“We’ve got one wall with an absolutely huge diagonal crack, through which we can see through to the other room; you could easily put your fingers in it and chunks of plaster are falling off,” says Henry Biggs, 49, from Stroud in Gloucestershire.

He and his partner started noticing cracks in their family home in June 2025, a few months after buying it, and filed an insurance claim for subsidence that was accepted by their insurer, Admiral, in the spring. Monitoring devices were only recently fitted, about a year after they first submitted the claim, and they have no idea when the damage might start to be repaired.

They are among a growing number of UK homeowners who face subsidence after two record-hot summers. August was the joint-hottest month ever recorded around the world. Signs of subsidence include widening and lengthening diagonal cracks, typically around window and door frames, as well as sloping floors, and sticking doors and windows.

Millions of homes are at risk of subsidence because of the worsening climate crisis, the British Geological Survey has warned. Under its worst-case scenario, 11% of UK homes could be at risk of subsidence by 2070, more than 4.2 million houses.

As hotter, drier summers and warmer, wetter winters become more frequent, the ground under houses can shrink and drag down a property’s foundations. Older properties with shallow foundations are more at risk, and those built on clay-rich soils. The most vulnerable areas include London, Essex, Kent and a tranche of land from Oxford up to the Wash on England’s east coast, according to scientists.

Insurers have experienced a rise in claims for subsidence in recent months. Hastings says it had record subsidence claims in August, up 140% on last August. So far in 2026, its claims are up by 30% year on year. Axa, one of the biggest home insurers, has talked of a “surge year” for subsidence, and Aviva is reviewing its reserves and pricing models.

During this year’s heatwaves the damage at Biggs’s house, which was built in 1970, worsened progressively. “There are cracks now throughout the house, diagonal cracks around almost every window, windows are getting harder to open and close, and the door lintels have dropped, so we have doors now that won’t close,” he says. “In the main part of the house, the kitchen, dining room, the hallway, the floor is dropping and cracking because it’s just falling away in the middle.”

He adds: “It’s quite upsetting when you’ve just bought your first home, and we can’t even decorate at the moment.” The couple have hired their own loss assessor as subsidence claims tend to be complex and lengthy, often lasting several years.

The average subsidence claim in the UK hit a record £20,000 between April and June, more than £2,000 higher than a year earlier, according to the Association of British Insurers (ABI). Insurers paid out £72m for domestic subsidence claims, compared with £60m in the same period last year.

Timothy Farewell, a geospatial environmental data scientist, whose company MapleSky advises 20 insurers, as well as water companies, on ground movement, says: “We have seen widespread drying of soils across the UK in 2018, 2022, 2025 and 2026 leading to an uptick in the number of cracking houses, bursting water mains and failing roads.”

It is all about “differential movement”, he says. “You can imagine if your house, road or pipe is built across two different soil types, with one soil more shrinkable than the other, then this differential movement is when you get significant problems, with one part moving more than the other. And differential movement could also happen when you have a tree on one side of the house that is drying out (and shrinking) the soil more on one side of the house than the other.”

As old water pipes are more vulnerable than houses to ground movement, summer failures on the water network can indicate that the subsidence risk is increasing in that region. While fewer houses are built on peat-rich soils, movement in these soils has a considerable impact on rural roads and pipe networks, Farewell adds.

Shaune Worrall, the deputy head of insurance of the British Insurance Brokers’ Association, has warned of a “double surge” of claims, as many subsidence claims from last year are still being processed.

As well as environmental conditions, modern housing layouts can affect the risk, he says. Open-plan extensions, larger kitchens and interconnected living areas can mean that extensive structural repairs are needed.

Subsidence excess is usually much higher than for other perils, and a figure of more than £1,000 has become common. This sum could rise to £10,000 for a property that has had subsidence in the past, despite underpinning works.

Melissa, who works in the arts and has two children, says she and her husband “reluctantly” lodged an insurance claim for subsidence last month. While the cause of the extensive cracks in their 1901 home in Walthamstow, north London, is still to be determined, the couple felt they had no choice.

“When we came back from holiday towards the end of August, our cracks had got a lot worse, in a short period of time. In some parts, wider than 1cm that you can fit a pencil in. Our front door was also sticking such that we could barely open or close it.”

Structural engineers have still not been round to look at the damage, with long delays due to the general surge in insurance claims. Repair schedules will also be affected, with insurers stating months before remediation. Melissa says she has been warned that even if it turns out not to be subsidence, once a subsidence claim is lodged, “that will potentially affect your ability to get future insurance with other providers and will likely drive up your premiums”.

Several homeowners told the Guardian that they might not make an insurance claim for subsidence because they worry about rising premiums, or not being able to get insurance cover in future.

Rachel Hogarth Smith, 58, a recently retired headteacher, says she has been “quite stressed” about subsidence at her late Victorian/Edwardian house. She has held off from making an insurance claim after her insurer warned her about the potential repercussions. She has been advised by a structural engineer to wait until the spring before doing any repair work, while an olive tree near the house should be removed because it sucks moisture from the ground, exacerbating the situation.

“I’m now not opening any of the windows in the bay window because they’re sticking a bit and I don’t want to be in a position where I can’t get them closed again,” she says. “There’s a small gap between the skirting board and the floorboards underneath the bay so you can see daylight in between them.” If the subsidence remedial works end up costing a lot more than hoped, she may file an insurance claim after all.

Modern homes are considered less vulnerable, but Richard Smith, the head of standards, innovation and research at the National House Building Council, says it is reviewing whether changes should be made to its standards.

Subsidence claims can be costly and complex, but underpinning or other remedial work should resolve the issues.

Sarah Dodd, founder of the law firm Tree Law, says: “In around 25 years working with tree-related subsidence cases [that led to legal disputes], I can recall fewer than 10 cases where significant subsidence has recurred following underpinning.”