How thick should your Ceramic fire proof board be ?

[Chops]

Thinking about using 1.6 " Thick Fireproof Board @ 2,300 F., for my 40" Dia. Pompei Oven ? Any thoughts /

[SableSprings]

Welcome to the forum community Chops! We normally advise 2" of ceramic insulation board as a minimum under the cooking floor bricks. It's a bit expensive, but well worth it. For those who don't want to use the CalSil board, a mix of perlite or vermiculite with a matrix of cement (5:1 ratio) works fine to create an insulating base for an oven. You need a minimum of 4" of the perlcrete/vermicrete & it's a bit difficult to work with. One of the minor problems with this method is the amount of water used takes much longer to drive out during the curing fires. We also recommend weep holes in the hearth slab and separating the reinforced slab surface from the base insulation layer.

Lots of well documented builds here & it's well worth your time developing a detailed plan for your build by reading these threads & asking questions. Good luck & again, welcome!

[Chops]

Hey! thank you for all that Good advice.

[mrotter]

Welcome to the forum community Chops! We normally advise 2" of ceramic insulation board as a minimum under the cooking floor bricks. It's a bit expensive, but well worth it. For those who don't want to use the CalSil board, a mix of perlite or vermiculite with a matrix of cement (5:1 ratio) works fine to create an insulating base for an oven. You need a minimum of 4" of the perlcrete/vermicrete & it's a bit difficult to work with. One of the minor problems with this method is the amount of water used takes much longer to drive out during the curing fires. We also recommend weep holes in the hearth slab and separating the reinforced slab surface from the base insulation layer.

Lots of well documented builds here & it's well worth your time developing a detailed plan for your build by reading these threads & asking questions. Good luck & again, welcome!

Separating reinforced slab surface from base inslution - how?

[SableSprings]

Mrotter: there are two common scenarios for base insulation of a wfo, using ceramic rigid board or a vermiculite/perlite insulating concrete mix (v/pcrete). For both, you want to separate the insulation from the concrete foundation top slab surface because it can wick or hold/transfer water to the insulation layer. The forum has been advocating weep holes through the concrete slab (4-5 holes, 1/2" diameter) in a pattern below the footprint of the oven. These can be cast in the initial pour or drilled. The purpose is to create an escape avenue for water/moisture from underneath the oven (drying process during the v/pcrete option or to clear water that has seeped in along the top of the supporting slab). In addition to the weep holes, a layer of sheet mosaic tiles (fairly cheap since you can buy discontinued/non-matching often at either tile or big box stores that work just fine). If you are using rigid board, lay the tile sheets upside down (webbing up) and line up gaps with weep holes as best as you can and place the ceramic board directly on top.

If you're going to use v/pcrete, you'll want to use some water permeable garden cloth over the top of the tiles to keep the insulating concrete from filling the tile sheet gaps. Since there is a lot of moisture that will drain off the insulating concrete, this will speed up the curing process of your finished oven build significantly. I've attached a link to a build that has some really good pictures showing this separation layer (rigid board/tiles) technique.

Hope that helps explain this...also, start your own thread if you're doing a build (hijacking a thread is considered bad form in our forum community...). Good luck and looking forward to seeing you start & document your build.

Sorry for the thread intrusion Chops

https://community.fornobravo.com/for...andpoint-idaho