Advice required on preventing 3rd main chamber collapse

[Digga Don]

Karagi Dave. Sketch of metal buttress. Considering moving so 50mm Cadillac board is between brick of main chamber and metal like your latest barrel vaults oven. Your thoughts please. There will be a red brick outer skin over insulation layer.

[david s]

It looks like it's too late now, but 1" of underfloor insulation is generally considered insufficient, 2" preferred. You will get a considerable amount of heat loss with only 1" of cal sil. The oven will still work but its fuel consumption will be higher and the heat loss from the floor will reduce retained heat cooking time.

[Karangi Dude]

Don, if there is enough room perhaps you could move the outer red brick sides out to about 100mm and fill the void with vermecrete at 7 to 1
lay the outer side walls about 4 to 5 courses high then fill the void and let dry for a couple of days this should be enough buttress to hold the arch bricks from spreading

[Digga Don]

Thanks Katanga dude, unfortunately I don’t have enough room for that and I’ve already purchased rolls of insulation. What are your thoughts on turning the steak around so the insulation board is against the bricks?

[Karangi Dude]

Don you need a solid material for the buttress even if it only goes up a couple of courses
you mentioned rolls are you referring to blanket if so that doesn’t have any compressive strength