Stove insulation and distance to combustibles

18 Feb 2010
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West Lothian
United Kingdom
Not sure where is best to put stuff about stoves, but this seems more regs related than anything else.

So, I am planning on a 5kW stove, which means according to regs I don't need a vent (old house with plenty of holes). Going for a type that allows 12mm hearth, as despite there being an old fireplace doesn't appear to be a hearth under the modern floorboards, so maybe it was removed.

The stove will be sitting in an old bare stone fireplace opening, and I am happy enough with all the distances etc etc outlined in the regs. The place where I have hit a block is the manufacturers 'distance to combustibles'. Most of the small stoves are generally around 400mm wide, and have side distance to combustibles of 400 to 500mm. Now my fireplace is quite wide, just over a metre, but in any of these scenarios the distance from the side of the stove and plaster/skirting is still going to be less than 400mm.

I was wondering if I was taking this too literally, but a search online confirms that plasterboard is officially a combustible, and there is no denying that a wood skirting is. There is no way that most of the stoves I have seen installed are meeting these requirements. In Scotland I don't need any building control signoff for this size of stove, and I don't personally believe that plasterboard is going to go on fire a foot away from a 5kW stove (least not one I am running), but I would still rather ensure that it meets regs, for insurance purposes if nothing else. I am also presuming here that regs, includes meeting the manufacturer regs, although I don't think the building regulations explicitly says this.

Any thoughts?
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Change stoves my opus melody only requires 150mm sides and back. Plasterboard sKim will crack if it gets too hot.
Thanks for the recommendation, expensive stove though, think its probably over my budget. A different stove might be the way to go, all the ones I have looked for so far have been at least 400mm from sides to combustibles, but maybe I need to find a different one.
Not sure on the guidelines, but stoves vary quite a lot, the sides and back of mine doesn't get hot only slightly warm at best, most of the heat is directed frontwards and up.
So stove choice may help... perhaps you could use cement board instead of plasterboard also.
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I have a Broseley Evolution 5

It meets the requirements for the 12mm non-constructional hearth. See hetas guide on the different zones.
Thanks chibs, I had planned to use cement board to line the fireplace, but don't really want to have to replace the plasterboard on my walls with cement board. A different stove might be the only way.

Thanks motorbiking, the Broseley appears to be only 180mm at the sides. Again, a bit more than I was going to spend, but then that might be the problem, perhaps the more expensive stoves are lined on the inside to focus the heat to the front, although some of the really cheap stoves don't seem to specify a distance to combustibles at all, beyond that required by the building regs.
perhaps the more expensive stoves are lined on the inside to focus the heat to the front
I don't believe so, no.

Can you design your hearth such that skirting doesn't have to come close to the opening, and the stove? Does the stove sit proud of the opening, or inside it? That is, can a straight line be drawn from the stove to the skirting?
The stove will almost certainly sit a little proud of the opening, and its from this part of the side that I think would be within the minimum distance. The skirting is probably less of an issue as this could easily be pulled back, and the hearth made wider, but its the plaster on the wall.

It sounds like I have two options:
1. Try and find a suitable stove that has a combined width + 2x minimum distance from combustibles, that is less than the distance from the outer edges of the stone fireplace opening.
2. Remove the plasterboard on the outside of the stone opening and replace with cement board to the distance required. I suppose I could make a cement board trim, or box out the whole opening with cement board and continue it out on the wall, paint it a different colour to the plasterboard to make a feature of it.
I believe it's plasterboard that is considered combustible, rather than plaster itself. If the walls to the side of your opening are dotted and dabbed, rather than plaster or mortar and skim, you could pull some of it off and redo in mortar and skim. But who is to know what is under the skim anyway? Plasterboard isn't going to catch fire, the worst that can happen is that the skim will crack, or the plasterboard will crumble. For what it's worth, I've had skim crack 6 inches behind a stove, but the skim a foot to the side of it was fine.
I completely agree, it is the plasterboard, due to the paper content, and I think it's highly doubtful that the plaster on the plasterboard would even crack say 300mm away from the side of a 5kW stove. I am not really worried about safety here, and in Scotland I don't need building control signoff, I was just keen to ensure that the install met all the regulations and I don't end up invalidating my insurance in the event of an unrelated incident and a clever insurance investigator! Unlikely scenario I know.

I suspect the manufacturers are just covering their backside with these distances, and there is also the fact that "combustible" isn't a binary thing. A bale of petrol soaked straw sitting within 500mm of the side of a stove, and plasterboard are two very different propositions but both fit the broad classification of combustible.

I had been thinking of taking that wall back to stone, insulating and re plastering so I might wait and do these things in conjunction. I have a new problem to deal with now as I have found out, referring to the picture below, the slop on the right which I thought was some kind of historic fireplace thingy, is actually a concrete slab, cemented in place to provide a path for an underfloor vent. Quite funny that I was staring at this thing for so long wondering what kind of historic function it had in a fireplace when its turned out that it was probably installed about 30 years ago. Obviously when blocking up the fireplace many years ago they decided to use the fireplace to add a vent and have butchered away the hearth underneath this too! As this vent is only just above ground level, and it needs to go down at this angle to get under the floor, its brought to my attention that the floor of this room, and obviously the joists, are below outside ground level which highlights a completely separate problem and why the room as had a historic dampness problem.

Old houses! $#$£# :)


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