I posted an idea for Insulated Earthbag Foundations for Yurts at Instructables.com. One reader who left a comment liked the idea, but needed a simpler design so he wouldn’t have to get a building permit. Here’s an idea for a very simple design that might get around building codes. Stack one course of earthbags in a circle and then fill the center area with sand, sand/gravel mix or an insulating material such as scoria. Spike the bags in place with saplings to prevent slippage. Berm earth against the earthbags to protect from UV rays and help hold them in place. The floor could be topped with a 2″ layer of subsoil to create a temporary tamped earth floor.
I know it’s rather crude, but it’s also super low cost, quick and easy. No concrete or lumber required, which means almost zero cost if you use recycled bags, and it should bypass the codes because it’s only ‘temporary’. (Har, har. This could last indefinitely if the bags aren’t exposed to sunlight, but don’t tell that to the code officials.)