Flexi flue

Dtp1979 · 20-01-2014 8:34pm #1

I'm pricing a job at the minute to install a stove. Problem is the chimney is the old type that you could literally climb up inside it. I'm used to using flexi flue and pouring vermiculite around it in an 8" clay liner. What options do I have. Surely I can't use the flexi liner cause when it's been cleaned in the future the movement of the pipe will probably break the seal. It's a 2 story house. Anybody come across anything similar before?

Robbie.G · 20-01-2014 8:41pm

Dtp1979 wrote: »

I'm pricing a job at the minute to install a stove. Problem is the chimney is the old type that you could literally climb up inside it. I'm used to using flexi flue and pouring vermiculite around it in an 8" clay liner. What options do I have. Surely I can't use the flexi liner cause when it's been cleaned in the future the movement of the pipe will probably break the seal. It's a 2 story house. Anybody come across anything similar before?

What is the setup type of stove if you want dec give me a ring

Dtp1979 · 20-01-2014 9:17pm

Robbie.G wrote: »

What is the setup type of stove if you want dec give me a ring

It's actually a cooker robbie. Flue going up a metre, then 45 into wall and then the old chimney. It's also heating rads but that's not gonna affect the flue! Any ideas?

Robbie.G · 20-01-2014 9:38pm

Dtp1979 wrote: »

It's actually a cooker robbie. Flue going up a metre, then 45 into wall and then the old chimney. It's also heating rads but that's not gonna affect the flue! Any ideas?

Check your email

Robbie.G · 20-01-2014 9:43pm

Have a look here it might be of some help
https://www.dropbox.com/s/6modha3rs51l99k/Photo%2020-01-2014%2020%2035%2043.jpg

Dtp1979 · 20-01-2014 9:48pm

Robbie.G wrote: »

Have a look here it might be of some help
https://www.dropbox.com/s/6modha3rs51l99k/Photo%2020-01-2014%2020%2035%2043.jpg

Thanks robbie. My main problem is the huge space that's gonna be around the flexi. There's no clay liner so the flexi won't be stable at all

Wearb · 20-01-2014 11:17pm

Have you considered a double wall insulated flue (if the chimney is as big as I imagine), like one you might use outside, or is that impractical.

DenisCork · 20-01-2014 11:20pm

There's a rockwool sleeve available for wrapping around flexi. It's one inch thick with foil On both sides. You wrap it around the flexi and then wrap a light wire roll on the outside. I've seen it in the UK but can't get hold of it here.

corkgsxr · 20-01-2014 11:22pm

Unless its much bigger than im used to. As it comes down the bends of the chimney theres very little movement after.

DenisCork · 20-01-2014 11:22pm

Wearb wrote: »

Have you considered a double wall insulated flue (if the chimney is as big as I imagine), like one you might use outside, or is that impractical.

You would need to support the flue along its length with brackets.

Dtp1979 · 20-01-2014 11:30pm

Wearb wrote: »

Have you considered a double wall insulated flue (if the chimney is as big as I imagine), like one you might use outside, or is that impractical.

Be an awkward one plus no where to bracket it

Wearb · 20-01-2014 11:34pm

Maybe put the flexi in some sort of metal conduit. Just throwing ideas about, never know but it might prompt someone to improve on an idea.
You could maybe consider going out through the back of the existing chimney, if its an outside wall. Wouldn't look the best though.

Dtp1979 · 21-01-2014 9:51am

Wearb wrote: »

Maybe put the flexi in some sort of metal conduit. Just throwing ideas about, never know but it might prompt someone to improve on an idea.
You could maybe consider going out through the back of the existing chimney, if its an outside wall. Wouldn't look the best though.

It's on an external wall alright but the flue would be going out onto a shared narrow lane that bearly fits the width of a car at the moment

Wearb · 21-01-2014 11:02am

Dtp1979 wrote: »

It's on an external wall alright but the flue would be going out onto a shared narrow lane that bearly fits the width of a car at the moment

If the chimney is as big as it seems, you may be able to get a bit of height in it before breaking into/out of it.

Dtp1979 · 21-01-2014 11:41am

Wearb wrote: »

If the chimney is as big as it seems, you may be able to get a bit of height in it before breaking into/out of it.

Maybe so but seems like an awful job to do

Wearb · 21-01-2014 11:56am

Dtp1979 wrote: »

Maybe so but seems like an awful job to do

It would a tough job. Some sort of steel conduit or something made up from box ducting would be neater. Talk to some of the experienced builders in your area. It must be something that has been done lots of times before.
Phone a few chimney cleaning companies for advice also. They might have come across a good solution.

Wearb · 21-01-2014 12:41pm

Wearb wrote: »

It would a tough job. Some sort of steel conduit or something made up from box ducting would be neater. Talk to some of the experienced builders in your area. It must be something that has been done lots of times before.
Phone a few chimney cleaning companies for advice also. They might have come across a good solution.

Just spoke to a property maintenance man who also installs stoves and he has put flexi's in a few unflued chimneys. He puts in lintels a few inches up the chimney after fitting the cast iron flue pipe and fitting the flexi to it. He then seals the bottom, fills with the granular insulation and caps and seals the top

Dtp1979 · 21-01-2014 3:18pm

Wearb wrote: »

Just spoke to a property maintenance man who also installs stoves and he has put flexi's in a few unflued chimneys. He puts in lintels a few inches up the chimney after fitting the cast iron flue pipe and fitting the flexi to it. He then seals the bottom, fills with the granular insulation and caps and seals the top

But it wouldn't be stable between bottom and top?

rightjob! · 21-01-2014 3:33pm

i would say you have thought of this and want to avoid it but i think you might have to break a couple of holes out and put in a few mupros in

Wearb · 21-01-2014 3:48pm

Dtp1979 wrote: »

But it wouldn't be stable between bottom and top?

Exactly the question I asked him. He said he cleaned the flue in one of such installations just before christmas and had no problems. He said that with the vermiculite bracing it somewhat and it being anchored at the top and bottom, he would have no fear of it being a problem when cleaning. The man was in his late 50's and is experienced, but would hold no installation certificates as such. He said he originally got the installation instructions (including the need to have a metal flue pipe at the beginning of the chimney) from the hardware store where he bought the materials and flexi.

That's it -nearly verbatim- for what its worth.

jimf · 21-01-2014 10:18pm

just saw this post now dtp and it brings me back to my childhood my grandparents house had 1 of those chimneys jesus you could actually climb up inside it often got my arse kicked for doing just that when staying with them on summer hols

Wearb · 21-01-2014 10:20pm

jimf wrote: »

just saw this post now dtp and it brings me back to my childhood my grandparents house had 1 of those chimneys jesus you could actually climb up inside it often got my arse kicked for doing just that when staying with them on summer hols

Sure isn't that how we were so gullible in the country. Santa could easily come down it.

DenisCork · 30-01-2014 9:59pm

Here you go -
http://stores.ebay.ie/Stove-Central-Shop/Chimwrap-Liner-Insulation.html

dara.obriain · 30-09-2015 11:56pm

I know this thread is old but have a related question that I hope someone can advise me on. had an 8k blacksmith bellows installed recently and wasn't overjoyed with the installer. Very messy and didn't use a metal plate where flue pipe joins old clay chimney flue and flexi liner. He said it's not necessary but I am unsure (gullible clown). He also said because it is a central chimney rather than an external one , it will be warm enough in the new flue and there is no need to insulate between old clay one and new flexi with vermiculite. He says that it will extend the life of the liner without the vermiculite. I haven't really lit the stove yet as its still warm weather but have a real feeling this guy is a bullshi@@er and am thinking of getting him back to do both of the things mentioned above. Any thoughts appreciated

Robbie.G · 01-10-2015 1:06am

dara.obriain wrote: »

I know this thread is old but have a related question that I hope someone can advise me on. had an 8k blacksmith bellows installed recently and wasn't overjoyed with the installer. Very messy and didn't use a metal plate where flue pipe joins old clay chimney flue and flexi liner. He said it's not necessary but I am unsure (gullible clown). He also said because it is a central chimney rather than an external one , it will be warm enough in the new flue and there is no need to insulate between old clay one and new flexi with vermiculite. He says that it will extend the life of the liner without the vermiculite. I haven't really lit the stove yet as its still warm weather but have a real feeling this guy is a bullshi@@er and am thinking of getting him back to do both of the things mentioned above. Any thoughts appreciated

He's right to an extent the flue doesn't need to be insulated as its and internal chimney it should be warm enough to create a draft also if you have a 6 in liner going down a 8 clay liner you are not going to get vermiculite around the flexible as you can't keep it central in the clay liner

dara.obriain · 01-10-2015 11:25pm

Thanks for the reply Robbie, that puts my mind at ease to an extent. I was wondering about when the flue goes up into the attic where it will be freezing in the winter. Is this too short a vertical distance for it to make a difference to the temperature in the flue? Also does a plate have to be used where vertical flue pipe from stove joins the liner inside in old clay flue or is it ok to join flue pipe directly to flexi liner? Thanks in advance.

Robbie.G · 02-10-2015 6:34am

dara.obriain wrote: »

Thanks for the reply Robbie, that puts my mind at ease to an extent. I was wondering about when the flue goes up into the attic where it will be freezing in the winter. Is this too short a vertical distance for it to make a difference to the temperature in the flue? Also does a plate have to be used where vertical flue pipe from stove joins the liner inside in old clay flue or is it ok to join flue pipe directly to flexi liner? Thanks in advance.

There's no need to worry about it going through attic as the chimney is constructed with 100mm thick block to form an opening of 300mm square the clay liners are 200mm wide then the gap is back filled so it's insulated in its self.
There are proper joiners for flue pipe to flexible liner make sure they are used.
There is no need for a closure plate to be fitted at the bottom. At the top there are two options you can use a pot hanger which holds the flexi in place or use a clamp across the pot then fill the gap between the flexi and the pot with
rock wool to seal and close the top.
Hope some of this has been of some help for more information you can check out oriel flues and mi flues website they have installation guides on them so you will have an idea if your installer is fitting it right.

dara.obriain · 04-10-2015 2:13am

Very helpful, thanks a million.

millionmystery · 12-10-2015 2:07pm

Hi, Ive this exact same issue as the poster, huge old chimney and want to put in a stove? How did you get around this? Afraid that the liner etc is going to well exceed the price of the stove at this stage

dara.obriain · 14-10-2015 11:10pm

Hiya million, we are up and running now and am delighted. Was a bit worried if stove would be the right size but heats all the downstairs like I planned and I can open the doors downstairs after a few hours to allow heat up the stairs. Research has paid off.
The liner and stuff might not cost more than your stove but when you add in the insulation and rebuilding the chimney with plastering, it definitely will. Knock out whatever you have to and put in some steal. I did both sides so the stove is effectively a doublesided one. Dirty job and a serious cleanup after (my installer was very dirty I'm afraid). But if I get the level of comfort we have had for the last week for the next 10 or 15 years which I expect from stove and liner, then yes, definitely worth the bother. Good luck.

Flexi flue

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