Typical signs include diagonal cracking around door and window openings, cracks that widen towards the top or bottom, doors and windows sticking, sloping floors, and separation between an extension and the main house. Any crack that is widening over time should be assessed by a chartered engineer or building surveyor.
Foundation movement usually shows itself in the pattern rather than the presence of cracks. Diagonal cracks running from the corners of openings, cracks that pass through both the inside and outside of a wall in the same place, and cracks that taper — wider at one end than the other — are more significant than fine straight shrinkage cracks.
Other indicators include newly sticking doors, gaps opening between skirting and floor, visibly sloping floors, and a distinct separation where an extension meets the original house. Movement is best judged over time, so photograph and date cracks and record their width.