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vermiculite alone or mix with concrete - Forno Bravo Forum: The Wood-Fired Oven Community


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vermiculite alone or mix with concrete

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  • vermiculite alone or mix with concrete

    my 43 inch Pompeii oven is up and running. I had some heat stop mortar left over so used it on the top of the dome. I was going to insulate the dome with plain vermiculite but wondering if I should get anothe bag of heat stop and put it all around the dome first or is this needed?

    Also, is it better to go with plain loose filled vermiculite around the dome or better to use a concrete vermiculite mix? If mix, what ratio do you use?

    any suggestions are appreciate.

  • #2
    Re: vermiculite alone or mix with concrete

    If you have a suitable enclosure, there's no reason not to use loose vermiculite. It insulates slightly better than vermiculite concrete, and there's less to carry, mix, and apply.

    It can leak out of surprising small openings. Check your enclosure with a strong light, and assume that if there's a light leak, there could be a vermiculite leak as well.

    You can block off corners of a cubic enclosure to reduce vermiculite use.
    My geodesic oven project: part 1, part 2


    • #3
      Re: vermiculite alone or mix with concrete

      "Also, is it better to go with plain loose filled vermiculite around the dome or better to use a concrete vermiculite mix? If mix, what ratio do you use?"

      If you do add cement, make it a very weak 12:1 mix. This will insulate almost as well as loose vermiculite. Some have done this to make sure the vermiculite stays in place and to prevent loose vermiculite from blowing around/sifting out of their enclosures. You might consider this if you are doing a well ventilated enclosure with large under eave openings.


      • #4
        Re: vermiculite alone or mix with concrete

        Instead of adding cement to the vermiculite to keep it from moving around in a well vented space just get some aluminum flashing material and place it over your vermiculite it comes in up to 36 inch widths here in Minnesota and wit a 6 inch overlap will keep the vermiculite in place without the added water required to do even a 12/1 mix.

        Or for a tight fit get a piece of aluminum soffit (un-vented) It comes in 12 ft lengths and 1 - 2 pieces should be able to cover the top of the oven space nicely. The pieces are slightly corrugated and slide together easily and will provide a nice tight cover to keep things from moving arround.

        Last edited by mrchipster; 07-19-2011, 08:39 AM. Reason: typos


        • #5
          Re: vermiculite alone or mix with concrete

          thanks for this idea. I'm about to start framing it in and was going to use cement board to hold my vermiculite in (then a wood frame outside of that for finishing). Your idea sounds easier than cutting a lot of cement board to go around a dome!
          Many thanks, wil look to see what sizes I can get out here in connecticut.