Our earth sheltered home relies on thin shell concrete to support the earth loads. I do know of large earth sheltered homes made of concrete domes that are less than an inch thick, but that sort of precision is difficult. My vaults are relatively small, but will be 6 to 8 inches thick of very strong shotcrete. Once that shotcrete has set, it will be very strong, but before it sets, it is very heavy and needs to be supported. Rather than build a separate frame to support the structure which will later need to be removed, I am embedding a rebar skeleton within the structure that will support it while it cures and then reinforce it for the next few hundred years until its final job is making it very difficult for someone to tear down. The #4 rebar is spaced 12 inches apart, tied and then welded. We then use metal lath on the inside, tied to the rebar, to catch the externally applied shotcrete. We have decided to add an additional layer of fine fiberglass screening to the bedroom. The fiberglass still needs to be backed by the stronger metal lath, but it should prevent the shotcrete from passing thru. More details can be found on the website. http://www.homeintheearth.com/2015/08/15/rebar-and-lath-on-the-bedrooms/ ... https://www.youtube.com/watch?v=j5GoClVi81c

This week, I attended a training for "Fox Blocks" ICFs. The training was given by Ken Williams who had been doing this for a long time and clearly knew what he was talking about. Full story here http://www.homeintheearth.com/2015/02/12/fox-blocks-training/ ... https://www.youtube.com/watch?v=-XAuKpYxJoY