We made the example of an adobe oven shown in this article in the first home we built. We had always planned to have a wood-burning fireplace as the heat source for the house. And if you’re going to build a fireplace, you may as well add a couple of steps to make it double up as an oven. That way, whenever you light a fire, you can bake bread, cookies, stew, whatever you feel like. It was such an awesome addition to our home and it only took two weeks to build.
Our fireplace is set in the SE corner of the house and has bench/bookshelves on either side of it, running along the walls. We made the foundation to it at the same time as that of the walls, so it all ties in from the ground up.
The benches have a rock base, adobe brick legs (which we poured in place rather than making the bricks first and then laying them), a wooden frame and seats, and an adobe back.
In between the benches, in the corner, we put an old, metal cabinet drawer. We put plywood around that drawer and then poured wet adobe mud around the plywood. When the mud dried, we removed the plywood. The drawer comes up to the same height as the benches and can slide in and out. It is beneath the hearth and serves as an ash box.
Most people, when building an adobe oven, make bricks first and then lay them in the shape they want. We did it a slightly different way.
We made a frame out of rebar and wire, and then covered it with adobe, firing each layer of mud as we went. The frame consisted of the backs of the benches, the main arch of the fireplace (with ledges for the hearth grill and oven shelf built in), and the part that connects to the flue.
So that the fire doesn't draw too much air from the warm room, we built in an air-intake. We have an old piece of muffler going through the rock wall of the house, pointing in the direction of our prevailing (and cold) wind.
We then adobed the outside of an air pocket, made out of rebar and wire. This pocket connects to the muffler and then comes out into the hearth.
For the most efficient draw, the area of the flue should not be smaller than 1/8 the area of the mouth. 12” stove pipe is ideal. We took a plum bob from the roof down to the start of the flue to decide where to cut our tin. The stack should be properly sealed to the roof to prevent leaks.
We attached a circular piece of sheet metal to a rebar handle. The disc of metal fits inside the stove pipe and the handle comes out into the room. We use the damper to control the temperature of the oven, once we have a bed of coals. We also keep it closed when we are not using it, to prevent a draft, unless of course a draft is required.
As an extra little heating device, we butted metal cans up against a section of single-wall stove pipe. We adobed around them, leaving the open end exposed into the room. They draw heat from stove pipe and send it into the room.