Campsite Cob Oven Construction

Reader Contribution by Eric Puro And Michael Beck
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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
closer together.

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 buildingcob 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.”