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GTD installations Ltd
HETAS registered installer since 2012

Crunchy soof removed from a chimney
Tar blocing a flexble liner

Does my chimney have creosote or tar build-up? 

19th March 2024

Creosote, a mix of tar and soot, is a byproduct of wood combustion. It's created when wood burns and smoke moves up the chimney and condensation from the rising heat sticks the residue to the inside of the chimney.

Creosote is a highly flammable compound and is very damaging if left to sit in your chimney or stainless steel liner over the summer months.


There are 3 stages to creosote and tar build up. 


  • Stage 1 - Appears as a light, brittle, dust-like coating. It can be removable by sweeping with standard chimney brushes. 


  • Stage 2 - Appears to be a lot thicker and contains flakes of hardened tar. Such a build-up may require specialist brushes or a chemical treatment to remove the build-up. 


  • Stage 3 - Appears as a thick, hard tar layer, coating the inside of the liner. As creosote and tar continue to be deposited, multiple coats may form. This kind of build-up is highly flammable and requires liner removal to avoid a chimney fire and installation of new. A blocked liner or chimney will cause incomplete combustion and can release harmful gases back into your room.

Avoid a chimney fire

An annual chimney sweep is a sure-fire way to identify and remove any soot, tar and creosote before it becomes a serious issue. The best time to do this is when you have stopped using your fire or stove for the summer. That way the sulphur and nitrogen from the soot doesn't have long to mix with the water in the air and form sulphuric acid and nitric acid and start to eat away at your liner. Book a chimney sweep online.


Poor Fuel Quality


Depending on the quality of the coal that you buy, you might have other dangerous chemicals lurking in your chimney. Burning wood is cleaner and creates less air pollution than coal.
Always buy from a reputable supplier and look for the Woodsure logo when buying wood.