Everything should have a solid foundation. But in the real world that is not always the case.
I was able to speak with a couple of very knowledgeable experts on this very topic. Whether you have a basement, crawl space, slab or a combination, You should give these guys a call. Don't think because you foundation isn't caving in or flooding you don't need their help. Not only do they do the big jobs. They also do the little ones like winterizing your crawl space to save you money on your utility bills. Take a few minutes to look over their website Ayres Basement Sytems.
Let me know if you need me to get you in touch with the local Ayres Professional.