Superadobe or earth bag building was developed by Nader Khalili, an Iranian American architect, writer, and humanitarian. He developed the superadobe system in 1984, in response to a NASA call for designs for human settlements on the Moon and Mars. It wasn’t taken to the moon but the project was used after the Persian Gulf War when refugees were sent into Iran. This is when he applied his research to emergency shelters.
Nader built monolithic dome-shaped structures with arches out of grain bags and polypropylene tubes filled with dirt; any kind of dirt, even dry sand (with cement). His buildings tended to be solid as a rock and where tested to withstand earthquakes.
When my family and I arrived to live in Brazil, my dad Andre Soares was lucky enough to visit Cal-Earth in California. He loved the technique and was determined to take it back to Brazil. In 2000 he started creating small superadobe structures. Public reaction was mixed. As you can imagine, some people thought it was crazy, others considered it a great proposal for the Brazilian reality.
At the time, Permaculture courses were happening regularly at Ecocentro IPEC so there was great demand for a closed kitchen. The weather and sometimes-cheeky monkeys would interfere with the cooking of the meals in our open space. Andre decided to create a social project of participatory architecture. The aim was to include the women that used the kitchen in the design and construction of the building.
So during one of our Permaculture Design Courses (PDC) the challenge was given to the students and many interesting projects resulted. These were presented to the local women’s group with the task to produce the kitchen. They made several appropriate changes and then decided on the final design. The group and the wider community also participated in the task force constructing the largest adobe kitchen in Brazil. And, as they say, the rest is history.
Super adobe is possibly the fastest way to build walls with earth without machinery. It is a very flexible technique that supports various types of soil. Unlike other natural building techniques, there is no need to sift the soil through a frame. With a bit of physical effort, the walls are erected quickly.
Super adobe only requires simple tools:
- A piece of pipe that will serve as a funnel (adapted from 250 mm PVC pipe)
- Lengths of polypropylene bags (acquired in rolls)
- Manual tamper (or ramming tool)
- Barbed wire (to use in between courses)
- Buckets (to move earth)
- Rubber mallet (to shape and finish the walls)
- Pliers, shovels, hose
The bag used for erecting walls is a large roll of polypropylene (coil), about 40 cm wide. The roll is cut into pieces the length of the courses to be laid, leaving a small extra length at each end of each course to be tucked at the end.
The procedure is simple. The bags or tubes are filled using a suitable pre-moistened earth laid in running bond. The PVC pipe works like a large funnel, making it easier and faster to introduce earth into the tube. After a course has been laid, it is thoroughly compacted with hand tampers.
Two strands of 4-point barbed wire are laid in between every row, which act as a “velcro mortar” cinching the bags in place. This provides exceptional tensile strength while allowing the rows to be stepped in to create corbelled domes and other unusual shapes.
It is essential that the bottom of the walls be sealed from direct contact with the soil to prevent moisture seeping through the building. When making a foundation, we use sand and cement to the ratio of 9:1. Complete the necessary courses until the foundation reaches a height of 20cm above ground level. It is very important that each course is very well pounded before the next. There is a point of compaction where you can “feel” the material as solid as a rock.
Superadobe walls can be structural and a few details of construction allow you to anchor a roof on to it. It doesn’t require the construction of columns or beams. The top of the wall requires a course similar to the foundation. Lintels are a tricky thing and arches over the doors and windows are easier built. Electrical and hydraulic installations can be built into the wall after compaction.
Like other natural building methods, super adobe has its pros and cons:
- Organised and clean work.
- Easy to learn and master the technique
- Fire proof walls
- Speed in the construction process of the walls
- Use of local materials
- High thermal mass in solid earth (40cm thick)
- Low investment with support materials
- Need special care and details to seal against moisture
- Requires at least 5 people for running a medium-sized work team
- High physical requirement for manual builders
Remember that the final product is hand made, and as such it is unusual to the eye accustomed to pre-fab industrial structures. So, if you like things that say “hand built” grab a bag, earth and start creating!C