The heat is on – how climate change is impacting below ground services insurance claims

This summer’s heatwaves, and the climate change behind them, are putting homes and business properties at greater risk from drainage, water supply and subsidence problems.

They are also causing the insurance industry to consider how to best provide the support customers need in a more complicated and costly claims environment.

Specialists like Catalyst Services UK, will provide an increasingly critical service in responding effectively to claims triggered by climate events, said the company’s managing director, Brad Jackson.

He added: “We’ve already entered what looks like being an extended period of change in terms of the risk profiles for millions of properties across the UK due to climate change.

“Our insurance provider clients are working hard to understand how best they can support claims customers. We’re looking to play our part by providing data that helps them understand these new risks.

“We’re also very keen to support claims customers with the best possible advice, so they understand claims decisions, and can best protect their properties as risks emerge and develop over the coming decades.”

More claims skills and tech to tackle climate change

Weather extremes created by climate change emphasise the importance of understanding how property risks can be interconnected when responding to insurance claims, says Catalyst Operations Director Paul Duddle, who is also Chairman of the Subsidence Forum.

He explains: “Subsidence, leaking pipes and drainage defects can be different facets of related property issues. It’s why technical expertise  matters so much.

“The industry needs to keep building knowledge and capability, including using new technologies, so claims can be investigated properly and progressed with confidence, while data insights are captured.

“At Catalyst, we’re directly responding to this by recruiting claims handlers who can work on the more complex claims we’re seeing. We’re also investing in our Catalyst Training Academy to grow skills internally and share knowledge with the wider insurance industry.”

Catalyst is actively working with technical and insurance bodies on these important trends. As well as supporting Paul’s leadership role in the Subsidence Forum, Brad is an active member of the Insurance Institute of Manchester, and Catalyst engages with other professionals through the I Love Claims networking body.

Climate change – what does the latest data tells us?

The Met Office’s latest annual report, State of the UK Climate 2025, just published, concludes that what was, just a few decades ago, termed as extreme weather is now “the new normal”.

It shows the hottest day of the year in the south of England is now typically 4.5C warmer than it was in 1961-1990, and the temperatures in the north of England are catching up fast.

The report states there is clear evidence that the UK is now experiencing the effects of climate change:

• 2025 was the warmest year on record since data began to be collected in 1884.
• The decade 2016-2025 was 1.33C warmer than 1961-1990.
• The number of days over 30C and nights over 18C has more than quadrupled for Greater London in the period 2016-2025, compared to 1961-1990.

4 big ways climate change is impacting our weather

What is the impact of climate change on drainage resilience?

These climate changes only reinforce assessments made over the last two years, including by the Environment Agency.

It has identified around 4.6 million properties in England in areas at risk of surface-water flooding, including around 1.1 million in high-risk areas.

Under its climate-change scenario, now being played out:

• The number of properties at flood risk could rise to around 6.1 million between 2040 and 2060, an increase of nearly one-third.
• Properties in high-risk areas could rise to about 1.8 million, an increase of 66%.
• The number of high-risk properties potentially experiencing water depths above 300mm could increase by 57%.
• The proportion exposed to depths above 600mm could increase by 73%.

The assessment notes that surface-water flood risk is higher in cities where drainage systems are less able to accommodate intense rainfall.

What is the impact of climate change on insurance claims?

There is evidence that the cost and severity of flood-related insurance claims are already rising.

UK insurers paid £312 million for domestic flood claims during 2025, 38% more than in 2024. The average payment to a homeowner rose by 60% to approximately £30,000.

These figures do not prove that climate change caused every claim, but they show the increasing financial impact of periods of severe weather.

The increasing flooding risks already identified by the Environment Agency could impact claims volumes:

• More claims following intense localised downpours.
• More sewer-backup and drain-overflow incidents.
• More repeat claims in vulnerable locations.
• Greater drying, cleaning and reinstatement costs where floodwater is contaminated.
• More complex claims involving several sources of water, such as surface runoff, sewer surcharging and high river levels.

Assessing claims risks for individual properties

In 2025, Flood Re, a government-backed and insurance industry-funded scheme to improve the availability and affordability of flood insurance, reported a changing claims environment.

The number of policies transferred into the scheme rose by 20% to 346,200 in 2024/25. It also saw more frequent and severe claims, including an increase in very large losses exceeding £100,000.

As exposure to risk and repair costs rise, insurers are likely to place greater importance on property-level information, including:

• Surface-water and flood-risk mapping.
• Previous flooding and escape-of-water claims.
• Local soil type and subsidence exposure.
• The age and condition of underground pipes.
• Drainage surveys and evidence of repairs.
• Use of non-return valves and property flood-resilience measures.
• Whether previous defects were repaired or just cleared temporarily.

What is the impact of climate change on drains and sewers?

Household and business drainage systems are now increasingly tested by weather extremes – high rainfall in winter (plus short burst of extreme rainfall at other times), and prolonged dry spells in summer.

Impacts include:

• Heavy downpours combined with compacted soils increasing the risk of surface water flooding.
• More blockages and pipe damage from debris entering drains and sewers.
• Clay soil shrinkage in the summer causing pipes to move, resulting in cracks and joint displacement.
• Odour problems in summer heatwaves.
• Tree root ingress into pipes during dry spells, causing blockages and cracks.
• Off-mains systems being overwhelmed by greater water use during dry weather – or inundated by surface floods during spells of heavy rain.

Signs of these drainage problems to look out for include:

• Slow-draining sinks, toilets or baths.
• Foul smells around drains or inspection chambers.
• Recurrent blockages.
• Wastewater backing up.
• Damp patches in gardens.
• Localised sinking near drainage runs.
• Gully overflows during heavy rainfall.

What appears to be a simple blockage may, in fact, point to a larger drainage defect, such as root ingress, cracking, displacement or drain collapse.

Where drainage issues are contributing to damage or claim concerns, Catalyst’s drain services can help identify the cause and recommend the right remedial action.

What is the impact of climate change on water supply pipes?

Water supply pipes can also be affected by prolonged heat, especially where buried pipework is older or already weakened.

As the ground dries and shifts, additional strain can be placed on pipes and joints.

Increased water demand during warm weather can put extra pressure on water pipes, either triggering leaks or making them more obvious, though rapid surface evaporation can also mask visible signs of leaks.

Signs of water pipe problems to look out for include:

• Unexpected increases in water bills,
• Water meter movement when no water is being used.
• A drop in water pressure.
• Damp or softened ground and unexpected green patches in gardens.
• Damp on walls, floors or ceilings.
• Musty smells and mould growth.
• Unexplained staining.
• Hissing, dripping or rumbling sounds.
• Pressure loss.
• Unexpected water usage.

Insurer claims data suggests that escape-of-water incidents are not confined to winter.

Aviva found that 25% of its escape-of-water claims occurred between July and September, with July recording the second-highest number of claims in 2025 after January.

If you suspect an issue with buried water supply pipes, Catalyst’s water supply pipe services and leak detection services are designed to investigate, repair and replace affected assets.

Or you can look at the Catalyst leak detection guide for detailed advice on the causes of leaks, plus how they’re detected and repaired.

What is the impact of climate change on subsidence?

Subsidence is the process whereby ground moves downwards, resulting in building foundations becoming less well supported, causing damage to buildings.

It is most commonly associated with clay soils, which shrink during hot, dry weather, and expand in winter when it rains again.

Climate change is expected to cause cases of subsidence to increase, become more severe and become spread over a wider geographical area to the north and north-west of the UK.

Subsidence surges occur when this process of soil shrinkage and expansion is at its most extreme. Climate change is expected to make these subsidence surges more frequent and more extreme.

Signs of subsidence to look out for include:

• New cracks in walls, ceilings or around door and window openings.
• Existing cracks becoming wider.
• Doors and windows starting to stick.
• Sloping floors or internal structural distortion.
• Cracks in external hardstanding area close to the property.

Not every crack that appears in summer is caused by subsidence, but hot weather can make movement more noticeable and highlight the need for closer investigation.

If hot weather has raised concerns about structural movement, Catalyst’s subsidence investigation services can help establish the cause and support the right next steps. Our three-part Catalyst Subsidence Guide also has valuable information and advice.

Brad Jackson says: “This summer’s heatwaves are a reminder that weather-related claims pressures are evolving. Hot weather can influence subsidence, water supply pipe failures, hidden leaks and drainage defects. Climate change is making these patterns more important for the insurance industry to understand and respond to.

“For insurers, loss adjusters and property professionals, the priority is to recognise those risks early and investigate them properly.

“A clear understanding of the cause will always support better decisions, better communication and better claim outcomes. That’s what we aim to deliver.”

Catalyst claims services

Catalyst delivers a comprehensive range of services to resolve claims for a growing number of insurance providers, brokers, and loss adjusters.

They include: subsidence investigations, drainage surveys and repairs (mains and off-mains), water supply pipe repairs and replacement, water leak detection, and environmental services.