This outdoor cob oven was built over the course of a few summer weeks, thanks in large part to my lovely sister Benita & her friend Candace who took it upon themselves as their contribution to our homestead.
Cob is a simple material to work with: similar to adobe, cob is a mixture of clay-sand-straw, and is shaped by hand. It is perfect for amateur builders, people of all ages (including kids!), and those who wish to build a long-lasting structure using natural materials.
For the foundation, we used concrete blocks & bricks which were reclaimed from the demolition of a nearby house built at the turn of the century. This yellow brick is characteristic of older homes in our city, as the brick was originally manufactured here. A variety of other foundation materials could be used, including wood beams or large stones. We recommend using what you have at hand, or that which is within your budget.
Sourcing the cob materials: Sand was dug from our garden, straw came from a nearby farm, second-hand clay was purchased from a local pottery shop, and hearth bricks were purchased at our local building supply store. A dome of sand was built to create the form for the oven, then cob layers were plastered over. It's important to make "sample bricks" out of the cob to test it's consistency. At this point more sand-straw or clay can be added, until desired consistency is achieved. Once the cob hardened to leather-hard, the door was cut and the sand scooped out. At this point any embellishments could be sculpted onto the cob oven. We had hoped for a bench, but ran out of time.
The cob was misted daily to ensure it dried slowly. If dried too quickly, particularily in the summer, the cob can crack. We also tarped the oven to protect it from direct sun & rain while it dryed. After one week, we began with a few small fires in the oven, then gradually built up the fires until they filled the entire oven cavity. This helped the oven to cure from the inside. We built a roof shelter, and fashioned a rustic door. Finally we were ready to bake!
Amazing results come from wood-fired baking - bread bakes evenly and quickly; pizzas are fabulous; cookies & granolas come out perfectly browned, and fruit & herbs can be dryed overnight in the left-over residual heat. We also like the added benefit of not heaing up our house on hot summer days!
Generally we find that the amount of firing time = the amount of "hot" baking time, i.e. 3 hours of large fire would give 3 hours of solid baking time. Pizzas are baked with a small fire pushed to the back of the oven, whereas breads are baked after the hot coals are raked out and the door is closed to let the heat sink into the hearth bricks. If using a wooden door we suggest soaking it for a good long while before setting it in place for baking.
Here are are a series of photos to demonstrate our building process: