Chimneys, liners and flues
Does yours need lining, what if there's no chimney at all, and looking after it once the stove is lit.
Does the chimney need a liner?
Not always. It comes down to the condition and the size of what you've got. The government's guidance, Approved Document J, says:
- a defective flue can be refurbished by lining it;
- a flue may need lining to reduce it to a size that suits the stove, because an oversized flue can be unsafe;
- a flue should be swept before it is relined;
- a flexible metal liner is for relining an existing chimney, not for building a new one.
The installer inspects the chimney during the survey and tells you whether yours needs lining, and why.
Replacing an old stove
Approved Document J says that where a chimney was relined with a metal liner in the past and the stove is being replaced, the liner should be replaced too, unless it can be shown to be recent and in good condition. Any stove you buy now must meet Ecodesign limits. Ecodesign
No chimney at all
A stove normally connects to a factory-made insulated metal chimney, usually called a twin-wall flue. It can go up through the house and out of the roof, or out through an external wall and up the side. It has to keep a safe distance from anything combustible, and it costs more than using an existing chimney. Costs
On a house the flue is usually permitted development, but not if it would rise a metre or more above the highest part of the roof, or in a conservation area, National Park or AONB where it faces a road at the front or side. Planning
Sources: Approved Document J, 2022 edition (GOV.UK); legislation.gov.uk, Class G.
Air and the hearth
A stove needs air to burn safely. Approved Document J sets out when a permanent vent is required: for a stove without a draught stabiliser in a less airtight home, which most older houses are, that is 550 mm² of vent for each kW of rated output above 5 kW. The stove also stands on a non-combustible hearth, clear of anything that can catch. Your installer works both out for the room and the stove.
The notice plate
When a hearth, fireplace, flue or chimney is fitted or extended, Approved Document J says a notice plate should be fixed in the house, next to the consumer unit, the chimney or the stopcock for instance. It records the flue and liner type, which appliances it suits, and the date. Whoever works on it next will thank you.
Sweeping
HETAS encourages a sweep at least twice a year when burning wood, and at least once a year on smokeless fuel. Best times: just before the heating season, and after a long spell unused.
Chimney needs looking at?
Say what you've got and where. It reaches one HETAS-registered installer, who gets in touch to arrange a look at the job. Costs you nothing, commits you to nothing.