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Earthbag building

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History

The notion of building walls with sandbags or earthbags has been around at least 100 years. Originally and into modern times these have tended to be burlap (hessian) fabric bags forming temporary structures acting as flood barriers or as military fortifications. Building permanent structures such as homes using earthbags is a more recent development.[1]

The earliest record of such construction methods appears to have occurred in Germany in the 1970s. Gernot Minke and others at the Research Laboratory for Experimental Building at Kassel Polytechnic College were investigating ways of building earthquake resistant structures without cement. They used polyester and burlap tubes filled with pumice to make domed structures. With the Francisco Marroquin University in Guatemala and the Centro de Estudios Mesoamericano Sobre Tecnologia Apropiada (CEMAT) a structure was built in Guatemala in 1978 out of lime soaked cotton fabric bags filled with pumice sand.[2]

The Earthbag building method was popularized by Persian Architect Nader Khalili who eventually developed a building technique he termed Superadobe, where polypropylene bags or tubes filled with moistened adobe soil were used to form often domed structures. Khalili went on to publish 6 books and found the non profit organization Cal-Earth Institute (California Institute of Earth Architecture) in 1981.[3] He has been criticized for attempting to capitalize on this technique at the same time as claiming it was "freely put at the service of humanity and the environment" when he attempted to patent earthbag building techniques in very general terms in 1991 and requested that all other promoters of earthbag building enter into a contract with him to continue their work.[1]

Terminology

Contained earth is the basic technique of filling containers with earth.

Contained Sand uses sand fill or any fill too dry or with poor cohesion that performs structurally like sand bags. Such bags must be solid-weave fabric have good protection from fabric damage. Contained sand needs more vertical reinforcement than contained earth. Structurally, alternative loose fills (like rice hulls) will create a wall more similar to contained sand than to contained earth.

Contained Gravel uses fill of any aggregate larger than coarse sand. CG can function as concurrent footing and footing drain material. CG can use either solid-weave or mesh containment.

Modular CE is the traditional earthbag material which is built in solid weave poly-propylene bags or tubes. Walls rely on attachment between barbed wire barbs and/ or added pins between courses.

Solid CE is a more accurate term for hyperadobe, developed by Fernando Pacheco of EcoOca in Brazil. A pliable knit raschel mesh tube is used, the same material used in packaging fruit. This mesh allows the earthen fill to solidify between courses as long as the fill is built damp. Solid CE has higher shear and out of plane strength than modular CE of the same soil, and may allow the use of wire mesh in addition to or in place of barbed wire. According to Nader Khalili, the contents of the bags settles into its permanent form within 3 days.

Containers

The basic vessel for contained earth building may be either numerous bags/sacks which are used as individual bricks, or long tubes which become the entire course. The fabric used in bags or tubes may also be a solid weave or a mesh.

Polypropelene

Polypropylene (also termed polypropene) is the second most commonly produced plastic in the world. Long rolls of polypropylene tubing are available from manufacturers. These large rolls of tubing are normally intended to be cut and stitched into individual bags and then used as rice bags, etc. Solid weave Polypropylene bags or tubes are the most popular type of container in earthbag building.

Polypropylene is cheap, durable, resistant to rot, water damage and insects. A study reported that polypropylene fabrics may have a half life of 500+ years in benign environments.[4] The tensile strength of such bags is higher than steel,[4] and they are resistant to circumferential forces produced by load bearing.[4]

Filler material

The Materials

  • Bags
  • Earth (most types-clay, sand, etc)
  • Barbed Wire
  • Gravel (optional)

The Tools

  • Shovels
  • Tamping tool
  • Bricks/weights
  • Nails/wire
  • Buckets
  • Hose
  • Sheetmetal Slider
  • Pliers
  • Ladder

As some of these tools may not be needed in your particular earthbag project, some may also become necessary. A leveling board, hoes for digging and other materials like rubber mallets may come in useful.

Procedure

The following is an excerpt from Earthbag Building: The Tools, Tricks and Techniques.

"Earthbag Building utilizes the ancient technique of rammed earth in conjunction with woven bags and tubes as a flexible form. The basic procedure is simple. The bags or tubes are filled on the wall using a suitable pre-moistened earth laid in a mason style running bond. After a row 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."

References

  1. 1.0 1.1 History of earthbag building on earthbagbuilding.com by Kelly Hart
  2. Building with Pumice by Klaus Grasser / Gernot Minke published by Deutsches Zentrum, 1990 (reproduced on earthbagbuilding.com)
  3. Biography of Nader Khalili on calearth.org
  4. 4.0 4.1 4.2 Earthbag Technology - Simple, Safe and Sustainable. Owen Geiger, Kateryna Zemskova. Nepal Engineer's Association (NEA) Technical Journal. Vol XLIII EC30 special issue on the Gorkha Earthquake 2015 (available on Good Earth Nepal website)

Further reading

Books

Websites

Videos

  • Flexible Form Rammed Earth Construction (Earthbag Construction). Case Study presentation by Frank Morris Matovu at the 4th Quarterly Roundtable Discussion Meeting on Appropriate Building (Low-tech Construction) at The African Heritage House, Kenya (2 parts available to view on YouTube by searching "Flexible Form Rammed Earth Construction (Earthbag Construction)"