Wood fired pizza--who doesn't love it? And making a pizza oven is a great small scale natural building project. If all the materials are on hand, a team as small as three or four could do it easily in the space of a weekend. And even if you don't have a team, you can do it by yourself over the course of several consecutive weekends. (And I promise you, friends will come out of the woodwork when you start cooking up those pizzas!)
"Urbanite," or waste concrete, is often free for the hauling and can make a good base. When the city required us to redo several sections of sidewalk, we had all the base material we needed for our oven.
(For a complete list of materials needed, as well as quantities and instructions, check THE earth oven book.)
Mixing clay and sand for the first layer. >> Because my subsoil was mixed with topsoil, using it to build with would have been very difficult. So instead I got half a dozen buckets of waste clay from a local potter. Together with sand from a nearby quarry, the clay worked great!
I love this oven, but next time I build one I would like to try out the two chamber approach (less smoke).
<<Urbanite foundation and the beginnings of cob construction. (Cob is a mixture of clay, sand and--sometimes--straw.) If you live where the ground freezes in winter, you should dig down several feet to start your foundation.
<<Working around the oven door makes it easy to get a good fit. Later on, when you are prepping the fire for cooking, you put the door on to soak in a bucket of water to help slow down the charring process.