Q: Do you have more info on how high you built with loose sand?

A: Yeah, on our first experimental dome we tried using the sand on our lot, since we are basically living on a big sand dune. It is a very fine, sugary sand that is spherical rather than sharply angular. I think that is the problem, because it just doesn't pack into a solid shape and stay there. It is more inclined to do what sand naturally does: shape shift.

Q: At what point did the corbel fail?

A: We got to just about door height before it fell.

Q: How did it fail? Slipping? Or deformation of sand in bags?

A: Deformation of the sand in the bags.

Q: Just cave in quickly? or?

A: I was working up on the wall when I noticed that the perimeter shape at the top had become a little lopsided...there was a straight section where it should have been curved. At that point I thought "This wall could fall in!", and I jumped off to the outside. Then I watched as the wall slowly collapsed, like in slow motion. Sort of like watching dominoes knock each other over. It was beautiful in a way, but also very depressing. The fact that I had tied all of the bags together with twine, as well as use the barbed wire, may have contributed to the whole thing falling in, because once it started to fall, it acted like a continuous fabric. Actually, the wall up to about 2 or 3 feet was fine, and I left it in place. Up to that height, the wall was nearly vertical, so it was not inclined to fall.