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I have recently noticed some damage on my brick wall, and I would like to understand what exactly is going on, and how it can be helped. To be clear, I am less concerned about hte black spots, and more concerned about the fact that bricks seem to break down under those spots.

See photos below:

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ikostia
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  • My first guess would be frost damage. I can't place the black discoloration though, mould growing on a moist brick perhaps? – MiG Aug 13 '22 at 22:39
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    @MiG I do not know of much natural damage that leaves squares/angles/ or straight lines. It is almost like they were branded(?) – crip659 Aug 13 '22 at 22:48
  • I'm looking at the damage where some of the surface seems to have disappeared. Perhaps local stress, or manufacturing defects. They're strange patterns though, could also be fire related (although I don't see how the surrounding bricks wouldn't be similarly affected). Curious if someone can come up with a fitting answer :) – MiG Aug 13 '22 at 23:39
  • Looks like original colors developed in the furnace and patterns deliberately developed during manufacture. – blacksmith37 Aug 14 '22 at 00:12
  • That's not really "damage" as such, and it's not recent. Those marks were on the bricks when they left the kiln at the brickworks. There's a name for it when it's done deliberately as a style or pattern - "overburn" or something like that. – brhans Aug 14 '22 at 03:20
  • @brhans , "clinkers" is the term I learned when the whole brick has been been baked long enough to turn the dark colors. I don't know if the term applies to these bricks here, but it is from the kiln. The marks are from how the brick were stacked in the kiln. Typically set on the narrow edge, with more bricks on top of them on their edges as well with spaces between them. Where the brick are touching, it doesn't get as hot, so the charring does not happen. Also, it only happens to the bricks closest to the fire, the ones farther away are more uniform in color, – Jack Aug 14 '22 at 07:12
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    Thanks for your comments, folks. I am less concerned by the black marks themselves, and more by the fact that bricks seem to break down under these marks. – ikostia Aug 14 '22 at 10:11
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    please add your concern to the question ... it does not belong in the comment section – jsotola Aug 14 '22 at 11:52
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    It kind of looks like there was, at one time, some sort of structure next to the wall, making contact with it. If so you should be able to see a pattern if you step back and ignore the mortar joints. – Hot Licks Aug 14 '22 at 13:29

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I believe you have brick spalling, which is caused by the brick absorbing water and then freezing. Surprisingly (to me) pressure washing brick can be the first step leading to spalling because it leaves microscopic fractures in the brick's finish.

Here's a website that discusses brick spalling and repair.

RetiredATC
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