Oven floor insulation

[kcwagner17]

I'm building a 42" Pompeii and I'm using vermiculite as my oven floor insulation. Should I build the dome on top of the insulation or the concrete base? The vermiculite seems a little too fragile to support the dome. TIA

[deejayoh]

I'm building a 42" Pompeii and I'm using vermiculite as my oven floor insulation. Should I build the dome on top of the insulation or the concrete base? The vermiculite seems a little too fragile to support the dome. TIA

Do a search on the forum for "vermicrete" - it's a mix of concrete and vermiculite for the floor insulation layer

[SableSprings]

Welcome KC! Many of us have used either vermiculite or perlite (or a 50/50 mix) with cement in a 5:1 ratio for the base insulation layer. You must have an insulation layer between your top concrete slab (the hearth) and your oven otherwise the concrete will actually act as a heat sink and getting your oven up to temp will be difficult & costly (if even possible). I used 5:1 (perlite:cement) under my oven and it's worked well for me since 2009. Be aware that you will want a minimum of 4"-5" of the insulating cement under your oven. The CaSi insulating board is expensive, but well worth it in terms of time & effort. Also the CaSi is a better insulator...only 2" needed to provide adequate base insulation.

Doing your dome insulation, you also have the option of using a ceramic batting or the perlcrete or vermicrete mix. If you use the insulating cement mix over the dome, it is done with a 10:1 mix ratio. david s is our casting expert and he has noted that if you choose to make the perlcrete or vermicrete, throwing in a handful of clay powder with each batch makes it easier to mix. We also have many successful builds on this site that build a "dog house" around their oven and simply pour in loose perlite or vermiculite to cover and insulate the dome.

Didn't mean to rattle on here, but I thought this info might be helpful for you...Good Luck and spend time looking at the builds on this site. A good place to start is the thread I've linked below for you.

https://community.fornobravo.com/for...n-the-archives

[kcwagner17]

Thanks for the information! So much good stuff to digest. I did a 5:1 vermicrete insulation base but it didn't seem strong enough to support the dome. It's been 5 days of curing and I'm starting to feel more confident that it will hold.

[CeceliaE]

Hi. We just received the Casa100 kit and the size matching cucina stand. We'll pour the concrete hearth tomorrow. We are confused about the ceramic FB that goes on top before the oven floor. In the pictures it looks like the FB is cut to be a few inches wider than the oven floor. The kit has (3) 24x36 pieces of FB but if put on top of the hearth, the FB would extend 10" or so beyond the hearth. In the instruction book it looks like the FB is precut. What is the best way to proceed? Can we put all 3 pieces of FB on the hearth without cutting it down? Suggestions / Recommendations? thanks so much! __PRESENT

[UtahBeehiver]

It depends on whether the oven is going to be in an enclosure or not. If you are enclosing the oven, ie dog house then you can leave the ceramic board long. If you are not enclosing then you cut the board a min, of the OD of the dome. The dome "must" have insulation underneath the bottom. You can even make the floor insulation "proud" (extend slightly beyond OD of dome). Cut with a jig saw, wear a dust mask and long sleeves, it is nasty stuff to cut or breath in.