A gap at the ceiling line means two parts of the house disagree.

Ceiling Gaps: diagnosed and explained.

A gap where the wall meets the ceiling means the wall and the ceiling structure have stopped moving together, and the cause is either seasonal truss uplift or foundation settlement. The joint is a meeting place for two different structural systems: the wall carries load down to the foundation, while the ceiling hangs from joists or roof trusses above, and there are two very different reasons they separate. The benign one is truss uplift: roof trusses in certain designs bow slightly upward in cool, humid months and settle back in warm ones, lifting interior ceiling edges away from non bearing walls. Truss related gaps appear near the middle of the house, come and go with the seasons, and stay roughly the same year over year. The structural one is settlement. When the foundation drops under a wall, the wall goes down with it while the ceiling structure, supported elsewhere, stays put, and the seam opens. Settlement gaps trend wider over time, favor one area or side of the home, and travel with company: cracks running down from the ceiling line, doors sticking beneath the gap, floors sloping toward the same zone. In Southern California, Arizona, and Nevada, that settlement usually rides on expansive clay swelling and shrinking with the seasons or desert soils compressing when finally wetted. The seasonal versus progressive distinction is the whole diagnosis, and a floor elevation survey resolves it with numbers instead of guesswork.

For the repair side of this, the foundation repair solutions page lists every method Dalinghaus installs, including the ones that fix problems other than ceiling gaps.