When I place the fire brick on the pizza oven form, the brick doesn't fit snugly between the elevated ridges. Did I get the the wrong size fire brick?

I am installing fire brick as I go up the foam I can see the bricks are 1/2" below the foam lines, is this normal. It seems that the firebrick should be in the grooves on the foam??

9" x 4.5" x 2.5" fire brick will fit snugly between the elevated ridges - if you have that much of a gap, I don’t think you are working w/ fire brick that is 2.5" in height. If you have a 1/2" gap, that means your firebrick is 2" in height - the oven kits require 2.5" fire brick…

Question - since most firebrick is 2.5"… and some are 2.25" - it’s rare to have a 2" fire brick.

If the fire brick is 2.25" - YOU ARE OKAY! The joints will just be a little bit thicker than normal - but still useable. If the bricks are 2"… that’s would be a tough call. Personally, I’d try to get a 2.5" or even a 2.25", but I would be torn on using a 2" fire brick.