Archive for October, 2009

One of the most frequent questions people ask is how much do earthbag houses cost? It’s a little difficult to answer because there are many factors that affect the total cost. A lot depends on what features you want to add, whether or not you have building codes, how much work is done by the homeowner, and the details of the building itself.

A small, simple house made of natural building materials could be built by a DIY builder for about $10/sq.ft. This assumes doing most everything yourself and using the low-tech building ideas explained on our websites. It doesn’t include things like land, building permits and utility hookups, since the price of these things vary wildly.

Keeping in mind it is much easier and lower cost to build with earthbags in rural areas with minimal building codes, let’s look more closely at one example. Here are the approximate costs of a 15’ interior diameter roundhouse with earthen plaster and floor, recycled materials where feasible, and reciprocal pole roof with sod on top.

Recycled earthbags @ .20/bag = $108
Soil = $100 (bag fill, plaster, floor)
Gravel bag foundation = $20
Barbed wire = $35
Roof poles = $25 (with firewood permit from national forest)
Salvaged barn wood roof decking = free
6 mil poly = $25 (for roof)
Reinforced concrete bond beam = $100
Doors, windows, hardware, bathroom fixtures, tile, etc. from yard sales/barter = $175
Sod = free
Plumbing/electrical = $200
Composting toilet = $20
Earthbags w/rice hulls ceiling insulation = $10
Reed mat ceiling = $40
Recycled wood for cabinets = $100
Nails, screws = $42
Total cost = $1,000

This works out to be less than $6/square foot for this 176 sq. foot roundhouse in a non-code area. I’m sure I’m forgetting a few things, but you could double this cost to cover gas and any extras and still have a nice little house for $2,000. Now you can see why we’re so excited by earthbag building. It’s a real game changer for those in need of affordable housing.

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I recently wrote an article about living walls for GreenHomeBuilding.com, and in doing the research for this I came upon an interesting approach to creating a kind of living wall or retaining wall using geotextile materials. Basically, loosely woven bags filled with a growing medium can be stacked to form walls that then support plant growth.


One company in particular, www.filtrexx.com, has been selling various systems for doing this for some time. This is a green alternative to hard-faced walls, and can create walls that are either completely vertical or slope up to 2:1. A variety of vegetation can be supported this way, depending on the location and purpose of the wall. They say that this is faster to install than conventional block materials used in retaining walls.

But if you look at the basis of the concept, it is not that different than building with earthbags: bags of material are stacked to form walls. But in this case, the bags are then protected by the plants that grow out of them, and this vegetation becomes the exterior interface with the environment, providing oxygen, filtering the air, and looking beautiful.


So how might this idea be utilized for buildings? Obviously the main issue is the moisture that inevitably will migrate into and through the wall to the interior space…unless there is some way to stop it.

One approach might be to build the earthbag structure as is frequently done, with compacted soil, and then cover this with a waterproof membrane to protect it from intruding moisture. A second skin of a “living wall” could then be applied over the membrane, both as protection for the earthbag structure, and as an insulating layer.

This would create the ideal situation for climate-responsive housing, where the inside is composed of thermal mass materials, and the shell of the structure is insulated to keep the interior from loosing its comfortable temperature.


Besides using the geotextile bags, it is also possible to use one of the variety of systems that have been devised for creating living walls that are attached to buildings, as shown above. Many of these sophisticated systems automatically provide the necessary water to maintain the plants, so there is very little maintenance over time.

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We want to thank Doug at http://www.dailykos.com/story/2009/7/18/754890/-NFTTFill-The-Sandbags!-Edition for providing us some additional information on the history of sandbags (earthbags).

Doug has kindly informed us that sandbags can be traced back almost 250 years to the Napoleonic Wars, during which time French troops were issued sandbags for use in the field.

And as you can see in the photo below, sandbags were also used in the Civil War. Thank you Doug for this fascinating information.

A sandbagged military position during the American Civil War.

A sandbagged military position during the American Civil War.

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Ziggy has the best info I’ve found on reciprocal roofs at his Year of Mud website. See: How to Build a Reciprocal Roof Frame

Reciprocal Roof

Reciprocal Roof

A reciprocal roof is a simple self-supporting structure made of poles or dimensional lumber that are arranged in a spiral pattern. No center support is needed. They are perfect for round buildings. Developed by Graham Brown in 1987, this type of roof is extremely strong and can incorporate a living roof of plants. They’re fast to build. A reciprocal roof on a small house can be erected in a few hours. It is also affordable, since it can be made with peeled poles from a local forest. (Poles can be gathered with a low-cost firewood permit, typically costing around $25 or so.)

The basic process involves bracing the initial pole called a Charlie stick and then working either clock-wise or counter clock-wise, placing and tying poles in position. The last pole goes over the previous pole and under the Charlie stick. Then, just knock out the bracing under the Charlie stick and the frame is self-supporting. Secondary rafters can be added between primary rafters.

Check out Ziggy’s site for pics and complete details. He even provides a good list of resources for further reading.

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I am pleased to announce that www.earthbagbuilding.com is now available online in 35 different languages. With the simple addition of a Google “Translate” box as part of the main menu, you can now choose to read all of the text on any given page in your language of preference. Once the new page is created (it only takes a few seconds), then the entire site can be browsed via the standard menu and all subsequent pages are also presented in translation. Amazing!

This should make the information more accessible to the millions of people around the world who might benefit by it.

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