Stove distance from wall ?

Builderfromhell

Just fitted a solid fuel burning stove in a renovated cottage.

The stove has been lit for the first time, and although a small fire was lit the plaster behind the stove got very hot. This resulted in the plaster cracking.

We fitted the stove 100mm from the external wall so as to comply with regulations regarding max. lenght of horizontal flue and to neatly get our 45 degree pipe through the wall to vertical flue outside.

I do not want to move the stove away from the wall as this would not look good. The manufacturer recommends using 24 gauge steel plate behind stove to protect 'combustible' materials. We do not have any combustible materials but may fit stainless steel sheet to protect plaster. If I do fit a section of steel my concern would be that it will fit fine but buckle once it gets very hot. Another alternative is to use ceramic tiles.

Nayone out there have experience of this or ideas as to best approach.

Thanks

AckwelFoley

Is the wall that has shown cracks a block wall thats skimmed? And how long between plastering and fire?

Poor Uncle Tom

I put in a SF stove and kept it 250mm away from plastered and skimmed block wall. I installed it in 1999, about 2001 cracks started to appear in the skim plaster, sanded the wall filled the cracks and re-decorated. It done the job, but I got fed up of it last year so I put a stone inlay 2m wide behind the stove and flue. This gives off heat for hours after the stove has gone out. I brought the flue pipe straight up and through the roof, it gives a lot of heat back to the room which is full height open to the roof.

Carlow52

normal skim is not that heat resistant: I lined the back of the fireplace with cement board and skimmed it with a material supplied by the same people. my stove is 150 from wall.
IMO the steel will buckle: ceramic tiles may pop off also.

Builderfromhell

snyper wrote: »

Is the wall that has shown cracks a block wall thats skimmed? And how long between plastering and fire?

Wall is built as follows;
Insulated plasterboard (Xtratherm) fixed to cavity wall with dabs.

Wall plasterd a long time ago but we cut hole for flue just last Tuesday. Once flue installed we patched up plaster around flue and skiimed over.
Owner lit small fire on Friday and this may have resulted in plaster drying out too fast. Stove is about 100mm from back wall.

Having read posts I'm tempted to glue fix a slab of liscannor stone. Will protect wall and store heat.

sinnerboy

Sorry BFH - I think you need to move the stove out - or remove to XT board locally for this

http://rwiumbraco-gb.inforce.dk/media/76040/rockliner-sec.pdf

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1650,en.pdf

.

sunnysoutheast

Hi Builderfromhell

Can you let me know if that solves the problem?

We have a similar issue with hairline cracks in the plaster.

Another option I thought of is to have two sheets of, for example, slate or glass free mounted in heavy bases (like a shop sign, if you see what I mean).

The plaster around the flue will discolour too!

SSE

Carlow52

sinnerboy wrote: »

Sorry BFH - I think you need to move the stove out - or remove to XT board locally for this

http://rwiumbraco-gb.inforce.dk/media/76040/rockliner-sec.pdf

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1650,en.pdf

.

I thoght the same until i re-read page 10 again.
It says 150 from edge of hearth in Dia 7 but 't' in dia 8 can be as low as 50mm or less.

....
Following on from post 10 below, I did not see the reference to PIR in the original post

SB had clarified it: thanks

Carlow52

Builderfromhell wrote: »

Wall is built as follows;
Insulated plasterboard (Xtratherm) fixed to cavity wall with dabs.

Wall plasterd a long time ago but we cut hole for flue just last Tuesday. Once flue installed we patched up plaster around flue and skiimed over.
Owner lit small fire on Friday and this may have resulted in plaster drying out too fast. Stove is about 100mm from back wall.

Having read posts I'm tempted to glue fix a slab of liscannor stone. Will protect wall and store heat.

Dont fit one big piece, fit say 4 with 2mm expansion gap

I have a 1.4 by 1m granite hearth and the supplier recommended the 4 pieces

sinnerboy

Carlow52 wrote: »

I thoght the same until i re-read page 10 again.
It says 150 from edge of hearth in Dia 7 but 't' in dia 8 can be as low as 50mm or less.

Diagram 7
shows relationships between stove and hearth - both of which could be in the middle of a room nowhere near a wall . There is no reference to a wall in Diagram 7

Diagram 6 - requires 75mm thick solid non combustible materials to the wall once the hearth is located within 150mm of the wall ( with or without an appliance sited on it )

Diagram 8
Non combustible material ( NCM ) is required behind .
NCM must be 200mm thick if stove is 50mm or less away from wall
NCM must be 75mm thick if stove is 51 ~ 150 mm away from wall

The PIR is combustible . It cannot remain in place

.

AckwelFoley

Ive seen hairline cracks to a chimney breast where a slab has being stuck because essentially there may have being a problem with the chimney construction that didnt allow for flue expansion due to the intense heat.

Im not fully convinced that the problem is to do with the essentially the close proximity of the stove to the wall, but possibly due to the slab itself, being stuck to the wall, because its the same detail that ive seen this problem before - a slab stuck to the chimney breast

Builderfromhell

Thanks for reply guys.

I should have thought of all of this earlier, but it's not the end of the world.
I've decided to take out a section of PIR insulation and plasterboard behind the stove. Fill with bonding. Stick foil backed plasterboard to bonding (to get some heat reflected back into room. Then, as there is a risk of cracking around new piece of plasterboard, I'll ask client if they want liscannor stone.
This may be abetter finish as it won't discolour and it will store heat while stove is operating.

On a seperate note, if PIR is combustible why is it allowed in dry lining. I always understood the fire risk is minimal as there is no oxygen. PIR does not burn that easily compared to Polystyrene.

I do not that it is not allowed around chimney breasts.

Carlow52

I spoke to Gypsum before I did my own fire and they told me that even the pink board would not 'hack' it at 150/250mm from a surface that could get to 350 or more. the problem is the plaster and not the paper:)
Hence I went for the cement board c/w the recommended joint tape and corner bead and plaster

it worked well

hence I dont think what u have in mind will be a good job.

....
In relation to the question of the requirement for solid non combustible material [NCM], if the requirement is for 200 mm solid non combustible material: does 225 hollow block satisfy the criteria?

sooty_soupy

Surely the pipe going through the wall is going to cause problems anyway. The insulation on the plater board will be combustible I would imagine. If we were installing a twin wall flue system we would actively encourage going straight up through the ceiling, and out through a flashing system. With this method you have to ensure clearance too, but the fact that the flue system is contained within the property for longer means less chance of cooling effects working on the system and also the fact that the chimney will be as close to vertical as possible which we should all be striving for. Bends in chimneys = problems. Have you ever wondered why the chimneys around mainland Europe, especially scandanavian countries, as well as the US and Canada have straight flues at the centre of the home, with the flue terminating at the highest point...They've been burning wood stoves etc for generations and know what they are doing.

I would avaid using a metal backing of any sort as it conducts heat as well as buckles. Something like stone cladding would be better and make a nice feature wall or something like a masterboard or supalux (looks like asbestos but isn't) would be better, and then it can be painted with a heat resistant paint...problem solved.

Have you taken the single skin black pipe through the wall or is the union to the twin wall made inside the property? It is imperative that the single skin be 3xD away from anything combustible including plaster board. You wont touch this pipe when the stove is burning, so it shouldn't go through walls or ceilings. 3xD = 3 x 5" means 15" away from combustibles, or 18" for 6" diamter stuff. Don't mess with fire folks. If it's your own house that burns down and you have done the work yourself, you wont get a penny from the insurance.....if you are installing for a customer and someone dies or is injured...expect a lawyer who has come to us as registered chimney technicians to have a report of everything you have done wrong and see how hard it is for your legal team to defend you.

gamblor166

sooty_soupy wrote: »

Surely the pipe going through the wall is going to cause problems anyway. The insulation on the plater board will be combustible I would imagine. If we were installing a twin wall flue system we would actively encourage going straight up through the ceiling, and out through a flashing system. With this method you have to ensure clearance too, but the fact that the flue system is contained within the property for longer means less chance of cooling effects working on the system and also the fact that the chimney will be as close to vertical as possible which we should all be striving for. Bends in chimneys = problems. Have you ever wondered why the chimneys around mainland Europe, especially scandanavian countries, as well as the US and Canada have straight flues at the centre of the home, with the flue terminating at the highest point...They've been burning wood stoves etc for generations and know what they are doing.

I would avaid using a metal backing of any sort as it conducts heat as well as buckles. Something like stone cladding would be better and make a nice feature wall or something like a masterboard or supalux (looks like asbestos but isn't) would be better, and then it can be painted with a heat resistant paint...problem solved.

Have you taken the single skin black pipe through the wall or is the union to the twin wall made inside the property? It is imperative that the single skin be 3xD away from anything combustible including plaster board. You wont touch this pipe when the stove is burning, so it shouldn't go through walls or ceilings. 3xD = 3 x 5" means 15" away from combustibles, or 18" for 6" diamter stuff. Don't mess with fire folks. If it's your own house that burns down and you have done the work yourself, you wont get a penny from the insurance.....if you are installing for a customer and someone dies or is injured...expect a lawyer who has come to us as registered chimney technicians to have a report of everything you have done wrong and see how hard it is for your legal team to defend you.

Hey, would gypsums fibre board or cement board be the same thing?

BryanF

gamblor166 wrote: »

Hey, would gypsums fibre board or cement board be the same thing?

im sure he has this sorted by now - btw this thread is 4 years old and now closed