web analytics
hearth slab - Forno Bravo Forum: The Wood-Fired Oven Community

Announcement

Collapse

Forum Issues Update

We are continuing to work diligently to resolve the issues currently being experienced with the PhotoPlog. Thank you for your patience!
See more
See less

hearth slab

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • hearth slab

    Hopefully someone can answer this, I'm building a bread baking oven that will be in daily use(Sunday excepted), a cross-section of the hearth will be as follows: 4" firebrick.4" thermal concrete reinforced 8" vermiculite mortar. Is this enough insulation and secondly should the vermiculite mortar layer given its thickness also be reinforced with a rebar matrix.

    David

  • #2
    Re: hearth slab

    Hi David,

    I can answer this question! Yes I think it is enough insulation under the hearth.

    My build is a bit of a hybrid, but my hearth is similar:
    115 mm of firebrick (about 4 1/2")
    100mm (4") reinforced concrete (as a "floating" slab, so separated from the surrounding base structure)
    150mm (6") Vermicrete insulation underneath.

    A link to my build: http://www.fornobravo.com/forum/f21/...ula-20323.html

    Admittedly I have only cooked in my oven twice, but on both occasions I had the internal temp up around 500C at the dome and under the Vermicrete it was mildly warm at best (OK to leave my hand there as long as I liked). My dome has no extra thermal mass but is well insulated, and the next day after firing the internal temp is still around 250C.

    I didn't put any reinforcing through the Vermicrete layer, and it didn't need it. I put a few large screws between the vermicrete and concrete layers, and I also put a few short pieces of rebar (3-4") from the sides of the Vermicrete into the blocks of the stand before I core filled them. I was a bit worried about the weight of the Vermicrete layer being held by those crews only. I'm still not sure if this was overkill but it didn't hurt. I think to put rebar all the way through the Vermicrete might detract from its insulating properties?

    Having said all that, I think there are probably better ways to insulate under the hearth slab. On my next build () I think I will investigate polystyrene blocks (eg Foamex) for under the concrete hearth slab. Surely these would be easier to fit and better insulators?

    Hope that helps.

    Andrew

    Comment

    Working...
    X