What is subsidence?
Subsidence is the downward movement of the ground supporting a building’s foundations, causing the structure above to move. It is distinct from heave, which is upward movement, and from settlement, which is the gradual bedding-in of a newly built structure. Policies define these terms individually, and the definitions matter.
What are common signs of subsidence?
The signs most often associated with subsidence are diagonal cracking that is wider at one end and visible on both sides of a wall, doors and windows that begin to stick or bind, and visible distortion or movement of the ground and structure around the property. None of these confirms subsidence on its own, and each can have other explanations, so the cause is normally established by investigation rather than appearance.
Cracking
Cracks associated with movement are often diagonal, wider at one end, visible internally and externally in the same place, and typically appear near openings such as doors and windows. Fine hairline cracking in plaster is very common in UK homes and frequently has other causes.
Doors and windows sticking
Frames pulling out of square can cause doors and windows to bind or fail to close. On its own this can also result from moisture, timber movement or normal seasonal change.
Ground movement
Rippling in paths and paving, gaps opening between extensions and the main building, and leaning garden walls can all accompany ground movement.
How do insurers investigate subsidence?
Insurers usually investigate before deciding, rather than at the point the claim is reported. That normally involves a period of crack or level monitoring, a drainage survey, consideration of nearby trees and vegetation, and a structural engineer’s report on the pattern and likely mechanism of movement. The scope of investigation varies with the property and the circumstances.
Monitoring
Crack monitoring or level monitoring may be installed and read over a period, in some cases covering a full seasonal cycle, to help establish whether movement is continuing and whether it appears seasonal. How long monitoring runs varies with the circumstances.
Drainage investigations
CCTV drainage surveys are commonly carried out, because leaking drains can wash out or soften supporting ground. Defective drainage is one of the causes frequently identified in subsidence investigations.
Trees and vegetation
On shrinkable clay soils, vegetation can draw moisture from the ground and cause seasonal shrinkage. Investigations may include root identification and soil moisture analysis, and remedies may involve managing or removing vegetation — which may itself require local authority consent where trees are protected.
Structural investigations
Trial pits may be dug to examine foundation depth and ground conditions, with soil samples analysed for plasticity and moisture content.
Engineering reports
The findings are usually drawn together in a report setting out the cause, whether movement is ongoing, and the recommended remedial approach. This report tends to govern how the remainder of the claim proceeds.
Repair methods
Where the cause can be removed — repairing a drain or managing vegetation — the building is often allowed to stabilise before superstructure repairs are carried out. Underpinning is used less frequently than many people expect and tends to be considered where stability cannot be restored another way. Superstructure repairs typically involve crack stitching, repointing, replastering and redecoration.
Subsidence repair costs
Costs vary widely, and no general figure is meaningful for an individual property. What tends to drive the cost is a combination of factors:
- the cause, and whether it can be removed — a drain repair is a different order of work from foundation strengthening;
- the extent of movement and how much of the structure is affected;
- the length of any monitoring period before repairs can begin;
- access to the affected elevations, and whether scaffolding or excavation is needed;
- the age, construction and finishes of the property, including matching materials;
- professional fees for engineers, surveyors and drainage specialists;
- whether temporary accommodation is needed while works are carried out.
Claims of this kind also run alongside practical issues such as project duration and the property’s future insurance and saleability.
Why a subsidence claim may be rejected
Common grounds include a conclusion that the movement is not subsidence as defined, that it is historic and pre-existing, that it results from an excluded cause, or that the available evidence does not establish the cause.
Subsidence claim rejected or unpaid?
Read our guide to causation disputes, drainage findings, pre-existing movement and the investigations that tend to matter.
Subsidence claim rejected: what are your options?If the insurer has accepted the claim but the amount offered does not appear to match the works, see our guide to a home insurance settlement that looks too low. For the general steps that follow any refusal, including the complaint process, see declined home insurance claims.