If I lay them out with a half-brick on each end (so they will stagger properly, I lose 3 inches of depth on my oven cavity. I don’t really want to do that, because it means the side margins of the hearth will remain exposed.
If you line up the firebrick in the back of the oven w/ the foam… then mark the portion of the firebrick that is overhanging in the front, you can simply cut off that overhang - and it will NOT be seen if you are closing off the front of the oven and wrapping w/ CFB.
I’ve considered, when closing off the front of the oven, laying the brick horizontally instead of on their sides. That will take a few more brick, but it will leave enough room for the door and it will “finish” the hearth edges.
We need to make sure you have enough room at the front of the oven… If you are using firebrick to close off the front of the oven, you will need to apply at least 1 layer of CFB to protect the firebrick from the elements (and that means an inch of stucco too). If you lay the firebrick horizontally… then add an inch of blanket… with an inch of stucco (and any veneer on top of that) - you might be cutting it close for the required 4" of depth needed by the door. And you probably don’t want the door resting on the very edge of the base. If you close off the front of the oven w/ regular clay brick, you don’t need the blanket - but use high-temp mortar for the joints.
I’ve also considered cutting the brick to stagger at the 3 inch mark, but that seems a little wasteful, especially since I already have 20 half-bricks!
I can lay whole bricks, and then I have just an inch overhang at the full length of the foam mold. That doesn’t leave me with much offset for the vertical joints.
All these possibilities are what make building a project like this so much fun!
Given these options, I’m open to other suggestions. What have you done to solve the firebrick length for your materials?
One more suggestion, and I know @bikerbudmatt won’t make this mistake, but for the other builders reading this post… please stagger those mortar joints! You DO NOT want 2 or 3 rows of firebrick sharing a single / long mortar joint - incase you get a hairline crack. If you get a hairline crack in a mortar joint, it will stop once it hits the next row of staggered firebrick. If the brick isn’t staggered, the crack will continue until it reaches another firebrick.