I see. (I'm being thick).
You will want an insulation layer somewhere in the hearth to keep heat from leaking down. I talked with a builder the other day who build a commercial oven on a 6" concrete hearth, and could feel the bottom of the hearth getting hot to the touch while cooking. His oven was cooling down too fast and his wood costs were higher than he had predicted.
You can insulate directly under the cooking floor in you are only doing pizza and light baking. Otherwise, you would want to insulate under the sandstone hearth to keep the cooking floor and sandstone hot.
Does that make sense?
Jerald, what is the logic behind using sandstone in the hearth?
James |