Crack is chimney breast

annosullivan10

I recently got a stratford back boiler insert stove 16kw installed with flexiflue lining in chimney.
I am now noticing hairline cracks in wall over fireplace when stove thermostat is set at 5 and as stove get warmer the crack becomes wider eventhough the wall just feels warm. Does anyone know whats going on here or is the chimney cracked.

patrickjlyons

Hi Ann,
I have the same problem with a crack on the chimney breast - in our case the plaster is blown (come away from the wall behind) and as a result cracked with the heat.
You can tell if its blown by tapping/knocking on the plaster around the crack and it sounds hollow compared to else where on the chimney breast. If this is the case it would need to be knocked off and re-plastered to resolve the cracking problem. Also at this time the block work behind the plaster could be checked for cracking as well.
you should ensure you have a carbon monoxide alarm in place in case there are any leaks from the crack when you are using the stove. Since you have a flue liner in place that's unlikely to be the case.

annosullivan10

Hi Patrick,
Thanks for the reply to my question. When I tap the chimney breast over stratford insert stove it sounds hollow. the crack seems to get bigger the hotter the chimney breast gets when the fire gets going. I had plummer back he said the reason chimney is hot is that the flue in chimney is too near the chimney breast wall and that, thats the way the chimney was built by the builder (house 20 yrs old). He said its safe and that won't cause chimney to crack, but may need to re-plaster the wall as you said, so will probably have to do that. Have you had any cracks since you re-plastered? Also does your wall over stove get very hot when you have good fire on in stove.

patrickjlyons

Hi Ann,
I have yet to get the chimney breast re-plastered so we still have that crack that expands when the fire is lit and gets going.
The area where the crack is on the chimney breast gets warm alright, but not very hot. When the fire is not lit the crack is less noticeable as it contracts when cold. I think the crack is same as yours and because its blown plaster, it cracked easily and is now growing with the expansion caused by heat from the fire. I will be getting it re-plastered in the new year, and hopefully it will resolve it.

annosullivan10

Hi Patrick, thanks for getting back to me on stove issue, if you get your chimney breast re-plastered will you let me know how you get on with it.

patrickjlyons

Hi Ann.. will do, it will probably be Feb /March at least before I get to it, as there is a queue of other stuff to do in our house :-)