Please ensure that no euphemisms are hurt during the production of this thread…

I have chosen a stove. mistakenly thinking it was a 125mm outlet. Not bought yet but I WANT THAT ONE.

Now a previous fitter suggested not to bother lining the chimney – nothing to do with flue size particularly, he just thought that it was unnecessary. I’ve had a couple more out to do surveys and they seem to think that the liner would be a much better option. Reading around, I tend to agree.

What are my options? The chimney is 7″ square at the base but there are constrictions further up that would require a flexible flue liner to get around. 5″ liner seems feasible but not 6″. Is there any advantage to putting a 6″ liner up “as far as possible” and leaving the remainder unlined, are there any ultra flexible liners that might be suitable?

I know that I can’t use a 5″ liner with an adaptor for legal reasons. What is the worst that could happen if I leave it unlined? Pics below.
P1020462 by craigbart, on Flickr

P1020459 by craigbart, on Flickr

I run mine un-lined. Hasn’t been an issue.

Is there any advantage to putting a 6″ liner up “as far as possible” and leaving the remainder unlined,

Think you’re onto a loser there. You might as well get the entire chimney checked in its current state, and go with a register plate setup.

What exactly are the ‘constructions’ that prevent a flexible liner going in?

Our experience of a wood burner and unlined chimney was not good. For reasons why unlined chimneys aren’t good see Chimney Relining. We have now had relining done and the difference is fantastic – much happier!

my salesman bullshit-ometer went off the scale there.

its up there with the british gas radio advert which is a radio broadcast weather report saying the winters going to be a bad one.

yes liners are needed but unlike that link – they are not always required and certainly some of their reasoning is tenuous at best.

mrmonkfinger – the constrictions are narrowings within the chimney construct, which seem to give approx 45 degree bends. I think their purpose is to increase draw.

So perhaps I’m not going to die if I leave it unlined. The ultimate for me would be to get it lined with a 6″ flue liner that was flexible enough to be able to manoeuvre around the constrictions. Not sure if such liner exists though. I have a small section of standard liner and although classed as ‘flexible’, it doesn’t bend that much.

hmmm.. why would you ‘line’ a perfectly good chimney.. get it swept before installation and bingo.. save a packet.. your old chimney was designed to do a job.. be a chimney and your after a chimney.. a match made in heaven… why on earth would you want to restrict it by fitting a 5 inch flexible liner when you can have the real thing..

No, you won’t die.

Are you DIYing this whole thing or leaving it to ‘experts’?

the constrictions are narrowings within the chimney construct, which seem to give approx 45 degree bends. I think their purpose is to increase draw.

CB – are you completely sure that the existing flue narrows to 5″?

From the pic it looks like it’s made from precast sections so I’d be surprised if it did narrow down. Bends in a flue will not speed up the gasses, they will slow them down – AFAIAK any bends are there to either get around obstructions or to stop rain falling directly into the fireplace.

sharkbait – You are right in that they are precast – by design in other words rather than a defect and preventing rain sounds feasible. It might not ‘narrow’ – it might be that the precast sections are simply offset to create that shape – you can see it in the 2nd photo where the circular hole to the sky is partially blocked.
In effect it creates a bend that a liner would have to go around. The precast box sections may still be 7″ but to get a 6″ liner to bend sufficiently in such a limited ‘vertical’ distance seems unlikely.

Totalshell. As I understand it, a liner would heat up much quicker than a wider chimney thereby giving greater efficiency and all together less faff when lighting. Also restricts any nastiness regarding creosote formation (although I will attempt to burn the right things and not burn overnight).

Mrmonkfinger – DIY is limited to the first photo – everything else will be “expert” led. That said, some of the fitters that I have around have been shameful (suggestions of reg avoidance including one recommended strongly on here!!)

have you considered using a thermocrete liner?

dickyboy – just looked that up. Not sure that would solve my problem as my existing chimney is sound, its just unsuitable for a 6″ flue liner. Actually, from the previous posts, not sure I have a problem as such. If I want the stove that I have chosen, I either leave it unlined or get the restrictions taken out effectively ‘straightening’ the existing chimney (then dropping a liner straight down).

Ah, having now seen a second youtube clip, I see where you’re coming from. Rubberised flue guide then infilled to account for bends. I wonder how spendy that process is?

I wonder how spendy that process is?

if you are in the south east try giving chimneycare a call for advice / costs, no idea if they would be off the scale or not

Our stove fitter advised against a liner, said it was an unnecessary cost. I was unconvinced and suspected he didn’t want to faff about on the roof, but it turned out he contracted the work out anyway, we had one guy open up the fireplace, he did the hearth, a guy for sweep/smoke test and fitting a cowl to the pot, and a guy to fit the stove, who it turned out was also a sweep. So I’m sure he would be able to find someone to fit a liner if he wanted to make an extra few quid on it.

So I can’t see why he would advise against a liner otherwise. Anyway, the stove has been in over a week and it seems to be running fine without a liner 🙂

cb the stove we have fitted in November last year went into a fireplace with a [standard] precast 7″ flue. There were a few bend in the route (way more than yours) but the fitter slotted a 6″ liner down with a little shoving.
The liners are pretty flexible and frankly yours is almost a straight drop down so you’ll be fine. Just get on with it.

You don’t need a liner, you’ve got a perfectly good Class 1 precast flue in pretty clean condition.

Get a chimney sweep to look at it not a stover fitter, he is less likely to sell you something you don’t need and he will give the correct advice on fitting the stove.

DO fit a stainless steel cowl though to keep the rain out.

He needs to attach the stove to the flue and I’ve heard bad things about the stove/clay liner adapters (which is why I didn’t use one).

As far as I know our stove pipe goes up through the register plate and into the bottom of the flue, I don’t know what the sweep did when he fitted it all for us – all I do know is that he fitted a rodding port in the front of the stove pipe for ease of sweeping, something he says most people forget to do.

If he can fit a register plate then all should be fine with your system – it’s what I’ve done with our other stove but that flue is external to the house so I’ve put a soot door outside to give access to the top of the register plate.
Our other stove replaced a standard 16″ fireback so no hope of a register plate.