How to Make an Earthen Oven

This updated post will show you how to build an earthen oven for traditional, sustainable baking. Earthen oven plans vary because you can build them in different ways with different raw materials. Here is how we built ours.

Stacy Lyn and Scott building an earthen oven - scooping out the sand form from inside the hardened mud dome

Why Build an Earthen Oven

My husband Scott had been itching to build an earthen oven. So over one Thanksgiving holiday, we finally made a family project of building one. It was great fun, but it was also an important step in our lifelong goals of sustainable living and survival preparedness.

Mud / clay / earthen ovens are time tested.

The earthen oven, also called a mud oven, adobe oven, cob oven, or clay oven, has sustained people the world over for thousands of years. Moreover, this oven design is still in active use today in some unexpected places. You know that wood-fired pizza oven your local pizzaria uses? It’s based on this age-old type of oven.

They are simple and efficient in design.

An earthen oven makes professional food using only natural resources. The design is so efficient that the heat last for over twenty–four hours, giving you time to cook many meals. This not only saves on the power bill but saves time you would have spent in the kitchen. In little time, I have food made for a whole week thanks to our earthen oven!

They are easy and fun to build!

And it’s so easy to make one! The materials for the project were as simple as the process: fire bricks, clay, sand, newspaper, and straw. This simple construction creates an oven that will last for many years.

We had lots of fun making our oven. The younger kids had a blast “building a sand castle” when making the form and “playing in the mud” when mixing the sand and clay to form the cob layer. The older kids readily helped, too, anticipating the loaves of delicious, crusty bread that the oven would soon bring forth.

Earthen ovens made delicious food for centuries and still do.

For centuries the earthen oven fed our ancestors. For example, the town bakers of the early American colonies depended on these ovens for their profession. Home cooks also put them to use. At the end of a long day of baking, cooks would put a large kettle of beans in the cooling oven and baked them overnight to enjoy the next day. The birth of the “baked bean” started from there. How cool is that?

On Christmas Eve after we made our oven, I took advantage of this efficient feature. I first baked my breads, then my pecan pie, then boeuf bourguignon, and ended my earthen-oven holiday bakefest with shepherd’s pie. My large, extended family did not know what hit them on Christmas day.

Rustic Bread Straight from the Oven
Rustic Bread Straight from the Oven

They work sustainably for cooking in rustic conditions.

Aside from the amazing food an earthen oven can bake, it also serves survival advantages. Most important, it requires no electricity. There are no gadgets on it; if the “furnace” cracks you can simply patch it with a little mud. If the power goes out or thieves rob everything but the kitchen sink, you have something you can easily make delicious food from.

Click here to see and learn how to bake bread in an earthen oven.

How to Make an Earthen Oven

This section will take you step-by-step through the earthen oven construction. The components are simple and for the most part, easy to find.  You will need firebrick, sand, clay, newspaper, and straw.  We went to our local masonry shop to obtain the firebrick and clay.  Clay from the riverbank would have worked fine, too, but is harder to tote and difficult to get the proportions right when mixing with the sand.  

This is the list of exactly the materials we used in building the oven:

  • 40 fire brick
  • 700 lbs. all-purpose sand (approx. 290 lbs. for the form, 400 lbs. for the oven, and another 10 lbs. to finish the mouth)
  • 200 lbs. (dry weight) fire clay
  • One or two days’ worth of newspaper
  • About a quarter bale of straw, hay, or the like

Equipment you may need to transport and mix the materials includes: shovels, a wheelbarrow, and canvas tarp. You’ll also need a piece of chalk, a tape measure, some string, and a flat board. You’ll use your bare hands for sculpting the form of the oven.

Here is how we built our earthen oven. 

Create a Base and Draw the Form

Form a firm base for the oven on a flat surface. Flatten out a spot of ground or build a sturdy foundation.  Lay the firebrick out on the working surface. Try to get the surface as flat as possible because this will be the floor of your oven. We had enough thin and thick firebricks to make a second layer. This will further help to insulate the oven and clean up the yard at the same time. The 32’’ x 45’’ oven we built is 8 bricks wide by 5 bricks deep.

After the base is set, you draw and build the form. Start by drawing the general shape of the oven with chalk on the brick. Tie a piece of string to the chalk and pivot it around the base, making three concentric circles.  The first circle should touch both of the outer edges and back of the floor of bricks. Then draw another circle 3’’ closer in and the final one another 3’’ in. This will be your template for the dome and the two layers of sand and clay cob. Next, draw the oven mouth by centering two lines 4’’ from the edge with chalk. Then draw another pair of lines, each coming 3’’ closer to the center. Stop each line about 7’’ from the front edge. You will need that space later. So the inside circle for your oven should be 20’’ and the mouth approximately 12’’.

Build the Form with Sand and Newspaper

Now for the fun part: the building of the form with sand. This is where the shape of the oven takes place. Dust off your sand-castle skills from your childhood! You will need to finish this step in one day, or the sand will start to dry and blow away.

Add water to the sand until just wet with the right consistency for shaping. Form the wet sand into a mound in the shape of the oven.  Basically go as to a desired height, but follow this one ABSOLUTELY NESSASARY RULE:  the height of the dome to mouth ratio must be between 60-65%.  If the mouth is to high, the oven will not carry heat properly, and if the mouth is too low, the smoke will not draw and the fire will not burn well.  We built our dome and mouth around 16″ and 10″’’”, respectively.  It is a good idea to place a flat board at the mouth of the oven to keep the front straight and square.

Cover the form in strips of wet newspaper.  This will make it easy to remove the sand later.

Make the Earthen Oven Layers

Now it is time to play in the mud!  Spread out a tarp or canvas and place two parts sand to one part clay on top.  Add water and start incorporating the mix with your feet.  Get the kids out to do this — they’ll love it.  The consistency you are looking for is something very workable, not sloppy and not crumbly.

Start piling the mud insulation on the sand form. Bring the mud nearly to the “second” chalk line, anticipating settling as you build up.  Treat the mud like bricks, keeping the mud square and stacking it.  After you complete the first layer, let the oven set for a day or two.

Add the Next Mud Layer with Straw / Hay

Now for the next layer of cob — a mixture of sand, mud, and straw. First, scratch the surface of the first layer of your mud oven so the second layer will adhere well.  Mix the mud as before, but this time add some hay to the mix. This organic matter will act as rebar and strengthen the mud into a cement like layer.  Layer the same way as the first layer.  After completion, again let set overnight before finishing the mouth of the oven.

Remove the board from the front of oven.  Mound the remaining sand to continue out another couple of inches.  Place newspaper as before and then create a nice round mouth to your oven with some more mud mix.

Hollow Out the Oven and Let It Dry

After the oven has stiffened some (around a week) dig out some of the sand from inside. Watch for cracking.  Wait a couple more days if any form.  Continue to remove a little over several days until empty.  After the sand is out, the oven should start drying more rapidly.

Let the earthen oven dry before using it, which will probably take around 4-6 weeks, depending on the weather. While waiting for it to dry, make a door for it by cutting out a piece of wood in the shape of the entrance.  Making a cardboard template first helps a lot to get the right shape.

Before you bake your first loaf of bread, start a fire in the oven to get rid of the remaining moisture.  Don’t be tempted to bake a loaf of bread in it (believe us, we know); the oven simply will not hold the heat while any moisture remains.

After the first fire, cracks will appear on the oven. Don’t be alarmed.  Simply rub some of the mud mix into the cracks.

You are done!  The oven, as hard and durable as it feels, is literally made of mud and straw and will need to be covered from the rain by a tarp or some other source.

Next, learn how to bake bread in your earthen oven.

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5 Comments

  1. So looking forward to how you made the oven! How exciting! I can already smell the breads that would come from it, from how good they smell when we bake them IN the house! Love how you all come together to get the job done, that’s so fun!
    Always Experiencing Him,
    Jody

    1. Stacy Harris says:

      Thanks Jody!! We are going to have written instructions and video. It really is not that hard. You can just make it on the ground, but we wanted ours to be more permanent. Let me know what you think!

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