Can’t wait to do my safe room😁
Sink this in the side of a hill and stack another full level on top. This is what I am planning. Serious.
Just remember when you put the second level in to turn it 90 degrees for better structural integrity. You are cutting several structural walls out so if you stacked them in line the center container would likely crumple under the weight.
Are you going to do ladders or a staircase to the second level? If you do ladders you could have 3 separate rooms above (or one smaller and 1 master) without having to gut the walls in the second set. All you’d have to do is cut hatch holes in the connected roof/floor and seal the gap.