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Building a Cob Oven | Sourdough Companion

Building a Cob Oven

Cob Ovens are a relatively inexpensive way to bake, with all the benefits of wood-fire such as a hot hearth. Materials are raw and often sourced locally from the land. This Cob Oven was built leading up to the 2008 Forest Festival held in Jackeys Marsh, Tasmania. The oven is a design from Build your own Earth Oven by Kuko Denzer. Many thanks to Jenny for the photos.

 

The Base

The base of the oven is a circular dry stone wall. As the wall is built, the cavity is filled with smaller stones and gravel. Rocks were sourced from gullies around the site.

 

Hearth

Sand fills the final layer of the base. The surface is leveled out and fire bricks are placed to make the hearth.

 

A dome of wet sand is molded above the hearth. This dome will form the cavity of the oven.

 

 

 

Wet newspaper covers the dome to prevent the next layer, clay, from binding with the sand. Clay is now layered over the newspaper.

 

Progress! The clay dome is up. The clay dome is made up of 2 layers. The inner layer is pure clay while the outer layer is made up of clay and straw for added strength. Hatchings are made on the inner layer to help bind both layers together. When the clay is hard enough, the once supporting sand dome is then shoveled out:

 

The Finished Oven

The finished oven with clay mantel.

 

Please let us know your thoughts and questions in the comments.

 

15 comments

How rustic! My questions :)

1. How long does a cob oven last?

2. Does or will it have a door?

3. Does it keep heat as efficiently as a brick oven?

4. How long does heat hold?

 

 Very cool.  How long did the clay have to set up before you dug the sand out?  Is there any kind of temperature gauge in the oven?

Love the look, Maedi. I've dreamed of having a wood-fired oven in the backyard ever since I watched a TV cooking program hosted by Jacque Reymond called Secet Recipes - that was quite a few years ago now. The program featured traditional family recipes from a variety of ethnic communities in Australia. The Macedonian, Italian, Greek and Slav folk featured on the program all had home-made wood-fired ovens in their backyards. As soon as I saw the amazing stuff they were turning out of their ovens, I was sold.

My Greek and Italian friends say the peasanty style of backyard wood-fired ovens are a dying art, and that the younger generations can't be bothered with the work involved. If they have wood-fired ovens at all, they prefer to buy them. Thus, the knowledge of the older generations in relation to constructing these ovens in traditional ways is in danger of being lost. And I have to say, I don't like the ones typically manufactured commercially, with the decorative ceramic tiles etc...far prefer the rustic look.

Which is why I'm really interested in the cob oven you've shown here. I'm just wondering, though, without a chimney, would it smoke too much for a suburban backyard?

Another query: is it built to last, or would something like this be intended only for the shorter-term?

Also interested in the questions TP and LD have raised.

Cheers!
Ross

I need to sell up and move to a rural location so I can build one of these in my backyard!  I think Auckland City Council would have seven kinds of fits if I put one of the babies up!  But I LOVE it Maedi!  I often go back and look at all the photos Matthew posted when he built his brick oven.  It's gotta be so great - much better than indoors in my "special needs" wee oven. 

KC.

Hi Guys! Thanks for all your questions and sorry for not replying earlier.

I've been in contact with Jenny and she was able to give more insight. Jenny is based in Canada and is setting up a small bakery at her farm. She's actually just built another Cob Oven there and can confirm the following:

There is only enough heat for one bake and all movements in and out of the oven have to be extremely efficient. The temperature has been up over 500 and will depend on quality of wood and outside conditions.

@TeckPoh :)

To answer your questions to the best of my knowledge:

1. I've heard that Cob Ovens can decline after a few years or so from weather and structural factors. An oven built well and protected from the elements could potentially last quite a while. I will have to ask Jenny about this.

2. This one didn't have a door. Though Jenny built another Cob Oven at her home, with a door and chimney.

3 and 4. With her oven at home, Jenny closes the door and covers the chimney at baking time. The bread bakes on retained heat once the oven reaches 450 degrees.

@LeadDog

How long did the clay have to set up before you dug the sand out?
It took a few days for the clay to set, with a tarpaulin covering the clay intermittently. Regarding set time of the finished oven:

It's best to let the cob dry naturally but at Jackeys marsh we lit an ever increasing hotter fire over a week so that we could use the oven at the festival

Is there any kind of temperature gauge in the oven?
I don't believe there was at Jackeys marsh.

 

Jenny sends her best wishes. Feel free to ask and I will forward on your questions, or I can grab her email for you.

Maedi

 

I made one like this a few years ago - but at ground level - this is a much better height. We made the opening the right size to fit a lean-to door from an old wood heater (Coonara type). We kept an old half a water tank over it for weather protection when not in use. The clay adobe degenerated a bit anyway - could be repaired with more clay. It's due to be knocked down now I think and maybe graduate to this or the brick greek type model which is very permanent especially when under a bit of a roof. But mainly I am concentrating on getting the sourdough bread right at the moment!

Interesting. I didn't think these types of ovens were still in use. Very cool.

 

Jon.

It looks great. I'd like to make such one. I think it is quite interesting to try to cook anything with its help. I've also found a video where people built Cob Oven http://www.tubesfan.com/watch/building-a-cob-oven-at-riverfront-farm-in-... . It seems to me it was more complicated that it was decribed here, but I think it is still possible to make it and enjoy the bread which was baked inside.

What are the base's diameter and the top's diameter of the rock foundation?

I think it needs a chimney  to exhost the fumes. You dont want a smoked bread nor to get it on your face every time you approach the oven. Right?

 

Maedi

Brilliant Clay oven...I love it. Are you still using the oven and have you any recent pics?

Terry

I live in Minnesota where the frost line is a good 4 feet down. I was wondering if there was any foundation under this other than just rocks and sand. How it might this hold up to numerous winters and freezing?

Thanks!

You should have the foundation reach to below the frost line.  Frost heave will greatly shorten the life of your oven.

I built a cob oven using Kiko Denzer's instructions too, although I added the insulation layer  of slip and sawdust between the outer and inner layers.   Using an IR thermometer, I have measured the temperature of the interior of the oven and have maxed out at about 1400 degrees Fahrenheit.  When I fire, I usually heat it up and cook pizzas with the fire still in the oven, when I'm finished cooking the pizzas, the temperature is still over 700 so I put the door in and let it cool down, and let the heat equilibrate so the whole interior is about 500 or so.  At this point I can generally cook 2 or 3 loads of bread (4 small loaves or 2 to 3 larger).  When that is done I put in a Dutch oven full of beans and let them cook in the declining heat.  Depending on weather, firing schedule, and wood quality, I have measured the temperature at over 200 more than 12 hours after firing it.

My oven does have a chimney at the front, mostly because I hate to get smoke in my eyes.  That said, the oven fires so well that it produces very little smoke after the first 15 minutes or so of firing.

Mark

I built a wood fired oven a few years ago and use it for pizza, roasts and bread etc, a great way to cook.

i have a series of photos that I took during construction is anyone is interested.

Cheers, john