Build the wall of the dome outside the FB Board.

[Joaam]

Hello Great Community,

After several answers to my first post about floor insulation and analyzing all the great recommendations received, I decided to purchase the FB Board but my budget only allows me to buy 2 boards instead of 3 that are recommended for a 36" oven.
My question is if I could place my exterior walls outside the board and if this could represent a serious problem to the insulation, I have the material to cover the dome with the 3" of blanket but the base of the floor will be outside the board.

[Les]

Originally Posted by Joaam

My question is if I could place my exterior walls outside the board .

Are you referring to the dome wall? If so, the answer is no. If you are referring to the enclosure wall, then no problem.

[Joaam]

Hello Les, actually I was talking about the dome wall, do you think I could use refractary cement in the 3 or 4 inches remaining outside the board?

[brickie in oz]

Originally Posted by Joaam

Hello Les, actually I was talking about the dome wall, do you think I could use refractary cement in the 3 or 4 inches remaining outside the board?

Dont do it.
All the heat from the dome will just flow away to the supporting concrete slab and you will be forever trying to keep the oven warm never mind hot.

[Les]

Originally Posted by brickie in oz

Dont do it.

What Brickie said...

[Gulf]

Joaam, Have you thought about vermiculte or perlite and portland. It may be a cheaper alternative (depending on the sources in your area). Also, are there any sources for Calcium Silicate board in your country? That may be an excellent alternative. I was given enough to insulate under mine, howevert just prior to that I was quoted a price of 87 US dollars plus tax for 27 square feet of 2" Calcium Silicate to pick up at a local industrial insulation supply business. Anything you can find locally, even if you have to pour it thicker would have to be cheaper than the importing/shipping charges. Do anything you can to get full coverage insulation under the floor and dome.

[nrobert]

I would also think that you could fill in around the FB board with vermiculite insulation. You could also consider putting down two inches of vermiculite, laying your FB board on top of that and then filling in around with another 2" of vermiculite. That's assuming that your board is 2" thick which would bring you up to an even surface and give you a total of 4" of vermiculite where you don't have the insulating board.

[Joaam]

Thank you Gulf and nrobert for your comments, What do you all think of a set like this one in the attachment?

* To use the ceramic board on all the dome and the Refractary Cement bed only at the entrance of the oven.

[Lburou]

I have a 4 cu ft bag of zonolite (vermiculite treated with silicone) left over....I wonder how much it would cost to ship it from Texas (76049)? You pay the shipping and its yours. It weighs around 15 pounds or so.

With the vermiculite, you could make an insulative foundation for your oven landing.

[Joaam]

I don't know what to say Lburou, thank you so much for your kind offer, but the problem I have is that the Builder I hired is already working on the foundation and the time to deliver the bag from Texas to Honduras will be too long even if I could pay (Which I can't afford) an expedite delivery option.
But let me tell you that I think you definitely are a "Master Builder" as stated in your signature.