Woodburner - cracking of plaster behind

[Luke]

Hi, I put a woodburner in during the autumn last year. This was part of a total refurbishment of the room, so the old fireplace was taken out, a flue liner put in, and the area behind and around the woodburner was all skim plastered. Under the skim, there is an inch or so of bonding coat and then brick wall.

Unfortunately, behind the woodburner, the skim coat and, to some degree, the bonding coat, has cracked - no doubt because the woodburner is too close to the back wall and the plaster is not a suitable material to have in such close proximity to the heat of the stove.

Now summer's here I want to redo the area behind the woodburner. What would be the best material to use and the best way of going about it? Possibly fire resistant plasterboard ("Fireshield"). Possibly some other fireproof board material. Or possibly something applied directly to the wall - cement render maybe?

It is imperative that the newly finished wall is at the same level as the existing wall, due to a nice new granite hearth which has been cut to fit! FYI the woodburner is about two inches proud of the back wall at present.

Unfortunately I don't have a close-up photo of the cracking, but I don't suppose this is really necessary. I do however have couple of photos of the overall effect:

(towards the end of the album - should be self-explanatory)

Any advice most welcome.

Thanks

Luke

[geraldthehamster]

We had a stove installed recently - the installer recommended at least

100mm clearance to avoid the risk of cracking the plaster behind. Having said that, our neighbour has less clearence than you, and has had no cracking, so it's going to be down to local factors. The installer also suggested that lime render would be less prone to cracking than cement render - a suggestion I've seen made quite often, on the internewts.

Cheers Richard

[The Natural Philosopher]

either really, or fire grade tiles or iron or steel sheet.

I've got painted render behind mine. It's good.

[Tabby]

Either strip back to the wall and lime render it, or just install a small very quiet out of sight fan. More air movement back there maens lower peak temps - and more dust build up.

NT

[David WE Roberts]

(towards the end of the album - should be self-explanatory)

Perhaps an obvious question, but how bad is the cracking? If the cracks are relatively minor (due to the plaster drying out more than usual) then do you expect more cracking in the future, or can you just make good with filler?

[Luke]

Well, the cracking is bad enough for about a dinner-plate sized piece of skim coat to come away completely. Underneath that you can see fine cracks in the bonding coat. I had thought of making good with filler but I'd spend every evening peering at it again wondering if it had cracked. To be honest due to the extensive nature of the cracks I don't think filling it will cut the mustard.

I will look at lime render. Metal sheet is worth considering, but I can foresee difficulties in making good around the register plate and at the hearth where the plasterwork in these areas is already quite intricate. I'm sort of leaning towards a board material but the question is, what specific type? "Fireshield" is only about a tenner a sheet, whereas something like Supalux (Class 0 fire rating) is =A3116 for an 8*4 sheet. Ouch!

can see that fan would make a difference but that strikes me as extra hassle and a bit weird.

Luke

[Tim Watts]

(towards the end of the album - should be self-explanatory)

I rendered mine:

Silversand (playsand), snowcrete (white cement) and lime. applied a snowcrete slurry to the bricks first - then rendered in the usual way. It's survived the blistering heat of hot iron 2" away. The mix is actully a little yellow (the sand) so I whitewashed it with some home made stuff.

I suspect the lime content helps a little with the flexibility - but also being 1/2"-3/4" thick does too.