Damp, often in the corner of a room is sometimes seen by HouseCheck home inspectors.
This is likely to be rising damp, or it may be damp from a leaking pipe in an adjoining bathroom, or maybe penetrating damp caused by a garden sprinkler continually wetting an outside wall.
Rising damp is usually caused by a failed damp proof layer at floor level, or incorrect outside ground levels. This is where the ground level outside is higher than the damp proof course.
A good home inspector armed with a moisture meter, considerable experience and knowledge and with good powers of observation, should be able to diagnose the cause of the damp and recommend a solution.