The Center for Ecological Design

Earthbag homes

by Emily Nicolosi, PhD. May 7, 2020

“What type of house would you rather live in? One that is thick, quiet, energy efficient, non-flammable, non-toxic and dirt cheap? Or one made of sticks and toxic materials that burn like crazy, offgass toxic fumes, leak energy and cost a small fortune. Earthbag is inexpensive enough that you don’t need a mortgage. Instead of spending 30 years paying off a mortgage, build super inexpensively and have far more time to spend with your family and friends, and help build community. This also lessens the influence of big banks, which are wrecking society with their greed.” -Owen Geiger

An Earthbag home is exactly what it sounds like: a home made of bags filled with earth. At first, the concept is a bit shocking- like, bags of dirt? Is that actually stable? Does it not rot or smell or look just like a pile of dirt? After digging a little deeper, you’d be surprised to find out that earthbag homes can be made in incredibly beautiful forms and can even withstand earthquakes.

An Earthbag home. Image: Inhabitat.com Jose Andres Vallejo.

Time

.81 hour per square foot of exterior wall surface, according to expert Owen Geiger’s calculations.

Expertise

Earthbag homes are not technically difficult to construct. Materials and tools used are also basic. There are several books on the subject, an Instructable, and many YouTube videos. In-person and online workshops are also available from Cal-Earth and others.

Cost

$10/sq/ft. Building costs for earthbag homes are extremely low. The earth used in the bags is usually acquired on-site. A 200 sq ft earthbag home would take 4 people one week to build and cost $2,000.

History: From Bunkers to the Moon

Sandbags have been used for more than a century. Their original uses were for flood control and the military- images of soldiers in hunkering in sandbag bunkers may come to mind. It wasn’t until the mid 1970s that researchers at Kassel Polytechnic College in Germany found that fabric-packed earth material was a viable approach for using natural materials for houses without the addition of binders. Nader Khalili, an Iranian architect, developed “Superadobe” and popularized the idea, even proposing it to NASA as a solution for lunar settlement!

An earthbag home under construction. Image: Owen Geiger

Building Process

Earthbag homes can be made into an almost endless variety of shapes. The soil needs to be tested to ensure it has the correct ratio of clay to sand- 30% to 70%. Foundations depend on site location, but most Earthbag homes do not use a concrete foundation, some opt for rocks to help with drainage. Door thresholds and bucks are laid next. The bags are filled with earth and staked. Rows of bags are tampened, then layed with barbed wire. Metal or wood anchors are secured every few courses to window and door bucks, anchors for electrical boxes and window bucks are installed as necessary. A bond beam is installed before the roof.

Insulation

The earth also acts as a good insulator which keeps heating and cooling costs low. Walls greater than 12 inches thick create a thermal flywheel effect, absorbing heat during the day and releasing that heat with cooling night air temperatures.

Safety

Superadobe has been tested to 1991 Uniform Building Codes by Architect Nad Khalili, found to withstand seismic, wind, and snow loads. Superadobe structures have been approved in San Bernardino County California, earthbag buildings have been accepted in several other states, local officials should always be consulted. For a summary of earthbag testing research, see earthbagbuilding.com/testing.

This earthbag home was built by a couple in Hawaii for about $6k. Image Jay Eisnberg

An Earthbag home is a great choice for someone with limited financial resources, tolerance for tedious and strenuous labor who wants a relatively quick solution for an earth building.

Advantages

Inexpensive
Relatively easy to build
Significant creative freedom in form and shape
a wealth of free and open-source information online about earthbag building

Disadvantages

Building permits can be challenging, see this useful guide
Tedium
Physical strength and strain

Materials

Earth. 70% sand 30% clay, insulating material (lava stone, scoria, pumice, perlite, vermiculite) optional
Bags. Polypropylene bags are recommended. Bags can be obtained cheaper if you look for misprints or recycled grain sacks. Cal-Earth sells round tube bags which maybe easier but are more expensive.
Barbed wire.
Plaster. Covers the earthbags inside and outside of the home.
Wood. For framing windows and doors.
A tamper. Compresses the soil; a wooden pole with a heavy metal plate attached.
Basic miscellaneous tools. Wheelbarrows, shovels, drills, etc.

Further Resources

Websites

Cal-Earth.org for the SuperAdobe approach

EarthbagBuilding.com

Instructable

How to Build and Earthbag Roundhouse

Free Earthbag floor plans

Video

Building with Bags: How We Made Our Experimental Earthbag/Papercrete House.

Books

Kaki Hunter. Earthbag Building: The Tools, Tricks and Techniques. New Society Publishers, 2004. $8

Kelly Hart. 2018. Essential Earthbag Construction: The Complete Step-by-Step Guide. New Society Publishers. $34

Kelly Hart. 2015. Earthbag Architecture: Building your Dream with Bags. Hartworks. $20

Owen Geiger. Earthbag Building Guide. NOOK Book. $10.

Ceramic Houses & Earth Architecture: How to Build your Own. Cal-Earth. $10.

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