So how can you tell the difference? Well there are other signs to look for in order to determine if there is a structural issue, such as cracking at the walls above the affected door jamb. When a house settles or shifts, door and window penetration frames can also shift. If a house settles to the point that causes door and window frames to shift, the wall coverings attached to the frame, most likely either lath and plaster or drywall, will show signs of cracking. A tell-tale sign of structural settling or shifting is a diagonal crack above the corner of a window or door that is larger at one end than the other. If any portion of the crack is wider than ¼ inch, it could indicate a significant structural issue. In addition, if the door or window frame is out of square, this could also indicate structural issues (but may have been caused by installation errors).
If there is no cracking or out of square framing, the culprit is most likely a loose door hinge, or a door hinge that is misaligned. There are a few tricks that can help to shift the door in a way that allows it to close without binding on the jamb. If it is a loose hinge, re-installing the hinge screws could help. If it is a misaligned door hinge, using a wrench to bend or re-position the hinge loops can also help to resolve the issue.
Check out the video below for more information about how to fix a binding door jamb.