Settling in floor

[jjenkins74]

Uh oh. I am on day 6 of curing my oven and noticed 2 bricks have sunken. Haven't pulled them up yet. I built the structure out of block cinders, paid 2 inch insulating Styrofoam, and then medium duty bricks. And idea why I'd see my bricks settling? Would it have melted the Styrofoam? I dont see any structural damage underneath.

[UtahBeehiver]

Sorry about the problem. Styrofoam does not have the thermal properties to be able to withstand the heat from a WFO oven. I'm afraid it is tear down time, typical floor insulation is CaSi board or a v/pcrete mixture.

[jjenkins74]

Well, I guess i can re use my bricks if I scrape them of the mortar. Should be a fairly quick re build since I've done it once.

[Gulf]

That is a bummer to have to rebuild! Since you made that miscalculation, no matter how "quick" that you think that it will be, don't go for a second rebuild . Do some intensive research and follow some successful builds on this forum.

[jjenkins74]

Appreciate the input / feedback. A re-built isn't the end of the world. So I'll order the 2" FB boards. Am I not okay to simply put down the FB boards on top of my concrete slab and then the firebrick? That's what the cross section shows on FB Pompeii Oven Instructions (see attached). I see some folks using both FB boards and verm-concrete. Should I put down a layer of insulatting concrete down first, then the FB boards, then the firebricks? I'll be using Perlite on the exterior eventually so I could put down that first to be super conservative.

Also, any concern with the fact that there will be joints between the FB boards?

[UtahBeehiver]

2" CaSi board in the minimum recommend thickness. 4" of 5 to 1 p/vcrete is about the same as 2" of CaSi. It depends on how you are going to use the oven on how much more insulation you need. I would look at some more current builds, placement of tile on the concrete hearth so the CaSi does not sit on the hearth directly where water could get in and sit and get the insulation wet is the current trend. Wet insulation is most common reason for poor oven performance. There are several well documented builds in the Newbie Section under treasure archives, this is where you need to research the best practices.

[jjenkins74]

Okay, so I've decided to pour a vermiculate base (likley 4 or 5 inches). I will then pour a skim coat of Fire Clay / Sand mixture to create a smooth and level surface. Then I will place the 2 inch FornoBravo CaSi boards on top. Then the dome! I should be able to withstand the heat from a nucular explosion with that.