Advice required on preventing 3rd main chamber collapse

[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

[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, 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

[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.

[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.

[Digga Don]

Version 3 completed today by adding last row either side and keystone. Metal buttresses inplace

[Digga Don]

Version 2

[Digga Don]

Calci board 25 mm in previous photo under floor and walls. Main chamber arch on version 2 formwork with slats and vented supports.

[david s]

A few considerations,

If building the end walls against the barrel vault, there is a tendency for thermal expansion of the vault to push the end walls out. The structural integrity of the form is increased if the end walls are built under the vault and some of the lower course bricks tied in at the corners.

Also if the problem of collapsing barrel vault bricks was caused by the removal of the form, it could be because you haven't used wedges which are not visible in the pic of your second attempt. (or wedges of insufficient height) under the form so it can be easily lowered and removed without damaging the brick vault.

An oven built at ground level will be hard to operate and also will be prone to moisture wicking from rising damp.

[Digga Don]

Vermicrete slab 100mm on drystone base with gravel and rubble fill over boulder

[Digga Don]

Dry stacked at home on formwork version 1

[Digga Don]

Arch bricks Floor bricks 100 mm thick

[Digga Don]

Site in winter to right of shed

[Digga Don]

Site of oven Cramps bay Great Lake

[Digga Don]

Previous photo first build. Wrong caption fat fingers