earthbag/cob wall: how to meet the earth?

I'd like to build an earthbag wall in my front yard, covered with cob. I've seen cob walls where the cob came all the way down to the earth, how does that work with moisture?

I live in central oregon, in the high desert, approximately 10" of rain a year, mostly in snow or quick thunderstorms. The soil is very sandy. I'm trying to get away with this without having to lay a concrete foundation or masonry.

Thanks for any ideas you might have!

i dont know about the soil type, but the earthbag building book ive read uses a rubble trench foundation, maybe you could work off that type of foundation with little concrete to make a bit of a raised foundation if you needed it

I would just lay the earth bags straight in the sand. Earth bags are mentioned as a foundation option in the Cob Builders Handbook. Then you could bring the cob down to just far enough off the ground to not soak up water in storms. If you're worried about UV deterioration of the exposed bags, you could use some kind of non-cob plaster at the bottom.

Maybe I will just use concrete stucco on the bottom few inches, and then cob the rest of the way up.

Thanks for asking this question, as the answer helps me, too.  I'm south of you, near Klamath Falls, with heavy clay soil that would probably be great for cob or light clay construction, but have hesitated to start a project because I don't have rock for a foundation, nor the funds for a cement foundation.  Earthbags would be affordable.

The other alternative that I thought of was tires filled with gravel -- I've actually started collecting tires for that purpose. 

Kathleen

Windmillium - A rubble trench foundation is a great suggestion - I would also consider using "concrete bag" blocks for your  first few levels under the ground to about 4 inches above the ground line.  You would then want to put down a "capillary break" using flagstone or any type of flat stone or tile, then stack the earth bags. 

The concrete bags will hold up well under ground - the capillary break will prevent water from crawling up onto your earth bags.  You should be able to use the cob all the way down to ground level to cover the earth bags and concrete bag blocks.  Good luck - this sounds like a fun project.