Traditionally called hornos in New Mexico, building an earth oven is a great way to learn the basics of adobe brick construction over the course of a small 3-day project. In addition to breads and desserts, hornos are great for baking pizza and cooking meats and vegetables. I always try to use natural, local materials when building an oven and have adapted the larger oven size often found in New Mexico to a smaller design which requires less fuel and time for firing.
- The oven foundation is usually a simple gravel pad.
- The square oven base is made of sun-cured adobe bricks.
- The oven floor can either be made of troweled mud or fire brick.
- Clayey soil taken from the foundation dig is used to construct the oven dome. Depending on your soil, additional coarse sand might also be needed.
- Ovens are usually finished with natural earthen plasters which are strengthened with wheat paste or cactus juice for water-resistance.
- Chopped straw is needed for the dome rings and plaster mixes.
- tape measure, mason’s string, 3-ft. carpenter’s level, Sharpie marker
- long-handled, pointed-tip shovel
- 5-gallon bucket
- 8” X 8” hand tamper
- mason’s trowel (optional)
- plaster trowel (optional)
- your hands (mandatory)
|Step 3: After the base walls have dried overnight, fill the center of the base with rubble from the building site (gravel, sand, adobe brick chunks or rocks) to within about 4” of the top of the base. Add the rubble using 3” lifts and be sure to tamp each lift well using your feet or a hand tamper before adding the next lift. Finish this step with about 2” of coarse sand on top of the rubble below if you are planning on continuing with a fire brick floor. Note: Some people also add a layer of insulation below the oven floor. Bottles covered with a straw clay mix work well.|
|Step 6: Create the thermal layer of the oven by wrapping a 3” thick layer of mud around the sand form. Start at the bottom and lay a complete circle around the sand form that is about 3” high and 3” thick. Continue with subsequent 3” X 3” rings until you have closed the dome at the top. The mud mix for this thermal layer should have a high clay content. A bit of chopped straw will make it easier to shape the mud ring and keep it in place. The mud should be thoroughly mixed with water but not too wet (cob consistency). You will know if your mix is too wet if the rings begin to slump as you place them. Thicken the mix with more dirt and a bit of straw if this happens. Once the layer is finished and still wet, use the tip of a mason’s trowel to scratch the surface to allow the next layer to key into it better. Finally, use a toothpick to draw the oven door outline. Good door dimensions for this size oven are 14” wide by 12” high. Once the line of the door has been marked and you are happy with the shape, use the tip of the mason’s trowel (or a knife) to cut the door shape out. Leave the cut section in place until the next morning.|
Questions or more help? I offer horno construction workshops at various times during the year throughout the Southwest of the US. Please contact me to find out when the next live instruction or internet class begins. The internet version of the class contains a series of videos covering the 9 steps outlined above in more detail as well as introductory videos on selecting and testing soil and making your own adobe bricks.