Lime behind a log burner, yes or no?

[Relicah]

Hi All,

Onto the next problem opportunity,

The wall behind our (installed before HETAS) log burner is both gypsum and far too close to the rear of the stove (approx. 50mm) - we can move the burner forward a small amount but not enough to allow the 150mm to the rear and 300mm to the front, plus this would have to come with a new offset flue

Question is, what is the best course of action for someone wanting both breathability of the rear wall and non-combustible heat protection - an installer has recommended a STS or hardiboard backer, i presume this will just trap moisture behind?

Thanks all!

 

[a twig]

Does it need moving? Are there damp problems at present?

 

[Relicah]

there are salts tracking up the gypsum, but I'm more bothered about moving the stove away to avoid a radiation fire in the plaster. I should also mention that the plaster directly behind the stove has blown off completely due to heat

 

[a twig]

Fair enough, just thought I’d ask the obvious question! I’d be surprised if you got a radiation fire in the plaster, it’s not something I’ve ever heard of with gypsum but can understand you wanting a belt and braces solution.

The easiest is just to whack a vermiculite board across the back - something like this?

HT - High Temperature Plasterboard

VITCAS High Temperature Plasterboard is a non-combustible fireproof board which does not contain any gypsum. Can be used with Vitcas Heat Resistant Plaster in areas where Vitcas Fireplace Render cannot be applied. Non-flammable rating A1 in accordance with EN 13501-1:2002. Fire and...

shop.vitcas.com

Fit it smooth side out, then paint with high temperature paint and use fire silicone or cement to tidy the edges.

If that doesn’t take your fancy they also do a high temp plaster mix you can apply to the wall directly.

I used to live up the road from Vitcas, surprisingly small company and factory for what they produce, so have used a lot of their stuff, and been very happy with it, plus none of the houses I used their stuff on have burned down either

 

[Relicah]

Thats great, thanks - next question however is will a vermiculite/vitcas HT crumble if it traps moisture behind it, or would you just presume the fire would drive any moisture away?

 

[housewinnie]

You could also get an old cast iron fireback. Rest against the wall at a slight angle should deflect the heat

 

[paulc]

If you do end up using lime plaster, you will find it very tolerant of heat. I used it above my stove, and the chimney breast gets very hot (highest temperature recorded to date, around 180°C). Just a couple of hairline cracks have appeared, but they are barely noticeable.
One advantage of lime plaster is that you can mix pigments in, so no need to paint afterwards.