We recently found ourselves touring around the UK promoting the
sustainable building experience anywhere people would listen. Through our travels, we met some amazing
people, some of whom wanted our assistance building sustainable structures
for various purposes. We ventured to
Swattesfield Campground in Suffolk for this purpose. It was a mutually beneficial visit — we were needing
a space to have some meetings and he had a community he wanted to bring
Here is yet another possible building project presented to you which requires no formal training, very little money, and techniques/methods that anyone can use. This blog intends to inspire you to take on a natural building project like this one. Don´t have fear if this is your first time working with these techniques and materials — it often for us also!
Swattlesfield Campground is frequented by many kinds of people for various reasons. The owner, Jonathan, wanted to introduce some activity which would draw people together. We had the perfect idea: pizza! Food, especially food that requires waiting, has a tendency to attract people. And once humans have a good reason to be in the same place, the rest (socialization) has a tendency to just work.
We spent one day planning our cob oven design. It was to be built mostly out of cob (a mixture of sand, clay, water, and straw; amounts depend on the local resources), tires (we absolutely love using "trash" for build projects), rocks (of various sizes), fire bricks (the only cost of the build, and there really are not any other options), and love. And you always need love.
The idea was to build the foundation out of two stacks of firmly packed tires. On the larger stack of tires we would build the oven, and on the other, a small preparation table. Experience cooking pizzas in a cob oven convinced us of the small table — it allows people to create their pizzas, cook them, and enjoy them all in one space, keeping social interactions and enjoyment to the maximum. In other words, we created our design to suit the use of the oven.
The oven would have a fire-brick-covered floor to do the cooking on and the dome would be made out of cob — very, very thick cob. The thicker the better here when the goal is to make lots of pizzas. The heat put off by the fire inside the oven takes longer to heat up the walls if they are thicker, but it also ensures that the walls keep releasing lots of heat inside the oven for many hours after the fire has been extinguished. We figured a sign reading "Pizzas for Hours" would be the best to see near dinner time. Once again, we are making sure the use dictates the design.
Understanding the heat flow elements of a cob oven design is extremely simple and applies to many structures, including houses. Dense heavy material will hold its temperature for a long time and material that is light and airy will stop heat from transferring from one environment to another. With this information, you can make lots of really good decisions. If you want the oven to stay warm for a long time, make the walls as thick as possible with dense material (cob with only a little straw), and the outermost layer a little lighter and airy (cob with higher amounts of straw) to stop the heat from escaping.
Thermal dynamics lesson over; you have your cob oven design. Now how do you build it?
The easiest way is to make a round pile of sand on the oven foundation (packed tires with a layer of fire bricks on top) and cover it in cob. This pile of sand then molds the cob into the desirable shape. Scoop the sand out once the cob is mostly dry, and you have the inside of an oven.
Now it is time to build the archway which will serve as the door. Loren and Michael had a great time arching the bricks. We learned the key to the whole arch is finding a good keystone — who knew?! Join this archway to the dome with a little more cob. You will want to make sure the cob for making the dome is still a little wet, or just add a little water to the dry cob to maximize bonding.
We spent two days building and at the end had a cob oven and stronger friendships. We had to carry on to the next project before the cob was dry, but my guess
is that the pizza was amazing. A recent Google search of "Swattesfield Campground" returns a happy review praising the cob oven. Job well done!
I probably don´t need to tell readers of MOTHER EARTH NEWS this, but becoming more and more intimate with materials, processes, and activities enriches your life. Integrating more into your life and outsourcing less, leads to a smile on your face.
Want to bring your community closer and build something great like this? Create a build project listing named "[Insert your name here]´s smile-creating and sometimes roof-of-the-mouth-burning cob oven" on thePOOSH.org and find some assistance.
Want to get some experience building cob ovens? Check out all the build projects that people have posted on thePOOSH.org. Remember, as Llyod Kahn (author of Shelter) says, "If you're unsure what to do, just start."