Subsidence is moving back up the property-risk agenda after Britain's record summer. Hastings Direct reported almost 140% more subsidence claims in August 2026 than a year earlier, while the insurance industry's latest figures show the average domestic subsidence claim has reached a record £20,000.
The increase follows a period of unusually persistent heat and dry weather. The Guardian reports that insurers experienced a particularly busy August after five heatwaves, with claims expected to remain elevated as the effects of prolonged soil drying continue into the autumn.
For homeowners, the obvious concern is the cost and disruption of a structural claim. For borrowers, there is another issue: subsidence sits directly at the intersection of property valuation, buildings insurance and mortgageability.
A borrower can have a strong income, substantial assets and a conservative mortgage requirement but still encounter difficulty if the property being offered as security shows signs of movement that have not been properly investigated or documented.
What Has Changed?
Hastings Direct reported almost 140% more subsidence claims in August 2026 than in August 2025, according to reporting published on 5 September.
Separate Association of British Insurers data shows insurers paid £72m for domestic subsidence claims during the second quarter of 2026, with the average claim reaching a record £20,000.
The British Geological Survey identifies London and parts of south-east England as among the areas particularly susceptible to clay shrink-swell, making the current conditions especially relevant to owners of older high-value property.
Why the Record Summer Matters to Foundations
Subsidence occurs when ground beneath a building moves downwards and the foundations move with it. There are several potential causes, but prolonged dry weather is particularly important where properties sit on shrinkable clay soils.
The British Geological Survey explains that clay expands as it absorbs water and contracts when it dries. When the volume change beneath a building is uneven, one section of the property can settle differently from another, producing structural movement.
This risk is concentrated geographically because not every part of Britain has the same underlying geology. London Clay is particularly susceptible to volume change, while significant shrink-swell susceptibility is also present across parts of the South East.
The problem can be amplified by trees and large shrubs, whose roots remove further moisture from the ground. BGS also notes that areas with many older properties and old-style shallow foundations can be seriously affected.
Why Prime London Is Particularly Exposed
The overlap with London's high-value housing stock is commercially important.
Many of the capital's most valuable streets are dominated by Victorian, Edwardian and earlier houses built long before modern foundation standards. These properties can combine shallow foundations, mature trees, clay soils and substantial extensions or alterations undertaken at different points in the building's history.
That does not mean an older London house should automatically be regarded as a subsidence risk. Nor does a crack automatically indicate structural movement. Properties naturally settle, plaster can crack, thermal expansion occurs and buildings can exhibit historic movement that has been stable for decades.
The problem begins when a valuer or surveyor cannot confidently distinguish benign or historic movement from an issue requiring further investigation.
A £3m Borrower Can Be Financially Strong and Still Have a Mortgage Problem
Mortgage underwriting does not end with the borrower. The property itself must also be acceptable security.
If a lender's valuer identifies significant cracking, movement or evidence of previous structural repair, the mortgage can become dependent on what further investigation shows — even where the borrower has substantial equity and easily meets affordability requirements.
The Mortgage Problem Often Appears at Valuation
A homeowner may have lived in a property for ten years without considering an old crack, historic underpinning or an insurance claim to be relevant to the mortgage. The issue can reappear when a remortgage valuation is undertaken.
RICS residential mortgage valuation guidance specifically identifies the apparent condition of the property, major defects and liability to subsidence among factors that can have a material impact on value and should be considered by the valuer.
The valuer is acting for the lender rather than providing the borrower with a full structural survey. Where something significant is observed, the lender may be alerted and further evidence can be required before a final lending decision is made.
The resulting problem is therefore not necessarily that the bank has decided the building is suffering active subsidence. It may simply be that insufficient evidence exists for the valuer and lender to become comfortable with the security.
Active Subsidence and Historic Subsidence Are Not the Same Thing
This distinction is central to mortgageability.
A property showing current progressive movement is a materially different proposition from a house that suffered subsidence 15 years ago, was professionally investigated and repaired, and has remained stable ever since.
Historic subsidence does not automatically make a property unmortgageable. Lenders and valuers can consider repaired properties where suitable evidence exists, although appetite varies significantly.
The quality of the evidence can therefore become as important as the fact that an issue once occurred.
Historic Underpinning Does Not Automatically Stop a Mortgage
Underpinning can sound alarming because it indicates that structural intervention was considered necessary at some point. From a mortgage perspective, however, the fact that a property has been underpinned does not by itself determine the lending outcome.
The questions are why the underpinning was required, whether the cause was addressed, whether the work was appropriately designed and completed, whether subsequent movement occurred and whether the property remains adequately insured.
A well-documented historic repair with years of stability can therefore produce a very different lender response from recent underpinning where movement remains under investigation.
The lender universe can still be narrower than for a comparable property with no structural history. That is precisely why lender selection matters.
Insurance Can Become as Important as the Structural Report
Buildings insurance forms part of the mortgage security framework. The UK Finance Mortgage Lenders' Handbook requires conveyancers to establish that appropriate buildings insurance is in place by completion, and its standard list of potentially required insured risks includes subsidence, heave and landslip.
A previous subsidence claim can therefore affect more than the valuer's view. The borrower may need to establish whether satisfactory continuing cover is available, whether the existing insurer will maintain cover after a remortgage and what exclusions or excesses apply.
The exact insurance requirements are lender-specific, and the borrower should obtain specialist insurance advice where necessary. Willow does not advise on insurance underwriting.
The practical mortgage point is that a structurally acceptable property can still create difficulty if the lender's insurance requirements cannot be met.
Why a Refinance Can Expose a Problem That Did Not Matter Previously
A property may have remained with the same lender for many years. If the borrower has simply taken product transfers, there may have been no fresh physical valuation and no new legal process requiring historic structural information to be reconsidered in detail.
A remortgage to another institution is different.
The new lender is making a fresh credit decision on the property. It can instruct its own valuation and its solicitor will need to satisfy the lender's current legal and insurance requirements.
That is why a borrower can suddenly encounter a question about an old subsidence claim, underpinning or movement history that has not affected the existing mortgage for years.
The Timing Problem Can Be More Serious on a £2m Remortgage
For a high-value borrower, the mortgage balance itself can narrow the lender universe. Add a history of structural movement and the pool can become narrower again.
If the issue is first identified three weeks before an existing £2m interest-only facility matures, the borrower may have little time to locate archived engineering reports, obtain updated professional advice, confirm insurance and identify an alternative lender if the original bank declines.
The result can be a completion delay unrelated to affordability.
The Borrower Risk Is Often Timing, Not Automatic Rejection
Historic movement does not necessarily prevent a mortgage.
The avoidable problem is discovering during a live refinance that the lender requires structural or insurance evidence that the homeowner no longer has readily available.
What If the Valuer Spots Cracks?
Cracking has many potential causes and visual appearance alone does not establish subsidence. Where a mortgage valuer considers an apparent defect significant, however, the lender can require further investigation before deciding whether to proceed.
The ABI advises homeowners to pay particular attention to cracks that appear suddenly, diagonal cracks, cracks wider than around 3mm, cracking visible internally and externally, and doors or windows that suddenly become difficult to open or close.
These signs are not a substitute for professional assessment. A chartered building surveyor or structural engineer may be required to determine whether movement exists and what caused it.
From the mortgage perspective, commissioning the correct investigation quickly can be more useful than approaching several lenders with an unresolved structural question.
Why Trying Another Lender Is Not Always the First Answer
When one lender declines a property, there is a temptation to assume that another bank will simply take a different view.
Sometimes lender appetite genuinely differs. One institution may accept a historic movement history that another will not. But where there is evidence of potentially active subsidence, moving from lender to lender without resolving the underlying concern may simply reproduce the same problem.
The first question should therefore be whether the property issue is understood.
If professional evidence demonstrates historic, repaired and stable movement, the finance adviser can then focus on lenders whose criteria and valuers are capable of considering that type of security.
A Lower LTV Does Not Make Structural Risk Disappear
A borrower might reasonably assume that substantial equity solves the issue. If a £3m property has only a £1m mortgage, the lender appears to have a large financial cushion.
That can help the overall credit proposition, but it does not remove the lender's need to hold acceptable security.
The lender still needs confidence that the property is marketable, insurable and capable of being valued appropriately. A structural issue that materially affects saleability can therefore remain relevant even at a conservative LTV.
This is an important distinction for HNW clients whose strong balance sheet may lead them to expect property condition to be secondary. In mortgage lending, borrower strength and security quality are separate tests.
Prime London Buyers Should Investigate Before Exchange
The issue is equally relevant on a purchase.
A Victorian townhouse with beautiful period features may also have a history of underpinning, tree-related movement or previous insurance claims. That history may be entirely manageable, but buyers should understand it before exchange rather than assuming that mortgage approval proves the building is structurally sound.
A mortgage valuation is not a structural survey. A high-value purchaser may therefore want their own appropriately qualified surveyor or engineer to assess relevant concerns independently.
Where historic movement is known, obtaining reports early also gives the mortgage adviser more time to identify lenders capable of considering the property.
Subsidence Risk Is Not Confined to Prime Central London
London is a clear focus because of its clay geology and density of older property, but the risk extends well beyond the central prime postcodes.
The British Geological Survey identifies significant susceptibility across parts of the South East, including Kent. Its 2026 climate-related research also highlights northern and central London boroughs including Camden, Islington and Barnet among areas particularly exposed to future shrink-swell risk.
High-value homes across Essex, Kent, Surrey and other clay-rich locations can therefore present similar mortgage questions, particularly where older properties sit close to mature trees.
The underwriting issue is property-specific. A postcode does not establish that a house has subsidence, just as living outside a recognised clay-risk area does not remove every possible cause of ground movement.
Climate Risk Is Becoming a Longer-Term Property-Finance Issue
BGS research published in June 2026 projects that warmer, drier summers will increase the number of properties exposed to high levels of clay shrink-swell risk.
Under its medium-emissions scenario, BGS estimates that more than 26% of London properties could fall within highly likely or extremely likely shrink-swell susceptibility by 2070, rising much further under its high-emissions scenario.
Those are long-term climate projections rather than predictions that a quarter of London homes will suffer subsidence. Susceptibility does not mean a property will necessarily experience structural damage.
Nevertheless, the findings underline why lenders, insurers, surveyors and homeowners are likely to pay increasing attention to physical property risk alongside conventional affordability and valuation considerations.
A £20,000 Average Claim Can Understate the HNW Consequence
The ABI's record £20,000 average claim provides a useful measure of the growing insurance cost, but the financial impact on a high-value borrower can extend beyond the repair itself.
A delayed refinance can expose a client to an expensive reversion rate or require an extension to existing borrowing. A purchase can be delayed while structural investigations take place. A property valuation can be affected, which in turn changes LTV and borrowing capacity.
For a landlord, structural work can also create periods when part or all of the property cannot be occupied normally.
The mortgage problem is therefore not accurately measured by the average insurance payout. On a £2m or £3m financing transaction, delay and reduced lender choice can become materially more expensive than the underlying investigation.
Do Not Treat Bridging as a Shortcut Around Active Subsidence
Short-term finance can occasionally have a legitimate role where a property requires work before it can move onto a longer-term mortgage. That does not mean bridging should be treated as a generic answer to unresolved subsidence.
A bridge lender still needs to understand its security, and the borrower still needs a credible exit strategy.
If the intended exit is a conventional mortgage, active structural movement that remains unresolved can simply reappear as the same mortgageability problem at the end of the bridge.
Where repair-and-refinance finance is being considered, the structural issue, scope of remediation, cost, timescale and realistic refinance lender appetite should therefore be assessed as part of the same plan.
What Should a Subsidence Mortgage Readiness Review Include?
For a known or suspected movement case, the objective is to build a clear property history before choosing the lender.
| Evidence | Why It Can Matter |
|---|---|
| Date and nature of movement | Establishes whether the issue is recent, historic or potentially recurring. |
| Structural engineer's evidence | Can identify the cause, severity and whether movement remains active. |
| Monitoring records | Can demonstrate whether cracks or levels have changed over a defined period. |
| Insurance claim file | May contain reports, investigations, repair history and the insurer's conclusion. |
| Remediation documents | Shows what was done, whether underpinning was required and how the cause was addressed. |
| Current buildings insurance | The proposed lender will normally require suitable insurance to remain in place. |
| Mortgage balance and LTV | Allows the finance adviser to assess which lenders may be realistic once the property history is understood. |
| Completion deadline | Determines how much time exists for further investigation, valuation and lender selection. |
Surveyors and Structural Engineers Can Unlock the Finance Conversation
This is an area where professional roles need to remain clear.
A mortgage adviser should not diagnose subsidence. A lender's valuer does not normally undertake the same work as a structural engineer. The insurer has another set of responsibilities, while the client's surveyor may be assessing the property for the purchaser rather than for the lender.
The mortgage adviser becomes useful once the property risk has been defined sufficiently for lenders to assess it.
That is particularly valuable where a property has been professionally repaired and demonstrably stable but a mainstream lender's policy or valuer remains uncomfortable. Another lender may have a different appetite, subject to its own valuation and underwriting.
Historic Subsidence Is Not the Same as an Unresolved Structural Problem
A documented movement history with completed repairs, professional evidence and continuing insurance can be financeable with the appropriate lender.
Active or unexplained movement needs professional investigation first. Specialist lender access cannot replace structural evidence.
Why Owners Should Review Old Property Files Before Refinancing
A surprisingly practical first step is simply establishing what documentation still exists.
Owners of high-value properties can inherit decades of building history when they buy. Structural works may have been completed by previous owners, insurance claims can pre-date the current mortgage and engineering reports may sit with a former solicitor, insurer or surveyor rather than in the homeowner's immediate records.
Locating those documents when there is no transaction deadline is considerably easier than trying to reconstruct the history after a lender has raised a valuation query.
For homeowners planning to refinance within the next six to twelve months, particularly after the extreme 2026 summer, reviewing any known history of structural movement now can therefore be worthwhile.
How Willow Private Finance Can Help
Willow Private Finance works with high-value and complex property cases where the issue is not simply the borrower's income or loan size but whether the property fits the lender's security requirements.
Where a London or South East property has historic subsidence, underpinning, previous structural repairs or a recent survey concern, the first step is to establish what professional evidence is available and whether the movement is understood.
Once that picture is clear, we can assess lenders according to the property history, required loan, LTV, borrower profile and transaction timetable rather than submitting the case to a lender whose policy is unlikely to accommodate it.
For HNW clients, that assessment can extend across specialist large-loan lenders and private banks where the mortgage balance or wider borrower profile requires it.
The objective is not to describe a structurally compromised property as mortgageable when it is not. It is to distinguish a genuinely unresolved risk from a historic, repaired property that may still have viable lending options.
Refinancing a High-Value Property With Historic Subsidence or Structural Repairs?
A previous claim, underpinning or movement history does not automatically prevent a mortgage. What matters is whether the issue is understood, documented and acceptable to the lender and its valuer.
Willow Private Finance can assess the mortgage market once the structural evidence is available, helping identify lenders capable of considering the property before a refinance becomes time-critical.
Explore Complex & HNW Property Finance →Frequently Asked Questions
Key questions for homeowners and buyers dealing with historic subsidence, underpinning or structural movement.
Can you get a mortgage on a property with historic subsidence?
Potentially. Historic subsidence does not automatically make a property unmortgageable. Lender and valuer requirements vary, but structural reports, evidence of completed repairs, monitoring records, insurance history and evidence that the movement is no longer active can all be relevant.
What happens if a mortgage valuer notices cracks that may indicate subsidence?
The valuer may report the apparent defect to the lender and recommend further investigation before the property can be accepted as security. Depending on the findings, a lender could request a structural engineer's report, impose conditions, alter the valuation or decide the property falls outside its appetite.
Does underpinning stop a property getting a mortgage?
Not necessarily. A property that has previously been underpinned may still be mortgageable, but lenders can require detailed evidence about why the work was needed, how it was completed, whether the building is now stable and whether satisfactory buildings insurance remains available.
Why is subsidence particularly relevant to London property?
The British Geological Survey identifies London and parts of south-east England as particularly susceptible to clay shrink-swell. Clay can shrink during prolonged dry periods, and older properties with relatively shallow foundations can be more vulnerable to uneven ground movement.
Should I investigate historic subsidence before applying for a remortgage?
Where a property has a known history of movement, underpinning, structural repairs or an insurance claim, preparing the available reports and insurance documentation before lender placement can reduce the risk of discovering missing information after valuation or during legal work.