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oven weight over vermiculite mix - Forno Bravo Forum: The Wood-Fired Oven Community

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oven weight over vermiculite mix

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  • oven weight over vermiculite mix

    I am planning all my thoughts out for a build this spring i have a question on the insulated hearth i get the 3.5" thick slab what i am wondering is about the insulating vermiculite/portland mix how hard does it dry and will it hold the weight of the oven base and dome i'm having thoughts that it is a fluffy kind of mix i was thinking that all the bricks will weigh it down causing it to shift. Will this be a problem or not?

    vermiculite is readily available from and online store called "ULINE" it is a paper/shipping store it is sold by them for packaging hazzmat materials if a if a hazzardous material was to leak in transit the vermiculite would soak it up..interesting..

  • #2
    Re: oven weight over vermiculite mix

    You can build your oven on up to a 12 to one perlite if you put the walls on the floor and 8 to one if the floor is inside the walls, and still have a safety margin of hundreds of percent. The following chart shows up to 8-1 (which is the most I recommend for workability reasons, not compressive strength).

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    • #3
      Re: oven weight over vermiculite mix

      Thanks for the replies. I'm lost with the chart, I would like to hear of people who had there ovens sitting for a while through a couple winters.

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      • #4
        Re: oven weight over vermiculite mix

        Originally posted by GIANLUCA View Post
        Thanks for the replies. I'm lost with the chart....
        Just look at the first two boxes on the left...those are your cement/perlite(or vermiculite) ratios. Then go six boxes to the right ( compressive strength header).

        Remember that standard concrete is right around 3000 psi ( normally) Tscar outlined a couple ratio parameters. I get that you want to hear first hand if someone did this, but there won't be a problem if you do it. In fact, in my current build, the whole oven...floors and walls, will rest on the insulating 'crete.
        Old World Stone & Garden

        Current WFO build - Dry Stone Base & Gothic Vault

        When we build, let us think that we build for ever.
        John Ruskin

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        • #5
          Re: oven weight over vermiculite mix

          To break it down. For a normal oven designed around the FB plans, you can mix 8 parts perlite/vermiculite* and get a floor that will easily hold the weight of the oven, is cheap and is also a very good insulator.

          In the U.S., one bag of portland cement of 94+/- pounds equals one cubic foot of cement. Commercial perlite is usually packaged in 4 CuFt bags. 2 bags of perlite, plus 1 bag of portland and 16 gallons of water will net you 8 cubic feet of 90-125 PSI concrete upon which to build the oven. Don't try and mix it all at once.



          *I have never worked with vermiculite so that is a guess and should be checked.
          Last edited by Tscarborough; 02-15-2013, 07:14 PM.

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          • #6
            Re: oven weight over vermiculite mix

            Originally posted by Tscarborough View Post
            To break it down. For a normal oven designed around the FB plans, you can mix 8 parts perlite/vermiculite* and get a floor that will easily hold the weight of the oven, is cheap and is also a very good insulator.

            In the U.S., one bag of portland cement of 94+/- pounds equals one cubic foot of cement. Commercial perlite is usually packaged in 4 CuFt bags. 2 bags of perlite, plus 1 bag of portland and 16 gallons of water will net you 8 cubic feet of 90-125 PSI concrete upon which to build the oven. Don't try and mix it all at once.



            *I have never worked with vermiculite so that is a guess and should be checked.
            Expect around 20% reduction in volume once you've mixed it.
            Kindled with zeal and fired with passion.

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