[Cob] gravel bag foundation

[Georgie Donais]

Shody,

The bags retain their structural function after the mix is dry in 
that, if the place gets flooded, the bags hold the contents in place 
so that the dirt does not get washed away. Other than that, the 
rammed earth holds itself together nicely, like cob does (no straw 
though). The mix is sand-heavy, so that these particles are locked 
together by the clay, offering the same kind of compressive strength 
we see in cob. In between courses goes a double strand of barb wire, 
which acts as mortar and keeps courses from slipping off one another.

There is lots of info about earthbagging at 
http://www.okokok.org/index.php . Nadir Khalili was, I believe, the 
originator of the technique; his site is here: http://www.calearth.org/

I find earthbagging to be a very interesting foundation option. Easy, 
fun, requires mostly the same materials as cob, children can be 
involved in most aspects (except maybe using large tampers and laying 
barb wire) and, although tons of material is moved, it's done in 
little bits, which means small people can do it. It's easily as 
labour intensive as foot-mixed cob, but seems to build a little faster.

Georgie


At 08:26 PM 8/8/2007, Shody Ryon wrote:
>Micheal,
>If I understand earth bag construction, the bags are
>forms and intended to hold material in place until it
>sets or drys. James seemed to imply this in his post.
>After that, it is not structural, so I do not
>understand how it could be used without other
>stabilization. I too would like to hear from someone
>who could explain this system of gravel bag
>foundations.
>Don't forget to post to the group, if you are
>intending to.
>Cheers,
>Shody
>
>Prior message sent to me:
>
>Shody,
>
>Exactly what I was thinking. From my inexperienced
>background, it seems that the pressure from the cob or
>earthbag walls above would cause the sides of the bag
>to bulge and burst at some point, even with plaster
>applied to the bags. However, this technique is shown
>in Building With Earth and is included in Hand
>Sculpted House and Build it With Bales as an
>experimental/low-cost foundation technique. I was
>hoping someone might have had some direct experience
>with how well they hold up over time.
>
>Michael