Structural or Insulating

[Mojoe]

For the hearth slab, do I pour regular concrete first then cap with the insulating concrete or insulating concrete then regular concrete?

[james]

Welcome aboard Mojoe,

The structural layer is below (at the bottom), and the insulating layer (either SuperIsol or vermiculite concrete) sits on that. The oven in turn sits on the insulation, and you really only need insulation below the oven floor itself.

[Mojoe]

Makes perfect sense. Is the insulation layer hard enough to anchor J bolts for sidewalls and a roof?

[asudavew]

From what I have read it is better to put the J bolts in the bottom layer.

[Mojoe]

One of these days I should learn to trust my gut instinct... back to the store for longer bolts.