Earthship in Clay Soils

Has anyone had experience in building or designing an Earthship in expansive-clay soils?

- Is if feasible?
- How important is it to work with dry clay (so it does not compact further in the tires)?
- How important is it to keep the tire walls dry during construction?
- What about the back-filling? Clay OK? Dry?
- What about structural strength - will a tire-wall withstand the pressures of surrounding expansive wet clay?

This question has matured into a post which covers everything I have come up with so far on the subject:
http://bhudeva.org/blog/2012/01/06/is-it-possible-to-build-an-earthship-in-moist-freezing-expansive-clay-soil/

Still hoping to get some feedback from people with hands on experience.

Very interesting article, Ronen. Thank you for sharing it with us.

I wish I had some hands on experience to share. We will be starting construction this year, building an earth sheltered home in the side of a "silty clay" hill. Our plan is to use earthbags rather than rammed earth tires for the walls, but other elements of construction seem to be similar. I'll be looking forward to your updates.

Good luck with your build Lolly

Do you have an architect or engineer on board your project? Have they offered any input on the expansive-clay issue?

Also I am curious why did you choose earthbags instead of rammed tires?

No, I don't have an architect or engineer involved. My educational background starts with mechanical drafting (including architecture) then ramps up to manufacturing technology with emphasis on materials and systems. I've been doing specific research for several years. All the bits and pieces have been thrown into my mental cauldron and are melding together. I think the resulting stew is finally ready to be realized in our future home.

Why earth bags rather than tires? Several reasons, in some sort of order ...

I'm not as young as I used to be. Hauling a 50# bag of earth will be easier on my back than all the ramming that tires would require.
A source for new bags has them available for less than 20 cents each. Bags don't take much room to store when they are empty.
I think it will be easier to sell the local office that has to sign off on my house plans. A healthy ratio of cement in the bags should be the winning argument.
There are various sites available that have architect approved plans for earthbag homes, in the event that I need them.
Earthbags will allow me / us to use a modular approach that can be enlarged as necessary. Since this will be home to an extended family dynamic and only one house is allowed on the property, that versatility is important.
Oh yeah, there is also the "build as you can afford it" element.

Ronen Hirsch wrote:Has anyone had experience in building or designing an Earthship in expansive-clay soils?

- Is if feasible?
- How important is it to work with dry clay (so it does not compact further in the tires)?
- How important is it to keep the tire walls dry during construction?
- What about the back-filling? Clay OK? Dry?
- What about structural strength - will a tire-wall withstand the pressures of surrounding expansive wet clay?

Everything I've read about expansive clay soils in building has made us steer away from the earthbag and towards the rammed tires. In the earthbags, it can expand and crack the plaster where in the tires the force is on the steel belted rubber. The rubber is strong enough to protect the plaster. At least that's the way I have read the resources out there. We are building in West Virginia in the US and we have a very heavy expansive clay soil. From personal experience I can say that a damp clay is much easier to work with than a hard dry clay. Rainy days cause us to lose a day of work but it makes the next day much easier to dig and pound the damp clay.

Since I've posted this question I've come across some really interesting information. It seems that clay soil is only expansive and only a problem because of moisture ... or to be even more precise ... changes in moisture. Clay expands when it absorbs water. So, if you keep the soil dry ... it is no longer expansive and therefore no longer a problem. The solution is basically an insulated (moisture and temperature) umbrella that spreads 6 meters beyond the house ... and it is part of an entire system of insulation that does wonders for energy efficiency & air quality (goes way beyond the superficial "south facing passive solar" mantra) ... more on that here:
http://bhudeva.org/blog/2012/01/23/building-an-earthship-in-a-cold-climate-stop/

Ironically, in recent weeks we've been thinking about looking into earthbags ... because getting used tires in Romania has proven to be very difficult. I am still just getting started with earthbag theory and don't know, yet, if it can be feasible to build with them underground.

Ronen Hirsch wrote:Since I've posted this question I've come across some really interesting information. It seems that clay soil is only expansive and only a problem because of moisture ... or to be even more precise ... changes in moisture. Clay expands when it absorbs water. So, if you keep the soil dry ... it is no longer expansive and therefore no longer a problem. The solution is basically an insulated (moisture and temperature) umbrella that spreads 6 meters beyond the house ... and it is part of an entire system of insulation that does wonders for energy efficiency & air quality (goes way beyond the superficial "south facing passive solar" mantra) ... more on that here:
http://bhudeva.org/blog/2012/01/23/building-an-earthship-in-a-cold-climate-stop/

Ironically, in recent weeks we've been thinking about looking into earthbags ... because getting used tires in Romania has proven to be very difficult. I am still just getting started with earthbag theory and don't know, yet, if it can be feasible to build with them underground.

According to the studying I have done it is feasable to build with earthbags underground but more frequent buttressing or smaller curves are likely necessary. also stepping back is a good move too. IF you can add rebar or other metal reinfocement it is easier.
Check out the book "Earthbag Building: tools, techiniques, and tips" I think is the title, very informative and useful, if a little narrowly focused on what they had hands on with.

We packed our tires with black clay when we began our earthship 8 years ago. We went about a dozen rows up...still standing today.

I would agree to use dry clay. Clay, depending on variety, can swell up to 500 times its dry size. If you pack when it is wet, it will shrink as it dries, and wont be packed as tightly. Also be sure to keep it dry (under a tarp or plastic) until it is weather sealed.

We built a french drain type burm around our perimeter as we get lots of rainfall 40"/year.