steel or concrete for bunkers of that type. i beleive you want to be atleast 10ft in depth just for fallout area and beyond , not sure about if your in the actual blast zone. you want air scrubbers equiped for fallout, you want to seal your structure wehter it be steel or concrete a good coat of tar paint will seal it , you also want to prep it for ground water so put in a drainage system around it before back filling , also when setting your structure put a lvl sand base down to prevent settling. you want 2 accesses to the bunker a main entrance and an escape hatch of some type ,these doors you want to be air tight! you can bury water tanks and plumb them in so you have water if your stuck because of fallout , you also want a septic system so you can have working plumbing sink, toilet ,etc. but anyway there are alot of great websites and youtube videos on this that will fill in the rest . one more thing the deeper your bunker the greater your protection, remember you dont have to dig your hole deeper then planned to do this just mound the dirt on top the higher the mound the greater the protection!
