The Long Hot Summer- A Subsidence Surge?

Subsidence, an insured peril since 1971, is in the spotlight more than ever before due to more frequent warm, dry summers. So what are the chances of a surge in claims following the hot dry summer of 2025 and beyond? 

The consensus of those that work within the subsidence arena is that 2025 appears to have all the hallmarks of being a surge year. A surge year is generally defined as being one where the number of subsidence claims rises significantly above the norm and will likely exceed 50,000.00 in that given year. Previous recent surge years include 2003, 2006, 2018 and 2022.

The Chartered Institute of Insurers (the ‘CII’) confirmed record payouts by insurers in 2023 of £54 million, following the surge year of 2022. One loss adjuster reported a 500% increase in claims during that period. In the same year, it was estimated by the CII that there were 4.5 million homes at risk of subsidence damage in the UK and further predicted an increase of 27% by 2050, which would put 1 million more homes at risk. 

For the uninitiated, subsidence is essentially damage caused to buildings, usually in the form of tapered cracking to the walls, internally and externally. The damage is rated according to the Building Research Establishment (BRE) guidance and in some cases can be so severe as to leave the property uninhabitable. 

Properties founded on clay soils, predominantly those in the South-East of England, and which are situated near trees, are most at risk. The risk will depend on various factors including the plasticity of the soil under the foundations (its propensity to shrink and swell), whether roots extend beneath the foundations and whether the soil is desiccated etc. As water is extracted from the soil, it shrinks and during rehydration it expands, causing downward and upward movement in property foundations respectively. The amount of downward movement will determine if and to what extent damage occurs. 

Not all properties are affected, and some seasonal movement can be tolerated. Trees extract moisture from the soil during the growing season and, if their roots extend beneath the foundations, that can cause the soil to become desiccated (dehydrated) causing downward movement and damage. In warmer, drier summers, the increased lack of natural hydration and action of the trees seeking to extract what moisture there is creates a greater risk of damage to property founded on shallow foundations. 

It is not surprising then that insurers and other interested parties, not least homeowners, are concerned about the effect of climate change and the more frequent warm and dry summers in the UK. At the time of writing, provisional Met Office statistics show summer 2025 has been the warmest on record. 

Further, Met Office statistics show that 2025 has been on a par with two previous surge years, 2018 and 2022, in respect of soil moisture deficit (SMD) levels. It surpassed both years at the beginning of September. These are calculated using their meteorological office rainfall evaporation calculation system (MORECS). This is a further indicator that 2025 will be a surge year. 

It is estimated that warm dry summers, like 2025, are 70 times more likely than they would have been naturally, without global warming caused by greenhouse gases. Notably, since records began in 1884, the top warmest summers, in order, are: 

(1)    2025
(2)    2018
(3)    2006
(4)    2003
(5)    2022

The above years were all classed as surge years and so the likelihood of 2025 being the same is naturally high. However, it remains to be seen whether the number of reported claims to insurers in 2025 will cross the threshold and become a surge year. 

Most claims are reported towards the end of summer and into autumn or later for various reasons. Homeowners don’t always report claims when first noticing signs of damage. 

Subsidence is generally seen in older properties (due to shallower foundations built prior to the NHBC regulations being introduced) and cracks are sometimes perceived as part and parcel of an old property. If they continue to get worse, as the summer progresses and the movement potentially increases to the property due to increased moisture deficit, claims are more likely to be reported. Homeowners are not always aware of subsidence and don’t necessarily think about reporting to insurers and quite often claims are only prompted by contractors who advise that damage is reported to insurers as a potential subsidence issue. Others may simply bury their heads in the sand (or should I say clay!) and hope that it will go away before reporting. 

Whatever the reason, it is too early to say whether we will have a 2025 surge. September has been wet but not the wettest, and that may mitigate against a surge. Another mitigating (and ironic) factor could be that the trees are going to save the day themselves! The lack of water has seen some trees adapt into an emergency self-preservation mode by adopting an early autumn; this is where they drop their requirement for moisture (because there isn’t any) by closing the stomata holes on the leaves or by dropping their leaves entirely. This reduces water demand which they would normally use to cool down and to promote photosynthesis. Whether there are enough trees in this state, and whether it is enough to save the day, is not known but it may be possible.    

That said, MORECS this week still shows SMD levels above 300mm, higher compared to the 2018 and 2022 figures for the same week.

Time will tell whether 2025 will be another surge year but there remains every possibility that it will. One thing is for certain though, and that is that such years are becoming more frequent and at higher cost to insurers. Here at Weightmans, our team of subsidence experts would be delighted to assist with any subsidence-related issues.