Loose brick what to do?

I built the oven in 2019 and it’s been performing great but recently cracks developed around one of the bricks and is loose. Do I completely remove it clean it and mortar back in? or try to re-point.
I think I’ve put some stress by adding one extra course of chimney bricks and later added a 24" Duravent duct, cap and damper exhaust. Thanks.
2019 picture:

Well, I’d start off by saying you should be very, very conservative about what you do here. When we talk about removing hearth brick, for example, we’re discussing a horizontal surface that is not load-bearing. The spot you’re concerned about is at the apex of two stacks of firebrick that are in a perpetual state of “falling” into each other, and that row is Hercules keeping the two stacks apart. Simply pulling a brick is like tickling Hercules.

(I decided to stay with a classical metaphor, but you could also think of it as pulling out a critical block in a Jenga tower.)

I presume the crack is in the mortar, not the brick itself.

I would recommend repointing it. You need some support under the loosened brick while you do that, just to keep it up where it should be. You can use one of the silicone high-heat products mentioned elsewhere on the forum (just search), or if you have left-over high-temp mortar mix available make a loose-ish mix and pack it in as best you can. Either method will not cure completely until the oven is back under fire again.

Again, I’d be very cautious about pulling out that particular brick.

And not to distract, but that “roof” over the oven looks simply amazing! How has that been working out for you?

Good luck, and let us know how it works out.

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