If it's cracked, sunken, or gone soft, it comes out.

Removal is the part most people don't think about until they're standing on a driveway that's heaved three inches or a patio that's sunk on one corner. Before we quote it, we need to know why it failed — a slab that cracked because of a tree root close to the surface is a different job than one that settled because there was never a real gravel base under it. We check both before we say what it'll take. Once we're on site, the old concrete gets broken up with equipment, loaded, and hauled off — that's most of the labor and most of the time on a removal job, especially on a full driveway where the slab is 4 to 6 inches thick and reinforced with wire mesh or rebar that has to be cut free. Underneath, we're looking at the subgrade: is it compacted, does it drain, is there old asphalt or debris buried in it from a prior pour. Roanoke's clay soil doesn't drain fast, and a lot of the cracked slabs we tear out cracked because water sat under them through a few freeze-thaw cycles. What goes wrong when this is done badly is almost always in that step nobody sees. New concrete poured over an uncompacted or poorly graded base will crack and settle again, sometimes within a year, no matter how well it's finished on top. Skipping control joints, or cutting them in the wrong spots, means the concrete cracks where you don't want it instead of where it's supposed to. And matching height and slope to a driveway apron, a garage floor, or an adjoining walk sounds simple until it isn't — get it wrong and you've got a trip hazard or water running toward the house instead of away from it.