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2 questions for the experts: Too much vermiculite?? Weatherproof brick dome???

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  • 2 questions for the experts: Too much vermiculite?? Weatherproof brick dome???

    Hello pizza fanatics, I have 2 questions for you.

    Here's a picture of my backyard 42" pizza oven -- a work in progress. The inner dome is complete, I took great care with it and made all of the mortar lines (high temp thermoplastic) super tight and clean. The oven works very well, and produces some delicious pizza. Stage 1 complete -- and everybody's pleased.

    Next: What you see in this picture was a secondary layer of cement and vermiculite that I wanted as an insulating layer. I'm wondering if I mixed in too much vermiculaite. I believe I followed a mortar recipe from the forno bravo handbook. But it didn't survive the winter (yes it was covered with plastic). So either it absorbed humidity and then froze and cracked, or had already weakened from thermal expansion. Should I try again?? Or just layer on my thermal blankets??

    My other question is about the outer dome. I was planning to build another BRICK igloo dome over the insulation, about 6 inches out from this inner dome. But I live in Chicago. We have a proper winter, of course. Are brick and mortar joints weatherproof? (masonry is not my forte!) Obviously brick WALLS can survive getting wet, but it would be a different story when there are numerous places that water can seep VERTICALLY between the joints. So, yeah.... are all these brick domes that I see on the internet built in warmer climates? Should I abandon that plan and build a flat roof of some sort?? Or coat the brick dome with a waterproofing layer of something??

    Thanks for any input.
    Attached Files

  • #2
    Taking account of the weather where you live I believe you would be better off with a roofed structure and loose insulation within the walls


    • #3
      It could have been any or all of those things. The fact is, all masonry has to be protected from moisture. Espescially when dealing with freeze/thaw. Wet, damp P/Vcrete will also swell when heated. A layer of ceramicc fiber blanket works very well as an insulation but, also as an expansion joint between the brick and the p/vcrete and or stucco layer. Toomulla has given you the easiest solution to your problem. Having the roof of the (enclosure) extend out over the work area of your oven will also extend the amount of days per year that you can operate the oven efficiently. If you are insistent on having the igloo design you may want to think about an open roof over design. I went with an A frame (scissor truss) design.
      Joe Watson, "A year from now, you will have wished that you had started today"
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      • #4
        I just wanted to respond and thank you guys for your input.

        I opted for NO dome, and instead lots of insulation protected by a proper roof. A pizza hut, if you will.

        Not quite done yet. The stucco needs more work at the corners and then a final top coat. A few pieces of drip edge, and some paint... also some brick work at the bottom. And thinking of adding a countertop along the side for pizza prep.

        But everyone is very happy with what we cook! Love this forum. It's a very valuable resource. I'll post more pictures one of these days. Thanks again