Hotter, drier summers are increasing the risk of subsidence in susceptible ground conditions. But what is the best way for construction teams to establish this? Adnan Qureshi explains
An occupant notices a crack beside a window. The contractor wants to know what to repair, while the client wants to know whether the building is safe. Monitoring and a drainage survey are suggested, but what will they establish?
The issue is timely given our recent summer. The Met Office reported on 1 September that summer 2026 was provisionally the UK’s warmest on record. In August, the Association of British Insurers reported that the average domestic subsidence claim had reached a record £20,000 in the second quarter. Prolonged dry weather can increase movement risk in susceptible ground, but it does not make every crack subsidence.
The challenge is to act promptly without jumping to a conclusion. A crack is evidence, not a diagnosis. The aim is to turn that evidence into a managed decision.
Safety comes before the investigation
The first question is whether the building can safely remain in use. Significant distortion, displaced masonry, rapidly worsening damage or other signs of instability may require urgent assessment by a suitably competent structural engineer. Restrict access or arrange appropriately designed temporary support where necessary. Neither monitoring nor a desktop review should delay urgent precautions.
For the client, recognising when specialist competence is needed is different from making the engineering diagnosis. Agree responsibility for immediate controls and their review. If the building cannot safely remain occupied, suitable alternative arrangements may be necessary.
Read the building, not just the crack
Once immediate risks are addressed, review the building’s age, construction, previous reports, repairs, drainage, nearby excavation, vegetation and alterations. Compare photographs and look for associated distortion, including sticking doors or windows.
Cracking may result from shrinkage, thermal movement, settlement, alterations, material deterioration or ground movement. Some movement is historic or seasonal rather than progressive. BRE Digest 251 helps classify visible damage in low-rise buildings, but its categories are not a diagnosis: crack width alone cannot establish the cause or whether movement is continuing.
Good records help the engineer start with a better question, not a predetermined answer.
Investigate a question, not a checklist
Drainage surveys, trial pits, boreholes and monitoring serve different purposes. The scope should follow a credible hypothesis and relevant specialist advice.
Consider an illustrative low-rise housing case with recurring diagonal cracking and a history of drainage repairs. Rather than commissioning everything at once, establish what needs to be known first. Could defective drainage be contributing? A targeted CCTV survey may help. Is foundation depth or form uncertain? A trial pit may be appropriate. Do the ground conditions require investigation? A suitably designed ground investigation may be needed.
BS 5930:2015+A1:2020 provides the current code of practice for ground investigations. The work itself must also be safe. HSE warns that even small excavations can undermine nearby walls or foundations. Identify buried services, plan excavation support and obtain engineering advice where required before intrusive work begins.
Finding a drainage defect does not automatically establish the cause of movement. Each investigation should test a plausible explanation. What will we know afterwards that we do not know now?
Monitoring can help establish whether movement is continuing, but it is neither a substitute for safety assessment nor an indefinite holding position. The engineer should define the measurements, locations, reliable reference points, frequency and review period, together with trigger levels and the actions required if they are reached.
On shrinkable clay, seasonal moisture changes can affect movement, so a short period of readings may not establish stability. The Institution of Structural Engineers’ 2023 Subsidence guidance provides an end-to-end approach to diagnosis, investigation, monitoring and remediation.
Collecting readings is not the objective. The point is to understand the results and decide what happens next.
The repair must follow the evidence
Immediate safety measures and permanent remediation are different decisions. Temporary support may be necessary before the cause is fully understood. Permanent works should be based on a sufficiently established diagnosis and competent design.
Depending on the mechanism, the response might involve drainage repair, local strengthening, foundation work or another intervention. Underpinning should not be automatic simply because subsidence is suspected. Repeatedly filling a crack while movement continues may conceal evidence and result in the defect returning.
Notify insurers promptly where relevant, and consider necessary statutory, party wall and other approvals before works proceed. The investigation should justify the solution, not merely produce a report.
The client owns the gaps between the specialists
In client-side housing work, I have found that the difficult part is often not obtaining the first report, but coordinating what follows. An engineer may assess the structure, a drainage specialist inspect the pipes, a geotechnical consultant investigate the ground and a contractor deliver the works. Each can perform competently while the case still drifts.
One clear record should capture the working diagnosis, safety controls, outstanding evidence, responsibilities and next review date. Residents and building users also need understandable updates about safety, the investigation and what happens next.
Closure needs evidence that agreed works are complete, relevant risks addressed and necessary follow-up concluded. A closed works order is not necessarily a closed structural case.
Good investigations reduce uncertainty, protect people and support timely, proportionate repairs. When the next crack is reported, the useful question is not simply, “What survey should we order?” It is, “What decision will the next piece of evidence allow us to make?” That is what turns a collection of investigations into a managed structural case.
Adnan Qureshi is a survey and investment manager at the Royal Borough of Greenwich
