Urban Farming Oz

Our Earth Oven is now built, and has produced pizza, excellent pizza. Some work is required to fit the door and finish off the grouting of the base.

I delayed these steps until we have the roof and walls finished.

We started the project just before Christmas, 2010. While cleaning out the bottom dam which was dry we decided to collect clay for the oven at the same time. Just over a cubic metre was removed and stored on a piece of corrugated iron behind our old large garden, which now house the Muscovy Ducks.

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Next we built the base out of local stone from our property, slate. As it rose in height a mixture of coarse river sand and gravel with cement added was added to the centre creating a solid base 900mm high to support the oven. I read extensively on the net and looked at many designs and chose to use a bricks on a bed of sand as the floor. The bricks are ordinary pressed commons with a frog (hollow) on the base not the extruded bricks as the have much less mass and are more likely to fail in the high heat. The bricks were laid on their side so they sat flat on the sand with no hollow space underneath. The oven has now been in use for 11 months with no sign of deterioration of the bricks.

For sand I purchased a ton of course builders sand, not beach sand as that often has round grains, course angular grains are what is needed to help with the bonding process. While this was happening one rainy day I built a door for the oven out of hardwood planks. Using the formulae and many comments on the web from other builders the door height was 400mm, two thirds of the inside dome height of 600mm. This is an important ratio to ensure the oven burns well, retains heat and cooks well. There is no chimney in the design as the smoke vents out of the door opening as can be seen in the photo.

The final dimensions of the interior of the oven are roughly 700mm wide 800mm deep and 600mm high. I built a giant sand castle, covered in newspaper to support the cob as I built the oven. This was then scooped out after a allowing the oven to dry for few days to allow it to dry from the inside.

The oven has 4 layers of clay sand mix. The first inner layer in the thermal layer 50% sand and 50% clay about 50mm thick. The next two layer are cob, 75% sand and 25% clay with a handful of straw added for strength and insulation properties. This layer is approx 100mm thick. The final layer was a thin 25mm of the 50% sand and 50% clay mix.

In December 2010 we finally added the roof and also installed a 100 year old cast iron oven we bought next to the pizza oven, so we will have a full outdoor kitchen. If you look carefully you can see the beginnings of the log wall that will protect the cast iron stove from the rain. The result this wet evening was to say the least delicious.

Now it is 2012 and the oven is still going strong. The brick floor is still level and the bricks are holding up well. Extended visits from family and friends end up with a pizza day, quite a feast.

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