Using the ground as insulation?

[JRDeMeo]

I just poured my hearth today on the ground since I'm building my oven flush against my retaining wall.

Do I need to pour the typical insulating layer on top of my hearth since I have the base on the dirt or can I get away with using the ground as insulation?

To my knowledge you have the insulating layer because there is the free space for wood underneath the hearth and you don't want the heat escape out the bottom so with that being said if I have my hearth on the ground do I need to have the insulation on top as well?

[christo]

You will want an insulation layer. Go for it if you can.

The slab will act as a huge heatsink and the floor of your oven will have a long hard time heating up.

if you are worried that the oven floor will be too high, my oven opening is about tenns swing high and it could be a little higher in my opinion.

Christo

[DrakeRemoray]

You will definitely want insulation between the slab and the oven! No doubt about it...

Drake

[dmun]

Your oven floor will never be hot enough to cook pizza, or much of anything else, without insulation. You will waste tons of wood and time trying.

Soil is not an insulation.

[DrakeRemoray]

Originally Posted by dmun

Soil is not an insulation.

And even if it soil was a good insulator, you need insulation between the slab and the oven!!

[dvonk]

without insulation you virtually will try to heat up the whole Earth and somehow all the Universe
its quite long and expensive work - since the Earth under your slab is VERY big

[JRDeMeo]

Well it looks like i'm insulating!

[jengineer]

depending on where you are in California and what the amount of runoff from watering the trees you will want to create a drainage system that will keep the water away from the base of the oven.

[berryst]

you have been saved