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Insulation below or above concrete base for Oven Hearth - Forno Bravo Forum: The Wood-Fired Oven Community

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Insulation below or above concrete base for Oven Hearth

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  • Insulation below or above concrete base for Oven Hearth

    Hi, I was away for a week on vacation and took with me the Pompei Oven plans and read through them. Something I never realized in searching the forums lately is that sometime between 2005 and now, the recommendation for the vermiculite insulation has switched from being poured below the conrete to above the concrete just below the oven hearth fire bricks.

    As I recall the last oven I built the vermiculite mixture below the concrete is hard but appears more crumbly than regular concrete. Does this introduce any complications in setting fire brick level or in finishing the exterior facade? I imagine most people would want to completely cover the vermiculite even around the edges.

    Thanks
    Check out my build at:
    http://www.fornobravo.com/forum/f8/t...uild-4678.html

  • #2
    Re: Insulation below or above concrete base for Oven Hearth

    Yes you will cover it...it remains quite porous and crumbly...it works much more efficiently being on top of the structural layer. You can screed a thin layer of fireclay on top of the vermicrete to make it easier to level the floor bricks or just a dry layer of sand and fireclay. Should cause any real complication
    Best
    Dutch
    "Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity. " Charles Mingus
    "Build at least two brick ovens...one to make all the mistakes on and the other to be just like you dreamed of!" Dutch

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    • #3
      Re: Insulation below or above concrete base for Oven Hearth

      There is no way that I would put the vermiculite below the concrete pad as it would add to the termal mass.
      I agree with Dutch that the vermiculite cement is crumbly, I would say mor like a cork consitancy than crumbly though.
      I found in my installation, the it was quite easy to get nice and smooth and flat but iI did have some suitable rectangular aluminium screeding lengths and topped it off with a steel cement trowel. It was almost shiney, flat and smoot, ideal for laying the hearth bricks directly on. I did however have to lift the ocassional one uo dur to minor thickness variations with the seconhand bricks that I used.
      You will have to address the problem of rendering the edges or tiloing the edged of your base but that is an easy venture with the adhesives that are available today.

      Neill
      Prevention is better than cure, - do it right the first time!

      The more I learn, the more I realise how little I know


      Neillís Pompeiii #1
      http://www.fornobravo.com/forum/f8/n...-1-a-2005.html
      Neillís kitchen underway
      http://www.fornobravo.com/forum/f35/...rway-4591.html

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      • #4
        Re: Insulation below or above concrete base for Oven Hearth

        Cork is a great description...couldn't find the right word! Thanks Neill!
        Dutch
        "Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity. " Charles Mingus
        "Build at least two brick ovens...one to make all the mistakes on and the other to be just like you dreamed of!" Dutch

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        • #5
          Re: Insulation below or above concrete base for Oven Hearth

          What about putting the vermiculite mixture below the concrete and then separating the firebrick hearth from the concrete with the insulation board. I presume that would also work although not sure the vermiculite is offering any benefit and could just as well be excluded?

          Thx
          Check out my build at:
          http://www.fornobravo.com/forum/f8/t...uild-4678.html

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          • #6
            Re: Insulation below or above concrete base for Oven Hearth

            Originally posted by tdibratt View Post
            What about putting the vermiculite mixture below the concrete and then separating the firebrick hearth from the concrete with the insulation board. I presume that would also work although not sure the vermiculite is offering any benefit and could just as well be excluded?

            Thx
            What are you trying to accomplish with that setup? What is the function of the vermiculite layer then?

            ...two different separated insulation layers? That sandwiched concrete layer would act as a long term thermal mass/heat sink

            Yes, exclude the vermic layer or put it above the hearth with the board for better insulation!
            Sharing life's positives and loving the slow food lane

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