A cautionary tale about fireplace brick in RMH

[josephcrawley]

A 6 inch p channel style stove was built in the fall of 2018 and has been in use ever since with a heating season that runs from late September until early April.

At the beginning of this season an inspection revealed significant cracking in the firebox brick.

Here's a link to photo of the fire box remnants.
photos.app.goo.gl/ksn3NoYWh5g6BmmY7

These brick were "fire brick" obtained at a local brick yard. Interestingly the ceiling had no cracks what so ever and the port side had no intact brick. Looking into what these brick are rated was a dead end but some internet sources rate these as light duty. A good rule of thumb is if it's 4 inches wide it is a light duty fire brick. All the proper fire brick I've seen is 4.5

[fuegos]

"Fire brick " can be a bit like "refractory cement" meaningless terms unless accompanied by a technical specification sheet, something that should be available for all construction materiales sold in Europe.In my own case i used reclaimed "firebrick" form an old dome type bread oven that was being dismantled near me.These probably date from the 1930s & were hand made, some having thumbprints on them.After 18 months of twice weekly firing the soldier course -between the firebox and mixer - on my riserless core oven was starting to crumble & taking out the oven floor revealed lots of cracked bricks.I do wonder if the number of cold starts,sometimes from -8c has had an effect ? The floor & outside wall of the core show no sign of cracking.Apart fom the sodier course the cracking wasn't a problem.

[josephcrawley]

These were purchased from Adams old castle a popular brand carried by some of the box stores as well.

[gadget]

I ran some cheap firebrick purchased from a tractor supply store. I had some cracked bricks that where in the firebox also. I used them in a tiny RMH but it was forced induction so it saw very high temps often. The roof brick that would often get to a bright orange color survived just fine even with fused melted ash bonded to it. I guess the firebox bricks see more physical abuse and more temperature swings or temp gradient.

Those cheap bricks have less pure ingredients and less accurate ceramic forming during manufacture.