Building with earthbags (sometimes called sandbags) is both old and new. Sandbags have long been used, particularly by the military for creating strong, protective barriers, or for flood control. The same reasons that make them useful for these applications carry over to creating housing: the walls are massive and substantial, they resist all kinds of severe weather (or even bullets and bombs), and they can be erected simply and quickly with readily available components. Burlap bags were traditionally used for this purpose, and they work fine until they eventually rot. Newer polypropylene bags have superior strength and durability, as long as they are kept away from too much sunlight. For permanent housing the bags should be covered with some kind of plaster for protection.
There has been a resurgence of interest in earthbag building since architect Nader Khalili, of the Cal-Earth Institute, began experimenting with bags of adobe soil as building blocks for creating domes, vaults and arches. Khalili was familiar with Middle Eastern architecture and the use of adobe bricks in building these forms, so it was natural for him to imagine building in this way. The Cal-Earth Institute has been training people with his particular techniques, and now the whole field has expanded considerably with further experimentation by his students and others.
I have taken Khalili's ideas of building with earthbags that are laid in courses with barbed wire between them, and come up with some hybrid concepts that have proven to make viable housing. Instead of filling the bags with adobe soil, I have used crushed volcanic rock. This creates a very well insulated wall (about as good as strawbale) that will never rot or be damaged by moisture. As a covering for the earthbags I used papercrete (see the papercrete page). This seems to be a very good solution to the need to seal the bags from the sun and the weather, without necessarily creating a vapor barrier...the walls remain breathable. Papercrete may not be a good choice in warm and humid climates, however, because mold could form on it.
For a much more thorough look at every aspect of earthbag building,
I am very pleased to announce that a prominent engineering firm that is licensed in 27 U.S. states is now offering engineering services for earthbag construction in both seismic and non-seismic areas around the world.
The Native Spirit house plan blends a hexagonal dwelling with a soaring tower, all built of earthbags. If one chooses, the un-bermed portion of the main house can be built with strawbales. The first floor of the tower serves as a cool pantry that keeps food cool without electricity. Other levels can be used as office space, a second bedroom or storage. The top level is an observation deck - truly a stunning feature in such an affordable home. The hollow, central column in the main structure can be built with stone or CEBs (compressed earth blocks). The stove pipe runs up through the column and the thermal mass helps stabilize indoor temperatures. Large south-facing windows create an attractive plant shelf and provide excellent solar gain. Other features include a large built-in bench, fold-out bed and home office. An airlock entry has a washer and dryer, coat closet and bench.
Specifications: 565 sf interior, plus 291 sf tower (4 levels) for a total of 856 sf; 1 bedroom (fold-out bed), 1 bath, plus cool pantry and 2 bonus rooms.
For more information about this plan, and many others, visit our sister site www.dreamgreenhomes.com, where you will find a wide range of plans for sustainable homes, greenhouses, small buildings, garages, and food storage space for sale. Dream Green Homes is a consortium of outstanding architects and designers, who have pooled their talent and expertise for your benefit.
This is our first experimental earthbag dome. The interior diameter is 14 feet and the dome stands about 16 feet high. At first we tried filling the bags with the fine sand that it is built upon, but when we were partly done, the dome fell in because the sand couldn't hold the shape. Then we filled the bags with crushed volcanic rock (scoria) that provides better insulation and holds its shape much better. The arch over the doorway was created with a wooden form that was later removed. We kept the dome tarped most of the time until we papercreted the exterior. We did this to keep the sunlight off the bags because the UV will eventually destroy the bags.
This is the beginning of the large elliptical dome that became our kitchen and living room. It measures approximately 30 feet on the long axis and 20 feet on the short axis. Because we are building on sand with excellent drainage and no problem of frost upheaval, there is no foundation other than a pad of 6 to 8 inches of the crushed volcanic rock (scoria). You can see the pile of scoria in the background, and a large wagon wheel in the foreground that will be use to support a circular window opening.
Because of the elliptical shape, this dome required a rigid pole framework to help support the second story. I would not recommend building anything but a circular dome after this experience, because otherwise the forces are just not balanced enough. You see the large arch form for the six-foot wide doorway. The house is a passive solar design, so we needed large openings to let in the sunlight. After several failures and much experimenting, we devised a double bag technique to create such a large arch. Double, side by side, bags are used for columns at every doorway in the house.
Here I am applying a coating of papercrete to the outside of the large dome. I did this as soon as I could to protect the bags. Thermal pane glass was embedded in the papercrete on the outside over all of the circular windows.
This is the papercrete tow mixer that was used to mix most of the papercrete. An invention of Mike McCain, the tow mixer is an amazing machine. It is made from a car rear end, a metal stock tank, a lawnmower blade and a few other parts. To make the papercrete, water is filled to within about 6 inches of the top, sand is added if desired, dry paper of virtually any description is added, and one bag of portland cement thrown in. One slow trip driving around the block produces a thick slurry that is total mush. This is drained through a sieve to eliminate the excess water, and then applied to the building. One mixer load yields between three and four wheelbarrows full of papercrete.
On the left is the 16 foot interior diameter bedroom dome, and on the right is part of the large dome. Between them is the connecting portion of the house under construction. The back (north) bag wall is a section of a sphere that is braced into place with the rafters for the southern roof/wall. Other braces within the attic space help hold the shape.
This is the southern aspect of the house after the final papercrete stucco was applied. The section of roof between the domes is covered with metal roofing and supports an array of eight photovoltaic panels. (That's why we needed a straight surface.) Solar water heating panels will be mounted below them. Beneath this roof is a bay of windows that extends outward to create a greenhouse space.
This view from the north shows the earthbag vault entryway/mudroom with its bell tower. The mound in the foreground is a completely bermed pantry that is accessible inside, from the kitchen. On top of the large dome are two air vents and a stove pipe. There are also three inlet air vents elsewhere in the dome.
This view of the back of the house shows how well it fits into the landscape. The curved shapes blend in with the mountains in the far distance.
This shows the main entrance onto a landing, with the option of going up to the loft or down to the main level. Lots of natural wood was used to finish the interior components. An old wood stove for back-up heat is visible in the foreground
The flight of steps lead up to the loft over the kitchen. The lodge poles that help support the dome's shape can be seen with the final coat of lime plaster that was troweled on between them. The horizontal band of logs between each lodge pole was positioned to brace the structure rigidly when a steel cable was tightened around at the same level.
This is a view of Kelly's office space in the loft over the kitchen. Because the walls angle in rather sharply, the standing floor space is diminished. A built-in counter around most of the wall provides desk and equipment space, with lots of storage beneath it.
This is looking straight up from near the wood stove. You get almost a teepee feeling from the shape and the lodge poles. The two air vents are sealed with tether balls inflated to just the right size to fit snugly into the pipes. Long handles are attached to the balls to insert and remove them.
This is the view from the landing down into the living room. One of our dogs is standing on the flagstone set into the adobe floor. The rest of the floor in the large dome is poured adobe that was scored with a rocklike pattern. This is a classic passive solar arrangement, with lots of south-facing glass and dark colored thermal mass on the floor to absorb the heat. A window seat can be seen behind the dog, under the wagon wheel window. This seat was formed during construction with earthbags.
This is looking toward the large dome from the greenhouse in the connecting space. The tomatoes are happy. The wall next to the planter is papercrete stucco that was troweled smooth. A natural vertical log supports the horizontal beam that supports the entire south side of the attic.
A view of our shower stall made with natural local stone, tile and wood. This was a little tricky because of all the odd angles in the space, but it works. Eventually there will be more rockwork around a solar hot tub in the green house area, which will serve as more thermal mass that will be heated by the sun.
This shows the curved stairway in the bedroom that leads to a small loft. The stairs are made of earthbags filled with sand, and covered with papercrete. The coloration of the interior space was accomplished by brushing a small amount of latex paint mixed with lots of water onto the papercrete walls. This basically stains the wall without interfering with the breathablity through the wall.
Here is the office space carved out of the attic area in the middle section. The bag wall can be seen on the left, and the wood-framed wall is on the right. Wooden braces that help secure the shape can be seen near the top of the photo.
There is no concrete foundation; the house rests on a pad of scoria laid directly over the natural sand. Successive courses of polypropylene bags filled with sand (on the bottom few courses), and scoria (on the rest of the courses) are piled in an overlapping (brick-like) fashion to form the domes. Between each course are two strands of 4-point barbed wire. Each section of the house has a loft framed with conventional lumber. Some of the domes have poles arranged on the second story to help support the shape of the dome.
The earthbags are covered initially, both inside and out, with papercrete (recycled paper, with a small amount of Portland cement). The final layer is either a lime plaster (lime, silica sand and white Portland cement), or papercrete with sand added. In some cases the final coat of papercrete has been stained with latex paint thinned way down with water. All of the walls and roof areas remain breathable (except the central metal roof under the solar equipment). Floors are poured adobe, flagstone, tile, papercrete, wood.
(This house was built in a county that has not adopted the Uniform Building Code. The usual plumbing and electrical codes were required, and inspected for.)
NUMBER OF BAGS USED
Approximately 3 years of owner/builder time at about 30 hours a week. No hired labor. Occasional friends' help.
R-VALUE OF THE WALLS
I was recently given the opportunity to help demolish an earthbag house project that had been started in our community. The owner/builder had sold the property and the new owner wanted the land cleared. At first the owner wanted to have heavy excavation equipment come in and just push it all over and haul the debris away. I offered to help carefully take the structure apart so we could recycle some of the materials and learn something about how easy it might be to tear down such construction.
There were three domes to be removed, two of them connected and the third freestanding. These domes were constructed similarly to my house: polypropylene earthbags were filled with crushed volcanic rock (scoria); the courses of bags had barbed wire between them and the bags were tied to each other with poly baling twine. Papercrete was applied to both the interior and exterior surfaces. Additionally, rebar stakes had been driven through several courses of bags in many locations.
The freestanding dome was a rather lacy affair, almost a gazebo, with four arched openings and several circular windows. The builder had experienced difficulty in erecting this delicate building (it had collapsed several times in the process), so at my suggestion he had wrapped the columns between the arches with two-inch chicken wire mesh before applying the papercrete, in order to stiffen the building and make it stronger.
This gazebo-like dome was built on a layer of about ten inches of scoria, which I started to collect for reuse. As I was digging around the base of the structure, it occurred to me that an interesting experiment would be to dig out from under a section of the wall and see how much could be undercut before the wall began to collapse. The section of wall I chose to undermine was about 15 feet long, between two arched openings. I dug alternately from one side and then the other, completely removing the scoria from underneath the wall. Like my house, there was no other foundation to this building.
I dashed home to get a camera to record the events, and continued undermining the wall, being careful to keep out of harm's way if it should suddenly collapse. The more I dug the more amazed I became. When the wall section was precariously balanced on about one foot of scoria in the middle of the wall, and nothing had happened except one bag had fallen out onto the ground below, I snapped the picture that can be seen here.
If anyone had any doubts about the strength and integrity of this system of building, this experiment should allay those concerns. Earthbag building of this sort can be STRONG! Eventually, as I continued to dig out from under the wall, it simply began to hinge downward from a point about ten feet up, above the arches. The wall itself showed no signs of falling apart. In fact when the owner tried to break it apart with an axe and a sledge hammer, he finally gave up and decided to have the backhoe tear into it! The fact that it was surrounded with the wire mesh and that he had used twice the amount of Portland cement as usual in the papercrete mix are factors contributing to the phenomenal strength.
Filling the Bags with Rice Hulls
Don Stephens has been experimenting with rice hulls in bags. He says, "I thought you might find this photo of interest...it's the bag-walled studio I'm mentoring/assisting the owners in building here in Spokane. The bags are just filled with packed, dry rice hulls and they are load-bearing, holding up the insulated bondbeam at the top and the poured-in-ricehull-insulated roof, which will end up planted, over its salvaged-carpet covered Mel-Rol waterproofing. There's been no settlement since construction and it feels SOLID, walking on the roof. The exterior will be stuccoed with slightly-stabilized cob and the interior will be earth plastered. The subfloor is of ricehull-liteclay, for insulation, and will be topped with cob-adobe.... : ) "
The issue #47 (Fall 2004) of The Last Straw has a lengthy article. If any one is interested, my company supplied the hulls for Don Stephens project. Contact jpereiraATrice-hulls.com.
earthbagbuilding.com is absolutlely the most informative site about earthbag building, created by Kelly Hart and Dr. Owen Geiger.
simpleearthstructures Patti Stouter has assemble this site that focuses on her work with earthbag concepts for inexpensive and sustainable housing.
calearth.org Nader Khalili's earthbag works.
greenlifestylemagazine.net features an introductory article about earthbag building.
superadobeserrano.blogspot.com this blog-style site is in Spanish, but you don't have to know that language to enjoy the many photos and videos of superadobe constuction in Argentina.
earthbagnetwork.com a forum where people can share information and network socially about earthbag building.
naturalhomes.org lists workshops from around the world that relate to earthbags.
karacadirearthbuilding.com offers workshops and training for building with earthbags and sustainable living practices.
brokenearth.org offers a program whereby those who have already taken a course and have helped others build a Beehive Home will get priority status in getting help to build their own Beehive Home.
nzdl.sadl.uleth.ca The basics of building with arches, vaults and cupolas
recycledrice.org offers internship programs that incorporate both earthbag building with rice hulls and their forgiveness ministry.
structure1.com Precision Engineering has embraced earthbag building and is prepared to provide structural engineering for earthbag projects.
icbo code central article outlining the chronology and results of testing done on Nader Khalili's superadobe system of building.
earthhandsandhouses.org the construction of Paulina Wojciekowska's earthbag dome project in Poland. is shown under projects/sandbags...
motherearthnews.com an extensive article by Owen Geiger about how he built a small earth-sheltered earthbag dome.
caicosdream show Doni Kiffmeyer and Kaki Hunter working on an earthbag project.
midpines.us a series of construction photos with captions about building an earthbag home in the Sierras of California.
calearth.org/Emerg This two-page PDF file outlines Nader Khalili's approach to building an emergency shelter.
archearth.com pictures and description of an earthbag "Sound Temple" in Thailand.
calearth.org links to a gallery of photos of projects by alumni of CalEarth
montelloalpacacompany.blogspot.com is a blog about building a multi-dome home in Nevada, among other things.
earthbagbuilding.com list many sources for bags and tubing material from around the world.
expressbagger.com manufactures a simple dual bag manual filling device for sandbags.
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