Hello all. I am new here but a long time believer in what this site is about. Here is my question. I live very close to several Nuclear Reactors and need to know some info about fall out. I am in the planning stage of a new house. I want the basement of it to be able to serve double duty as a SHTF shelter/fallout shelter. I am making the walls double layer of concrete blocks and providing for all of the other required items. The question is I know I need 3 feet of earth on top of the structure but what would that equate in concrete. Would the floor need to be poured 3 feet deep or would some other shallower depth work. If you have any insight I would greatly appreciate it. And yes I am planning it to be completely off grid. Thanks in advance.