Cementing firebricks to a metal plate

[eamonford]

I have a wood burning fireplace that was "renovated" by some previous owner in such a way that left a wooden stud exposed along the full width of the top of the firebox, just inside the front rim. I'd like to have that wooden piece covered up by firebricks so that it won't catch fire, but surface along the length of the wooden piece is covered by a steel plate, which means the firebrick would need to be attached to the steel plate somehow. My contractor used regular high-temperature mortar to cement the bricks to the steel plate, but they fell off within 3 days.

Is there a good mortar or other material that can be used to attach these bricks to the steel plate? I've considered Rutland 600°F RTV High Heat Silicone Sealant since I think it should be more forgiving with the bricks and metal expanding/contracting at different rates, but I'm not sure whether it has enough tensile strength to hold the weight of the bricks. I've also considered furnace cement which is supposed to be able to bond to both brick and metal, but it needs to be cured at 500 degrees and I'm not sure whether the very front of the fireplace could get that hot, even with a large fire going.

 

[DAKSY]

Can you post a pic of what you’re dealing with to clarify?

 

[bholler]

I have a wood burning fireplace that was "renovated" by some previous owner in such a way that left a wooden stud exposed along the full width of the top of the firebox, just inside the front rim. I'd like to have that wooden piece covered up by firebricks so that it won't catch fire, but surface along the length of the wooden piece is covered by a steel plate, which means the firebrick would need to be attached to the steel plate somehow. My contractor used regular high-temperature mortar to cement the bricks to the steel plate, but they fell off within 3 days.

Is there a good mortar or other material that can be used to attach these bricks to the steel plate? I've considered Rutland 600°F RTV High Heat Silicone Sealant since I think it should be more forgiving with the bricks and metal expanding/contracting at different rates, but I'm not sure whether it has enough tensile strength to hold the weight of the bricks. I've also considered furnace cement which is supposed to be able to bond to both brick and metal, but it needs to be cured at 500 degrees and I'm not sure whether the very front of the fireplace could get that hot, even with a large fire going.

Just sticking some bricks over it isnt enough

 

[eamonford]

Can you post a pic of what you’re dealing with to clarify?

Here are some pictures from various angles. I’ve tried to circle in red the area that has exposed wood, although there is also some rock wool insulation tucked in front of it.

 

[eamonford]

Just sticking some bricks over it isnt enough

Could you clarify what you mean? Do you mean that the wooden piece will still catch on fire?

The reason I don’t think that area would get extremely hot is because it wouldn’t be directly exposed to continuous flames, since it is at the very front. Before somebody’s “renovation”, this part would have been on the outside of the surround but they extended it out by a few inches to add a new surround on top of the old and a new frame.

 

[bholler]

Could you clarify what you mean? Do you mean that the wooden piece will still catch on fire?

The reason I don’t think that area would get extremely hot is because it wouldn’t be directly exposed to continuous flames, since it is at the very front. Before somebody’s “renovation”, this part would have been on the outside of the surround but they extended it out by a few inches to add a new surround on top of the old and a new frame.

Yes it is well within the area that needs to be completely non combustible. The wood needs to be removed

 

[bigealta]

Can you take a wider pic of the outside of the whole fireplace. Seems like something abnormal was added to the existing fireplace as your description implies.

 

[eamonford]

Can you take a wider pic of the outside of the whole fireplace. Seems like something abnormal was added to the existing fireplace as your description implies.

Here is the whole fireplace. I believe the entire surround that you see was built on top of the previous surround, but with wooden studs between the old and the new one. The studs are used as spacers to account for the unevenness of the rocks in the old surround.

 

[bholler]

View attachment 342450
Here is the whole fireplace. I believe the entire surround that you see was built on top of the previous surround, but with wooden studs between the old and the new one. The studs are used as spacers to account for the unevenness of the rocks in the old surround.

The wood studs need to go. So that all needs pulled off

 

[eamonford]

The wood studs need to go. So that all needs pulled off

Can you help me understand why it all needs to be pulled off? If the front of the firebox gets to say 250 degrees but the wood is covered up and doesn’t get above maybe 150 degrees, wouldn’t that protect it from charring?

 

[bholler]

Can you help me understand why it all needs to be pulled off? If the front of the firebox gets to say 250 degrees but the wood is covered up and doesn’t get above maybe 150 degrees, wouldn’t that protect it from charring?

Because 150 is plenty to cause pyrolysis in that wood slowly lowering the kindling point more and more. Until one day it ignites. I have rebuilt after fires caused by wood much further from the firebox than that. It is not a question of if that will catch fire. Its a question of when