Poured concrete walls, with solo builder doing the
form work and reddy mix dumping the concrete in??
In this area there are quite a few earth shelters. In
front look like a normal ranch but back and both ends
are more like basement walls. If you dig into the
side of the hill with a tractor, then form the inside
of the three walls, using undisturbed earth as the
outside of the "basement" walls. Then the front wall
and roof would be standard frame construction.