Things To Consider When Building A Cob Oven

building cob oven base

We’ve seen a lot of ovens in the past few years. We’ve watched fire dance in their bellies and we’ve had the pleasure of eating from a few of them too. Every oven is slightly different, no doubt because every group that builds an oven is slightly different. We’ve yet to construct an oven that doesn’t bake a mean pizza but here are a few pointers for you if you are wishing to make the most out of your oven making experience. This list is certainly not exhaustive and we hope to grow it with your help. If you have a pointer, a $100 tip, then please share it and we’ll add it to the list. So here’s what we suggest is worth doing, or at least giving some thought to, before you get started:

  • Place your oven in a space that you’ll use but not too close to anything combustible (keep a clear path above the door).
  • Source your materials early, especially your clay soil. Get a sample, or several, and test them thoroughly with different ratios of sand to clay. Clay-rich soil will need more sand, while sandier soils will need much less. Remember, you want strength with minimal cracking and it’s always better to do a few tests before committing to a full project.
  • Build a good base. By good I mean something that will compliment the cob – dense, heavy, fireproof – something that will stand the test of time. Wood is easy but not necessarily the best choice when you’re dealing with temperatures approaching 1000 degrees Fahrenheit.
  • Applying Insulation To The Cob OvenDon’t skimp on the insulation. You should insulate under the hearth (the firebricks), as well as on the outer shell. This speeds up cook times and reduces the amount of wood you need to burn to get things up to temperature.
  • Add more mass under the firebricks. Your walls will likely be 9 inches thick, while the firebricks are just 2.5 inches thick. If you want nice crusty pizza bases it’s advised to add more density under the bricks (and above the insulation). Sand is okay but another layer of bricks, cob, concrete pavers, etc. are denser and therefore a better heat sink.
  • Give yourself plenty of time and don’t leave getting started too late into the season. Cob must not freeze before it’s perfectly dry.
  • Make sure your oven gets a good hat. Cob hates water so build a good roof for your oven. Trying to waterproof it is generally a bad idea, as all that water in your food needs to get out and when the door is on it travels right through the cob.
  • Get yourself a good set of firebricks. You need the mass in the base, so be sure to get the thick ones (at least 2.5” thick). The fewer chips the better!
  • Once built, let you’re oven dry naturally before exposing it to a bunch of heat. Too much heat when it’s wet and you’re bound to get some serious cracks.
  • Earthen plaster for cob oven.Take the time to plaster your oven. There is so much work and love that goes into an oven, so take the time to put those finishing touches on it, so that others are inspired to want to build with cob!
  • Don’t over-fuel your oven. Too much wood and you’re bound to get plumes of black smoke. Oh, and make sure your wood is clean and dry.
  • Get yourself some good tools for cooking. You’ll want a hoe or “rooker” to get the hot coals out, a yacht mop to clean the base before cooking, and a pizza peel for loading goodies in and out of the oven. Fireproof gloves are a nice addition too.

Again, we’d love to hear from you, so if you have a tip please get in touch, and we’ll add it to our list!

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