Wood Burner & Flue liner

3 Nov 2010
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United Kingdom
Not sure if this is the right forum or not, but we've opened up our 1930's fireplace, and have cleaned out the chimney.
We were going to buy a stove with a 5" flue, and thus bought a 5" flue liner, and that is now installed.
The problem is we've now been given a stove with a 6" flue hole, though looking at the manufacturers web site, it seems it was 5" about 6 months ago, and it's now 6" on the new model, seemingly to accomodate the "multi-fuel" option. We only ever intend to burn wood, as we have tons of the stuff ready dried (and more growing) and ready to burn...

So, key question is... do I have to pull out the 5" liner and spend another fortune on a 6" liner, or can we use the 5" liner?.
If we can use the 5" liner, how can we connect the 6" flue pipe to the 5" liner?
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I do have to say that its annoying when manufacturers dont keep their web sites up to date and make significant changes without updating their published details.

If you had employed a registered installer then it would have been his problem.

Unfortunately, you have adopted a DIY approach and encountered this difficulty. I would suggest you search for the post I made recently about a DIYer who was fined £4000 for not notifying Building Control of his DIY installation.

Only the manufacturer can give you a definitive answer but I expect that you MUST have a 6" liner to match the boiler flue spligot.

If I had been fitting that stove then I would have got the appliance first and then the flue because as a heating engineer I am aware of possible pitfalls like that. But if I had been totally diligent and still ended up with that problem I would be seeking to claim for the extra costs from whoever in the supply chain was to blame.

In your case I expect that when you analyse exactly what went wrong you will find that only you are significantly to blame. manufacturers always have the clause that they reserve the right to make modifications to their products. There is no legal requirement for them to update their web sites in a timely way.


Thanks for this - We've already informed Building Control. It's quite difficult for us to do anything without Building Control knowing, as one of the Officers is our neighbour (which is useful for consulting!).

But, as you say, we need a 6" liner...

So, anyone want a 5" liner?!?
Hi Tony,
Flue Size
The diameter of any flue used (stove flue pipe, liner or twin wall pipe) must not be smaller than the size recommended by the stove manufacturer - generally the diameter of the stove outlet.

If a wood burning stove has a diameter of 125mm (5") then Building Regulations do recommend using a larger 150mm (6") liner, however manufacturers installation instructions do take priority.

Ventilation for stoves
Stoves use air from within the room for combustion. Any solid fuel stove which has an output higher than 5kws requires a permanently open vent with a cross sectional area of at least 550² mm for every kW above 5kW.

A vent can be placed in the walls or the floor of the room containing the stove and can either vent directly outside or through another room or loft space which has permanent ventilation to outside.


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Morning icornish.

If you bought it 'unseen' and had it delivered and it's within 7 days of you receiving it you can always send it back under distance selling regulations, no reason need be given. You might have to pay the postage but that depends on the small print in what the supplier said.

And you can ignore any of the nonsense in the manufacturer's terms which say they can change their specifications and stuff the consumer. Doesn't work that way, law is solidly on the consumer's side here, if they change the spec and are still advertising the old model on their web site just call them up and tell them to collect and give you your money back. No seven day limit on that. If they don't and you paid by credit card then call your credit card company up and tell them to refund you and give the supplier a couple of days next week when it is convenient for you and they can collect at their cost.
150mm minimum diameter flue for any stove on which wood could be burnt unless it's Defra Exempt, even if the stove outlet is only125mm. I believe most HETAS installers won’t use 125mm liner any longer. It’s also strongly advisable to insulate the liner to keep the upper flue temperature up to avoid condensation & tar deposits.

The Regs. regarding permanent vents got a bit more complicated since the change on October 1st but I haven’t yet had a chance to read it through & understand what it all means in practice. :rolleyes:
Thanks to all. Have spoken to supplier and it will be rectified...
Can someone point me at the updated regs re the air requirement, as I can't seem to find them. Our house has many draughts and airbricks at the moment, so want to ensure it's done properly.

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