Hybrid Oven: Brick Walls with Cob Dome

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

The vermiculite layer is the insulation. What is clay insulation??

On traditional cob ovens the insulation layer is typically clay slip (clay and water mixed to a heavy cream consistency) mixed with saw dust or straw.

[david s]

Re: Hybrid Oven: Brick Walls with Cob Dome

Look up "light straw clay" it is effective and cheap.

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

Here is a pic of the progress. So far i have covered the brick walls and formed the dome with an adobe mixture. I used about 3 1/2 parts silica sand to 1 part fire-clay. Once the dome is dry i will remove the sand mold (used to shape the dome) and the orange supporting bricks. I will then add the brick archway, chicken wire, vermiculite, and finishing layer in the upcoming weeks. Will post pics along the way.

[brickie in oz]

Re: Hybrid Oven: Brick Walls with Cob Dome

Once the dome is dry i will remove the sand mold (used to shape the dome) and the orange supporting bricks.

Wont it just collapse?

[david s]

Re: Hybrid Oven: Brick Walls with Cob Dome

I think you should have curved the top of the oven doorway to make it self supporting. Time will tell if it works ok or not.

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

Wont it just collapse?

Its only the 2 columns of orange bricks in the center of the pic, not the bricks on the outside.

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

I think you should have curved the top of the oven doorway to make it self supporting. Time will tell if it works ok or not.

I am adding a curved brick archway to the front of the oven which will be attached with more adobe mixture. The reason its not in the pic is because my mortaring skills suck and the brick arch was not secure enough at that time. I will post more pics this weekend

[brickie in oz]

Re: Hybrid Oven: Brick Walls with Cob Dome

Its only the 2 columns of orange bricks in the center of the pic, not the bricks on the outside.

I was aware of that, but what is going to hold the roof and flat entry up?

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

I was aware of that, but what is going to hold the roof and flat entry up?

Based on all the earth ovens I've seen, I believe the cob should support itself. I'm also adding in arched entry way made of brick to help support the front. I'm hoping that will be enough.

[dimitrisbizakis]

Re: Hybrid Oven: Brick Walls with Cob Dome

I was wondering if anybody has ever made an oven with refractory brick walls and a sand/clay thermal oven dome? I originally wanted to make an all earthen/cob oven, but when i found out how many cracks form using all clay, i revised my plans. So far for the thermal layer, i have built the walls about 12.5 inches high using refractory brick. Its currently in a "U" shape.
My next step is to build the dome using a clay/sand mix. My question is, if i use a clay slip & saw dust mixture for the next layer (Insulation), will the insulation mixture stick to the brick like it will the clay dome section? Also, do you see any potential problems that could happen? I'm think if the bricks expand faster/slower than the clay dome section, it may cause unnecessary cracks. Any advice or comments would be greatly appreciated. i will also post pics later for anyone that would like to try this hybrid oven.

From my try with I should warned you....don't mix brick with clay, the have different time of expand and you will get more cracks!
If you hade cracks with clay sand, why didn't you add ore sand to the mixture?
My ratio was 5 sand 1 clay and with a little pation in curing a had a few hairline cracks....hey it's a cob oven!Dont think it to much, if it won't work ok just tear it down!,
Good luck man.

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

From my try with I should warned you....don't mix brick with clay, the have different time of expand and you will get more cracks!
If you hade cracks with clay sand, why didn't you add ore sand to the mixture?
My ratio was 5 sand 1 clay and with a little pation in curing a had a few hairline cracks....hey it's a cob oven!Dont think it to much, if it won't work ok just tear it down!,
Good luck man.

I did think that was a definite possibility, but was too far into my build so i'm hoping for the best. i decided to extend the first cob layer from the dome all the way to the floor, blanketing the brick, to add a bit more structural support. My thinking was that if i didnt it would crack right where the cob dome meets the brick wall. I also added wire mesh and chicken wire hoping to support it further. i will post pics in a moment.

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

Heres one before pic and a few after pics with the wire mesh just added. Needs to be adjusted still but its a work in progress. i still have another couple layers to add. let me know what your guys think, thanks!

[dimitrisbizakis]

Re: Hybrid Oven: Brick Walls with Cob Dome

Heres one before pic and a few after pics with the wire mesh just added. Needs to be adjusted still but its a work in progress. i still have another couple layers to add. let me know what your guys think, thanks!

It's pretty low ceiling right?
What are you going to bake?
In my point of view i dont see enough angle on the dome, it's like a flat ceiling.
I'me afraid for you roof that may drop on the first fire because you did't gave enough height with a bigger radius.
Hope this hold up but as i said before...its a mud oven!

[mrchipster]

Re: Hybrid Oven: Brick Walls with Cob Dome

You need to butress your arch those bricks will push the sides out in no time without additional support.

Chip

[mfugee1234]

Re: Hybrid Oven: Brick Walls with Cob Dome

You need to butress your arch those bricks will push the sides out in no time without additional support.

Chip

How do you do that?