A paver patio installation in Fort Mill, SC is judged on the top inch and decided by everything below it. The pavers are what homeowners compare between quotes, and they are close to the least important variable in how flat the surface is ten years on.
In the Carolina Piedmont the thing acting on a patio is the red clay beneath it. Clay holds water, swells when saturated and shrinks as it dries, repeatedly, within a single year here.