mini pompeii oven questions

[mathewnorris22]

OK, so I have read loads on the forum, but nothing really answers the basics questions I have.

Firstly I an intending to build a mini pompeii oven (30") with an internal diameter of 25.5 in, I have already constructed the concrete hearth base, so here comes the questions.

1: What thichness should the concrete hearth base be? I have currently poured a 2.5in base with 10mm reenforcing bars, and am thinking this should be considerably thicker?

2: Should I place an additional insulation topping on the hearth and then place a firebrick floor on top of that, or would 65mm thick firebricks directly on teh concrete hearth be sufficient ?

3: Is a fire brick floor what I should be cooking on, or should this again be covered with something?

4: As my oven will be pretty small I am unsure of the oven dome height, I looked at some figures and tried to work out a proportional ratio
I rekon for my 25.5in internal diameter a dome height of 13" from cooking floor to ceiling does this seem to shallow for the dome height.

look forward to comments

[ggoose]

Hello Matthew,
I am just starting my 28" oven.
-Based on everything I have read the 2.5" base seems a bit thin, though input from more experienced builders may suggest otherwise.
-Base pour (or hearth), then insulation, then firebrick, which is the cooking surface.
-Cook directly on the firebrick.
-If you utilize an indespensible tool for your build, the dome height will be exactly half of the diameter of your oven, so a 12.75" height for your 25.5" diameter oven.
My two cents.
Good luck,
gene

[david s]

The quality of your mix and if it is cured properly are questions which need answered. If your mix was measured accurately and the exact amount of water added, then I think 2.5" could be ok if the stand supported in the middle as well. You must insulate between the slab and the floor.
Cook directly on the floor bricks.
Oven height is normally half the diameter, but this can be varied a bit without impairing function. You don't want the door on a small oven to be too low. Stick with the 63% rule.

[mathewnorris22]

thanks guys
what is best to use as an insulant below the firebrick base
would a primary layer of firebricks be suitable or is there a better cheaper alternative

[mathewnorris22]

@ goose
how far have you got with your oven
would be great to see some pics as a comparison to my plans

[ggoose]

Not too far yet; just poured the slab yesterday. As soon as I make some headway I'll start a thread. As to the question of the best floor insulation, most seem to use either a hi-temp ceramic board or vermicrete (portland cement/vermiculite mix). I haven't decided which type I'll use yet...
gene

[dmun]

most seem to use either a hi-temp ceramic board or vermicrete (portland cement/vermiculite mix). I haven't decided which type I'll use yet...

Both work well. I used the insulating board because I wanted to minimize the thickness of the layer for visual reasons (two inches of refractory insulation board is recommended.) Perlite/vermiculite concrete is cheaper, but bulkier - You need four inches. There is also some labor involved in mixing and placing the vermiculite concrete, where the board is pretty much cut-and-place.

[C5dad]

Heat is heat is heat.

You need to follow the minimum dimensions for the floor thickness and the dome thickness/insulation layer. If you are worried about size, use the FB insulation for the floor and dome.