The firebrick are secured by the brick frame built around them. The idea is that if a refractory brick cracks (it happens), it’s easy to remove the pieces and replace it with a new brick.
The sand underneath the firebrick are used to level and set them without the use of any kind of adhesive. I know it’s not intuitive, because we’re so used to thinking of brick being associated with mortar, but it works.
Thanks for the reply and welcome. Yes it makes perfect sense now.
Yes, I do think in the terms of how to make sure everything is securely attached…
You’re welcome! (Sounds a little redundant, I know, but we mean it.)
I’m working on that very step right now. The sand cushions each firebrick and keeps it level. The herringbone pattern does a number of good things: if a brick were to rise, a pizza peel wouldn’t get caught on it; a more subtle benefit is that the horizontal force on each row of bricks does not ever go linearly from one side of the frame to the other. With firebrick reaching their heat potential, that means you’re not setting up a row of little jacks pushing outward.
Any gaps get filled up quickly with the ash from your curing fires; ashes don’t crack, and they let the brick move just enough to relieve stress. I believe that @BrickWood used to recommend spreading all-purpose flour over the hearth and working it into the small gaps, but it turns out the ashes from your fire work better for the purpose.
Having seen your inspiration photo on another thread, I know this is a dream working its way out. Bucket lists are a good thing, and may that bucket be a long way down the road for you.
IMPORTANT NOTICE! On the Materials List for the 47" x 56" Base, we listed (1) 50lb Bag of Insulating Casable (Dry). THIS NEEDS TO BE CHANGED TO (2) BAGS!
At the moment, we are unable to make the change to our website / directions, but if you run into this issue, please add an extra bag of Insulating Castable. If you choose to use Vermiculte or Perlite and Portland Cement, the numbers are correct.
I apologize about the error and we are working hard to get the necessary changes made!
Zoomed In:
Thanks for posting this. I ran into this in my build and thought it was just me. Could you also verify the amount of high temp mortar recommended for the mattone barile? I purchased 400 lbs as recommended and only used half. Thanks for your insight.
That seems like a very economical use of the mortar. My build is the slightly larger Grande, and among the brick border hearth frame, the barrel itself, the back wall, and the face, I’ve used well more than 400 lbs.
There are some variances, but wondering if you used regular mortar for any of those areas.
Hi Matt. I used regular mortar around the hearth frame as I could only get my hands on 400 lbs of high heat. Had I been able to get more I would have done the brick hearth frame too. I used high heat everywhere else except for the veneer. The only places I used high heat on the veneer was the oven opening and chimney. I thought it was odd but I have no gaps between the fire bricks and followed the instructions to a T.
I have to say, I love my oven! We have used it multiple times a week since I finished. We’ve made lots of pizza and what my kids call a smizza or a smores pizza.
That would more than account for the difference. It’s ideal to use the high-temp mortar in that frame because it comes into direct contact with the hearth. I can’t speak to long-term durability because I don’t know.
It sounds like in general you paid very careful attention to the areas where you’ll get direct heat and flame.
A “smizza” sounds like the perfect end to a summertime meal! I’m really happy for you!
Congratulations, and may you have many satisfying pizzas in your future. 
So, to clarify (since I am doing the hearth frame today and hoping to start the barrel tomorrow): will I have enough materials for the diy high-temp mortar mix if I bought what’s on the materials list? Or should I scramble today to get more fireclay before tomorrow? Thanks! Serena
How much fireclay did you buy and what’s your best guess how much is left?
I followed the instructions and had a good cushion left from the fire clay when I completed the barrel and chimney.
You should be fine. Checking back on my build, I recall now that I needed more high temp mortar for a specific reason. I had to redo my hearth frame because I learned the reclaimed bricks I used the first time had been doused with an herbicide. So the entire frame had to be chiseled off and replaced with new bricks.
You should be within the allowance, as @Newman says.
Hi all. Before step 51 in the base instructions it says that standard mortar is listed in materials list but can be substituted with fire mortar but that you will need 70lbs extra. I could only get my hands on 400 for the oven so I used standard mortar for the hearth frame. I ended up with 4 full bags of high temp mortar left over. And now wish I had used high temp for the hearth frame. I’m just drawing attention to my situation with 4 bags left over at a high cost. I’ve got plenty of people asking me to build them an oven so the materials will not go to waste!
And you will ALWAYS get full asking price when placing the bags on Craigslist or Facebook Marketplace.
