Are all cement boards created equal?

[Crofter]

After some online research I've decided to use a cement based backer board instead of plasterboard for the wall behind my woodburner, for increased fire protection.

I had assumed that hardiebacker was the only game in town but the different BMs I've phoned have offered me 'multi pro' or 'aquapanel' instead.

Is there any difference in the fire rating of these boards? And is there any other material that might be better for the job?

 

Thanks

[Simplysimon]

46 minutes ago, Crofter said:

 And is there any other material that might be better for the job?

 

Thanks

an old piece of flat asbestos, nice and cheap, for some reason, no-one wants it these days.

[Construction Channel]

if it is going to be visible you could look at "Glassroc". its painfully expensive but looks much better than the standard cement boards,

 

as for fire ratings i very much doubt there ill be much difference assuming they are all "cement boards" at the same thickness 

[PeterW]

2 hours ago, Construction Channel said:

if it is going to be visible you could look at "Glassroc". its painfully expensive but looks much better than the standard cement boards,

 

as for fire ratings i very much doubt there ill be much difference assuming they are all "cement boards" at the same thickness 

 

BG don't rate Glassroc anymore for fire surrounds - its got a 49c limit for exposure.

 

If you want full fire protection (at a price...) then go for a CaSil board such as Siniat BluClad - about £45 for a 2.4 x 1.2 board in 10mm but its Class 0 rated.

 

 

[Construction Channel]

fair enough, we had to use it to line a gas bottle store early part of last year, I just assumed it would be ok for this...

you know what they say about assumptions...

[PeterW]

tbh it used to be rated but like a lot of stuff they have started producing boards for specific roles and then hiking up the prices...

[Onoff]

This?

 

http://shop.vitcas.com/vitcas-high-temperature-plasterboard-709-p.asp?gclid=CImgu7TSwNECFbEW0wod8fgFiQ

[ProDave]

Most people put a slab of stone up the wall which looks really nice and is probably what we will do.  I take it you don't want that just want a cheaper option that can be painted and look just like any other bit of the wall?
 

[Crofter]

11 hours ago, ProDave said:

Most people put a slab of stone up the wall which looks really nice and is probably what we will do.  I take it you don't want that just want a cheaper option that can be painted and look just like any other bit of the wall?
 

 

Yes I'm not looking to have the wall look any different to everywhere else. I think having a big feature would look too cluttered in such a small space.

 

I'm not going to have a whole heap of choice available between my two local BMs. Probably need to go on and see exactly what they've got, and then look it up.

[Tennentslager]

Only tips I have are...

Cement board is hard stuff (and brittle) so use a counter sink drill bit or screws will sit proud.

Leave a 5mm gap (ply packers) between the cement board and the wall you are attaching to as the air gap provides for additional insulation and stops heat transfer. My cement board was on top of OSB.

Hope this helps

[Construction Channel]

+1 on the counter sunk drill bit

[Tennentslager]

I've posted this before but here you go again...love guys who do this sort of thing, it's the best bits of the inter web

http://www.stovefittersmanual.co.uk

Everything you need to know to get you started and much more... @ProDave

[Crofter]

20 minutes ago, Tennentslager said:

Only tips I have are...

Cement board is hard stuff (and brittle) so use a counter sink drill bit or screws will sit proud.

Leave a 5mm gap (ply packers) between the cement board and the wall you are attaching to as the air gap provides for additional insulation and stops heat transfer. My cement board was on top of OSB.

Hope this helps

 

I'm planning on using 12mm cement board instead of plasterboard, and behind that will be the service void, 25mm deep. However this will be faced with the plastic vapour barrier, so I'm a bit worried that a slight crease or fold in this would allow it to contact the rear of the cement board. Would it be prudent to use some 6mm cement board over the top of the vapour barrier? And should I be thinking about ventilating the service void in this area to help prevent heat buildup?

[Tennentslager]

It's a confidence thing. I'd say you will be 100% fine as you have outlined.

That said...sitting contemplating a roaring fire at 300℃ it's always good to know that for an extra forty quid or so your build is bulletproof plus extra plus OCD safe.

Add in the 6mm by all means (for the bit immediately behind/ near the burner) and relax knowing you've got belt braces and elasticated trousers!

[ProDave]

You are not supposed to ventilate the service void, at least not to a room above or a floor void, there are supposed to be fire stop battens in place,

 

[Crofter]

10 hours ago, ProDave said:

You are not supposed to ventilate the service void, at least not to a room above or a floor void, there are supposed to be fire stop battens in place,

 

 

Never knew that, but it does make sense, thanks.

I would be ventilating a single 600mm wide strip of the void, from floor to ceiling, immediately behind the stove and flue. Ventilation would be to the room only. Not sure what the neatest way of achieving that would be, though.