How to build a Adobe Oven
Or horno as it is called in Spanish-speaking parts of the world. Sun-dried mud brick construction, mud mortar, recycling (bottles) and mud plastering construction.
Build a base structure at a good hight, so you can use the oven in future without having to bee kneeling down all the time. For us this meant 110cm from the ground.
Build a brick wall around the base 190cm x 190cm and fill this with glass bottles and sugarcane and salt. About 50% of the hight then came about 2-3cm of the local soil and of top of that about 1cm of sand (we used river sand with smaller rocks).
In contrast to cob construction, where walls are directly hand formed by shaping thick layers of mud; adobe walls, domes and vaults are made of individual sun-dried mud bricks, bonded together with mud mortar.
On top of the sand we placed another layer of bricks. You should use bricks which are fireproof.
One of the attractive advantages of building with adobe is that suitable material is most often right under the workers’ feet. For our case this was not literally true because we had to bring the adobe mud bricks from Susudel in the Sierra which is located near the colonial city of Cuenca in Ecuador.
The bricks where placed directly on the sand and we just used some cement to connect the bricks sidewise. Just to fill the gaps between the bricks.
(2) Building the actual oven walls.
As you can see this is the base for the round oven. First layer is mortar. On top the dried adobe bricks are cautiously placed. Important detail is that the bricks are not rectangle in form but rather like an Isisceles Trapezoid. This helps tremendously in the building process.
Another important building hack is to fix a string to the center and then depending on the size of your oven draw a line so you have the perfect circle on the base. This is used for placing the adobe bricks in perfect position.
As you can see layer for layer has been placed in this photo. Also mud plastering inside has been started because later this gets more difficult, less access.
An ideal proportion for adobe bricks and mortar is 70% sand and 30% clay.
The oven entry door is one of the most critical parts of the oven. In our case we used a metal door and frame which helped to build the around the door and keep the round form with the bricks. The mud plastering on the outside has just started in this phase.
As you can see in the picture. The outside mud plastering is being done with dried grass halms which shall help the mud not to crack so easily when the temperature of the material will rise.
To complete the building of the adobe oven, the mud plastered oustide will get a additional thin layer of mud with 5% cement with some type of white sand like material which shall prevent the outside from suffering too much from humidity and possibly rain drops.
Before putting the fire in the adobe oven, it is best to let all the mortar and plaster to dry. This is why we need to wait now a few weeks before we can start using the new oven.
We at PermaTree plan to use this adobe oven primary for bread and second for pizza making.