Cooking floor question?

[plug2000]

Hi there, I’m getting ready to build a 42”” oven. Been researching and watching videos non stop. I’m about to start getting the materials and fire brick. My question is instead of using ceramic fiber board or perlit mix under the floor fire bricks, can I put a additional layer of firebricks recessed in the foundation? I’m sure I’ll have more questions! Thanks for the feedback, this forum Is a great resource!

[UtahBeehiver]

Only if bricks under the floor bricks are insulated fire brick (IFB). Typical fire brick has a K value (thermal conductivity) of about 0.47 W/(mK) where as CaSi board is 0.05. Insulated fire brick 0.15 but also 3 or 4 times more cost than standard fire brick. By placing two layers of floor brick "without" insulation will just be a gigantic heat sink. If you have not download the eplans from Forno Bravo, do so, only few bucks and a good baseline for building a WFO oven.

[Gulf]

Hi Plug2000,

Welcome to the forum. You have come to the right place. To get straight to your question, the answer is no. There must be insulation below the floor and the dome walls separating them from the structural hearth. The firebrick (both floor and dome) are a heat bank that needs to be separated from anything that will rob heat. Insulation is critical to keep that from happening. Another layer of fire brick is not insulation. It is just another layer of thermal mass that will need to be heated and will also transfer heat to the concrete below. It would take massive amounts of wood to heat the floor up to pizza temperatures. Even if and when that was achieved, the concrete hearth would probably spald. Be careful watching oven building videos on youtube. Not all are using "best practices".

[plug2000]

Thank you for the replies! I thought that would be the answer! I’ll probably go w a perlit mix under the floor!

[wotavidone]

Be careful watching oven building videos on youtube. Not all are using "best practices".

Bwahahahahaaaaaa........... a masterclass in the art of understatement right there.........

[UtahBeehiver]

5 to 1 ratio at least 4" thick is recommended for the floor with a 8 -10 to 1 for dome insulation.

[MrBravo]

Hi all, I have a cooking floor question also, thought I should put it here instead of starting a new thread.

I'm sure I've seen this discussed and answered here in the past but can't find it. so... Building the dome: on the floor bricks or should the floor bricks be inside the dome walls? I've seen pictures and videos both ways. Is there a right way? Are there advantages/disadvantages to either?

I've been lurking this forum for God only knows how long, well over 10 years. It's time to build!

[david s]

You can do it either way
floor inside dome~ pros as long as the bricks are laid loose replacement is easier.
cons brick cuts at the perimeter are more difficult and require curves.
dome on top of floor~ pros cuts at perimeter can be left very rough as they’ll be covered with insulation
cons you won’t be able to remove or replace a floor brick once the dome is sitting on top of it. This is very unlikely as the floor bricks that take a beating are the ones in the centre.
With the bricks laid loose floor expansion is not a problem, because the slight gaps between bricks are sufficient to allow for expansion movement.