Concrete slab + insulation layer thickness

[Sonicbeaver]

Hey folks. I'm in the middle of building a base out of red bricks. The walls will be double bricked - the outer layer several courses higher to accommodate the elevated slab. My question is what should the thickness ratio be between the concrete slab and the insulation (vermicrete) layer above?

A course of bricks is 2.5" high. So two extra outer courses will leave a 5" cavity. Would something like 4" for the concrete slab work, with a 1" vermicrete insulation layer? Or should I add an extra course (7.5" cavity) and go 4" concrete slab and 2.5" vermicrete?

Cavity depth is constricted to multiples of brick height as this will make it possible to perfectly level things off afterwards.I'm in the middle of building a base out of red bricks. The walls will be double bricked - the outer layer several courses higher to accommodate the elevated slab. My question is what should the thickness ratio be between the concrete slab and insulation (vermicrete) layer?
A course of bricks is 2.5" high. So two extra outer courses will leave a 5" cavity. Would something like 4" for the concrete slab work, with a 1" vermicrete insulation layer? Or should I add an extra course (7.5" cavity) and go 4" concrete slab and 2.5" vermicrete?

Cavity depth is constricted to multiples of brick height as this will make it possible to perfectly level things off afterwards.

[SableSprings]

These brick ovens are heavy! Most builders go with a 4" deep, rebar reinforced top slab. Also, using vermicrete as your base insulation, you'll want at least 4"-6" below your entire oven structure for the best efficiency (you don't want the concrete top slab working as a heat sink!) We usually look at optimal height of the cooking floor as about your elbow height. That way you're not stooped over or reaching up to work the oven.

So, it depends a bit on your height. Your stand height + a 4" top slab + 1/2" tile layer + 4" vermicrete + cooking floor brick thickness should come up to your elbow height. (P.S. Don't forget your brick or block mortar layers as they add up!)

[UtahBeehiver]

Sage advice from Sable Springs. I would add, that the ratio for v/pcrete under an oven should be 5 to 1 for suitable strength.