The short answer
Settlement is the gradual, expected bedding-down of a building under its own weight, usually in the first few years after construction or after an extension, and it normally stops on its own. Subsidence is the downward movement of the ground beneath the foundations, caused by something external such as drying clay, a leaking drain or a tree, and it tends to be progressive. As a rule of thumb: settlement cracks are often fine, vertical and stable, frequently appearing where an extension meets the original house; subsidence cracks are typically diagonal, wider than 3mm, tapering, and still growing, appearing near doors and windows and visible inside and out. The crucial test is movement over time — settlement settles, subsidence keeps going — which is why monitoring matters more than a single look.
The words sound similar but the difference is important: settlement is normal and uninsured, while subsidence is a recognised insured peril. The sections below set out how to read your crack against each, and how the two are told apart in practice.
At a glance
- Settlement causeBuilding bedding under own weight
- Subsidence causeGround moving beneath foundations
- Settlement timingUsually first few years / post-extension
- Subsidence timingAny time, often after dry summers
- DeciderIs the crack still moving?
Settlement: normal and expected
Settlement is the slight downward adjustment every building makes as the ground compresses under its load. It is most common in the first one to ten years of a new build, and around extensions, conservatories and porches where new foundations meet old. Settlement cracks are usually:
- Fine and vertical, often under 2–3mm wide.
- Located at junctions — typically where an extension or bay meets the main wall.
- Stable — they appear, then stop growing once the structure has bedded in.
Because settlement is anticipated, it is generally not covered by buildings insurance, and the usual remedy is simply to let it stabilise, then fill and redecorate.
Subsidence: external and progressive
Subsidence comes from the ground itself moving, not the building bedding down. Common triggers in the UK are shrinkable clay soils drying out (often worsened by nearby trees), water escaping from a damaged drain and washing soil away, and historic mining or made-up ground. Subsidence cracks tend to be:
- Diagonal and tapering, wider at one end, often radiating from the corners of openings.
- Wider than about 3mm and frequently still growing.
- Visible inside and out, passing through brick and mortar.
Subsidence is a standard insured peril on most UK home policies, which is why correctly distinguishing it from settlement affects whether a claim is valid.
| Feature | Settlement | Subsidence |
|---|---|---|
| Cause | Building's own weight | Ground moving beneath foundations |
| Typical direction | Vertical | Diagonal, tapering |
| Typical width | Fine, under ~3mm | Often over 3mm and growing |
| Behaviour | Stabilises | Often progressive |
| Insurance | Usually not covered | Standard insured peril |
Indicative comparison for guidance only. A chartered surveyor confirms the actual cause.
Where each tends to appear
Location is a strong clue to which you are dealing with. Settlement most often shows up at the junctions of different structures and in newer parts of a building: around an extension, conservatory or porch, where fresh foundations meet older ones and the new section beds in. It also appears in newly plastered or rendered areas as finishes dry and shrink. Subsidence, by contrast, tends to affect the original load-bearing structure: diagonal cracks radiating from the corners of doors and windows in the main walls, often on the elevation nearest a large tree or above a drainage run. If your crack is at a clean vertical join between old and new build, settlement is the likelier explanation; if it cuts diagonally across original brickwork near an opening and is visible inside and out, subsidence moves up the list. The pattern across the whole house matters too — scattered, varied cracks suggest age and minor settlement, while a focused set of diagonal cracks on one part of the building suggests localised ground movement.
The test that actually settles it
Visual clues point you in the right direction, but they do not prove the cause. The decisive evidence is whether the crack is still moving. Mark and date each end of the crack, or fix a paper tell-tale across it, and photograph it monthly through a full change of seasons. A crack that holds steady is almost certainly settlement or old, dormant movement. A crack that keeps widening — particularly with the diagonal, through-wall, near-an-opening signature — points to active subsidence and should be referred to your buildings insurer or an independent chartered surveyor, who can investigate the cause with drain surveys, soil tests and trial holes.
Frequently asked questions
Can settlement turn into subsidence?
They are different processes, but a property can experience both at different times. Initial settlement after construction can stop, while subsidence may begin years later if external conditions change — for example a tree grows large enough to dry out clay soil, or a drain fails. Each is assessed on its own evidence.
Is settlement covered by insurance?
Generally no. Because settlement is the expected bedding-in of a building, most UK buildings policies exclude it. Subsidence, heave and landslip are the recognised insured perils, which is why insurers care about distinguishing them and may investigate before accepting a claim.
How long should I monitor a crack before deciding?
Monitoring through a full seasonal cycle — often several months to a year — gives the clearest answer, because clay-related subsidence tends to be seasonal. If a crack is widening rapidly or the structure feels unsafe, seek professional advice straight away rather than waiting.
Sources & further reading
- RICS — subsidence and your home
- Association of British Insurers — subsidence
- HomeOwners Alliance — subsidence guide
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property. They are guidance, not a quotation.