Is my flue suitable for a woodburning or multi-fuel stove?

Is my flue suitable for a woodburning or multi-fuel stove?

When installing a wood burning or multi-fuel stove, it is important to ensure that your chimney meets the standards set out by relevant building regulations (Document J). These building regulations determine the size and position your chimney and flue should be so your fire can burn as efficiently as possible and you reduce the risk of fire hazards or burns.

Tests are conducted on flues and appliances to ensure they are safe and ready for use (i.e. not too big or too small and free from obstruction). The building regulations explain in detail how these tests work and why they are performed, mainly to ensure that smoke is not leaking into the house and there are no obstructions preventing a good draw. The following provides a brief summary of flue test procedures:


 Coring ball test:

A heavy ball is lowered from the top of the flue to the bottom on a rope. If an obstruction prevents the ball from moving easily down the flue, the object is removed and the test is repeated.

While this test removes obstructions, it will also determine the size of an existing flue. This can help determine which stove you should buy. A flue that is too wide can be decreased by inserting a flue liner.


Smoke test:

Building regulations stipulate that an existing chimney must be swept before a smoke test can be carried out. During the smoke test, all doors and windows in the room should be closed. The flue is heated and then pellets are lit in the stove. Once lit, the stove door is closed and smoke should be seen to leave freely from the top of the flue. The flue is then temporarily sealed at the top to ensure no harmful emissions leak into the house when smoke is held in the flue.

This test helps to establish if there are any faults in the flue and, therefore, whether or not it is safe to use the stove without causing harm to those in the house.

 The relevant building regulations (Document J) can be found by contacting your local authorities or visiting the government’s planning portal website. Information on how to make sure your chimney and flue comply with these regulations can also be given by a qualified heating engineer. A reliable stove provider will be able to give you more information on how to make sure your stove is safely installed and officially approved.


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Gr8Fires 2020-03-31 14:00:18
@ kevin Henchman Hi Kevin The first consideration would be whether the existing flue is of the
correct grade for use with a woodburner (if it's from a previous gas fire, it won't be). Yes, an
installer will normally do the full job. Thanks, Gr8Fires

kevin Henchman 2020-03-24 08:31:17
I have had a 4" flue fitted to my chimney. What log burner stoves can I have fitted? Do the
installers fit the plate above the stove and the chimney cowl and flue collar?

Gr8Fires 2019-11-05 15:59:36
@ Neil Gibbs Hi Neil, No, you'll need a new flue. That grade of metal won't hold up to the heat
from a woodburner. Thanks, Gr8Fires

Neil Gibbs 2019-11-05 15:24:15
Hi, I am just having a gas fire and back boiler taken out and a combi in. Can I use the existing
flue for a log burner or do I need a new one. 1973 bungalow.

Gr8Fires 2018-07-04 15:09:53
@ Paul Sheffield Hi Paul Here are some tips:

PAUL sheffeild 2018-05-20 21:23:49
Hi what’s best way to measure how long a flue I need thanks paul

John Hampshire 2017-09-18 21:24:42
Thanks GR8Fires curiosity solved .

Gr8Fires 2017-09-18 09:12:48
@ John Hampshire Hi John, It sounds like you're describing a concrete gas flue block, in which
case it would not be suitable for use with a stove. Thanks, Gr8Fires

John Hampshire 2017-09-16 17:50:15
Hi just wondering I live in a bungalow built in 1986 it originally had a baxi gas boiler but now
houses a Electrical fire. The flue is a concrete type not round but hard to explain let's say a big
letter box shape is this ok for a log burner without a liner. Cheers

Gr8Fires 2017-08-09 14:35:50
@ Julie Thurlow Hi Julie It's not essential as long as the chimney is sound (you would need to do a
test to check for leaks). There are benefits of a liner in terms of performance and, if you have an
exposed property, to improve the draw to stop smoke coming back down the chimney. Further reading on
all that here: Thanks, Gr8Fires

julie thurlow 2017-08-09 14:10:25
HI I wonder if you can help, I am just looking into getting a multifuel stove fitted, I have
followed you for while and read your very useful guides. Can you advise I have been told that
dependant on the smoke test, I may not have to have a liner fitted? is this correct?

Gr8Fires 2015-01-26 12:12:36
@Lyn Gilbert Hi Lyn, It's very unlikely that the gas flue would be reusable because they are not
made to withstand the same temperatures as woodburner flues. Thanks.

margaret 2014-12-28 12:27:12
Hello, I have a flue fitted for a gas fire which has not been used for some time. Will this flue be
suitable for a multi-fuel stove? Thanks, Margaret

Lyn Gilbert 2014-11-02 14:42:32
Hi we already have a gas fire and a flue fitted in a false chimmy breast fitted by the gas board
will we still be able to have a log burner thanks Lyn

Gr8Fires 2014-09-08 11:15:20
Hi Angela, You could get a HETAS engineer out to double-check, but the chances are probably not.
The oil flue is probably single skin in construction and not suitable for a wood-burning stove.
Thanks, Gr8Fires

angela marshall 2014-09-07 08:07:18
Hi, we are planning to remove a very old oil fired rayburn from our kitchen and replace with a
multifuel stove. Will the existing flue be ok as it is and ready to connect the stove to for
immediate use or will it need any modification. Thanks Angela 2014-01-16 14:58:10
Hi Philippe, You might like to try our Stove Installation Cost Calculator, which will help you work
it all out: Thanks,

Philippe Seiler 2014-01-11 10:25:41
I am looking for wood burning oven for about 6 kw, How much will i have to spent, I have an chimney
, but have not used for 10 years, what do you think I have to spent also I need an flue, etc I am
looking of total under 1000 Pound, stove,flue etc, installation 2013-12-12 17:07:12
Hi Bry, It's very difficult to say with any conviction without a proper inspection. It might be
worth getting a HETAS-approved installer out to have a look at the chimney for you. There's a bit
more information here: Thanks, Gr8Fires

Bry Wilson 2013-12-10 10:02:33
Our chimney was fitted with a full length pot flue/liner after our old Parkray fire more a less
burnt away like a furnace. The Parkray was taken out some time ago when we had a new central heating
system installed and a real flame gas fire was put in its place and this did not require a SS flue
liner fitting. Would this be the case with a stove??

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