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Does the outer arch need to be firebrick?

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  • Does the outer arch need to be firebrick?

    Some questions I have:

    1. Does the vent landing and outer arch have to be firebrick? If not, should I still use the flue set mortar? -- I think a lot of people have a one and a half brick length for their landing (from inner arch outward). I'm pretty sure the full length brick arch I'll make directly in contact with the inner arch will be firebrick. Then I was planning on using a half non-fire brick for the outer arch. Will this be okay?

    2. For the chimney, I'd like to do the clay flue then surround it with bricks, anything I need to consider for this? Once again, do I need to use flue set mortar for this? Do I even need the clay flue if I am using bricks? Thanks!
    My 36" build -&- Youtube Timelapse

  • #2
    I'd like to hear the consensus on these too. My current plan is to fire the oven and see how hot things get before i add the decorative outer arch, but i believe it will be cool enough to use normal brick for the waterproof and appearance aspects.


    • #3
      Digging around in the forums I've found some answers. It seems that you can use regular brick for the outer chimney, vent area, and even the outer arch. In addition, refractory mortar is recommended for these parts too, as they still get pretty hot. However, some use regular mortar. It is also recommended to leave an air gap between the vent/flue area and the outer decorative arch, to prevent the heat transfer and thermal expansion of the firebricks from interfering with the decorative brick and vent area/chimney structure. From reading, it appears the vent area gets to around ~300F so normal brick should be fine.

      In terms of my chimney, you use a clay liner with a small air gap between it and the brick to allow for thermal expansion and to prevent heat transfer to the brick (and to protect the brick from the corrosive gases).

      I think you'd be fine to use red brick for sides and front of the arch. I like that look and wished I'd done that when I built my oven.
      When I put a big scary fire in my oven some flame does spill out and into the chimney. If you used firebrick for the top of the arch I think you'd be quite safe.
      - christo

      Firebrick are only necessary where fire will or might be in direct contact w/them. There is no real need to use them anywhere else, unless that's just what you want to do
      - NCMan

      My $0.02 is that you don't want the firebrick to be exposed to weather. Soaks up water like a sponge. that''s why I put a decorative arch in front of the firebrick.
      - deejayoh

      I found some builds that use normal bricks for the outer arch and vent area (there are way more, these were the first to pop up):
      Johns 42 Aussie build
      SableSprings' build
      Denamontini's build

      Other light reading:
      My 36" build -&- Youtube Timelapse


      • #4
        There have been a few people who have cast their vent area from a castable homebrew mix with the stainless steel needles. I think a lot of the builds with out fire brick in the vent are in areas where they are very expensive. I never took readings on my vent but i know i cleared it several times so i believe that means it was at least 700F. I use to love to get the oven super hot though for cooking steaks in the entryway and would guess the oven temperature was in the 1300-1400F range. So basically so hot with a long oven mit it was hard to get close enough to flip the steaks. They were so good that way though.