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Insulating Hearth question

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  • Insulating Hearth question

    In the FB Pompeii Oven Instructions (v. 2.0), they show the insulating hearth layer as finished rough (image 4.5 and 4.6) and not trowel smoothed. Yet in the subsequent photos (5.3, 5.4, and 5.6), it appears that the insulating hearth layer is smoothed on the surface.

    Am I missing a step? My plan is to do a smooth finish as level as possible but was concerned that was some no-no that is not mentioned and that you instead fill the rough surface with the floor underlay material.

  • #2
    Re: Insulating Hearth question

    I'm assuming you are planning a 4"-6" insulation layer of either perlcrete or vermicrete on top of your concrete base slab that will be beneath both your hearth and dome base. You do want to make this insulation layer level (and big enough) but you don't need to make it perfectly smooth on top. Once the perlcrete/vermicrete layer has cured for a week or two, you will add a thin (1" or so) layer of sand & fire clay, wet it, smooth it, groove it (like for tile thinset), and start laying on your hearth bricks. Each brick is leveled/tapped solid into the sand layer...the grooves in the sand give you the "wiggle room" to lay a level hearth.

    Once the hearth bricks are laid, you start building your dome, leaving a small gap between the hearth brick circle and the dome base. This gap allows the hearth and the dome to move independently during the operation of the oven...and the reason you don't put the dome resting on the outer edge of the hearth bricks is so if you need to replace a hearth brick you can do so easily. (The outer ring gap will fill in with ash so don't fret about that.)

    So, since you're covering the insulation layer with the sand/fire clay mix in order to set the hearth bricks, absolutely smooth insulation layers are not required...being level however, is really a good thing

    Hope this long diatribe helps.
    Mike Stansbury - The Traveling Loafer
    Roseburg, Oregon

    FB Forum: The Dragonfly Den build thread
    Available only if you're logged in = FB Photo Albums-Select media tab on profile


    • #3
      Re: Insulating Hearth question

      Thank you Mike! That was extremely helpful.


      • #4
        Re: Insulating Hearth question

        Where do I get these instructions?


        • #5
          Re: Insulating Hearth question

          Go to the Shop menu drop down. Forno Bravo Store. Ebooks. Note that they have tons of really helpful installation parts and bits in the same section of the store.


          • #6
            Re: Insulating Hearth question

            The original FB plans are tedious to keep updated and are best used only as a general guide. Here's a great place to review nifty builds and get ideas to fit your style. The neat thing is that by sharing new designs the art of oven-building continues to evolve.

   (A newbie’s survey of the Forno Bravo treasures hiding in the archives)


            • #7
              Re: Insulating Hearth question

              Hello Thesharkbar

              Once you have read through the FB instructions and a few of the build threads post your questions and design thoughts. You will get a ton of help and advice here.

              The plans will give you a good outline to work to and the build threads are full of great ideas. There are a lot of different solutions to the oven build.
              This forum is the accumulation of years of build experience.

              Good luck.