Superadobe



Superadobe is a form of earthbag construction that was developed by Iranian architect Nader Khalili. The technique uses layered long fabric tubes or bags filled with adobe to form a compression structure. The resulting beehive-shaped structures employ corbelled arches, corbelled domes, and vaults to create sturdy single and double-curved shells. It has received growing interest for the past two decades in the natural building and sustainability movements.

History
Although it is not known exactly how long, Earthbag shelters have been used for decades, primarily as implements of refuge in times of war. Military infantrymen have used sand filled sacks to create bunkers and barriers for protection prior to World War I. In the last century, other earthbag buildings have undergone extensive research and are slowly beginning to gain worldwide recognition as a plausible solution to provide affordable housing. German architect Frei Otto is said to have experimented with earthbags, as is more recently Gernot Minke. It was Nader Khalili who popularized earthbag construction. Initially in 1984 in response to a NASA call for housing designs for future human settlements on the Moon and on Mars, he proposed using Moon dust to fill the plastic Superadobe tubes and velcroing together the layers (instead of using barbed wire). He came to term his particular technique of earthbag construction "Superadobe". Some projects have been done using bags as low-tech foundations for straw-bale construction. They can be covered in a waterproof membrane to keep the straw dry. In 1995, 15 refugee shelters were built in Iran, by Nader Khalili and the United Nations Development Programme (UNDP) and the United Nations High Commissioner for Refugees (UNHCR) in response to refugees from the Persian Gulf War. According to Khalili the cluster of 15 domes that was built could have been repeated by the thousands. The government dismantled the camp a few years later. Since then, the Superadobe Method has been put to use in Canada, Mexico, Brazil, Belize, Costa Rica, Chile, Iran, India, Russia, Mali, and Thailand, as well as in the U.S. While Superadobe constructions have generally been limited to approximately 4 meters in diameter, larger structures have been created by grouping several "beehives" together to form a network of domes. There is a 32′ (10m) dome being constructed in the San Ignacio area of Belize, which when finished will be the center dome of an eco-resort complex.

BBC News reported in March 2019 that superadobe structures have withstood earthquakes as severe as 7.2 magnitude.

Methodology
Superadobe's earthbag technique lends itself to a wide range of materials. Polypropylene tubing is ideal, although burlap is also sufficient. Likewise, while sand, cement, or lime are preferred, virtually any fill material (e.g. gravel, crushed volcanic rock, or rice hulls) will work.

After materials are gathered and the dimensions of the building are decided upon, a circular foundation trench is dug, approximately 1 foot deep and 8–14 feet in diameter, giving room for at least two layers of earthbags to be laid down underground. A chain is anchored to the ground in the center of the circle and used as a pair of compasses to trace the shape of the base. Another chain is fastened just outside the dome wall: this is the fixed or height guide and provides an interior measurement for the layers as they corbel higher, ensuring the accuracy of each new layer as it is laid and tamped.

Between layers of tamped, filled tubes, loop of barbed wire functions as mortar and holds the structure together. Window voids can be placed in several ways: either by rolling the filled tube back on itself around a circular plug (forming an arched header) or by sawing out a Gothic or pointed arch void after the filler material has set.

Once the corbelled dome is complete, it can be covered in several different kinds of exterior treatments, both for aesthetic reasons and to protect the structure from environmental damage such as that from ultraviolet radiation. Like the materials for the construction itself, there are multiple choices. While CalEarth names plaster as the most common finishing option, soil and living grass have also been used. Khalili has also used a mix of earth and plaster, further covered by a "reptile" layer of cement and earth balls that strengthen the finish by redirecting stress.

Emergency shelters
According to Khalili's website, in an emergency, impermanent shelters can be built with unskilled labor, using only dirt with no cement or lime, and for the sake of speed of construction, windows can be punched out later due to the strength of the compressive nature of the dome/beehive. Superadobe is not an exact art and similar materials may be substituted if the most ideal ones are not readily available. Ordinary sand bags can also be used to form the dome if no Superadobe tubes can be procured; this in fact was how the original design was developed.

In an interview with an AIA (American Institute of Architects) representative, Nader Khalili, Superadobe's founder and figurehead, said this about the emergency shelter aspects of Superadobe: "A 400 sqft house, with bedroom, bathroom, kitchen, and entry — I call it the Eco-Dome — can be put up in about four weeks, by one skilled and four unskilled people. Emergency shelters can go up much more quickly. After the Gulf War, the United Nations sent an architect here. We trained him, and he went to the Persian Gulf and put them up with refugees as they arrived at the camps. Every five incoming refugees put up a simple structure in five days. It's emergency shelter, but if you cover it with waterproofing and stucco, it will last for 30 or more years."

Usage of Superadobe in contemporary architecture
There exists a great number of Superadobe projects around the world. According to CalEarth, Superadobe domes and vaults have been built in at least 49 countries on six continents, including Algeria, Australia, Brazil, Canada, Colombia, Costa Rica, Guatemala, Hungary, India, Iran, Japan, Jordan, Mexico, Oman, Sierra Leone, Tanzania, United States, Venezuela, and the West Bank. However they range from backyard landscaping, to private homes to eco-resorts or community centres.

The superdobe was initially intended for temporary shelter and housing the displaced, because of its low-tech construction, the availability of its materials, and its resistance against natural forces. In 2004, the Aga Khan Award for Architecture went to a cluster of fourteen modest buildings in Baninajar, Iran by Nader Khalili. These domes were built ten years earlier to house refugees from the Iran-Iraq war and the construction was carried out by the United Nations Development Program and the United Nations High Commissioner of Refugees. The award also recognized the potential of these buildings as a prototype for a new kind of temporary housing.

Since then, many permanent private homes were built using the superadobe technique. For instance, house Quetzalcoatl in Costa Rica is composed of five full domes and four half domes using the earthbag technique.

Some buildings use it for other uses than residential. The 100 Classrooms for Refugee Children by Emergency Architecture & Human Rights hosts Syrian and Jordanian children in Za’atari village 10 km from the Syrian border.

The Langbos Children’s Centre, in the rural Eastern Cape of South Africa, was designed by Jason Erlank Architects to provide a multi-functional space for community-driven initiatives in Langbos. It consists of four domes of a total area of 217 square metres.

The Majara Residence on Hormuz Island in the South of Iran is a cluster of 200 small-scale interconnected superadobe domes that form a neighbourhood of 15 residences and public facilities and is designed by ZAV Architects. The domes and the landscape surrounding them covers an area of 10300 square metres, while the built space is around 4000 square metres. This project was preceded by a prototype called Rong Cultural Center which tested the Superadobe technique on the same island.