It was exactly a year ago that Polly Arrowsmith's basement flat flooded. Torrential rain and hailstorms saw 5in (13cm) of water gush into her home within minutes when drains and pipes were overwhelmed.

For Polly, it was a shock to see her home in Islington, north London, ankle-deep in water. She says: 'When it started, I thought it would be OK. But suddenly it breached both the front and back of the flat and there was nothing we could do. Water was coming up through the toilet and the bath.'

Polly, 59, who works in marketing, called her insurer to make a claim, but was told that while she could put one in, her premiums would go up and the flood would be logged against the property.

This would put a black mark on her home that could make it harder to sell later on.

About 6.3 million homes in the UK are at some risk from flooding. In the most extreme cases, a severe flood risk can cut more than 20 per cent off the value of a home and make it virtually uninsurable.

Polly says: 'I decided not to claim. I didn't want to be in a position where the insurance was going up and there could be problems with selling.'

She wore wellies around the house for a week, and it took about six months for the property to completely dry out, even with the help of dehumidifiers.

The carpets were ruined, the kitchen and bathroom flooring needed replacing and the flat was sterilised in case any of the water was contaminated. The total repair bill was about £10,000.

Polly says: 'It was quite stressful and I was worried it would happen again. We've done our best to flood-proof it now.

'It's irritating we had to repair it all ourselves, but I think it was the right decision because of the insurance costs.'

Homeowners living in previously flooded properties typically pay £254 a year more than average for home insurance, reports Compare The Market.

Rising risk 

New homeowners are facing a 'ticking timebomb' as hundreds of thousands of homes are still being built in areas at risk of flooding.

By 2050, there will have been a 66 per cent rise in the number of homes at high-risk of surface water flooding. Yet 45 per cent of people have not looked at the flood risk for their property.

One in nine new homes – about 44,000 properties – built between 2022 and 2024 were in areas at medium or high-risk of river, coastal or surface water flooding, research by Aviva shows.

Some 101,657 of the 396,602 new homes recorded by the Ordnance Survey in England over that period have some flood risk.

The UK's Rainfall was up to a third higher than usual in 2024 and, last winter, the Environment Agency issued more than 3,000 flood alerts, 1,600 flood warnings, and three severe flood warnings to people at risk.

Amy Norman, of research agency Public First, says: 'For most families, their home is their biggest source of wealth. But weather risks are starting to erode that, as some properties become harder to insure and mortgage.

'Without action in this Parliament, we estimate that, by 2050, up to half a million households could be left trapped in unsellable homes and potentially on higher mortgage rates.'

Mortgage prisons

Flooding can have a devastating impact on families. In 2025, insurers paid out £318 million for damage caused to homes and possessions by flooding – a 40 per cent increase on the year before.

Some 2,000 flood claims, totalling £64 million, were paid out in the first quarter of this year. The average claim was £28,600.

A paper by Public First has warned that by 2050 some 430,000 homes could become climate mortgage prisons because of flooding. More severe weather will lead to more claims with higher payouts, which could cause insurers to raise premiums or 'not renew coverage altogether'.

David Hollingworth, from the mortgage broker London & Country, explains: 'A condition of any mortgage will be that the property is insured. If frequent flooding results in the property becoming uninsurable, it would also render it unmortgageable.'

These homeowners could be left with fewer options or trapped on expensive deals.

Someone with a 25-year £250,000 mortgage at 5.4 per cent (the current average five-year fixed rate) would have monthly payments of £1,521.

On the average standard variable rate of 7.35 per cent, repayments would be £1,823 – an extra £3,624 a year.

House price penalty

Even where a home is insurable, some banks may see it as too risky to lend against.

They need to know that it can be sold in the event of a repossession, explains Mr Hollingworth.

He says: 'High insurance costs could also affect affordability and how much can be borrowed. All these factors could drag down the property value.'

House prices could drop by more than 20 per cent for those in the highest risk areas, the Public First research, commissioned by the UK Sustainable Investment and Finance Association has warned.

The constituency with the most potential mortgage prisoners is Boston and Skegness, in the East Midlands, with 8,600 mortgaged homes at high flood risk by 2050. This is followed by Thurrock, in Essex (7,700), and Goole and Pocklington, in Yorkshire (6,900).

The association has suggested mandating Flood Performance Certificates, a document similar to an Energy Performance Certificate that grades a home's vulnerability and resilience to flooding.

Jason Storah, from Aviva, says: 'We're calling on the Government to strengthen planning rules and prioritise the prevention of further at-risk property developments. We want new homes to be built with resilience as standard to minimise the impact of any future flood. This is crucial to ensure that homes are insurable in future.'

Homes built before 2009 are protected by FloodRe, a Government-backed reinsurance scheme, where insurers can pass on the risks of flooding, helping to keep premiums affordable for customers. But this is a temporary fix as the scheme is set to end in 2039.

But, crucially, homes built after 2009 are not currently protected. FloodRe says this is 'to avoid incentivising inappropriate development in areas at high flood risk'.

However, this means hundreds of thousands of new-build owners will find it harder to get insurance.

The actual cost and availability of insurance depends on a property's current flood risk and its history of flooding.

What you can do

Shop around for the best insurance deal. The Flood Directory is a list of specialist insurers for higher-risk properties, visit abi.org.uk.

You can check your flood risk on the Government website at gov.uk/check-long-term-flood-risk.

Those without home insurance who are flooded may be able to get emergency funding from their local authority or help from flood charities such as The National Flood Forum.

Those in at-risk areas could install flood doors and barriers, air brick covers, non-return valves and sump pumps, for example.

Raising electrical sockets and using resilient materials and flooring can also help. The average cost of installing flood protection measures at home is £1,000.

Some 99 per cent of proposed new homes planning applications complied with Environment Agency flood risk advice in the 2024/25 tax year.

A Government spokesman said: 'We are investing £10.5 billion in our flood programme until 2036 to protect nearly 900,000 properties against billions of pounds of economic damage.

'We will also build 1.5 million homes without compromising on safety and our planning proposals will ensure development should not go ahead where it would be unsafe due to flood risk.'