We excavated 7 feet out of the side of our mountain in Chiapas for our construction site. The excavated dirt and gravel will be used to fill the earthbags. The oak timber cleared will serve for roof beams.
The first courses of earthbags are with filled and tamped with gravel so as to protect the base of the house from moisture. As this first course of earthbags is sitting on hard gravel there is no need for a conventional concrete foundation. As we are building on a slope, I used a layer of cement block and mortar only on the lowest side to make the foundation level before placing the first layer of gravel-filled bags. In fact, most earthbag constructions do not use concrete foundations but rather a rubble-filled foundation in the traditional style of European foundations that Frank Lloyd Wright revived in the 20th century.
Earthbag constructions are very sturdy and earthquake resistant. With a design of continuous and interconnected hexagonal rooms all of the walls are tied together and are less likely to shift. Also, the bags of adobe are 22 inches wide 32 inches long, which gives each bag a great overlap over lower ones. Giant adobe earthbags can shift more freely than smaller, traditional adobes. Also, the thick walls remain very cool and the tropical heat does not penetrate them and heat up the house.
This is the first few layers of earthbag adobe bricks that are molded into recycled polypropylene bags. The earthbags are filled with a mixture of moist earth and sand and are tamped hard while damp so that they dry into dense, hard adobe bricks. Each layer has 2 strands of barbed wire to keep the bags from slipping. We cover them first with mud and then a lime plaster to protect them from the elements.
Don Rogelio sits atop the penultimate layer of bags. I found a friendly group of local coffee growers to help me out with the construction. They, as well as I, have built with adobe bricks but this was the first time for us to use earthbags. As campesinos, they are very practical and helped me refine construction techniques as we progressed. For a more detailed example of the earthbag construction techniques watch this short video with Owen Geiger.
A concrete bond ring is one of the few steps in superadobe construction which requires cement. This gives a firm base to build the roof and also ties all of the walls together to keep them from shifting. Vertical steel rebar hammered down to the base of the wall connects the bond ring to the adobe walls.
An impermeable layer of sand and lime reinforced by wire mesh gives protection and a natural, smooth finish.
Our land was almost completely untouched by human activity. Only some large pines and oaks were cut down before we arrived. This has allowed many closely growing oaks to grow upward instead of expanding. I cut down the straightest ones and will let the rest of them grow with more space to expand and become full trees. Oak is very hard and insect resistant and lasts for centuries.
A cupola serves to ventilate and cool the house.
The first room or cell in a hive pattern of 6 connected hexagonal rooms. I like this photo because one can see the rock high on the horizon which is the limit and highest point of our land. It is quite an extreme hike to reach the top.
The second room has a different style of cupola.
As we live in a tropical climate I left 2 walls open. One open side (to the left) will connect a kitchen and a living room. Glass windows and entrance doors will occupy the space in the front.
Editions to this document will be published on my blog as the construction progresses.