Longitudinal crack through firebrick after curing

It almost looks like one half is going to separate from other, I do keep it covered from rain using a tractor cover, how do I repair this?

Thank you for your help in advance.

Hi JP, and welcome to the BrickWood forum.

I’m sorry for the delayed response; your post landed in a spot that doesn’t always notify of us of new posts.

I don’t know what to make of those photos. If the sides of your arch are resting properly on the hearth slab, the oven itself is not going anywhere. Am I looking at a brick veneer in the second photo?

I’ll make sure @BrickWood sees this as well. He may have more specific advice for you on this.

Is the hearth cracked? I have a similar crack at the arch in front of my oven and it broke a brick as well. But mine is not broken at the back like yours ran like yours. Masonry cracks quite often but so far mine has not expanded so I am just monitoring. I think i may have had a freeze issue over the winter from a leak around the chimney pipe.

I’m thinking the curing processes was a bit rushed. It’s got to be fired slowly or it will crack (thermal expansion w/ some moisture still in the brick and mortar). And that’s a lot of soot on the front of the oven for still being in the curing process. But those front-end cracks can be fixed w/ a tube of high temp mortar from AMZ. It’s about $5 and you just pump it into the hairline crack and it will practically disappear.

What I’m curious about is that crack in the back. There should be little-to-zero hairline cracking on the masonry / veneer when applied over the ceramic fiber blanket. Did you apply 2 layers of blanket in the back / sides / top of the oven?

That crack in the back of the oven can be filled w/ HTM - but again, that’s an odd crack and shouldn’t be there.

Can you send a few pics of the construction process so I can see exactly how the oven was built?

Well I had total 5 fires to cure the oven, it rained after curing fire no. 4, I knew gradual drying is important and oven settles over time,

I think you are right though, after the rain I should have start over instead of continuing to go up in heat,

Yes there is a blanket in the back,

There is no veneer, all solid bricks outside and fire bricks inside, blanket in between, I do not know how many layers though, I hired couple of guys, printed instructions and gave it to them.

Thanks for recommending sealant, I will use it?

Thank you for the reply!

I’m not at all happy about that crack in back. I know it will never been seen - but it shouldn’t be there as there is very minimal heat in the back of the oven. Not enough to crack the mortar.

  1. Before conducting ANY repair, please use the oven as normal for a full year. This will give your oven a chance to stretch her legs… and settle into shape. You may develop a few more cracks, but once the oven is a year old and the mortar is good and hard - we will know where to apply mortar patches for a long-term repair.

  2. Seal the oven w/ an organic masonry sealer. Make sure it’s organic since you will be applying heat to the oven (and sealant). If it’s not organic, it may contain toxic chemicals that could be inhaled during the heating process. And will probably be stinky too…

Sounds good, we already had one pizza session and everything went great, I continue to use cover but being in north Caroline the humidity gets in,

I have decided to start it 3 hours early and let it warm up before firing it up all the way to 700 degrees.

Thanks for all your help and suggestions.


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