Key points
- Subsidence is only one possible cause of cracking.
- Extensions and altered openings can move differently from older construction.
- Drainage, trees, soil and foundation depth can all be relevant context.
- Monitoring can establish change, but causation may require further evidence.
What do the terms mean?
Subsidence is downward movement of the ground beneath a building after construction. Settlement is movement associated with the building or its foundations adjusting to loading and ground conditions. Other movement can arise from thermal effects, material shrinkage, differential behaviour between building parts or structural alterations.
These mechanisms are not reliably distinguished from one crack photograph. The building history and the wider pattern are important.
What context helps distinguish the cause?
The surveyor may consider the age and construction of the property, foundation type where known, local ground conditions, nearby vegetation, drainage, previous repairs and structural alterations. A crack at the junction between a rear extension and the original house may have a very different explanation from a stepped crack through the main elevation.
- whether the crack is internal, external or continuous through both;
- whether openings are distorted;
- whether floors or walls show related displacement;
- whether movement is concentrated at one building part;
- whether drainage defects, trees or historic repairs are nearby.
When is further investigation justified?
Further work is proportionate where the visible pattern cannot be explained confidently from a non-invasive inspection or where the consequences of getting the diagnosis wrong are significant.
This may include monitoring, drain CCTV, trial pits, arboricultural input, structural engineering or review of historic plans and repair records. The right investigation depends on the evidence rather than following one fixed sequence.
Relevant SurveyAll service
Crack & Structural Movement Investigation
SurveyAll can record and assess the visible pattern and identify whether monitoring or specialist investigation is justified.
Common questions
Questions people often ask
Is every diagonal crack subsidence?
No. Diagonal cracks can arise from several mechanisms, including local movement around openings, alterations, shrinkage and differential movement.
Does underpinning always solve subsidence?
Underpinning is a major intervention and is not required in most movement cases. The cause should be established and proportionate repair considered first.
Can drainage cause movement?
Drainage defects can be relevant because leaking drains may alter ground conditions locally. Where the pattern and location support that possibility, drainage investigation may be appropriate.
Sources and review
Recognised sources used for this guidance
These sources support the general guidance above. They do not replace property-specific inspection, current legal advice or specialist testing where those are needed.