Insulation Slab Newbie Forum Discuss Insulation Slab in the Good Background Information forums; I have come to the point where I am laying my insultaion slab and have a few questions. I have ...

[OvenBoy]

I have come to the point where I am laying my insultaion slab and have a few questions. I have my foundation done as well as the base and now have come to the part just below the hearth. I found on another website(heatkit.com) that when a guy used the vermiculite, he used a 6:1 ratio with cement. When doing that, what consistency should it be because the pictures still seemed pretty grainy/gritty. Do you mix it with water? Also once the inslutaion slab is layed, do you put the concerete base on top of that or under the vermiculite? If the insulation is below the concrete and not directly under the firebricks, what are you insulating? Thanks for all the help.

[maver]

The original instructions called for an insulating layer under concrete to increase the thermal mass of the oven. For home ovens this is a bad idea if the primary purpose if pizza as it markedly increases the firing time - even if you want to do bread it only makes sense to increase thermal mass if you are doing multiple batches. Pour the reinforced concrete hearth first, then pour insulation layer on top.

The vermiculite/portland mix is strange stuff to work with as the vermiculite will take up a lot of water - you do mix in water but only enough to get it to clump a little if you squeeze a ball of it in your hand - it will not feel "muddy" like most cement mixes.

[DrakeRemoray]

Also, you may want to look at this thread:

http://www.fornobravo.com/forum/showthread.php?t=1236 (Insulating Hearth Too Big, no room for anchors)
and this one:
http://www.fornobravo.com/forum/showthread.php?t=530 (New hearth slab design question)

when considereing how to anchor your enclosure on top of the insulating slab...

Drake