Why is Commercial Flood Insurance in London Becoming Harder to Find?

When considering whether a property is at risk of flooding, many people immediately think about its proximity to a river or the coast. If a building is well away from either, it’s easy to assume flooding is unlikely. However, the reality is more complicated.

Flooding can occur almost anywhere, including places that have never experienced a major flood event. Heavy rainfall, overwhelmed drainage systems, surface water and ageing underground infrastructure can all contribute to flooding, sometimes affecting properties that appear to be at relatively low risk.

For property owners, landlords, and businesses, this can create confusion, especially when an insurer’s flood-risk assessment differs from information shown on government flood maps. So, how do insurance companies determine whether a property is at risk of flooding, and what does that mean when arranging suitable insurance cover?

How do insurance companies assess flood risk?

Insurers use a range of information to assess the likelihood of a property flooding, along with the potential financial consequences if an incident occurs. Although individual insurers may approach flood risk differently, their assessments typically consider several factors.

Location and geographical characteristics

A property’s location is an important starting point. Insurers may consider its proximity to rivers, coastlines and other watercourses, together with the surrounding landscape. However, being on higher ground or outside a recognised floodplain doesn’t necessarily mean a property is free from flood risk.

Historical flooding and previous claims

Records of previous flooding can provide valuable information about a property’s vulnerability. Insurers may examine historic flood events, previous insurance claims and whether nearby properties have experienced similar problems. A property that has flooded before may be considered higher risk, especially if the underlying cause hasn’t been addressed.

Surface water and drainage

Surface water flooding occurs when rainfall cannot drain away quickly enough, allowing water to accumulate on roads, paved areas and around buildings. This can be particularly problematic in urban areas, where large areas of concrete, tarmac and other impermeable surfaces prevent rainwater from soaking naturally into the ground.

Insurers may therefore consider local drainage capacity, surface water flood modelling and the potential for water to collect around a property.

Property construction and use

The building’s characteristics can also influence an insurer’s assessment. For example, a property with a basement may be particularly vulnerable to water entering below ground level. Similarly, commercial premises containing expensive machinery, electrical equipment or stock could face substantial financial losses following a flood.

The way a property is occupied and used may also affect the level of cover required.

Flood modelling and specialist data

Many insurers use commercial flood risk models and mapping services alongside publicly available information. These models may combine geographical data, rainfall patterns, ground levels, historic flooding and other information to estimate the likelihood and potential severity of flooding.

Because insurers may use different data and underwriting criteria, their assessments of the same property can vary. Greenfield Insurance works with a range of insurers, so we can likely find a policy that works for you.

Do insurers use Environment Agency flood maps?

Government flood maps provide a useful starting point for understanding the potential flood risk at a location. In England, the Environment Agency provides online mapping tools that let property owners investigate the risk of flooding from rivers, the sea, and surface water. These resources are valuable, but it’s important to understand their purpose and limitations.

Government flood maps communicate flood risk and support decisions about planning, development and flood management. They do not necessarily reflect every factor an insurer considers when deciding whether to offer cover or calculating a premium. An insurer may use Environment Agency information alongside its own modelling, claims experience and property-specific information. This means a property that appears to have relatively low risk on a government map could still be considered a higher insurance risk.

Similarly, being located in an area identified as having a greater likelihood of flooding does not automatically mean insurance will be unavailable. You can view the Environment Agency’s flood mapping through the government’s Check the Long Term Flood Risk for an Area in England service.

Why might an insurer classify a property as high flood risk?

One question property owners sometimes ask is why their insurer considers a building high risk of flooding when it is nowhere near a river or the sea. The answer often lies in the different ways that flooding can occur.

For example, a property might sit outside a recognised river floodplain but in an area susceptible to surface water accumulation after intense rainfall. Local ground levels, nearby roads, drainage arrangements and the capacity of underground infrastructure can all influence how water behaves during a storm. Previous incidents can also be significant. Even when flooding is relatively localised, insurers may consider this information when assessing future risk.

Importantly, flood risk is not always uniform across a postcode. Two neighbouring properties may have different levels of exposure because of their elevation, construction, drainage or the position of entrances and basements. This is one reason why a more detailed, property-specific assessment can be valuable.

Flooding doesn’t always come from rivers or the sea

Although river and coastal flooding often gets the most attention, it isn’t the only cause of serious flood damage. In many urban environments, surface water and drainage-related flooding can present significant problems.

During prolonged or particularly intense rainfall, drainage systems may struggle to accommodate the volume of water entering them. When surface water cannot escape quickly enough, it may collect on roads, flow toward lower-lying buildings, or enter properties through doorways, ventilation openings, and basement access points. Flooding can also occur when sewers become overwhelmed or blocked, potentially causing wastewater to back up into buildings.

These risks can be less obvious than a nearby river, especially when the responsible infrastructure is hidden beneath streets and buildings. They also demonstrate why assessing flood risk requires a broader understanding of the surrounding environment.

London’s hidden flood risk: Victorian sewers and overwhelmed drainage systems

London provides a particularly useful example of why flood risk cannot be judged solely by proximity to a major river. The Thames is an obvious consideration when discussing flooding in the capital, but London also faces significant risks associated with surface water and its extensive underground drainage network.

Much of London’s sewer infrastructure dates back to the Victorian period, when major engineering projects transformed how wastewater and rainwater were managed. Parts of the network use combined sewers, which carry both wastewater and rainwater through the same system.

Although this infrastructure has been maintained, upgraded and supplemented over time, the demands placed upon it have changed considerably. London’s population has grown, development has intensified, and buildings, roads and paved surfaces have replaced many previously permeable areas.

During heavy rainfall, large volumes of water can enter drainage systems over a relatively short period. If the network cannot accommodate the flow, water may accumulate above ground or, in some circumstances, contribute to sewer flooding. The consequences can be particularly serious for basement properties, lower-ground-floor premises and buildings situated in localised low points.

Why London’s flood risk extends beyond the Thames

A property doesn’t have to be close to the Thames to experience flooding. Surface water can affect locations across London, including areas where residents and businesses might not traditionally associate their surroundings with flood risk. We have produced a London-specific guide.

The severe rainfall events in July 2021 showed how quickly flooding can develop across parts of the capital, affecting homes, commercial buildings, roads, and transport infrastructure. For insurers, this highlights the importance of considering surface water pathways, local drainage conditions, and individual property characteristics, rather than relying solely on river floodplain mapping.

It is also worth distinguishing between surface water flooding and sewer flooding. Although both can be associated with heavy rainfall and overwhelmed infrastructure, they have different causes and may be treated differently under insurance policy wording.

For landlords, businesses, and managing agents, understanding these distinctions is particularly important when reviewing insurance arrangements. The Greenfield Insurance team will be happy to offer guidance.

What does a high flood risk assessment mean for insurance?

If an insurer identifies a property as being at increased flood risk, this may affect the terms on which it offers insurance. Depending on the circumstances, an insurer might charge a higher premium, increase the flood excess, impose specific conditions, or decline to provide flood cover. However, these decisions are not necessarily consistent across the insurance market.

Different insurers have different risk appetites, and some may be better equipped to assess properties with more complex flood exposures. The building’s nature, its claims history, and any measures taken to reduce the potential for damage may all be relevant.

For commercial properties, flooding can also have consequences beyond immediate physical damage. A business may face trading interruptions, loss of stock, equipment damage, or temporary closure while repairs are undertaken.

Landlords and property owners may face additional costs for repairs, alternative accommodation, or lost rental income, depending on the cover arranged. Therefore, consider not only whether flood insurance is available, but also whether the policy provides protection appropriate to the property’s circumstances.This highlights the importance of working with a specialist broker, such as Greenfield Insurance.

Can you obtain flood insurance for a high-risk property?

Being classified as a high flood risk does not necessarily mean that suitable insurance cannot be arranged. While some insurers may be unwilling to provide cover, specialist insurance providers working with Greenfield Insurance may be able to explore alternative options.

For commercial property owners, landlords and those responsible for blocks of flats, this can be particularly important.

Flood Re, the government-backed scheme designed to improve the availability and affordability of flood insurance for eligible domestic properties, does not apply to every type of building or insurance arrangement.

Many commercial properties and certain residential property arrangements fall outside its scope. As a result, businesses, landlords, and managing agents may need to explore insurance solutions available through the wider market.

A member of the Greenfield Insurance team can assess a property’s circumstances, explain the cover available, and identify insurers willing to consider particular flood exposures.

What can you do if your property is considered high flood risk?

If an insurer has identified your property as high flood risk, consider these practical steps.

Check the available flood risk information. Government flood maps can help establish whether the property is potentially exposed to river, coastal or surface water flooding.

Understand the reason for the assessment. Where possible, ask your insurer or broker which factors have influenced the decision. This may help identify whether the concern relates to historical flooding, local drainage, surface water or another issue.

Review previous incidents. If the property has flooded before, establish what caused the incident and whether any improvements have subsequently been made.

Consider flood resilience measures. Depending on the building, appropriate measures might include flood-resistant doors, non-return valves, drainage improvements, or changes to the positioning of vulnerable electrical equipment.

Review your insurance requirements. Check the extent of flood cover, policy exclusions, excesses and any relevant conditions. For commercial premises, you may also want to consider business interruption protection.

Seek specialist insurance advice. If conventional insurers won’t offer suitable terms, an experienced broker like Greenfield Insurance may be able to explore alternatives.

Understanding flood risk is the first step towards suitable protection

Flood risk is rarely as straightforward as checking whether a property is situated close to a river or the coast. Government flood maps provide useful information, but insurers may consider a much wider range of factors, including surface water, drainage infrastructure, historic flooding and the characteristics of individual buildings.

London’s extensive underground drainage network shows why some of the most important flood risks aren’t immediately visible.

For property owners, landlords and businesses, understanding how insurers assess these risks can help when reviewing existing policies or seeking alternative cover.

At Greenfield Insurance, we understand that properties with complex flood exposures can require a more considered approach. We can help you explore insurance options for commercial premises, landlords, and blocks of flats, including properties in areas where flood cover may be challenging to obtain.

If you’re concerned about your property’s flood risk or having difficulty arranging suitable insurance, contact Greenfield Insurance to discuss your requirements.

Frequently asked questions

Can I get flood insurance if my property is in a high-risk area?

Potentially, yes. Although some insurers may restrict or decline cover, specialist insurance providers may be willing to consider properties in areas with an elevated flood risk. Availability, premiums, excesses and conditions will depend on the individual circumstances.

Why does my insurer’s flood risk assessment differ from the Environment Agency map?

Insurers may use additional flood modelling, claims information and property-specific data alongside government mapping. Different datasets and assessment methods can therefore produce different results.

Does flood insurance cover water coming up through drains?

Cover depends on the policy wording and the cause of the incident. Flooding caused by overwhelmed sewers or drains may be treated differently from damage caused by a blocked pipe or a water escape. Check the relevant definitions, exclusions, and conditions.

Can a property flood if it isn’t near a river?

Yes. Surface water, overwhelmed drainage systems, sewer flooding, and groundwater can all cause flooding away from rivers and coastlines.

Does a previous flood claim affect insurance premiums?

It can. Insurers may consider previous claims and the likelihood of future flooding when assessing a property. However, the impact will vary depending on the insurer, the circumstances of the claim and any subsequent improvements to flood resilience.