How thick do firebricks need to be for the cooking surface.

[WoodywWun]

I'm planning a Pompeii type oven and just designing the cooking surface at the moment. Looking around I've found various thicknesses of firebricks available. OK, so I guess the logic is that the thicker they are, the more heat they will hold but the price goes up as well. In the UK I've found thicknesses of 32mm (1.25"), 64mm (2.5") and 76mm (2"). Will the 32mm ones be just fine or do I really need to go thicker?

[UtahBeehiver]

64mm is your recommended floor thickness for a general purpose oven. 32mm does not have enough thickness to be able to store heat (IE thermal mass) well enough for cooking unless you are just after cooking a pizzas for a small group and not planning on extended cooking, Some of our bread making WFO's have 3" plus.

[WoodywWun]

Thanks for the reply. So there's no negative side to having a thicker cooking surface? It takes longer to heat up? I've seen a deal that would actually be cheaper to buy a thicker brick.

[Petter]

You wish to have similar heat up time for the dome and floor. Otherwise, you will be wasting wood once either is saturated. Get the floor thickness somewhere between 100 to 50 % of the dome thickness and you'll be good.

[WoodywWun]

Thanks for your reply Petter. When you say "floor thickness", I'm guessing that you mean the cooking floor and not the various layers under itincluded?

[Petter]

Yes, the hot face.

[WoodywWun]

...sorry Petter, I should have asked as well... The "dome thickness" is fire-bricks + insulation layer + any outer concrete protection from the weather that I might put on? Thanks, again.

[Petter]

Think of it as the thermal mass.

The oven is constructed (seen from the inside) of a layer of thermal mass (fire brick), insulation and an outer layer (like stucco or slab) in every direction. You wish to have balance in the thermal mass of the dome and floor so they heat eavenly and at the same rate. Heat rises, which makes it more suitable to have a thicker dome than floor.