Drought and clay shrinkage: assessing subsidence claims on reactive soils

The mechanism: shrinking ground, moving foundations

Clay soils swell when wet and shrink when dry. When a drought or a hot summer lowers the moisture content, particularly where thirsty trees and shrubs draw water from the ground, shallow foundations can drop unevenly. The result is the classic subsidence pattern: diagonal cracks, often wider at the top, doors and windows that jam, and gaps opening between extensions and the main house. When rain returns, the opposite movement, heave, can follow.

This problem is well known in parts of south-east England built on shrinkable clay, and reactive clay soils are a familiar issue in many Australian cities. Similar expansive soils cause damage in parts of the United States and Canada, though the insurance treatment there is quite different.

How cover differs between countries

In the UK and Ireland, standard buildings policies commonly include subsidence, heave and landslip, usually with a higher excess and exclusions for new buildings settling, coastal erosion and damage to walls, paths or patios unless the house itself is also affected. In the US and many Canadian policies, earth movement is typically excluded from standard home cover and only available, if at all, through specific endorsements. Australian policies frequently exclude or restrict damage caused by soil movement unless it results from an insured event such as a burst pipe or storm. Always confirm with your own wording.

What the investigation involves

Insurers usually pass drought subsidence claims to a loss adjuster or a specialist subsidence firm. The process is methodical and can take many months, because the investigators need to prove what is driving the movement before they will fund a lasting repair.

• Initial visit: crack mapping, level checks, photographs and a review of trees, drains and garden layout.
• Site investigation: trial pits to expose foundations, boreholes to test clay plasticity and moisture, and root samples to identify which vegetation is responsible.
• Drain survey: to rule out leaking drains as the real cause of softened or eroded ground.
• Monitoring: crack and level readings over several seasons to show whether movement follows dry and wet cycles.
• Mitigation: often tree removal or pruning, sometimes root barriers, before repairs start.

Trees, neighbours and local authorities

Because vegetation is so often the trigger, claims can involve trees that belong to a neighbour, a council or a highway authority, or that are protected by planning rules. The insurer may seek to have them removed or pursue a recovery claim against the owner. Removal of a protected tree typically needs permission, which can delay the repair and become a point of friction.

Repairs: superstructure fix or underpinning?

Once the cause has been stabilised, often by dealing with the vegetation, many insurers prefer superstructure repairs: crack stitching, resin injection, re-pointing, replastering and redecoration. Underpinning, piling or raft foundations are reserved for cases where the ground cannot be stabilised or where movement continues. Policyholders often want the more robust option to protect resale value, so the repair method is a frequent battleground.

Practical items also matter: alternative accommodation if the house becomes uninhabitable, temporary storage, moving furniture, matching finishes and the cost of building control approvals and engineer sign-off.

Points where homeowners and insurers part ways

Each of these is ultimately a technical argument backed by evidence, which is why independent engineering input often decides the outcome.

• Whether the cracking is recent subsidence or historic movement that predates the policy.
• Whether the damage is subsidence at all, or settlement, thermal movement or poor construction.
• Responsibility between successive insurers when the problem spans a change of policy.
• The length of monitoring and the decision not to underpin.
• Exclusion of boundary walls, drives and outbuildings when the main house is unaffected.

Working with your own expert

A loss assessor or public adjuster engaged by the homeowner coordinates an independent view: they can bring in a structural engineer or arboriculturist, check that investigations were adequate, scrutinise monitoring data and challenge repair proposals that seem likely to fail. They also keep a long-running file moving, which matters in claims that can last more than a year.

If agreement cannot be reached, the next step is usually the insurer's formal complaints process followed by the national ombudsman, such as the Financial Ombudsman Service in the UK or AFCA in Australia. A well-documented technical case makes those routes much more effective.

Is it worth it for your claim?

Independent support tends to pay off when the claim has been declined on causation grounds, when the insurer proposes only cosmetic repairs on a building that keeps moving, when a protected or third-party tree complicates matters, or when the property has suffered repeated episodes. Where the insurer accepts liability quickly and proposes a sensible scheme, close monitoring of the process yourself may be enough.

Drought subsidence claims are marathons decided by soil tests, tree evidence and monitoring data. expertdassure.com advises keeping a dated record from the first crack and seeking an independent opinion whenever the insurer's reasoning or repair plan seems unconvincing.