this is a part answer to your question. we use a structural engineer first. costs around $350. however, he will tell you what you really need to have done, then have the foundation company do what he says. usually will save you on some pier costs. also, one time he advised us to NOT have foundation work done (wasn't needed) and to float a section of floor. however you slice it, you call 5 different foundation companies and you will get 5 totally different opinions of what you need, whether it is needed or not. then you never know who to believe. hope that helps.
