Build a false chimney? Ive seen pictures of this but....

[TheOriginalTableLeg]

Thanks Richard,

With regards to the Vermiculite, how exactly is this done?

The lintel area of the false chimney is going to be open allowing the flue to pass behind the lintel. My understanding of the Vermiculite is that you would mix it and add into the void which I don't have.

I don't know if you can get some kind of plate to go behind the chimney which the flue could pass through but that would hold the Vermiculite.
Any idea's?

The Victus plaster/screed instructions say to PVA before the screed (onto the bricks) and then onto of the screed before the plaster on top.

Have you found a problem with PVA'ing onto the brick surface?

Is the choice of using a sand/cement/lime render (5:1:1) as the base coat over the Victus screed merely one of cost? or is it a better way of doing it?

Thanks again.

 

[Richard C]

With regards to the Vermiculite, how exactly is this done? The lintel area of the false chimney is going to be open allowing the flue to pass behind the lintel. My understanding of the Vermiculite is that you would mix it and add into the void which I don't have. I don't know if you can get some kind of plate to go behind the chimney which the flue could pass through but that would hold the Vermiculite.
Any idea's?

You must have a register plate at the bottom of the false chimney (it’s not really false now anyway) which fits around the flue liner or a vitreous enamel flue pipe if it’s going to be on show; this closes the void around the flue liner off otherwise all the heat from the room will escape up the void & all manner of things will drop down including dead pigeons; I found one very stiff in my grate at the start of this fire season but Christ knows how it got through the small gaps in the cap.

Vermiculite is a granular insulation material;
http://www.protonsupplies.com/Vermiculite-c319.html?gclid=CN-7vrq_t6UCFQhO4QodOlU_YA
You don’t mix it with anything. Fit flue liner, fit & seal the fire registration plate (at the bottom), climb up on roof with bags of Vermiculite & pour it down the chimney around the flue until you cant get any more in, fit top plate, pot & cowl.

The Victus plaster/screed instructions say to PVA before the screed (onto the bricks) and then onto of the screed before the plaster on top. Have you found a problem with PVA'ing onto the brick surface?

Although Vitcas recommend PVA for their plaster (normal practice over a porous surface), I’ve had a quick look at the spec sheet & I can’t see any reference to PVA before applying their screed which I would expect. I don’t use Vitcas screed but a 5:1:1 sand/cement/lime render & you would not normally PVA with that, just damp down well with water.

Is the choice of using a sand/cement/lime render (5:1:1) as the base coat over the Victus screed merely one of cost? or is it a better way of doing it?

Yes as far as I’m concerned; if correctly done it seems to do just as good a job, it’s how it used to be done.

 

[TheOriginalTableLeg]

Thanks once again Richard for the reply.

I think I should clarify my install as there appears to be some confusion over it.

My proposed stove install will be onto a wall where there is no chimney.
I also live in a bungalow.

Therefore, I could have the stove fitted near to the wall, the flue would top exit and pass through a register plate at ceiling level (plasterboard ceiling), it would then pass a very short distance through the loft before passing out through the tiled roof with proper flashing etc.

Whilst this is perfectly adequate for a lot of stove installs these days with no chimneys I wanted to try and create a chimney effect through which the flue would pass (in the living room only).

Therefore the chimney breast I propose to build only serves as a false chimney effect. It would not be open to the loft (because of the upper register plate, so no pigeons dropping in ).

Does this therefore change your opinions at all?

I could conceivably add another register plate but my local stove shop recommended Twin wall flue from the stove over the full length to reduce the temperature within the false chimney breast and keep the heat within the flue.

 

[Richard C]

That clarifies matters a little & I now understand that you propose only a decorative chimney within the property to disguise the flue liner. Twin wall flue liner will (should) be the norm now as far as I’m aware so I don’t know what else your stove shop would have recommended but the level of heat insulation isn’t going to be that great & you will still get a great deal of heat loss through the liner. For little additional cost, I think you would still benefit from Vermiculite insulation around the liner within the false chimney your building up to the loft (& I would even consider wrap insulating the liner above that) by way of better burn efficiency & protection to whatever finish you put on the false chimney.

 

[TheOriginalTableLeg]

Thanks once again Richard,

I have read and been told by stove installers, that fitting a freestanding stove usually would have single wall flue upto the register plate on the ceiling whereby (from memory) 6" before the plate you have to switch to twin wall to pass through the plate.

This explains why nearly all of the pictures I have seen of free standing stoves you can clearly see the transition between the single wall and twin wall near the top.

I'll definitely have a look at the possibiltyof using a 2nd register plate (one at the bottom).
If thats possible that I could look at using the insulation you referred to.

 

[hotrod]

TOTL on the off chance you haven't read it / are unaware of it Approved Document J - Combustion Appliances and fuel storage systems is well worth a read if you are not going to use a HETAS guy and are going to DIY this and get LABC in to inspect for BRegs compliance.

Heavy going in parts at 92 pages long, though it's not all applicable to stoves.

hth

Rich - cheers, I'll be in touch

 

[TheOriginalTableLeg]

Thanks Hotrod,

Yes I already have a copy and yes it is hard going!


Thanks again to the both of you for your replies.

 

[TheOriginalTableLeg]

Richard,

FYI, here is the usage instructions for the Vitcas screed/plaster that states about PVA'ing the blocks/bricks.

http://www.vitcas.com/VITCAS_Heat_Resistant_Plaster_Instructions.pdf

 

[Richard C]

There is no mention of using PVA under the screed in the written instructions (which I looked at) but you’re right that the block picture at the bottom of page 2 does show PVA under the screed as well as the plaster. This goes against what I would normally expect so I have asked Vitcas for clarification; I will come back when (& if) I get it.

 

[TheOriginalTableLeg]

Thanks once again Richard

 

[TheOriginalTableLeg]

would you guys be able to help me with sizing the false chimney breast?

Are fireplaces normally a nominal size?

Do I need to plough through part j regs to determine clearances or is there a simple rule I can use to determine the opening size into which the stove would sit?

 

[Richard C]

Much easier to understand than Part J, all the relevant regulations are in here;
http://www.stovesonline.co.uk/stove_building_regulations.html

There is generally no "normal" size, what size you make the fire opening (if you have one at all) depends on what type of stove you want to fit so you need to decide that first. Cheap log burners usually need air space around them to prevent overheating & damage; the manufacturer’s installation guides will tell you how much. Inset log & multi-fuel stoves require virtually no clearance at all. The size of the false breast you build rather depends on what sort of visual effect you want to achieve.

 

[TheOriginalTableLeg]

Thanks Richard

 

[Richard C]

There is no mention of using PVA under the screed in the written instructions (which I looked at) but you’re right that the block picture at the bottom of page 2 does show PVA under the screed as well as the plaster. This goes against what I would normally expect so I have asked Vitcas for clarification; I will come back when (& if) I get it.

Just received this response from Vitcas;

Thank you for your enquiry.
Yes we can see that there is some inconsistency here. Usually you would only damp down the wall
as you say underneath the screed, PVA can be used in situations where the underlying material needs to be sealed
for example where the surface is quite poor.
The important point is that PVA must be used underneath the plaster to ensure good results.

Kind Regards
Edward Shaw

VITCAS LTD

 

[TheOriginalTableLeg]

Excellent, well done for getting clarification

Over the past few days I have visited another couple of Stove shops and asked for advice.

In summary my options seems to more than I first realised.

1, Build a concrete block fireplace and use lintels, then run a twin wall flue inside the hollow created, with as you suggested a register plate at the top and the bottom and the void around the fluefilled with Vermiculite

2, Build a concrete block fireplace and use lintels, use Isokern Pumice blocks to extend a pumice flue up and through the ceiling & roof

3, Build a concrete block fireplace and use lintels, use pumice liner system

I have no idea at this stage how the compare in cost, but certainly the stove shop I visited today (two guys, one works in the shop and the other is an installer, they were very nice and helpful) recommended the pumice system.

Any comments?