They are not the same thing
Settlement is a building bedding down under its own weight, usually early in its life, usually stopping. Subsidence is the ground beneath the foundation moving downward, and it does not stop on its own. The remedies and the costs are entirely different, which is why the distinction matters.
What tends to indicate something structural
Diagonal cracking, particularly running from the corners of openings. Cracks wider at one end than the other. Cracks visible on both the inside and the outside in the same place. Doors and windows that have started binding. Cracking that is measurably changing over weeks or months.
What usually turns out to be cosmetic
Fine straight cracks at plasterboard joints. Cracking along the line between different materials. Hairline cracking that appeared and then stopped. Shrinkage in new plaster. These are common, they are not structural, and they get worried about far more than they deserve.
Why monitoring is often the right answer
Where movement is suspected but not established, a period of instrumented monitoring produces evidence instead of opinion. It tells you whether anything is actually moving, how fast, and in which direction. That is usually cheaper than the argument or the unnecessary remedial work it prevents.
Trees, drains and clay
The common causes are related. Clay soils shrink and swell with moisture. Trees draw moisture out. Leaking drains put it back in the wrong place. An investigation that ignores the drainage and the vegetation has usually missed the mechanism.
What to do first
Photograph the crack with something for scale, note the date, and photograph it again a month later. If it has changed, that is worth knowing. If it has not, that is worth knowing too.
Tell us what you are building.
Send the drawings or describe the project. We confirm scope, deliverables and a realistic timescale.
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