DIY Cob Oven :: step 2

Hello! Welcome to our four part series on how to build your own cob oven. This is our very first attempt at building with cob and we by no means know what we’re doing. Please use these posts as a rough guide and learn along with us. If you are interested in building with cob, we strongly suggest finding a “hands-on” workshop to participate in.

Let’s get started with step 2!

Now we are going to build our core “place holder” out of sand. Fire up your sandcastle skills! This place holder does just that; it gives you a structure to build the cob oven on and is removed later. Much like when you do paper mâché (you build the newspaper onto a balloon then pop the balloon).
You will need three (50 lb.) bags of wet sand. Go for the cheapest sand available… no need to get fancy here although I noticed that the finer the sand, the better it holds it’s shape.

Get ready because here comes the math. If the diameter of your oven body circle is 30″ inches (like ours) than the height of the main dome needs to be 21″ inches tall (within 6″ inches of 63% of the diameter). The height of the door entrance needs to be 63% of the dome height which makes the door height 13 1/4″ inches tall. The height of the door related to the dome height is crucial for proper air flow. For this size oven you also don’t want the width of the door/entrance to be over 13″ inches. Here’s an overview of our oven’s measurements.
Oven body diameter: 30″ inches
Oven body height: 21″ inches
Door/entrance height: 13 1/4″ inches (or 63% of 21″ inches)
Door/entrance width: 12 to 13″ inches

Cover your wet sand core with wet newspaper. The newspaper will keep the cob layers from sticking to the wet sand core making it easier to scoop out later.

Next in “step 3” we start the cob!

Posted in DIY

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