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Problem with insulating Vermiculite layer - Forno Bravo Forum: The Wood-Fired Oven Community



I'm Peter Reinhart! Ask Me Anything! Monday, February 15, 2016 7:00-8:00 pm EST

To kick off our AMA feature, we have invited author, chef and master bread maker and host of Pizza Quest, Peter Reinhart, to be our first host! Peter will be in the Forum on Monday, February 15th, from 7:00 - 8:00 pm EST. If you are unable to be online during the live session, you can post your questions in the sticky post. Peter will answer those questions during the live session on February 15th. You can view Peter's answers to your questions as well as what happened during the live session in the session thread.

Ask Me Anything New Forum Feature

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Problem with insulating Vermiculite layer

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  • Problem with insulating Vermiculite layer

    Hi Everyone

    I'm building my own 42" pompeii oven and yesterday I hit a snag. I poured the insulating layer ontop of the concrete supporting slab (see pic) and this morning I realized that I screwed up the ratio. Instead of doing 5 parts vermicultie to 1 part portland, I did 5 parts portland to 1 part vermiculite. I realilze it's a totally amateur mistake, but it's done now so I'm stuck with the problem.

    Question: Is this somehow salvagable or do I need to break it and rebuild it the insulating layer?

    The reason I ask is because in the FB Pompeii Oven Instruction manual, page 30 (fig 4.2), it appears as though the FB board can be applied directly on the wet concrete slab. I thought the FB had to go on the insulating slab that contains the vermiculite (5:1). I've purchased the FB Board and was planning to put it on top of the vermiculite insulating layer, so that my firebricks rest directly on the FB board.. Do I need both FB board and vermiculite insulating layer or can I do either or, inwhich case putting my FB board on top of this incorrect insulating layer would be ok?

    What about the concern of the heat ultimatley transfering down to this incorrect insulating slab? Should I be concerned about it crumbling from underheath and ruining my oven? Keep in mind this layer has only portland and vermiculite.

    If anyone can help me out it would be greatly appreciated.



  • #2
    Re: Problem with insulating Vermiculite layer

    You would probably be fine from an insulation standpoint with the board over it, but structurally, 5 to 1 is going crack and shrink badly. I would break it out and redo.


    • #3
      Re: Problem with insulating Vermiculite layer

      Thanks for the reply scarborough. Are both nsulating layer and FB board required or can I simply remove the bad layer of insulating layer and apply the FB board on the concrete slab?


      • #4
        Re: Problem with insulating Vermiculite layer

        How thick is the board?


        • #5
          Re: Problem with insulating Vermiculite layer

          Each board is 2 inches thick


          • #6
            Re: Problem with insulating Vermiculite layer

            With 2 layers you do not need the vermiculite.


            • #7
              Re: Problem with insulating Vermiculite layer

              OK thx

              Upsetting set back