Although the rustic look of the oven in just its cladding has a certain appeal, for optimum heating there needs to be a layer of insulation. An outer wall needs to be built so that this insulation can be put between it and the cladding. This is the story of how Greg built it -
The first thing to do was to weld together an open box frame out of rebar. Sections of wire fencing were tied between the rebar, such that it would be in the cement wall for structural support. The front and back bottom rungs of this box rested on the cinder cement curb at the front of and at the rear of oven table/base. You may recall that there is a wider section of the curb at the front of the oven, that the whole entryway was built on. Greg extended the outer edge of the base table before he began pouring the cement for the walls. The side outer rungs of rebar are embedded in that extended white curb.
With this rebar in place, cement forms were built so that the wall could be poured to a height of 10-12 inches at a time. There were two reasons for this. One is the recurring desire to use up fewer materials for the framing. The second reason was to make it easier to pour 2 inch thick walls. Keeping the height limited with each pour made it possible to pack the cinder cement and avoid bubbles. Wider walls would have meant more weight for the whole oven.
The space between the cladding and the outer wall was about 3 inches near the base, as well as up along the vertical section of the cladding. It would get larger as the cladding curved in. The walls were built up to be 6 inches taller than the top of the cladding, with angled peaks in the front and back walls. When the cement was cured, this whole space was filled with loose cinder.
In the photo to the right, the wire on the rebar is more obvious. We were already “testing” the oven’s ability to cook the best pizza regularly from this point on. :-) One pizza is being taken out of the oven with the handshake.
The first section of the chimney wall was poured in place, to make sure it would fit the arch well. Subsequent sections were poured in a free mold, then stacked over the liners. This cement was also mixed with cinder. A piece of wire mesh was placed inside the clay liner as a spark arrester. It also deters birds, who became immediately interested in the chimney.
The little cement house is estimated to weigh almost 2 tons, but looks like it belongs in a fairy tale with some mythical creature living in it. Possibly a miniature fire-breathing dragon? As long as it cooks pizza, we can let it live.
Next up will be: how the roof tiles were made and put in place.