Mortar froze while curing during a cold freeze

So, I laid the barrel of the oven the other day while the temperature was in the 40s and I wasn’t paying attention to the weather and it dropped to the 20s overnight and i didnt cover it or anything. When I came out in the morning everything was covered in frost and there were icicles dripping from some of the joints that were frozen solid. Now the mortar feels crumbly after almost 2 days of drying and some of it feels soft and the parts that chip away I can crumble with my fingers. Will the curing fires make the mortar set enough where it won’t matter? Should I break the barrel apart and lay the brick again in warmer weather? (I sure hope not) if it’s necessary though I will do that and wait for sunnier days

Not what we wanted to hear on this Holiday weekend! Can you attach several photos so we can see exactly what the mortar situation looks like? I’m not going to say you should fire the oven w/out getting a good look at that mortar (from all angles - inside and out), but this might be a situation where you fire the oven before you finish the oven… but again - we need to see those mortar joints first.

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Oh no!

Just adding on to @BrickWood ’s request, please give us a closeup of one of the joints that you said was “crumbly.” My experience with the high heat mortar is that it completes its initial set within an hour, so I am very interested to see what this looked like after setting overnight. The icicles in particular seem odd.

Let’s figure it out.

It does feel harder and less crumbly today. But I am still worried because it still seems a bit softer than the mortar between the red bricks which is the same high temp blend

From what I see, I am recommending that you DO NOT tear down the oven. This oven looks better than many oven pics I have seen over the years!

I suggest you purchase an inexpensive tarp that will cover the entire oven AND the exterior red brick. Then place a small space heater (not the big dish kind, but a small bathroom heater) inside the middle of the oven and turn the heater on for 3 or 4 days.

Normally, I wouldn’t recommend curing the oven before finishing the oven, but in this instance, let’s go ahead and cure that oven (even before adding the chimney brick). After you have completed the 6-day pizza oven curing cycle, take a good look at those mortar joints in question and let us know what you see (plz include pics &/or video).

I’m betting my wife’s entire paycheck that you will be a-okay!

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In my opinion that’s pretty much how those joints are supposed to look. I completely concur with @BrickWood on this. The reason we’re both saying to dry it out and then follow the curing cycle now instead of waiting until after your insulation is in place is simple: the high heat mortar does not fully cure until it is fired. You want to do it according to the “book” — low and slow, and building up so that you drive out the rest of the moisture in the first 3 fires and then fire-cure the mortar in the last 3 fires.

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Okay great! Should I lay the back of the oven before doing this? I feel like it would need it to keep the fire contained.

Yes. I didn’t pick up from your earlier messages (though you said it!) that you have just the barrel laid right now. Yes, do the back, then place the heater in for three days as @BrickWood recommended. You want the mortar to feel “set” to the touch before you go ahead and fire.

The order for your oven will be: build back, low heat for three days or until mortar dries to touch, then follow the initial curing directions scrupulously. **Be very careful ** not to push the curing sequence, even though the first couple of fires will make you wonder whether you accomplished anything.

What we’re trying to do here is get the mortar to its final set form without cracking it.

Once you’ve got curing fires done, you won’t have to worry about the cold weather again. Winter conditions suggest you will want to tarp the oven after this and pick it up in the spring rather than trying to install insulation and stucco, but you know your local conditions better than I do.

Keep us posted…especially now that @brickwood has a wager riding on this!

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So I’m a little worried after reading this post. I have a contractor working on my patio and they are expected to start building my oven either tomorrow (12/1) or the following day. Should I be concerned based on the expected forecast?

Where are you located? Can you expect the temperatures to drop further than that over the next couple of weeks?

There are a number of stop points built into the construction (for concrete, mortar, and so on to cure). If you typically get harsh winter cold during December, you may want to talk this over with your contractor. The fact that they seem ready to start on December 1 may mean they aren’t too worried about the cold, but you should talk it over with them.

It will likely drop even further. I live in Pittsburgh. I think they were planning on doing the oven over a couple of days through the weekend unless they need to stop at certain points. The base is already built. They would just be finishing the upper oven.

Understood. I’m trusting they are following the general instructions for the build and are confident in their ability to finish the upper oven this weekend.

Word to the wise: do not give in to any temptation to fire up the oven as soon as they finish their work. It will need five days to air cure and then the low and slow 6 day fire curing process. Follow the tip above regarding a small heater inside the barrel during the air curing phase.

Good luck! The base of the oven looks right on, and that’s going to be one popular patio when it is finished.

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They held off on finishing the oven until it got warmer. The temps have been between 40-65. Do I still need to use a heater in the oven? Should I leave the door off the oven while it is curing?

They made a good choice.

Using a heater might still be a good thing if you want, but we are really only talking about that for temps below freezing.

Yes, for sure leave the door off. You want good air circulation for this phase. And when you get to the fire cure, also leave the door off until your flames burn down. Then put it on once the flames die down, because you are more interested in heat retention at that point.

It’s really going to be fine and can’t wait to see some final photos!

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I am still waiting on the countertops so that I can add my Big Green Eggs and a gasser for my wife. There’s going to be a lot of cooking going on out here!


HOLY SMOKES!!! Please tell me you took a Photo &/or Video diary of this project!! I REALLY want to post these pics!