[gjbingham]

I'd defer to Canuk Jim and Dutch. He and Dutch are the barrel vault oven masters here. (please excuse me if I've forgotten others).

I'm not one hunddred percent sure I understand your meaning, but I'm thinking though that it might be a bad idea to place the walls external to the floor, simply because the expansion of the floor bricks as the oven heats might break your mortar joints at the base of the wall. Just a guess.

Listen to dmun carefully. He speaks great truths.