· Soil
Much of North Texas sits on clay that changes volume with moisture. In a wet spring it swells; in a dry August it shrinks and cracks.
Why the edges move first
The soil under the middle of a house stays more even. The soil at the edges dries and wets with the weather, the gutters and the sprinklers, so the perimeter moves more.
What helps
Even moisture around the foundation: gutters that carry water away, soil sloped away from the house, and steady watering in drought where your city allows it.