Over the past few years, I’ve watched the conversation around UK property shift. It used to be all about location, schools, and transport links. Now, more and more buyers are asking me about what’s happening underground. That shift isn’t random. The British Geological Survey (BGS) now forecasts that under a medium emissions scenario, more than 1.8 million properties could be affected by subsidence by 2070. That’s not a distant, abstract number. It means roughly one in every 14 homes in the country could face ground movement serious enough to damage foundations, reduce property value, or make a mortgage impossible to get. If you’re buying a home in the next decade, this isn’t a niche concern — it’s a core part of due diligence.
I’ve been covering property risk in the UK long enough to see the same pattern repeat: buyers fall in love with a house, then discover too late that the ground beneath it is slowly shifting. The problem is that geological risk is invisible. You can’t see shrink-swell clay or a future erosion line from the estate agent’s photos. But the data exists to check it. The BGS’s Property Subsidence Assessment dataset scores every building in England and Wales from 1 to 100 for subsidence susceptibility. That’s the kind of information you want before you exchange contracts, not after. Here’s what you actually need to know.
What Shrink-Swell Subsidence Actually Means for Your Home
The most common geological risk for UK property isn’t sinkholes or earthquakes. It’s shrink-swell. That’s the term for clay-heavy soil that expands when wet and contracts when dry. When we get a hot, dry summer — and 2025 was the warmest spring on record — the ground dries out and shrinks. If your home’s foundations sit on that clay, they can sink unevenly. That’s subsidence.
The areas most at risk are no secret. The BGS has mapped a clear band running from Oxford up to the Wash on England’s east coast, plus London, Essex, and Kent. Anna Harrison, a BGS scientist, described it as a “double whammy” because those areas have both the most reactive clay soils and the biggest projected changes in rainfall and temperature. If I were looking at a property in Camden, Islington, or Barnet — all named as highly susceptible — I’d want a full ground survey before I even thought about an offer. The same goes for large parts of Kent. A quick check using a free postcode risk report can tell you whether you’re in a high-risk zone before you spend money on a surveyor.
Why This Matters More Now Than It Did Five Years Ago
This isn’t a problem that’s staying the same. It’s accelerating. In the first six months of 2025 alone, insurers paid out £153 million in subsidence-related claims. To put that in perspective, that’s just half a year. The BGS’s GeoClimate dataset projects that under a medium emissions scenario — which is closest to where current global trajectories sit — the number of affected properties could exceed 1.8 million by 2070. In London alone, that means more than a quarter of all properties could be affected.
What I notice is that buyers often assume subsidence is something that happens to other people’s houses. But the data shows it’s becoming a widespread issue, especially in the South East. The BGS notes that properties built with shallow foundations — common in older homes — are particularly vulnerable. If you’re buying a Victorian terrace in London, the foundation depth might have been fine for the climate of 1880. It may not be fine for the summers we’re seeing now. A thorough understanding of land conditions before purchase isn’t optional anymore. It’s the difference between a sound investment and a financial headache that takes years to fix.
Where Buyers Get Tripped Up
Most of the mistakes I see aren’t about ignoring the risk entirely. They’re about misunderstanding what the risk actually looks like and how to check for it. Here are the most common ones.
Relying on a standard home survey for ground conditions
A RICS HomeBuyer Report is useful for visible defects. It is not designed to assess geological risk. The surveyor will note cracks in the plaster, but they won’t dig into the soil type or check the BGS subsidence score for your postcode. That’s a separate check. The Property Subsidence Assessment dataset gives each building a score from 1 to 100, broken down by factors like geology, foundation depth, and tree proximity. You can access this data through a conveyancing environmental search. If your solicitor doesn’t offer it, ask for it specifically. It costs a fraction of what a subsidence repair will.
Ignoring trees near the property
Tree proximity is one of the six factors the BGS scores in its subsidence assessment. Large trees, particularly poplars, willows, and oaks, draw huge amounts of water from clay soils during dry periods. That accelerates shrinkage. If there’s a mature tree within 10 metres of your property on clay ground, that’s a red flag. The fix isn’t always to cut the tree down — that can cause the ground to heave as it rehydrates. A proper arboricultural report and subsidence survey are the right first steps. A Wi-Fi water leak detector won’t stop subsidence, but it can alert you to the first signs of pipe damage caused by ground movement, which is a common early indicator.
Assuming coastal erosion only affects cliff-top houses
Coastal erosion is a separate geological risk, but it’s often overlooked by inland buyers. The National Coastal Erosion Risk Mapping (NCERM) data shows that around 24,000 UK postcodes sit within 200 metres of a projected erosion zone. That doesn’t just mean houses on the edge of a cliff. It can affect properties near estuaries, tidal rivers, and low-lying coastal plains. If you’re buying within a mile of the coast, check the erosion projections for that specific postcode. The data is free and publicly available through the LocalRisk service.
Not checking the postcode-level average score
The BGS dataset includes a postcode-level table showing the average subsidence score for all buildings in that postcode. This is a quick screening tool. If the average is high, you know the area is problematic. But here’s the nuance: property-level risk can vary significantly within a single postcode depending on building age, foundation type, and ground level. A low postcode average doesn’t guarantee your specific property is safe, and a high average doesn’t mean every house is doomed. It’s a starting point, not a conclusion. Use it to decide whether you need a full structural survey.
→ Scroll right to see all columns
| Risk Factor | What It Measures | Score Range |
|---|---|---|
| Geology | Soil type and shrink-swell potential | 1–10 |
| Foundation | Depth and type of building foundations | 1–10 |
| Drainage | How water moves around the property | 1–10 |
| Building Type | Construction method and materials | 1–10 |
| Building Storey | Number of floors and load distribution | 1–10 |
| Tree Proximity | Distance and type of nearby vegetation | 1–10 |
How to Check Geological Risk Before You Buy
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If you’re serious about avoiding geological surprises, here’s the process I’d follow. It takes about an hour and could save you tens of thousands of pounds.
Run a free postcode risk check first
Before you pay for any surveys, go to LocalRisk.co.uk and enter the property’s postcode. You’ll get a free report covering flood zones, heat projections, air quality, ground movement, and coastal erosion. The ground movement data comes directly from the BGS GeoClimate dataset. This is a screening-level indicator, so it won’t replace a professional survey, but it will tell you immediately whether you’re in a high-risk area. If the ground movement risk is marked as elevated, you know to proceed with caution. If you’re in a high-risk zone, a comprehensive land buyer’s checklist can help you track what additional checks you need.
Request a conveyancing environmental search
Your solicitor will handle this as part of the conveyancing process, but you need to make sure it’s comprehensive. A standard environmental search includes flood risk, ground stability, and contamination. Ask specifically whether it includes the BGS Property Subsidence Assessment data. If it doesn’t, request an add-on. The cost is usually between £30 and £60. That’s trivial compared to the cost of underpinning a foundation, which can run into five figures. The search will give you the property’s individual subsidence score from 1 to 100, plus the breakdown across the six risk factors.
Get a structural survey if the risk score is moderate or above
If the environmental search shows a subsidence score above 50, or if the geology factor is rated 5 or higher, don’t rely on a HomeBuyer Report. Instruct a structural engineer or a chartered surveyor to do a full building survey (RICS Level 3). They will look for diagonal cracks around windows and doors, sloping floors, and signs of previous underpinning. They can also advise on whether tree removal or drainage improvements are needed. If the property has had subsidence repairs in the past, check whether the work came with a structural guarantee — and whether that guarantee is transferable to you as the new owner.
Check future climate projections for the area
This is the step most buyers miss. The BGS GeoClimate dataset doesn’t just map current risk. It projects how risk will change under different emissions scenarios. Under the medium scenario, highly populated parts of London including Camden, Islington, and Barnet are most susceptible, with more than 26% of properties affected by 2070. If you’re buying a home you plan to keep for 20 or 30 years, the future risk matters as much as the current one. You can find this data through the BGS’s GeoClimate reports or through the LocalRisk service, which incorporates the same projections. A property lawyer can also help you understand how these risks might affect your legal disclosures when you eventually sell.
Frequently Asked Questions
Can I get a mortgage on a house with past subsidence? ▾
Does home insurance cover subsidence damage? ▾
What’s the difference between subsidence and heave? ▾
How accurate are free postcode risk reports? ▾
What are the visible signs of subsidence? ▾
Sources and Further Reading
Essential water supply considerations for buying property in the UK — Water supply and drainage are directly connected to ground stability. This guide covers what to check before you buy.
Millions of homes in London, Essex and Kent at risk from climate-related subsidence. The Guardian, 2026.
Property Subsidence Assessment Dataset. British Geological Survey, 2021.
LocalRisk — Free UK Postcode Climate Risk Reports. LocalRisk, 2026.
