caution and order one that’s too long rather than too short. It can always be cut to fit.

If you’re unsure as to how long your chimney is (and as a result, what length flue liner you need) then a Chimney Sweep should be able to measure your chimney length for you. You can find your local Chimney Sweep via the National Association of Chimney Sweep’s national register.

After You’ve Connected Your Flue Liner To Your Wood Stove

Once you’ve finished connecting your flue liner to your wood burning stove, there is a final task to complete.

(Pictured: 5”-6” 316 Super Flex Chimney Flue Liner Full Fitting Kit).

Whenever a flue liner is installed or renovated it is a mandatory requirement that a Check List and Notice Plate be completed. The purpose of the Check List is to ensure that the installation has been carried out correctly. The Notice Plate acts as a record of the installation, the appliance and fuels that can be used with the chimney.

The Notice Plate must be located in a convenient and accessible location, such as next to a utility meter. Completion of the data on the Notice Plate can be done by the heating appliance installer, builder, chimney supplier/installer or other competent person.

Once those tasks have been completed you’re ready to start enjoying your wood burning stove!

If you’re looking for a flue liner for your wood stove, then explore Trade Price Flue’s range of flue liner kits which provide everything you need in one package.

If you’d like some free advice about flue liners then contact us or use our live chat (you’ll find it on the bottom right of this screen) and we’ll be happy to provide you with our expert advice.

More buying guides and advice you might like…

How do You Fit a Chimney Liner? | Do I Need to Insulate My Chimney Liner? | How to Connect Your Flue Liner to Your Stove Pipe

4th Mar 2021 Trade Price Flues

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