Chimney flue crack-caused by Stove use

Widescreen

My external chimney flue has a small crack which shows deposit of brown, creosote colour deposit on the external wall just above where the stove is.

I have been advised to get a flexible flue liner fitted and just have a couple of questions regarding this.

1. Should this be stainless steel and what is the spec/rough cost?

2. Should this be insulated? One person in trade said yes, vermiculite, the other also in trade said no.

3. Also I was told that if a liner is fitted the timber surround on the fireplace may not suffice?

When my stove was installed 8 years ago, there was no cowel on chimney and it was installed into existing flue.Basically with the rain coming in over the years there could be potential corrosion on the stove from this I was advised, but this won't be visible until the stove is uninstalled as part of the process.

I'd appreciate if anyone could comment on the above and also advise a reputable company within the area to carry out these repairs? thanks.

upupup

1.A flexi flue will do the job,no need for steel
2.Insulation is not essential,the flexi flue warms very quickly to do its job but insulation is not expensive if you want to put it in.
3.The liner has nothing to do with the fireplace surround.

If the stove has been in use regularly there shouldn't be rust problems because of the rain but it all depends on the pipe setup exiting the stove and if there is anywhere horizontal for the rain to pool inside the pipe

Widescreen

Appreciate the reply.

Was talking since to a chap who can do as you indicate.

Just two things to clarify if you wouldn't mind?

1. The guy said that he doesn't fit the linings with insulation. Thinks they are fine without. I was just thinking that condensation might be an issue at times and also movement of the liner within the chimney? Especially when being swept maybe? Appreciate yr thoughts on that.

2. Regarding the timber fireplace surround , ( obviously the body of fireplace around the stove is marble), someone had mentioned to me that the wood would get much hotter with the liner in and was trying to encourage me to replace it with the likes of marble I suppose?

We don't want to do that only as last resort. Thoughts appreciated on this.

We have agreed a reasonable price for getting the chimney lining put in with cowel etc and the stove removed/refitted as required so am going towards this, but just seeking final opinions on these two issues.

Many thanks.

upupup

Widescreen wrote: »

Appreciate the reply.

Was talking since to a chap who can do as you indicate.

Just two things to clarify if you wouldn't mind?

1. The guy said that he doesn't fit the linings with insulation. Thinks they are fine without. I was just thinking that condensation might be an issue at times and also movement of the liner within the chimney? Especially when being swept maybe? Appreciate yr thoughts on that.

2. Regarding the timber fireplace surround , ( obviously the body of fireplace around the stove is marble), someone had mentioned to me that the wood would get much hotter with the liner in and was trying to encourage me to replace it with the likes of marble I suppose?

We don't want to do that only as last resort. Thoughts appreciated on this.

We have agreed a reasonable price for getting the chimney lining put in with cowel etc and the stove removed/refitted as required so am going towards this, but just seeking final opinions on these two issues.

Many thanks.

Condensation is caused by warm moist air hitting a cold surface.The air/smoke will be in the flexi flue so it can not condensate on the old clay liner.It is possible that moisture can collect on the clay flue due to weather conditions but amounts would be small and evaporated easily too.
The flue is flexible so it can move a bit when being swept and there is no need to have it exactly in the middle.
Insulating around it will give you peace of mind and a feeling of a better job but in reality its doing very little.One thing it will do if it is absorbant is soak in any moisture/rain and release it when things warm up but the amount of moisture would be small.

The new flexi flue may improve the performance of your stove making it a little warmer but if the timber surround has been ok with the stove for the last 8 years I don't think you will have any problem

Widescreen

Thanks a lot for your thoughts much appreciated.

Just one final thing.

As my chimney is external, basically on gable end of the house, would I still get away without insulating the liner or do you think it would be only slight difference? Just thinking it would be cooler.

thanks.

upupup

Widescreen wrote: »

Thanks a lot for your thoughts much appreciated.

Just one final thing.

As my chimney is external, basically on gable end of the house, would I still get away without insulating the liner or do you think it would be only slight difference? Just thinking it would be cooler.

thanks.

It would be colder if not used every day as the blocks of the chimney and filling will heat and retain heat when used every day.A two story chimney will take longer to heat than a bungalow.Here is a link with some good info.https://www.stovefitterswarehouse.co.uk/pages/should-i-insulate-my-chimney-flue-liner

Dayo93

With regards to the wooden fireplace , I think it is generally called out in the spec of the stove how much distance you should allow for a wooden fireplace , that's the way it was for ours anyway

listermint

Id put the liner in, it's a better more professional Job. Some lads don't like doing it as it's messy and adds a bit of time to the finish.

Do it right of you're going to do it at all.

upupup

listermint wrote: »

Id put the liner in, it's a better more professional Job. Some lads don't like doing it as it's messy and adds a bit of time to the finish.

Do it right of you're going to do it at all.

It only gives the impression of a professional job.It takes time and costs extra and does very little for the stove and that's why some lads don't like doing it as its pointless in most cases

Widescreen

upupup wrote: »

It would be colder if not used every day as the blocks of the chimney and filling will heat and retain heat when used every day.A two story chimney will take longer to heat than a bungalow.Here is a link with some good info.https://www.stovefitterswarehouse.co.uk/pages/should-i-insulate-my-chimney-flue-liner

Thanks, actually, we wouldn't be too worried about it heating up too quickly, it was just whether there would be an adverse effect from not having the liner insulated, ie. liner not last as long etc?

The Continental Op

upupup wrote: »

It only gives the impression of a professional job.It takes time and costs extra and does very little for the stove and that's why some lads don't like doing it as its pointless in most cases

Not using a liner massively increases the risk of a chimney fire.

No professional should be installing a stove without a liner.

pdpmur

Widescreen wrote: »

My external chimney flue has a small crack which shows deposit of brown, creosote colour deposit on the external wall just above where the stove is.

I have been advised to get a flexible flue liner fitted and just have a couple of questions regarding this.

1. Should this be stainless steel and what is the spec/rough cost?

2. Should this be insulated? One person in trade said yes, vermiculite, the other also in trade said no.

3. Also I was told that if a liner is fitted the timber surround on the fireplace may not suffice?

When my stove was installed 8 years ago, there was no cowel on chimney and it was installed into existing flue.Basically with the rain coming in over the years there could be potential corrosion on the stove from this I was advised, but this won't be visible until the stove is uninstalled as part of the process.

I'd appreciate if anyone could comment on the above and also advise a reputable company within the area to carry out these repairs? thanks.

My professional advice to you is
1. Flue - yes, particularly if your existing chimney is cracked.
Flue material - Stainless Steel is a must. Refer to Building Regulations TGD J Section 2.5.10 (http://www.housing.old.gov.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad%2C37240%2Cen.pdf) - I.S. EN 1856- 2:2009 and meeting the performance level specified in sub-section 2.5.7
2. Insulation - Yes (vermiculite)
3. Timber surround on your fireplace - I can't comment as the particular circumstances will dictate
4. Rain Cowl on chimney outlet - strongly recommended - this normally comes with the stainless steel liner. All good systems (e.g. Mi-flues System 35) come with a rain cowl at outlet

Widescreen

The Continental Op wrote: »

Not using a liner massively increases the risk of a chimney fire.

No professional should be installing a stove without a liner.

I wasn't thinking of not using a liner, query was about the insulation.

Widescreen

Dayo93 wrote: »

With regards to the wooden fireplace , I think it is generally called out in the spec of the stove how much distance you should allow for a wooden fireplace , that's the way it was for ours anyway

Thanks, we had the insert stove installed by professional Limerick company, into our existing timber surround, inner marble, fireplace eight years and have had no issues with excessive heat. The wood may get warm immediately above the stove, and marble would be hotter but not issue. Installer suggested a small canopy at the time which fits over the stove to deflect any heat, seems to do the job.

My question is that if we have a chimney liner installed now, is it going to make the heat more excessive from the stove or would that still be manageable by how much fuel is burnt at the time?

The Continental Op

Widescreen wrote: »

I wasn't thinking of not using a liner, query was about the insulation.

But I didn't quote you.

The insulation is much more a labour cost than anything. A bag of Vermiculite is about €20, so if you need 4 bags which I doubt then with a bag of cement is going to cost less than €100 on materials. Mixing that and pouring it down the chimney is the main cost.

The advantage of insulation is also that it supports the liner and if the liner is held straight during pouring then it will stay straight. Poorly installed liners can sag at the bottom and this is a bad thing if someone overfuels a stove leaves it open and walks away. The bottom of the liner is more prone to overheating where there is a bend (sag) at the bottom so in that case insulation is a good idea. The insulation isn't half as important as a correctly installed liner.

Another point to mention is that the liner is not designed to take the heat created at the connection to the stove. Ideally use a section of enamelled flue for the first few feet. (Worst of all is a liner directly attached to the stove with a sag in it just above the join).

Also get the chimney well swept before lining. The less tar sealed in the less that can come out if water gets in there. Possibly another reason for insulating the chimney as that may reduce any future movement of tar from inside to outside.

You shouldn't notice much/any difference in the heat output at the stove end. Lighting may be easier because the liner will warm up quicker