Hello!

Yesterday I noticed after using our fireplace that two large pieces had come off a brick. So this morning, I tapped on the brick a bit more and more pieces came off. I think now the loose pieces are gone, but there are still some cracks in the remaining brick.

What's the best way to proceed? Should I remove the entire brick and replace it, or should I just apply fireproof mortar where there are indentations?

I appreciate all tips and advice.

Crumbling brick inside a fireplace with loose bricks and ash scattered on the floor, showing signs of wear and damage. Damaged brick in a fireplace with loose and broken pieces, showing cracks and debris on the ground. Damaged fireplace brick with cracks and missing pieces.

All the best,
Johan
 

Best answer

Claes Sörmland
Knock it loose and replace it with a new firebrick, I think. I wonder if the stone cracked because it was built with rigid fireproof mortar. It should probably have been set with clay mortar so that it can expand and contract as it becomes hot and then cools down.
 
Claes Sörmland Claes Sörmland said:
I suggest knocking it loose and replacing it with a new firebrick. I wonder if the stone cracked because it was set with stiff fireproof mortar. It should probably have been set with clay mortar so that it can expand and contract as it heats and cools respectively.
Thank you very much!
When I mortar in the new stone, should I choose clay mortar instead of fireproof mortar, do you think?
 
Claes Sörmland
WzOn WzOn said:
Thank you very much!
When I mortar the new stone, should I choose clay mortar instead of fireproof mortar, do you think?
It's more a question of what you want to maintain. With fireproof mortar, you risk the stone. But with clay mortar, the joint weathers. Either way, you'll have to maintain one of them. I have tile stoves, so here clay mortar is an obvious choice.
 
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Claes Sörmland Claes Sörmland said:
It's a bit of a question of what you want to maintain. With fireproof mortar, you risk the stone. But with clay mortar, the joint weathers. One of them you have to maintain in any case. I have tiled stoves so here clay mortar is an obvious choice.
Hm, yes, that's a bit tricky. I have a recollection of reading that you can plaster the inside of the stove with clay mortar to save the joints. Do you think that could work?
 
Claes Sörmland
WzOn WzOn said:
Hm, yes that was a bit tricky. I recall reading that you can plaster the inside of the stove with clay mortar to save the joints. Do you think that could work?
Yes, that's the standard model for tiled stoves (where historically they haven't used firebrick). But expect to have to re-plaster every summer as the clay mortar comes loose and falls down. It's also standard maintenance.
 
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Claes Sörmland Claes Sörmland said:
Yes, it is the standard model for tiled stoves (where historically fireproof brick has not been used). But expect to have to re-plaster every summer as the clay mortar loosens and falls down. That is also standard maintenance.
Then I have a bit to ponder. Thank you very much for your help!
 
Claes Sörmland Claes Sörmland said:
Yes, that is the standard model for tiled stoves (where historically refractory bricks have not been used). But expect to have to replaster every summer because the clay mortar comes loose and falls off. That is also standard maintenance.
Now I have knocked loose the middle stone, but I had to take the bottom stone as well because it cracked. But what bothers me is that the stone above is a little bit movable but otherwise intact and nice. Should I leave it in place, or does it also need to be knocked out? Or will it remain stable with a little mortar and a new stone underneath? I fear that the stone above it might become a bit loose then.

Damaged chimney structure with removed and cracked bricks, showing rubble and loose stones. Upper brick appears intact but slightly loose. Renovation in progress. Damaged bricks and mortar in a wall, with one brick cracked and removed. A slightly loose brick remains above, surrounded by a blackened surface.
 
How did it go?
 
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R Razer167 said:
How did it go?
It went perfectly! Everything is rock-solid and the stone above is stable after new stones underneath. The new firebrick is thinner than what was there before, so I set double stones and it turned out great. I've fired it up maybe 20-30 times since I fixed the stove and it works flawlessly.
 
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