Earthquake-resistant Earthbag Building Details

There’s obviously a great deal of concern about the recent earthquake in Haiti. Disasters like this are all too common, and so we’re working hard to develop at least two low cost, easy to build earthquake-resistant earthbag house designs.

We hope to be better prepared in the future with plans ‘ready to go.’ But in the meantime, we are making good progress. Kelly Hart and I have roughed out some basic design details. Adobe engineer Bill Druc has offered to help with the calculations and designer Patti Stouter has offered to do some drawings. Also, numerous organizations have expressed interest in raising donations, sending building materials and trainers, and constructing houses in Haiti. For the latest news, see Comments at Responding to Catastrophe.

Earthbag buildings tend to flex and distort during an earthquake rather than suddenly collapse as wood framed, adobe, brick and concrete block structures do. Barbed wire and plaster mesh hold the bags together in case of collapse, thus greatly reducing risk of people getting crushed.

Key building details for earthquake-resistant earthbag houses in Haiti:
– Use compact shapes for greater seismic resistance: round, curved, hexagonal, octagonal shapes or domes when culturally appropriate.
– Avoid long unsupported walls.
– Foundation: gravel-filled earthbag foundation (double-bagged for strength) on rubble trench. Best to have at least two continuous courses of earthbags below door threshold.
– Barbed wire: two strands of 4-point barbed wire between courses
– Limit the size and number of doors and windows: these may be available from collapsed buildings or acquired locally to save shipping space. No glass in windows, only shutters that can be locked. Concrete breeze block or screened openings can reduce number of windows required.
– Steel-reinforced concrete bond beam: 6” high x 16” wide
– Truss anchors in the bond beam: embed L shaped rebar anchors or truss anchors at 24″ on center and weld or bolt to rafters/trusses
– Lightweight roof: about 3:12 pitch, metal roofing for roofwater catchment
– Plaster mesh: poly fishnet is the lowest cost, won’t rust and can easily be stuffed into barrels full of building materials. (Barrels are later used for roofwater collection.) Add fishnet to both sides of earthbag walls and connect with poly twine.
– Plaster: cement or lime plaster on exterior; earth plaster on interior

Virtually no structure can withstand a direct hit from a major earthquake, but by combining the building details listed above there is a very good chance the structure will hold together even if the walls should topple. While not perfect, this strategy could save countless lives over the current building methods used in Haiti.

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Counties with Few or No Building Codes

Many readers are looking for inexpensive land where they can build their earthbag home. Unfortunately, building codes are often overly restrictive and make it difficult to build with alternative materials such as earthbags, straw bales, etc. But the good news is some counties have very few code barriers. As explained in previous posts, these counties are typically in remote, rural areas.

While responding to a reader’s inquiry about this subject, I realized it wouldn’t be very difficult to locate these lenient areas if several volunteers worked together. One possibility is for each person to take one state, contact the regional building authority in each county and then compile a list of counties with few or no building codes.

I’m guessing each state could be canvassed in about eight hours or less by using the Internet to locate the phone numbers. This is made easy because most counties now have their own websites. You could probably ignore highly developed counties to save time. Some counties post their building codes and related information on their websites, although it may be faster to call each county building department and ask a few questions about their policies on alternative building: What building code do they use? Do they require a building permit? What are their policies on building with straw bales, earthbags and other similar materials? Do you need special approval (engineer’s stamp) to build with alternative building materials? What’s the minimum house size allowed by code?

Once you locate one county that’s open to alternative building you might ask them if they know of other counties with similar policies. I would also do some background research. For instance, you may find a site like Sustainable Building Codes Blog by Tom Meyers. Mr. Meyers posts about this very issue and offers lots of good advice. One post says “Our current area of preference lies in the heart of Delta County, Colorado. This is one of 11 or so counties in the state with no adopted building code.” There you go! Send him an email and maybe he will tell you which counties in Colorado are code-free.

Out of curiosity I searched the Delta County website, clicked on Departments, then Planning and Community Development, then Building Information. Sure enough, it clearly states “No building permit is required for the construction and placement of any structures in the unincorporated area of Delta County.”

To get the ball rolling, I’ll help coordinate the process. I suggest each volunteer collect a list of county websites from one state (those with few or no building codes) and send them to me. I’ll make a new web page and post the results as they come in. Email me at strawhouses [at] yahoo.com if you would like to volunteer for one state.

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Responding to Catastrophe

The internet has been vibrating along with the earth since the great quake in Haiti, and I have received quite  a few emails responding to this catastrophe, often with suggestions about ways to assist the Haitians. I’ll quote from one particularly thoughtful response:

“I would like for you and your colleagues together to present our president (probably through USAID) with a proposal for rebuilding Haiti with earthbag and other environmentally sustainable technologies. Such a project would serve the dual purpose of providing affordable, earthquake/hurricane resistant housing for Haitians as well as to advance the global shift toward a more sustainable green paradigm by example. Due to this humanitarian catastrophe, both the monies and the political will for such a project are at their peak. No better opportunity exists for the Haitian people to receive durable, affordable housing in the wake of this disaster and no better opportunity may be seen in our life times to demonstrate the utility and affordability of earthbag construction to the world and our posterity.”

In response, I wrote the following:
The plight of Haitians in the wake of the earthquake is heart-wrenching in the extreme. These long-suffering people must now endure even greater hardship. It doesn’t seem fair, but life rarely does. How can those of us who are more fortunate in other parts of the world assist them?

I have been following the blog of Father Marc Boisvert (pwojeespwa.blogspot.com) who runs an orphanage outside of Port-au-Prince, where their facility was undamaged, but they must deal with lack of fuel, electricity, adequate food, and the suffering of friends and family members. They are expecting over a hundred new orphans to arrive from the city. Of course they can use all the money that might be sent to them (and I encourage you to visit their website www.freethekids.org and make a donation). Marc often ends his blog posts with “Keep us in your prayers.”

I first found out about this orphanage because they had built an earthbag house and were promoting this ecological way of building. You can see a description of this at earthbagbuilding.com. There are many reasons to recommend earthbag building in this impoverished country, and resistance to seismic events is among them. Just how resistant earthbag housing might be to earthquakes is not known for sure. Very little testing has been done to prove this one way or another. The initial seismic tests done at CalEarth and other places are encouraging, but not conclusive (see earthbagbuilding.com). Some members of Engineers Without Borders are currently gearing up to do some more testing, so we will hopefully know more in awhile. This technology is still in its infancy, so there is much more to learn about its potential.

Earthbag housing can be used for emergency shelter, and we have posted a number of possible options at earthbagbuilding.com, including one proposal that Dr. Owen Geiger and Patti Stouter assembled to present to the UN. This sort of emergency housing has the advantage over tents and other immediate structures in that it can often be used and improved over time to become more permanent.

Another kind of housing that can withstand practically any sort of catastrophy are shipping containers that are converted to dwelling places. These steel shells have become surplus items at many ports around the world because of trade imbalances. There have been some very innovative designs for incorporating these modular units into quite livable spaces (see an article I wrote at www.greenhomebuilding.com). I participated in assembling a proposal to the UN for arranging this concept to be employed in Haiti. Here is another proposal in the same direction: www.clemson.edu . Such structures do need to be insulated to make them livable in most climates, but this is possible and can be done with earthbags filled with a variety of materials.

I agree with you that in some ways the devastation in Haiti does present an opportunity to rebuild with green sustainable principles, and I hope that this can be manifested. We each can do our part.

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Grand Plans for Earthbag Building in Mexico

According to an article in the Spanish language newspaper El Heraldo of Chihuahua, Mexico on January 11, 2010, a Mexican affiliate of the CalEarth Institute has just started construction of a demonstration “Superadobe” structure. This will become the Nutrition Rehabilitation Center for the Municipality of Guachochi, Chihuahua,  the first  prototype in the state of Chihuahua. It will serve as both a demonstration and a shelter for women who have just given birth to their babies in  the eco-room.

The engineer is Mr. Quintana, a graduate of  the University of Chihuahua  and he will coordinate the construction work.  The mayor of Guachochi announced plans to build a hundred houses in a subdivision of the mountain city, with this superadobe technique.

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Earthquake-resistant Earthbag Houses

It deeply saddens me to see one disaster after another occurring around the world, especially since much of the tragedy could be prevented by building earthquake-resistant earthbag houses.

The recent earthquake in Haiti is but one more example of this. Theo (Father Marc Boisvert) runs a project for the poor in Haiti. Their earthbag Sun House fortunately escaped unscathed even though nearby structures were devastated. According to Theo’s blog “…no one hurt and no structures damaged.”

Earthbag Sun House in Haiti was undamaged by recent earthquake

Nearby structures were severely damaged

Note: the Sun House example by itself is not conclusive proof of seismic resistance. More testing is called for, but anecdotal evidence and test results keeps growing and so far is extremely compelling.

Bryce Daigle’s testing and thesis, for example, details how earthbag walls obtain maximum compressive strengths almost 10 times as great as those typically achieved by conventional stud-frame housing in terms of load per metre of wall length. Testing Proves Earthbags Very Strong

Nadir Khalili’s tests in Hesperia, California demonstrated how earthbag structures exceeded the strength of the testing equipment with no deflection or failure, and received code approval in the most dangerous level — seismic zone 4.

Properly built reinforced concrete structures, which can be engineered to high earthquake-resistance, are not affordable in Haiti and countless other areas around the world. So even if building codes are in place, builders in these areas will find a way to circumvent them. That, and excessive codes will prevent people from building affordable housing. After years of studying the situation, earthbag and strawbale construction appear to be the most practical solutions.

Additional resources:
Earthbag Testing page
Post-tsunami Affordable Housing Project
Emergency Earthbag Shelter Proposal
Additional testing is underway by Engineers Without Borders at the University of Florida.

Contact the author from our About Us page for more information.

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New Video of Up-scale Earthbag House

See www.youtube.com for a slide show set to music of  building a home with earth bags, earth plaster for the exterior and interior walls, and milk paints for the drywall…all with imagination for detail. This was a four year, artistic project completed by one woman along with the help of others here and there. Built in Paonia, Colorado. The house has irregularly shaped vertical walls with a fairly conventionally framed roof. Nice job!

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How Long Will Earthbags Hold Up in Sunlight?

It’s difficult to know for sure how long earthbags will hold up in sunlight. Some brands fall apart pretty fast, as soon as a few weeks. Equatorial and high elevation areas may experience slightly more rapid deterioration due to increased UV levels. From my experience and what I have heard and read most bags hold up okay for about 2-3 months. The safest way is to buy tarps or black poly and keep them covered as much as possible.

However, tarps are prone to blowing around in the wind and can be a bit of a nuisance. If you’re doing a large job, then you can either buy UV resistant bags, which cost more, or in the case of vertical walls do one wall section at a time (including adjacent corners) and apply at least one coat of plaster as soon as possible.

Note from Kelly: One good indicator of how long the polypropylene material will last if exposed to the sun are the tarps themselves, which are often the same material. My experience is that they just get progressively weaker as time goes by, and may show signs of deterioration after about two months’ exposure and usually by about 8 to 10 months it is pretty easy to punch holes in them with a finger. And these tarps are often supposedly UV resistant. Obviously the best thing is to not take chances and keep the bags covered at all times, except when working on them.

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Call for Greater Earthbag Sharing/Testing

We can all learn a lot from each other, and so I’m encouraging everyone to send us their earthbag building experiences (favorable or unfavorable) so we can share the information with other readers.

Earthbag builders are regularly experimenting with new ideas and techniques. If you have learned something interesting and think it can benefit others, please leave a comment to this post. (Click on Comments below.)

If you are an engineer and would like to volunteer with earthbag testing or writing technical reports, please email Kelly or myself from our About Us page.

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Post and Beam Designs

In many cases, buttresses are not the optimum solution for bracing earthbag walls. Post and beam designs are often preferable and have many advantages. Besides being less obtrusive, post and beam designs are suitable for wider range of styles, require less plastering, take up less space, and are faster and easier to build in many cases. Plus, exposed timbers look fantastic! Using poles from a forest obtained with a low cost firewood permit, this option doesn’t have to cost a lot.

You could bury posts within the wall, next to the wall or even set them apart from the wall. One option is to use round posts of say 6”-8” diameter and cut 2” off one side. This provides a flat surface to go against the wall, making plaster work somewhat easier by eliminating recesses behind posts. This also enables you to stack uninterrupted earthbag walls, which is faster and easier than working around posts.

How to connect posts to the walls? Easy. Cut strips of expanded metal lath as ties. Nail one end to the back of the post, bend to 90 degrees and pin to top of bags. You could use the same technique using scrap metal. For pins, strawbale builders make U-shaped pins out of heavy duty galvanized wire.

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