How often should you sweep your chimney?

UK sweeping bodies, fire services and the government do not all give the same interval. This guide shows what each says, side by side. NACS says the right frequency depends on the fuel, the appliance, how long it is used, the moisture content of the wood and the type of chimney, and that its sweeps advise on this at each visit ². This is general information, not advice.

What each body says

NACS lists its figures “for guidance purposes only” ². The ICS calls its list “a general homeowner guide” ⁴.

Fuel	HETAS 1	NACS 2	ICS 4	Devon & Somerset FRS 7
Wood	At least twice a year	Quarterly when in use	Twice a year when used regularly	Every three months
Smokeless fuel	At least once a year	At least once a year	At least once a year	At least once a year
Bituminous coal	Not stated	Not stated	Twice a year	At least twice a year
Oil	Not stated	Once a year	At least once a year (flues)	Once a year
Gas	Not stated	Once a year	At least once a year (flues)	Once a year

Other points:

• A second NACS page lists bituminous coal as “quarterly when in use” ³.
• Dorset & Wiltshire Fire and Rescue Service says chimneys should be swept twice a year by an approved sweep. It adds “depending on what fuel you burn” and does not split this by fuel ⁸. The page is dated 1 September 2025 ⁸.
• HETAS gives no figure for coal, oil or gas ¹.
• Defra does not split by fuel. Its “Burn better” page says to get your chimney swept at least once a year ¹². Its 2023 leaflet says to get it swept regularly, “up to twice a year” ¹³.
• The Guild of Master Chimney Sweeps pages I read give no interval by fuel. A 2019 Guild article says the government “has formally stated that flues should be swept twice a year”, and that even gas and oil flues need sweeping. It does not name the document ⁶.
• For thatched properties, the ICS says twice a year, “or as advised by your insurer” ⁴.

When to sweep

HETAS says to sweep just before the heating season, and after a long period without use. If you sweep twice, do the second after the peak of the heating season ¹. The ICS lists these triggers: before the main burning season, after regular use, if smoke is not drawing correctly, and when a property has not been used for a while ⁵.

Sweep certificates and insurance

NACS says to ensure you receive a NACS Certificate of Chimney Sweeping. It says its sweeps issue one for every chimney cleaned ³. The ICS says its members issue a sweeping certificate for your records ⁴. Devon & Somerset Fire & Rescue Service says to use a professional, accredited sweep and ask for a certificate after the work ⁷.

NACS members must hold valid insurance for chimney sweeping ³. None of the pages I read says your home insurer requires a certificate. Check your policy. For thatched homes, see the ICS advice above ⁴.

Wet wood and Ready to Burn

In England, wood sold in volumes under 2 cubic metres must be certified as Ready to Burn. That confirms a moisture content of 20% or less ⁹. For 2 cubic metres or more, suppliers must give customers a notice on how to dry, store and check the wood ⁹. These rules apply to sellers. Local authorities enforce them, with a £300 fixed penalty for storing wood above 20% moisture or for labelling errors ⁹.

The ICS advises never burning wood with a moisture content above 20% ⁴.

Smoke control areas

In a smoke control area you cannot release smoke from a chimney. You can burn only authorised fuel, unless you use an exempt appliance approved by Defra. Wood is unauthorised, so it can be burned only in an exempt appliance ¹⁰. In England a smoking chimney can bring a penalty of up to £300 ¹⁰. GOV.UK says to ask your local council whether you live in one ¹⁰.

Carbon monoxide alarms

Since 1 October 2022, landlords in England must fit a carbon monoxide alarm in any room used as living accommodation that has a fixed combustion appliance. Gas cookers are excluded. This covers log-burning stoves ¹¹. The rules apply to homes let by private or registered social landlords. Owner-occupiers are not covered ¹¹. Local authorities enforce them, and a fine of up to £5,000 can follow failure to comply with a remedial notice ¹¹.

If your chimney catches fire

Devon & Somerset Fire & Rescue Service lists these signs of a chimney fire ⁷:

• a loud roaring noise, as air is drawn in;
• sparks and flames shooting from the chimney top;
• a glowing, shimmering or vibrating appliance outlet or connector;
• flames visible through tiny cracks in the outlet or connector;
• a smell of smoke in other rooms or the loft;
• a hot chimney breast or flue pipe, in the room with the fire or rooms the flue passes through.

Its advice if your chimney is on fire is to close the door to the room and get everyone out of the house, stay out, and call the fire service on 999 ⁷.