COPPELL

Coppell built out largely through the eighties and nineties and then ran out of room, so the housing stock is unusually consistent in age: most of it is now thirty to forty years old and sitting on Blackland Prairie clay.

That is a useful thing to know, because it is roughly the age at which slabs poured in that era start showing what the ground has been doing to them.

Thirty summers of shrinking and thirty springs of swelling is enough cycles for a difference in support to turn into a visible crack.

What the ground under Coppell is actually doing

Coppell sits on the most demanding ground in our service area. Heiden leads at a linear extensibility of 13.6, and Trinity — under a further 8% — is 68.7% clay, the highest clay fraction we have measured anywhere.

Soil like this does not need anything to go wrong to move a house. A normal North Texas year, wet spring into dry August, is enough. In Coppell the useful question is almost never whether the soil is active, because it certainly is; it is whether the watering, drainage and tree cover around the house are keeping that movement even. Even movement a foundation can live with. Uneven movement is what cracks it.