An exterior door binds at its top corner and the gap along its top edge is wedge-shaped. What is worth considering?

A wedge-shaped gap is a geometry clue, and geometry distinguishes causes that otherwise look alike. A door that binds because the slab swelled binds where the slab grew, usually along the latch edge and usually seasonally, and the gap stays roughly parallel. A door binding at one top corner with a gap that tapers along the head means the slab and the opening are no longer parallel — the opening has racked out of square. That points outward and downward to the structure: foundation settlement, a sagging header over the opening, or framing movement. The inspector's job is to notice that the pattern implicates the opening rather than the door, report it as possible structural movement, and look for corroborating evidence elsewhere on the same elevation before recommending evaluation.

A tapering gap along the head means the door and the opening are no longer parallel, which indicates the opening has racked rather than the door having changed. That points to settlement, a sagging header or framing movement.

Door and window openings are built square and plumb. When a foundation settles differentially or a header deflects, openings rack out of square, and the resulting out-of-parallel gaps around doors are often the first visible evidence.

Wedge Means the Wall Moved. Even gaps blame the door; tapered gaps blame the opening.

Look for confirming evidence on the same elevation — cracked drywall at the corners of openings, sloping floors, or exterior cracking. One racked door is ambiguous; three on one wall is a pattern.

• •Attributing a racked opening to hinges or seasonal swelling
• •Adjusting for the symptom without noting the possible structural cause
• •Failing to look for corroborating evidence elsewhere on the elevation