I own a 1,560 sq foot ranch house that's kind of unique to the area (Nebraska) because it's built on a concrete slab with no basement and the area does have some tornados each year. My question is: How feasible and affordable is it to consider adding on a sunroom or something similar that has a small basement under it? There's room to build out back off the TV room but I'm also willing to consider any option that will add shelter. Thanks for your time and input.

When I lived in Oklahoma, we had a standalone flat-topped concrete storm cellar that was close enough to the house we could have built a sunroom or something similar, with a little creative rigging. The house was pretty old though, and on pillars, not a slab, but I don't see where that would matter any. I had thoughts of doing something similar at ground level and using the top as a patio. As long as you don't compromise the foundation in some way I don't see why it wouldn't work. It sounds like a great idea to me. Take care though that if, God forbid, your house collapsed on top of it you wouldn't be trapped inside. You'll also want some kind of ventilation. Ours had just a 4 inch piece of pipe in one corner with two ells to keep rain out and a screen to keep the critters out. That might look funny stubbed up into your sun room!

Let me know how things work out. lamarlowe@hotmail.com

The first thing that jumps out at me would be how to excavate the new addition without compromising the existing foundation. I assume that your existing footings are about 4 ft under grade right now - so that means that you have to dig down roughly another 4 ft directly next to that for the new footings. Personally I would never take a chance doing that. Too much risk of something going wrong with the existing foundation being that you would be removing the very soil that the current foundation sits on.

If it were me I would make part of the new addition a slab that matches the existing house (the part that butts against your existing house), and part a basement. The rule of thumb is that you need a 45 degree angle down from the bottom of your footing for bearing. Meaning that if you had a difference of 4 ft height between the new footings and old, you would need to come out 4ft horizontally into the new addition before you could start the basement portion - so in effect, the new additon would have 4ft of slab on grade and the rest could be basement.