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Cob oven foundation

 
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I’m planning to build a cob oven in Montana. How deep do I need to make the concrete pad?  Does it need to be floating foundation/monolith style?
 
pollinator
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Location: Stevensville, Montana; Zone 5b
56
hugelkultur forest garden food preservation
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Hi Eileen, sorry this is a late reply, but if you are set on doing a concrete pad it does not need to be set deep at all. A floating pad for something as small as an oven would only need a concrete surface of 4" deep. I recommend digging down 4" as well and backfilling this with road base or gravel, then create a form with 2x4 lumber and pour your concrete pad.

Alternatively I would suggest not pouring a pad, but using larger rocks or urbanite from old cement walkways for the foundation. This works well and will save you money and labor. I still suggest doing the gravel base though. A small pad of concrete or stone, even if it heaves, will not matter much.

Are you planning a roof structure over this oven or just a water resistant finish?
 
Eileen McGurty
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Thanks, Daniel. That was what I had thought. I might do a cover. It would be best but not sure I have it in me this year 🤪

Since I wrote the initial post, I’ve started thinking about doing an earthen rocket oven instead. Do you have any experience with that?
 
Daniel Ray
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Location: Stevensville, Montana; Zone 5b
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hugelkultur forest garden food preservation
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No, I haven't done a rocket oven, only rocket mass heaters--but there are many here who will gladly help

I suggest starting at the following link if you haven't read it yet. Definitely the way to go.

https://permies.com/wiki/60370/Rocket-Powered-Oven-build-super

and here is the ebook link

https://us.permacultureprinciples.com/product/rocket-powered-oven/
 
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