Hi Julia, In your part of the country, most homes are built w/ out basements and have "monolithic slabs", where the slab and foundation act together to withstand the force of settling. Many homes there are built with "post tensioned" cables running through the slabs which effectively tie the entire slab together and ensure one area will not move if another area has settling. They are a better solution than the traditional thick edged monolithic slabs, which can heave or cave in the center. One thing to consider also, is that there are many water leaks in slabs that are moving, as pipes are placed in the slab at time of building and can't withstand the pressures of heaving and settlment. Also, ductwork for air conditioning is often run in the slabs, as well, and will also suffer from settlement. The piers you referred to may be "helical piers" which are like large augers screwed into the ground at points around the building where settling has occurred. I'd be surprised if they went around the entire house. After screwing these into the ground and reaching somewhat solid soil, they are then bolted to the foundation and help to distribute weight. Ask about any guarantees on the piers, as many are installed by factory trained personnel, and if done correctly, may come with a transferrable warranty against future settlement. Still nothing may stop the center from heaving or collapsing if that too is a problem on very poor soils. Structural engineers perform residential inspections all the time prior to purchase, and though it would be a few hundred dollars, it may be money well spent to avoid serious problems down the road. Good Luck.