Adding a second story to my house: thoughts/advice?

I need some advice. I'm looking at adding another floor to my house, but I've hit a snag. Right now, it's a two-story setup—basically a garage and storage space on the bottom level with the living quarters above. I want to go up one more level, but the foundation isn't strong enough to support the extra weight. Does anyone know how I might reinforce the foundation so an addition is actually possible?

Why don't you just try asking over in the housing subforum instead?