Nobody buys a house thinking about the concrete underneath it. Then a door stops latching, a crack creeps up the drywall, and suddenly you're wondering how bad it is. Sometimes it's serious, often it isn't — and the difference usually comes down to whether the movement is still happening. Here's how to tell them apart, what actually causes foundation damage, what real repairs cost, and how to hire someone who won't sell you piers you don't need.