Creosote and Wood-Burning Stoves

Creosote and Wood-Burning Stoves

What is Creosote? and how can it affect my Wood Burning Stove?

Creosote is a fairly unhelpful by-product created during the burning of wood. It is a flammable and corrosive substance.

It builds up in the chimney, which is obviously somewhere that you don’t want anything that is likely to set on fire or corrode.

Creosote is created from the gases that are produced when wood is burned. In the case of a wood-burning stove, these are called flue gases. The flue gases are predominantly made up of steam and vaporised carbon.

When these gases solidify they become creosote, and that causes problems when it happens in your chimney.

What causes creosote?

There are several causes that can contribute to creosote build-up in your chimney. Perhaps the main problem is a chimney with a poor draught. If the gases are not drawn up the chimney sufficiently, it is more likely that the flue gas will cool and solidify in the chimney.

One factor that causes this sort of poor draw is a restricted air supply, both down the chimney and in the room where the stove is situated. This ultimately becomes self-fulfilling because creosote itself can restrict air supply.

Using green, unseasoned wood is another cause of creosote build-up. Seasoned dried wood burns more efficiently and hotter. If the wood is unseasoned, the fire isn’t as powerful and the flue is cooler. The gases cool more quickly and will solidify in the chimney.

What are the dangers of creosote? 

The main danger, and worst case scenario, of creosote build-up is chimney fire. The flammable deposits can be set alight by a spark or extreme heat from the fire below. It goes without saying that the consequences can be devastating.

On a less life-threatening level, creosote build-up can also cause your wood-burning or multi-fuel stove to run less efficiently and, therefore, cost you more money.

How to avoid creosote build-up

Creosote build-up is nowhere near as much of a problem with modern stoves as it once was. Most stoves are fitted with a baffle and secondary air system, both of which are technologies created to maximise the amount of gas that is burned in the firebox and minimise the amount of flue gases that are produced.

Using dry, seasoned wood is another way of avoiding creosote build-up. This is also a way to increase the intensity of the fire in the stove and ensure that more gases are burnt.

It’s also important that you regularly get your chimney swept. This removes any creosote that has built-up and reduces the risk of a chimney fire.

To ensure that the job is done properly, call upon the services of a Hetas-approved chimney sweep. It’s also worth checking out the National Association of Chimney Sweeps – itself a Hetas-approved training centre – which does excellent work as a professional trade association to promote the highest standards of chimney sweeping, inspection and maintenance.


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Gr8Fires 2019-02-06 16:42:08
@ Ian macpherson Hi Ian Some smoke could come into the room during refuelling, but also through
the air vents if there's a ventilation issue (i.e the draw into the room is greater than the draw up
the chimney). Depending on whether you're working in Farenheit or Celsius, you might be operating
the stove too cold. You should be aiming for around 250C on the stove pipe. Operating it too cold
could result in excess smoke being created and a weakened draw up the chimney. Thanks, Gr8Fires

Ian macpherson 2019-02-02 19:56:59
Thanks for your response. We also get the issue when refuelling. We've had the stove on foe 2-3
hours without an issue. The temperature gauge is at 300. When the tar appears and we turn up the
air intake to max it stops. Burning that hot makes the room unbearable. Should fumes/tar be able to
escape from inside the stove to outside?

Gr8Fires 2019-01-28 11:58:45
@ Ian Macpherson Hi Ian Theoretically, it could happen if smoke was escaping (for instance, during
the lighting process) and then condensing on the cold flue. But we'd double-check there are no
leaks because it sounds like this has happened pretty quickly. Thanks, Gr8Fires

Ian Macpherson 2019-01-27 20:55:47
If tar is formed within the stove could it escape onto the outside of the stove? I've just had a
stove installed, and after time tar comes out around the collar. The wood I've used shows 10% on my

June Barrow 2018-11-26 20:46:17
Hi We obviously bought some bad wood

Margaret Priddey 2018-08-18 19:00:39
Thank you for all the advice. I don't have a log burner yet!! But you have provided me with some
very usefull information it is very much appreciated.

Gr8Fires 2017-11-29 08:54:32
@ Stuart York Hi Stuart It should be fine, as long as the pallets haven't been treated, which could
damage the stove. Thanks, Gr8Fires

Stuart York 2017-11-29 07:04:31
I found this article very useful and a great guide to using my log burner. The addition of the links
is also very good. I burn quite a lot of chopped up pallet wood which is basically well seasoned
soft wood. Will this have any adverse effect on my stove or flue?

Gr8Fires 2016-09-20 11:22:06
@ John Locke Hi John, We don't have any suitable thermometers at present, but we're looking into
the possibility of sourcing something that would be appropriate for you. We'll send you an email if
we find something. With regard to getting the chimney swept, there is still the possibility of
twigs and other items having fallen down the chimney but it will probably be okay to hang fire for
now. Maybe get a sweep round at the end of the current burning season. Thanks, Gr8Fires

john locke 2016-09-18 10:16:05
Hi i have an inset multi fuel burner is there a thermometer i can use on this type of burner as i
see your ones are for the flue pipe?. We only had the stove fitted in April this year so have not
used it much only a few occasions will we still have to have the chimney swept this year?

Gr8Fires 2015-09-21 20:44:25
@vivienne egan. Hi Vivienne, Yes, you should still get the chimney swept at least once a year.

vivienne egan 2015-09-18 12:25:25
Hi, I use mostly maxibrite in my multi fuel stove. Do I still need to have the chimney swept
frequently? 2014-05-05 09:30:33
Hi Robert We definitely wouldn't recommend it. It's not likely to do you, your new neighbours or
your stove much good. Thanks, Gr8Fires

Robert Roe-Stacey 2014-05-04 06:59:27
The house that we are buying as old panel fencing which was probably originally treated with
something to stop it rotting. Can we burn this in a multi burner ?. Regards RRS