hearth insulation questions Introductions Discuss hearth insulation questions in the Good Background Information forums; I have a 4" hearth slab and need to choise an insulation material will the vermiculite and concrete mix hold ...

[stevedigangi]

I have a 4" hearth slab and need to choise an insulation material

will the vermiculite and concrete mix hold the weight of a pizza oven for all years that the oven will last, wont the cement fall apart from all the heat

What about using a castable insulating concrete like castilite 22 or delta crete 25 under the oven floor

can i insulate under just the floor and not under the first chain of bricks so that the weight of the oven is on the concrete and just the floor sits on the insulation

[dmun]

The vermiculite concrete doesn't have any tensile strength to speak of, but it doesn't need it. It has more than enough compressive strength to hold the weight of the oven. As far as heat is concerned, it's partly dissipated on the far side of the brick from the fire.

Most insulating castables are MUCH more expensive than the vermiculite/perlite mix. If you want to spend more money, and have better/thinner insulation go for the cal-sil or mineral wool boards.

The insulation should completely envelope your oven. There's no need to build your soldier course on an uninsulated surface, it will just be a heat leak to slow your oven from getting up / keeping up to temperature.

[JConk007]

I am also in NJ, I used a foot thick perlite mixture around oven and lean cement under hearth. I wish I would have used the insulating board offered here at forno. However the next day I am still at a solid 400 degrees great for cooking and roasting, so its holding the heat nicely
John