I try not to worry too much about the cracks in my walls. I like to see them instead as the price of living in a characterful older property.
But I’m going to be monitoring them much more closely from now on as this year’s extreme-weather combination of severe drought and expected heavy rainfall is a recipe for subsidence.
After all, the hit to property prices can be steep. Severe cases of subsidence can knock five to 10 per cent off your house price even after they’ve been put right, because a history of subsidence can make buyers, lenders and insurers a bit jumpy.
Active unrepaired subsidence, meanwhile, can knock as much as 25 per cent off a home’s value, and potentially even more than that according to Ian Pitt, of chartered surveyor Bruton Knowles.
Diagonal cracks around window and door frames are the biggest giveaway that your property is afflicted – especially if these are wider at the top than the bottom and if they open up suddenly rather than gradually through normal wear and tear.
As a rule of thumb, if they are wider than 3mm – meaning you can slot a pound coin into it – it’s time to seek an expert opinion from a survey (and resist the temptation to immediately carry out DIY repairs first).
Most cases of subsidence are the result of droughts draining moisture from the ground and dragging down the foundations. But heavy rainfall, which the strongest El Niño weather pattern in living memory is predicted to deliver this autumn and winter, can make a bad situation worse. It causes further disruption of the ground by swelling the soil back up again as it absorbs water; it’s known as the shrink-swell effect.
Clay-rich soils, which absorb more water, are particularly at risk. This puts clay-heavy regions such as London, Essex, Kent and an area of land from Oxford up to The Wash on England’s east coast at particular risk.
More than 1.8 million properties across Britain (around 5 per cent of the total) could be highly or extremely likely to be susceptible to clay shrink-swell subsidence alone in the next four decades, if the world’s planet-warming carbon emissions continue in the direction they are going, according to the British Geological Survey.
And it could be as high as 11 per cent (more than 4.2m homes) if ambitious global plans to curb emissions don’t come to pass.
Last year, the insurance industry paid out a record £307m in subsidence claims – a whopping 89 per cent more than just three years earlier, as the climate becomes warmer and wetter, according to the Association of British Insurers (ABI). And this year claims look set to be higher still. A record 13,000 new subsidence claims were made in July, August and September this year, a 63 per cent jump on the same period in 2025, according to the Association of British Insurers (ABI).
Payouts are jumping because more homes are suffering from subsidence and because those cases are becoming more severe, with average claims hitting a record £20,000 in the spring, according to the ABI.
The problem with making a claim, though, is that it whacks up the cost of your premiums, often pushing your home up from the “standard risk” bracket to “high risk”. And so homeowners are increasingly opting to finance work themselves, builders report.
The ABI says insurance companies aim to continue offering cover to homes where they have completed a repair following subsidence but concedes “homeowners often find it difficult or expensive… and there may be circumstances where continuation of cover is not possible”.
High street mortgage lenders require valid buildings insurance as a condition of their loans. And when a property suffers repeated and ongoing ground movement that is not properly rectified “insurers routinely withdraw cover or price premiums so high that the home effectively becomes uninsurable and by extension, unmortgageable”, Pitt told me.
For those homes which do still have cover, premiums are typically hiked by around £318 a year (at an average cost of £545, compared to £227 for an unaffected property), according to the Go.Compare insurance website – although increases vary considerably and can be much higher than that.
As well as rising premiums, the typical excess payable for the rest has also risen as the subsidence problem has got worse – from £1,000 to £5,000, according to the Financial Ombudsman Service.
But while most cases of subsidence are caused by shrinking and expanding soil, it can also be the result of poor foundations, leaking sewers and pipes (which wash away soil beneath the property) or nearby mining or construction work.
Trees are another big cause: oak, willow, poplar and elm, in particular, can suck hundreds of litres of water from the soil through their roots every day during the growing season.
“There are practical steps that can help homeowners manage their subsidence risk, from maintaining trees and drains to fixing leaking pipes,” Charlie Inwood, General Insurance Policy Adviser at the ABI, told me. That should stabilise the shrink-swell effect of water flooding and then being removed from the ground.