WoodburningStove Multiboard what to stick it on with

fzx5v0 · 5 May 2010

Hi
I am installing a woodburning stove and lining the fireplace with multiboard and the brickwork for the chimney is not flat and bowed a bit

What would you recommend to attach it to the brick work
was going to dot and dab it on but not sure it will with stand the heat or is there any other ways you would recommend

thanks
Grant

Richard C · 5 May 2010

Who advised Multiboard for your application? It's the wrong product. It’s a Gypsum based board & although certified to class O fire resistance, is only suitable for a one off exposure to high temperature, it’s not suitable for continual exposure to temperatures above 50 degrees, as is the case for any Gypsum based plaster or plaster based boards.

This is lifted directly from the British Gypsum spec sheet;
Limitations of use
Glasroc F MULTIBOARD is unsuitable for use in areas subject to
continuously damp or humid conditions and must not be
used to isolate dampness. Glasroc F boards are not suitable
for use in temperatures above 49°C, but can be subjected to
freezing conditions without risk of damage.

Read this archive thead (& there are ohters) & come back if you have more questions;
//www.diynot.com/forums/viewtopic.php?t=211524

roughcaster · 5 May 2010

Richard C said:
Who advised Multiboard for your application? It's the wrong product. It’s a Gypsum based board & although certified to class O fire resistance, is only suitable for a one off exposure to high temperature, it’s not suitable for continual exposure to temperatures above 50 degrees, as is the case for any Gypsum based plaster or plaster based boards.

This is lifted directly from the British Gypsum spec sheet;
Limitations of use
Glasroc F MULTIBOARD is unsuitable for use in areas subject to
continuously damp or humid conditions and must not be
used to isolate dampness. Glasroc F boards are not suitable
for use in temperatures above 49°C, but can be subjected to
freezing conditions without risk of damage.

Read this archive thead (& there are ohters) & come back if you have more questions;
//www.diynot.com/forums/viewtopic.php?t=211524[/QUOTE]

You wont get better information than that FZX.

fzx5v0 · 6 May 2010

Sorry
I lead you down the garden path what i ment to type was masterboard but when I checked with my supplier I could not get any but they have supalux board which is the product up from masterboard

Is the supalux board ok and how would you fix it

Richard C · 7 May 2010

Had a look at the spec sheet & it’s a fibre reinforced calcium silicate board listed as suitable for boiler backing so should be OK. I would not recommend fixing with dot & dab, I doubt very much if the adhesive will stand the heat; Superlux don’t recommend it either. Mechanical fixing is the way but weather you screw directly to the wall or over battens would depend on how much space you have; how do you intend to finish it?

I’ve never used these boards personally & prefer a conventional sand/cement/lime render which, done correctly, will withstand the heat. The walls surrounding the stove are also likely to reach temperatures well over 90 degrees C so Gypsum plaster/boards are not much use there either, you need a heat proof plaster or it will crack? Are you having a fire surround fitted?

fzx5v0 · 7 May 2010

Hi
I do not want to use wood battons behind it just incase so will try and use metal ones.

Due to the poor cunstruction of the chimney it has to be boarded out.

Not to sure what to finish it with yet but want a smooth finish

Souround will be probably be going on

I have some of this http://www.bostik.co.uk/diy/product/evo-stik/serious-stuff do you think it would be sutible for fixing it

I have looked at screwing it but do not want to use plastic raw plugs encase they melt in the bricks and ones with metal ones have a big bold head that i can noty counter sink due to the board only being 6 mm thick

Thanks

Richard C · 7 May 2010

fzx5v0 said:
Hi
I do not want to use wood battons behind it just incase so will try and use metal ones.

Yes I should have said don’t use wood.

fzx5v0 said:
Hi
Due to the poor cunstruction of the chimney it has to be boarded out.
Not to sure what to finish it with yet but want a smooth finish

Your going to be limited to either leaving the boards as is or use a heatproof finish plaster (ordinary Gypsum plaster will fail in a very short time) but the Supalux fact sheet also advises it can be difficult getting plaster to stick, as it can be with many construction boards; & then there is the heat factor again.

fzx5v0 said:
Hi
I have some of this http://www.bostik.co.uk/diy/product/evo-stik/serious-stuff do you think it would be sutible for fixing it

Again, the problem is that the product is not designed for use where temperatures exceed 100 deg C. I’ve measured temperatures well into the 90’s in the wall area 500mm above & 300mm to the side adjacent to a tiled stove surround, the fire opening itself will exceed that by a considerable margin. Heat proof plaster will stand up to 500 deg C

fzx5v0 said:
Hi
I have looked at screwing it but do not want to use plastic raw plugs encase they melt in the bricks and ones with metal ones have a big bold head that i can noty counter sink due to the board only being 6 mm thick

There’s not much you can’t cover & repair with sand/cement/lime render & I would still consider it; would save all that messing about with battens & problematic fixing. Have you seen this stuff;
http://shop.vitcas.com/vitcas-heat-resistant-plaster-16-p.asp

fzx5v0 · 7 May 2010

Hi
Thanks for that. I am going to give it a go at the weekend and have bought some Ceramix TC to stick the board on with which will withstand tempretures upto 1250 0c

thanks

jrplastering · 7 May 2010

im with richard c on this one sand and cement all the way we did some a few months back and had a special cement cnt remember the technical name for it though sorry but we just called it fire proof cement haha primative i know but then again im a primative bloke haha

Richard C · 7 May 2010

fzx5v0 said:
Hi
I am going to give it a go at the weekend and have bought some Ceramix TC to stick the board on with which will withstand tempretures upto 1250 0c

Personally I think your making a mistake relying purely on an adhesive bond, especially if the brick structure your bonding to is in any way suspect. With the huge temperature differential & all that expansion & contraction involved I think will fall off in the not too distant future; but your decision.

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WoodburningStove Multiboard what to stick it on with

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