I've been thinking about a pair of inter-modal shipping containers over a basement (and possibly a hidden sub-basement/root cellar to kelp out with floor insulation if nothing else) with a gap between them spanned my traditional wood joists sitting on a pair of lengths of angle iron and a roof with a partial loft area covering it all.
I'd have sleeping areas in one shipping container section. everything with plumbing in the other, and a living area between.
the basement would be an open span walkout, with all the plumbing mess to one side.
Those containers take a real beating. even with extra holes cut in the sides for doors and windows, they would still survive a tornado or earthquake that caught you off guard, and steel doesn't burn.
be sure to insulate like crazy. energy just gets more and more expensive, and post SHTF, it might be unobtainable. If a small wood stove can manage all of your heating, you'll be ahead of the game. windows that open and close easy are good for letting in the cool night air, then sealing it back up to keep a place livable during the hot days. would be nice too. some of the Scandinavian countries use a big stone fireplace and chimney as a thermal bank to keep temperatures consistent.
don't forget, when you are building is when you put in safes and hidden caches. Maybe even a dedicated gun room. I was thinking some drain pipe, angled down, but piercing the basement wall, then covered up with drywall or the like would be impossibly to find if you didn't know just were to look. A pair of cosmolined moisins, a tin of ammo, and a few gallons of honey hidden in such a tube would be a lifesaver after the worse came to pass, and cost less than $500 to build and stock.
a manual or solar backup to a well pump might also be a lifesaver.
if you do something like a pellet stove, have a small steel wood burning stove you can replace it with easily after the pellets stove is no longer an option.
if you are putting in a septic system. get a tank bigger than you need, an hopefully it won't eve need to be serviced. Its not like it will cost much more to do it that way first.
I'd also go for a steel roof. Lasts longer and fire proof. speaking of a roof, internal valeys are always weak spots, but on the plus side allow easy rain water collection.
Insulated concrete form pored walls might not be a bad idea either. good insulation, plus fireproof, tornado proof, and bullet proof. not to mention rot and insect proof too.
high windows let in light for when you have no artificial light, but don't easily permit a view of what is inside or an easy access point. Glass block does the same.
and for Pete's Sake, don't skip on the eaves
