I have a 2-storey home, built on a crawlspace.

I would like to add a small, one storey addition off of my kitchen.

The addition would be about 12' x 15' in area and I'd like to put a basement underneath of this. The basement would primarily serve as a storm shelter. The top of the basement would start even with my kitchen floor and go down about 8'.

I'd appreciate any constructive comments here from those who have experience with this kind of project.