Fireboard Liner Cracked

[Kasy]

We had a wood stove installed earlier this year (Contura 51L). The fireplace previously had a gas fire, which was knocked out and lined with heat resistant fireboard (this is what the installer said would be used).

We used the stove for about a month after installing before it was no longer needed, and have again been using for about the last 6 weeks.

I noticed yesterday a large crack has developed on the liner one side, and a smaller crack on the other. The larger crack also appears to be being pushed out slightly.

Should the fireboard have cracked like this? We were told this would be used rather than plaster, as it would be resistant to the heat. There is about four inches clearance either side of the stove and the liner. The fireboard does get hot to the touch, but I would have expected to get more than a couple of months usage from it?

Is this to be expected when the clearance between stove and liner is smaller than usual?

 

[begreen]

Is the stove in a completely masonry fireplace? If so, I am not sure of the benefit of the fireboard. Hard to say what this happened not knowing what material the installer used or how it was installed.

 

[Kasy]

Thanks, and yes, it is all brick behind in the fireplace. We did want it lined for a clean look, which is when the dealer and installer recommended the use of fireboard/cement board instead of plaster.
I did read somewhere else that this could be caused air pockets between the brick and board expanding and contracting over time? The cracks are around the hottest area of the board.

 

[Jags]

Fireboard/cement board - this is a confusing term for me. Is it cement board as in Durock (or one of its cousins), or is this fireboard a Roxul or vermiculite type of board?

 

[begreen]

One could hold a torch on real cement board and I don't think it would crack. What may be causing is stress due to how it was fitted or anchored or the board material.

 

[Kasy]

To be honest, I don't know whether it is cement or fireboard (wasn't aware of the difference between the two!).

In that case, would it be reasonable to go back to the installer and ask them to check and put right?

 

[begreen]

That sounds like a good place to start. If the wall was uneven behind the board it might be cracking over a raised brick behind it.

 

[Jags]

Yes - I would give them a call. Give them the opportunity to make things right.