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I have a bit of an unusual situation.  My husband and I are interested in buying a property that is off-grid and very secluded.  It is currently a hunting/recreational property but we are interested in running power out to it and making it a homesite for a tiny house which will become our full-time residence.  
On the property already is a 20x20' concrete bunker which they built into the side of a hill.  There is a cement slab for the foundation, the walls are made of mortared cement cinder blocks which have been plastered over, and there is a 20x20' concrete slab "roof" which is flat and exposed on the top side/top of the hill.  We are interested in converting this structure into the bottom level of our home, if such a thing is possible.  We are in the process of getting permission for a contractor/home inspector to ride out with us and examine the structure, but we are not even sure if what we envision is do-able.  Assuming the bunker is structurally stable, is there any reason why we couldn't build a second story directly on the existing foundation/structure?  Have you ever heard of anyone doing this?
My second question is about septic tanks.  Since the bunker is partly built into the side of a hill, making it a partially "underground" structure, what would your thoughts be on how to put in a septic tank for this building?  Is it possible?
Thanks for your help and any insight you might have - I know as a question, it's kinda "out there" :)

I would rely on the comments of your builder and inspector. The concrete roof may not be designed to carry floor load. You will probably need to penetrate the slab for plumbing on the new living level which could weaken it. you may be able to add additional bearing in the bunker to make the slab work.
I have never built anything like you are proposing but it does sound interesting.
Good luck,
M Hughes

Construction & Contractors

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Michael Hughes


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I have been an executive in the homebuilding industry for 20+ years

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