Insulation Mistake?

BrickWood Bulletin Board
1

I am trying to build an oven per Alan Scott’s plans. The hearth was supposed to have two layers. The first was to have 2 inches of vermiculite mixed with portland cement in a 6:1 ratio. Then topped with 3.5 inches of concrete (to be then topped with fire brick)

My mistake was mixing concrete with the vermiculite vice the cement. And used it at 5:2 vermiculite to concrete… Ugh

Question is will the insulation properties be sufficient? Should i cut it all up and repour before i do the dome work?
Thanks.

2

The Vermiculite / Perlite : Concrete should be between 4 parts V/P : 1 part Portland Cement all the way up to 8 parts V/P : 1 part Portland Cement.

We recommend 5 parts V/P : 1 part Portland Cement.

Now, covering that with 3.5" of concrete will nullify all that insulation work you just did and leave you with a non-insulated hearth slab.

If you were to go that route, you got it upside down. Here’s how it should look when built:

PIZZA OVEN

FIREBRICK

INSULATION LAYER

CONCRETE HEARTH SLAB

PIZZA OVEN BASE

EARTH

Here’s a link to download our instructions on how to build a pizza oven with a detailed materials list.