Over the weekend, Ladybug & I spent two glorious days on a farm near Morinville. I was learning how to build a cob oven with the capable folks at Shovel & Fork, and Ladybug was learning the joys of spending 8 hours outdoors with chickens, dogs, cats, mud, and no danger of being run over by a latté-crazed SUV-wielder.
Because reading books, looking at pictures and poring over blog posts only gets you so far, I recommend building a cob oven with the help of someone who has done it before. Chad and Kevin, our fearless leaders and all-round capable guys, have each built several cob ovens. Under their guidance, a team of about 18 people managed to put together a beautiful, large oven in 16 hours.
The design we followed is meant to be standing for “300 years”, according to Chad, and looked it as I sized it up at 6:00 pm on Sunday. It is not the simple cob dome you often see but a cob dome atop a monolithic hearth. The hearth has the function of adding permanence and strength to the structure, and raising the oven to the perfect height for fire maintenance and peel-usage without developing a crick in your back.
Our site was chosen in conjunction with the property owner to provide proximity to the kitchen and a great meeting place for outdoor parties. We dug a hole to source the clay for our cob. The hole was back filled with various sizes of gravel to provide drainage and a stable base on which to build the hearth.
We used urbanite, or recycled pieces of concrete, stuck together with cob, to build up the exterior walls of the hearth. The cob was a combination of clay, sand and water, and was mixed by human foot power on a tarp.
The interior of the walls was filled with “junk” that we sourced from around the yard, covered with sand, and topped with a thermal layer of empty wine bottles and a final levelling layer of sand.
The exterior of the top of the hearth will be skirted with regular, recycled brick, and the interior fire floor was made with pricey firebrick. According to Kevin, the firebrick were $4.25 each and comprised the major cost of the oven because everything else was salvage.
Once the hearth was in place, construction of the cob dome began. A dowel was cut to the agreed height and placed in the middle of the firebrick floor. Using the dowel as a guide, a dome of sand sprinkled with water, or “sandcastle”, was erected. This was covered in wet newspaper, “papier mâché” style, in order to mitigate the amount of sand that will fall on the first few food items prepared in the oven.
Using a slightly thicker cob, we made bricks by hand. These bricks were used to encase the sandcastle. Another layer of soupier cob with flax straw added was then put over the bricks to provide more insulation. The oven can be finished off with stucco, brick or left as is – this is entirely up to the discerning eye of the owner.
While the insulative layer was being added to the dome, a door was cut out using a plywood template. When the dome was complete at the end of the day, the sand and newspaper were scooped out of its interior. The oven will require some sort of roof, again up to the owner, as the cob needs protection from rain and moisture.
Over the week, there will be small fires lit in the oven to cure it. Next weekend, we are having a Mother’s Day pizza party using the oven. I will let you know how it all turns out. . .