question about hearth floor

[runnerduckfarm]

we are at stage of building hearth floor. there are 2 directions to go.

insulated conc. mix which is 2 parts
then the use of teh superslol

I am confused. the directions indicate a 2 stage pour for the insulated conc. pour and a reinforced 3 1/2" pour when using the superslol. where does the superslol go? is the firebrick placed directly on this?

we were anticipating using the ceramic fire blanker as it is readily available.

it seems like the directions are there for the insulated concrete but then skip right over the use of the superslol and go to building the oven floor.

help this is our intended weekend project for the holiday weekend!

thx
carla

[SCChris]

There is a goodly amout of heat that will push down and out of the oven, through the floor. I poured a 5 inch hearth slab and placed a 2" thick piece of insulation board on this slab. On the board I then placed my firebricks, the oven floor and the soldier course. If I were doing it again I think I go even thicker on the insulation board. If I were using Perlite or Vermiculite concrete, I'd make sure to go at least what is recomended in the FB plans and if the hearth is low enough I'd go for more thickness.

Someone here can comment on vermicrete thickness. I used the board and havn't been unhappy.

Chris

[dmun]

4" of vermiculite concrete, or two inches of refractory insulation board. Either or. Some people use both, and of course it's better to have too much insulation than too little, but it seems like belt and suspenders to me. I have two and a half inches of insblock19, and my slab almost never heats up.

Don't use the blanket form of the insulation under the floor. It compresses too much to be effective there.

[runnerduckfarm]

thanks for all the help. now bigger question is where to get this board. its not that we dont want to purchase from site, we just live clear across the country and the shipping will kill us. doing searches online isnt getting us anywhere either.

carla

[SCChris]

Check with James first and I'd bundle the board with the blanket to spread the cost of shipping over the two.

Chris

[SCChris]

I dropped you another message, Wow you folks are in between everywhere but not so close to anywhere that I could be sure that you can find what you need.

Please keep me informed, I hope I can help.

Chris

[kebwi]

Originally Posted by dmun

I have two and a half inches of insblock19, and my slab almost never heats up.

That's interesting. I have three inches of InsBlock 19 and I agree that the hearth doesn't got hot very quickly. However, several hours into my session I would say that the underside of my hearth is definitely warm.

I wonder how our ovens differ in this regard. I keep thinking my oven's thermal weakpoint is the floor, I frequently get the dome cleared and the entire dome maxing out my IR thermometer and the floor is still in the 600s, 700s if I clean off the coals and expose it for a while.

Quite strange, I thought I had a lot of floor insulation.

[SCChris]

Kebwi, I feel the same way about the floor being the overlooked area as far as insulation goes. I'm happy with the performance and how long the heat stays put, but it's in my nature to wonder about what if..

Chris