Requiring no machinery and minimal training, Cal-Earth’s Sandbag Shelters offer a building system ideally suited to providing earthquake-resistant emergency shelter, but equally effective for constructing family homes. Being easily adaptable to local materials, needs and circumstances, the timber-free arches, domes and vaults have been successfully transferred to over twenty countries across the world. Over 1,000 dwellings have been built and 400 apprentices trained.
Aims and Objectives
- To provide environmentally-sustainable housing designs, using simple materials that can be built quickly and easily.
- The building system focuses on the use of eco-friendly and indigenous materials.
- To transfer the approach through education and training.
In 1991, the internationally renowned architect Nader Khalili founded The Californian Institute of Earth Art and Architecture (The Cal-Earth Institute), a non-profit research and education organisation. The Institute is located in the Mojave Desert, 50 miles east of Los Angeles, in an area that frequently experiences extremes of heat and cold, as well as earthquakes and high winds.
Cal-Earth’s philosophy is based on the equilibrium of the natural elements of earth, water, air and fire and their unity for the benefit of the arts and humanity. As pioneers in earth and ceramic architecture technologies, Cal-Earth’s work ranges from technical innovations published by NASA for lunar and Martian construction to housing design and development for the world’s homeless for the United Nations.
This project carries out hands-on research into sustainable earth architecture through building and testing life-size prototypes and by educating the public in environmental architecture. It develops and uses simple technology based on eco-friendly and indigenous techniques.
Four main building types have been developed: emergency shelters, a small house, a three-vaulted system providing a standard three-bedroom home and a thin-shell brick or ceramic dome. Although the buildings developed by Cal-Earth have a diverse range of uses and applications, they are particularly appropriate as emergency accommodation, to meet the needs of displaced and homeless people, either in the aftermath of natural disasters or in war-torn areas where there are large numbers of refugees or internally displaced people.
Using the enduring form of arches, domes and vaults, this technology is applied to create single and double-curvature shell structures that are both strong and aesthetically pleasing. The shelters are highly energy-efficient in terms of passive heating and cooling and no timber is used in the construction. Conventional doors and windows can be included. A typical emergency shelter comprises one major domed space with some ancillary spaces for cooking and sanitary services.
The system has been particularly suitable for providing temporary shelter because it is inexpensive and allows shelters to be built quickly without machinery and with only minimal training. The project has expanded the range of low-cost and flexible construction options available for use in both temporary and permanent situations and has been utilised by both the United Nations Development Programme (UNDP) and the United Nations High Commissioner for Refugees (UNHCR).
The sandbag shelter system meets the stringent requirements for refugees of UNHCR, the host country, and the refugees themselves. Host countries often do not allow permanent structures to be built so as to encourage refugees to return to their homeland. The ‘superadobe’ technology builds shelters that last for one season before returning to earth, unless they are waterproofed and finished as permanent houses.
UNDP and UNHCR selected the project’s technology for use as temporary shelter for displaced persons because of the following characteristics:
- Flexibility in size, surface area and design.
- Speed with which shelters can be built.
- Minimum on-site skill requirements
- The temporary shelters have potential to be enlarged and upgraded to become permanent homes.
As a result of the project people who are made homeless by either natural or man-made disasters are able to have a safe and comfortable shelter and begin to rebuild their lives.
As the construction process requires minimum on-site skill it is possible for residents to build their own houses under the supervision of a trained person. The bags that make up the structures can be filled with on-site earthen material directly on the wall, and by as little, or as much, as the person building can manage. Heavy weights need not be lifted, and the whole family, including women, children and the elderly can be intrinsically involved in the construction of their new home.
People are empowered to build their own home, whilst at the same time preserving natural resources and energy, halting deforestation and reducing pollution. The flexibility of the plans and the finishes available allows the integration of indigenous, traditional aesthetic patterns, forms and colours.
After extensive research into vernacular earth building methods in Iran, followed by detailed prototyping, Cal-Earth developed the sandbag, or ‘superadobe’ system of construction. This involves filling sandbags with earth, compacting them with a hand-held tamper and laying them in courses in a circular plan. The circular courses are corbelled near the top to form a dome. Barbed wire is laid between courses to prevent the sandbags from shifting and provide earthquake resistance. The resulting structure is extremely safe and capable of withstanding flood, fire, hurricane and earthquake. Stabilisers such as cement, lime or ash can be added as ten per cent of the volume for increased durability.
The system has been used for structural arches, domes, vaults and conventional rectilinear shapes. This method can build silos, clinics, schools, or infrastructure like dams, roads, bridges, and also be used to stabilise shorelines and watercourses.
Earthen homes, although widely used throughout the world, are vulnerable to earthquakes and to rain and snow. Cal-Earth’s ‘superadobe’ constructions can be reinforced with barbed wire, using the sandbags filled with damp earth and have passed California’s strict seismic resistance tests. Following six years of engineering review and testing, California building permits for their use as housing were issued. This achievement, as well as gaining building approvals in other states across the United States, represents a major change on previous practice. Un-reinforced earthen structures had been forbidden in California for the last 50 years.
The initial capital used to establish the Institute was US$10,000. Capital costs for the construction of the dwellings are low at approximately US$650 for a simple dwelling and up to US$7,000 for a larger individual building in the United States. These costs are met by the commissioning partner organisations.
The work of the Cal-Earth Institute is supported by grants from a range of organisations, but for the most part is self-sufficient. Revenue from course tuition, house-plans and the sale of books and videos covers many of the annual overhead costs. These are kept as low as possible at between US$200,000 and US$250,000 per annum. Future revenue streams are also emerging from architectural projects, membership fees and the development of distance learning courses.
Cal-Earth has partnered with other organisations to transfer and adapt the building technology and prototype designs. These have included UNDP, UNHCR, United Nations Industrial Development Organisation (UNIDO), and other international non-governmental agencies.
There is an ongoing programme for both the educational and construction aspects of Cal-Earth’s work. Individual projects have been established in many countries of the world including the Bahamas, Belgium, Brazil, Canada, Chile, China, Ghana, Guatemala, India, Iran, Mexico, Mongolia, Nepal, Pakistan, Panama, Siberia, South Africa and Thailand. These range from small emergency shelters to large family houses. It is estimated that over 1,000 such dwellings have been built to date and 400 apprentices/trainers have been taught.
Why is it innovative?
- Low-cost houses of innovative design that can be made using easily available materials.
- Quick and easy construction methods enabling older people, women and children to be involved in building their own homes.
- Capacity to resist a variety of natural disasters including earthquakes, fire, flooding and hurricanes.
- Temporary construction that can be easily adapted into a permanent structure.
What is the environmental impact?
A key design principle of the sandbag shelters is sustainability. The energy used to build and maintain the structures comes form the sun, wind, gravity and from human hands.
The use of earth as the prime building material removes transportation costs as this is available at the build site. The earth is excavated manually, using simple tools, keeping the environmental cost of production very low. Sandbags and barbed wire are obtained locally.
Cal-Earth’s approach reduces the amount of timber used in construction and minimises the use of cement, bricks and steel. This greatly reduces the embodied energy of the project’s building materials.
The structures have thick earth walls and these ensure high levels of insulation against extremes of temperature. Wind funnels have been incorporated into the designs to ensure maximum cooling effects in hot weather.
Is it financially sustainable?
Overhead costs of running The Cal-Earth Institute are kept as low as possible. The current costs of between US$200,000 and US$250,000 per annum are met through a number of sources. Donations account for 29 per cent per cent of the required revenue and the remaining 71 per cent comes from sales of books and videos, course tuition and the provision of house plans. Net income each year is between US$5,000 and US$20,000.
It is anticipated that revenue will continue to come from the same sources in the future. Additional income will be derived from the distance learning services that have recently been developed and for which a fee applies to those able to afford it. This fee will be waived for those in need.
As the housing provided in this project does not rely on cutting trees, welding steel or manufacturing concrete the costs are kept very low. Made using earth and barbed wire, a family sized shelter can be built for the cost of US$ 650. The shelters can be built quickly, and with minimum onsite skill. Shelters take between one and seven days to erect, dependent on the size of shelter and the context within which they are built. In 1995, five Iraqi refugees built 14 of the shelters in six days. With Cal-Earth’s methods, it is possible to erect a permanent house for little more than the price of a tent.
What is the social impact?
The element of self-help in the construction process works to ensure high levels of cooperation in the construction of the housing units. Participation in the process of building their own home has been an empowering process for many. Communal building efforts in the event of a disaster help to bring devastated communities together.
The construction of these shelters requires minimal skills, which can be easily taught by skilled workers. Over 400 apprentices have been trained in the construction technology and they have passed on these skills to others. In the Pakistan project, for example, over 500 local people were trained by Cal-Earth apprentices.
The project’s building system provides safety and security in the post-disaster context, as well as a healthy indoor living environment. The shelters have been shown to be safe in the event of earthquakes, floods, fire and hurricanes and the low cost of construction enables those on lower incomes to provide themselves with a safe and decent home.
- Initially the technologies were met with much resistance from building officials who were opposed to construction methods and materials that did not rely on cement and steel for strength and stability.
- Whilst the technology provides jobs for many people, its lack of manufactured materials does not provide a profit for intermediaries and as a result is not promoted actively on a commercial basis.
- Host countries do not often allow permanent structures to be built as in many cases they wish to encourage refugees to return to their own countries.
- Cultural resistance to living in earth construction.
- People can provide their own shelters if they are empowered with the necessary knowledge and help with materials.
- If the technology is to be transferred at scale, the technical knowledge to enable others to develop the houses independently needs to be more widely shared. The distance-learning programme has been developed to enable the techniques to be more widely distributed.
California has some of the world’s strictest codes concerning earthquakes and thus the construction’s credibility for seismic resistance has been well established. It was based on this accreditation that the Pakistan authorities accepted its use in earthquake-devastated areas. The Hesperia Building and Safety Department (the local municipality where the Institute is based) continues to monitor the prototypes as they age and as new versions are built.
The construction method has been developed over many years of trial and experimentation. The prototypes have been rigorously tested by range of bodies including the Californian Building Regulations Authority (under the Uniform Building Code standards) and the UNDP built and tested a prototype prior to using the technology in the field. California is changing its building regulations scheme to the International Building Code, and so further testing is now being carried out.
Over 400 Cal-Earth apprentices are teaching and building sandbag shelters in countries around the world including Iran, India, Mexico, Chile, Pakistan, Siberia, Tibet, South Africa and the USA. Training centres are currently being established in Europe and the Middle East and the possibilities of further centres in Australia, Africa and the Middle East are currently being investigated. The recently developed distance-learning program will extend the accessibility to Cal-Earth’s training. Delivered in an interactive, hands-on format, the program will be available to universities, NGOs and those in need around the world.
The building method has been used throughout the world. Forty Khalili-designed buildings were built in Iran by the United Nations High Commission for Refugees after the Iran-Iraq war; and ‘superadobe’ designs are now being used in the Caribbean, as part of the effort to re-house people after Hurricane Mitch devastated the area in 1998. Cal-Earth has partnered with The Strategic Actions Social Impact (SASI) Foundation under the name Cal-Earth Pakistan. Four apprentices have been sent to teach the local builders in training centres close to refugee camps. Over 500 builders have been trained and many houses have been completed but the exact figure is not known with certainty.
A range of projects building on the ‘superadobe’ technology has been developed in California, the home state of the Cal-Earth Institute. This includes a 12 dormitory residence at a school, 12 cells for a monastery and 10 single family residences, including a large 400m² American-style home, which has been erected within four weeks.
At the national level, the Institute works mostly with private clients – both organisations and individuals. The design is being used for low-cost homes that are finished to contemporary US standards. Approximately 20 such homes have been completed to date.
Professional, Academic/Research, international agencies, donor agency, private sector