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Building 42 in Pompeii, any pearls regarding laying down 2 in FB BOARD beneath firebr

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  • #16
    I also agree that an oven needs to breathe. Used in normal construction, brick and stucco are supposed to be porous. However, they are meant to be exterior walls, not roofing material. I think that we can waterproof them for our application as long as we give the oven another "lung" from which to breathe .
    Last edited by Gulf; 07-28-2018, 06:08 AM.
    Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build

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    • #17
      Agree. There are "waterproofing solutions" that are vapor permeable and vapor impermeable.

      i just did a second coat of Thoroseal on my dome. The Thoroseal will shed liquid moisture, but will allow moisture vapor to pass through it. In essence, it'll minimize liquid water getting in to the structure, but when a fire is lit, it'll allow any excess moisture vapor to escape.

      Id never recommend coating a shell with something vapor impermeable like RedGard.

      Any of these ovens that are designed to be permanent will benefit from a roof overhead. The most carefully constructed shell can still suffer from a thermal crack. Or a freeze/thaw crack in winter.
      Mongo

      My Build: Mongo's 42" CT Stone Dome Build

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      • #18
        Are they any alternatives to CalSil in this design? Why not use perlite since it has better thermal retention?

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        • #19
          Do you mean “better insulative”? If so the answer is no. It takes about twice the thickness of a 5 to 1 perlite to Portland cement ratio to equal CalSil.
          Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build

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          • #20
            Originally posted by rwiegand View Post
            Lay down 4"?

            No one seems to suggest putting a vapor barrier between the board and the concrete. Since water can wick through the concrete and reach your insulation, depending on the enclosure design, that would seem to be a simple precaution. I don't know why it's not done. I didn't think about it in time or I would have put down a sheet of stainless steel under the insulation to create a barrier.
            I was in the "concerned" group, so I used RedGard on my slab. Once the RG was cured and the 4" thickness of insulation was down on top of it, I painted the edges of the insulation with RedGard as well. A couple of photos here:

            https://community.fornobravo.com/for...410#post392410

            Mongo

            My Build: Mongo's 42" CT Stone Dome Build

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