Flood Risk & Resilience Guide for Blocks of Flats
A comprehensive guide to flood risk management for residential blocks, covering flood resilience measures, flood insurance for blocks of flats, emergency flood response planning, and building recovery after flooding. Understand how to assess your flood risk, protect your building, and ensure your block is prepared for the increasing threat of flooding driven by climate change.
Understanding Flood Risk for Blocks of Flats
Flood risk is one of the most significant environmental threats facing residential buildings in England and Wales. For blocks of flats, the consequences of flooding can be severe, affecting not just individual leaseholders but the entire building, its communal systems, and the financial health of the service charge fund. Unlike a single house where the homeowner bears the risk alone, a block of flats involves shared infrastructure, communal areas, and collective insurance, making flood risk management a responsibility that falls squarely on the managing agent and the freeholder or residents' management company.
Flooding can originate from multiple sources. Fluvial flooding occurs when rivers overtop their banks. Pluvial or surface water flooding results from intense rainfall overwhelming drainage systems, and is the most common type in urban areas. Groundwater flooding happens when the water table rises above ground level, particularly affecting basement flats. Coastal flooding is driven by storm surges and high tides. Each of these types presents different risks and requires different mitigation strategies.
This guide explains the key types of flood risk, how to assess whether your block is at risk, what flood resilience measures should be in place, and how to plan for and recover from a flood event. For related guidance on building maintenance and safety, see our health and safety guide.
Types of Flood Risk Affecting Blocks of Flats
Understanding the different types of flood risk is essential for putting the right protection in place. Each type of flooding has different causes, warning times, and impacts on residential buildings.
Fluvial (River) Flooding
Fluvial flooding occurs when rivers or watercourses exceed their capacity following prolonged or heavy rainfall. Blocks of flats near rivers, streams, or in designated Environment Agency flood zones are most at risk. The Environment Agency provides advance warnings for fluvial flooding, giving managing agents time to deploy barriers and alert residents. Properties in Flood Zone 3 have a 1 in 100 or greater annual probability of river flooding and require careful risk management.
Pluvial (Surface Water) Flooding
Surface water flooding is the most common type of flooding in urban areas and is caused by intense rainfall that overwhelms the drainage network. Unlike river flooding, surface water flooding can occur far from any watercourse and often with very little warning. Blocks of flats with inadequate drainage systems, those on low-lying ground, or those surrounded by hard surfaces that prevent natural infiltration are particularly vulnerable to this type of flooding.
Groundwater Flooding
Groundwater flooding occurs when the water table rises above the ground surface or into below-ground structures. This is a particular concern for blocks of flats with basement flats, underground car parks, or plant rooms located below ground level. Groundwater flooding can be prolonged, lasting weeks or months, and causes significant damage to finishes, insulation, and electrical installations in affected areas.
Coastal and Tidal Flooding
Coastal flooding affects blocks of flats in seaside locations and estuarine areas. Storm surges combined with high tides can inundate coastal properties with saltwater, which is particularly corrosive and damaging to building fabric and services. Climate change is raising sea levels and increasing storm intensity, meaning that coastal flood risk is growing for many residential blocks that were previously considered safe.
Flood Risk Assessment for Blocks of Flats
A flood risk assessment is the starting point for protecting any block of flats. Managing agents and directors should understand the level of risk their building faces and use this information to guide investment in flood resilience measures. The Environment Agency provides free online tools that allow you to check the flood zone classification and surface water risk for any postcode in England.
The Environment Agency classifies land into three flood zones for planning purposes. Flood Zone 1 has a low probability of flooding. Flood Zone 2 has a medium probability, with between a 1 in 100 and 1 in 1,000 annual probability of river flooding. Flood Zone 3 has a high probability, with a 1 in 100 or greater annual chance of river flooding or a 1 in 200 or greater chance of sea flooding. However, these zones only cover fluvial and coastal risk and do not account for surface water or groundwater flooding, which must be assessed separately.
For blocks in higher-risk areas, a site-specific flood risk assessment carried out by a qualified environmental consultant is recommended. This assessment will consider the building's specific vulnerabilities, including the presence of basement flats, the condition of drainage systems, the location of critical services and plant, and the availability of escape routes. The findings should be used to develop a proportionate flood resilience strategy and to inform the building's buildings insurance arrangements.
Flood Resilience Measures for Blocks of Flats
Flood resilience measures are the physical adaptations and systems that help a building resist flood water entry and recover more quickly after a flood. Investing in resilience reduces damage, lowers insurance claims costs, and minimises the disruption experienced by residents. The following measures should be considered for any block of flats with identified flood risk.
- Flood barriers and door guards fitted to all vulnerable entry points including communal entrances, basement doors, and car park ramps
- Non-return valves installed on all drainage outlets to prevent sewage and floodwater backflow into the building
- Sump pumps with battery backup installed in basements, plant rooms, and any below-ground areas prone to water ingress
- Electrical installations in flood-risk areas raised above anticipated flood levels or fitted with quick-disconnect isolation switches
- Airbrick covers and vent seals stored on site and ready for rapid deployment when flood warnings are issued
- Water-resistant materials used for ground floor and basement finishes including lime plaster, ceramic tiles, and closed-cell insulation
- Critical building plant including boilers, distribution boards, and lift motor rooms relocated above flood level where feasible
- Landscaping and drainage improvements to direct surface water away from the building and reduce ponding around the foundations
The cost of implementing flood resilience measures is typically recoverable through the service charge as expenditure on maintaining and protecting the building. For significant works, the Section 20 consultation process will apply. Managing agents should keep detailed records of all flood resilience expenditure and the rationale for the measures chosen.
Insurance Implications and the Flood Re Scheme
Flood insurance is a critical component of the buildings insurance policy for any block of flats. The availability and cost of flood cover depends on the building's location, its claims history, and the resilience measures in place. Managing agents must ensure that the buildings insurance policy provides adequate flood damage cover and that the terms, excesses, and exclusions are clearly understood by the directors and leaseholders.
The Flood Re scheme, introduced in 2016, was designed to make flood insurance affordable for residential properties at high risk of flooding. Flood Re allows participating insurers to cede the flood risk element of a policy to the scheme at a capped premium. However, it is important to understand that Flood Re currently applies only to individual household insurance policies and does not extend to buildings insurance policies for blocks of flats. This means that blocks in high-risk areas may still face significantly elevated premiums or difficulty obtaining cover on the open market.
Where flood insurance is expensive or difficult to obtain, managing agents should work with specialist insurance brokers who understand the block insurance market. Demonstrating that the building has invested in flood resilience measures can help secure more favourable terms. For guidance on managing the claims process following a flood, see our insurance claims guide.
Emergency Flood Response Planning
An emergency flood response plan is essential for any block of flats with identified flood risk. The plan should set out clear procedures for before, during, and after a flood event, assign responsibilities, and ensure that all residents know what to do. A well-prepared building will suffer less damage, recover more quickly, and keep its residents safer than one that is caught unprepared.
Before a Flood
Register the building for Environment Agency flood warnings. Maintain an emergency contact list for all residents, key contractors, and the emergency repairs provider. Ensure all flood barriers, pumps, and protection equipment are serviced and accessible. Brief residents annually on the flood plan, including how to protect their own belongings and where to find flood warnings. Check that non-return valves are functioning and that drainage gullies and channels are clear of debris.
During a Flood
Deploy flood barriers and seal all vulnerable entry points. Activate sump pumps and check that they are operating correctly. Isolate electricity supply to areas at risk of inundation to prevent electrical hazards. Advise residents in basement flats and ground floor units to move valuables to higher levels and to evacuate if water levels are rising. Maintain contact with the Environment Agency, local authority emergency services, and the building's emergency contractor. Do not allow anyone to enter floodwater, which may be contaminated with sewage and chemicals.
After a Flood
Do not allow residents to return to affected areas until the building has been assessed for structural safety and the electricity supply has been checked by a qualified electrician. Notify the buildings insurer immediately and begin documenting the damage with photographs and written records. Arrange for professional drying and decontamination as soon as possible to prevent mould growth and secondary damage. Commission specialist assessments of electrical, mechanical, and structural systems before reinstatement work begins.
Building Recovery After Flooding
Building recovery after flooding is a complex process that requires professional management. Rushing to reinstate a flood-damaged building without proper drying and decontamination can lead to hidden moisture damage, mould growth, and long-term structural problems. Managing agents should follow a structured approach to recovery, working closely with the loss adjuster appointed under the insurance claim.
Drying
Professional drying is essential before any reinstatement work can begin. Flood water penetrates deep into the building fabric, saturating walls, floors, insulation, and structural timbers. Industrial dehumidifiers and air movers should be deployed by a specialist drying contractor, and moisture levels should be monitored using calibrated equipment. The drying process can take weeks or even months depending on the depth of flooding and the construction type. Attempting to redecorate or reinstate finishes before the building is thoroughly dry will result in further damage and wasted expenditure.
Decontamination
Floodwater is rarely clean. It may contain sewage, chemicals, silt, and other contaminants that pose a serious health risk. All flood-affected areas must be professionally cleaned and sanitised before they can be reoccupied. Porous materials that have absorbed contaminated water, including plasterboard, chipboard flooring, and fibre insulation, will typically need to be removed and replaced. Hard surfaces can usually be cleaned and disinfected, but specialist biohazard cleaning may be required where sewage contamination is involved.
Reinstatement
Once the building is dry and decontaminated, reinstatement work can begin. This is the opportunity to incorporate flood resilience measures into the rebuild, a principle known as building back better. Using water-resistant materials, relocating electrical sockets above anticipated flood levels, and installing improved drainage all reduce the impact of any future flooding. The reinstatement should be managed in close coordination with the insurer and loss adjuster to ensure costs are covered and that the building is restored to at least its pre-flood condition.
Basement Flat Risks and Climate Change
Basement flats in blocks are among the most vulnerable residential properties when it comes to flood risk. Water naturally flows to the lowest point, meaning that basements can flood even when the rest of the building remains unaffected. Surface water, groundwater, and sewer surcharges all pose particular risks to below-ground accommodation. The drainage and plumbing systems serving basement flats must be maintained to the highest standard, with functioning non-return valves and, where appropriate, pumped drainage systems that can cope with surcharge events.
Managing agents have a duty under health and safety obligations to assess and manage the flood risk to basement flats. This includes ensuring that escape routes are available and safe during a flood, that electrical installations are protected, and that residents are warned about the specific risks of living below ground level. Flood warning systems and automatic pump activation can provide an additional layer of protection for basement flats.
Climate change is increasing both the frequency and intensity of rainfall events across the United Kingdom. The Met Office projects that heavy rainfall events will become more common, increasing the risk of surface water flooding in urban areas. Rising sea levels are also extending the reach of coastal flooding. For managing agents and directors, this means that flood risk cannot be treated as a static assessment. It must be reviewed regularly as climate projections are updated, and flood resilience measures should be proportionately upgraded to reflect the changing risk profile.
Frequently Asked Questions About Flood Risk for Blocks of Flats
Is my block of flats at risk of flooding?
Whether your block of flats is at risk of flooding depends on several factors including its location, the local topography, drainage infrastructure, and proximity to rivers or the coast. You can check the Environment Agency flood map for planning to see whether your property falls within Flood Zone 1, 2, or 3. However, this only covers fluvial and coastal flood risk. Surface water flooding, which is the most common type in urban areas, is shown on separate risk maps. Blocks of flats with basements or lower ground floor units are particularly vulnerable, even in areas not traditionally associated with flooding. Climate change is increasing rainfall intensity, meaning that properties with no previous flood history may now face a growing risk. Your managing agent should carry out a flood risk assessment as part of the overall health and safety management of the building.
What flood protection measures should blocks of flats have?
Blocks of flats should have a range of flood protection measures proportionate to their level of risk. At a minimum, this includes non-return valves on drainage outlets to prevent sewage backflow, flood barriers or door guards for vulnerable entry points, and sump pumps in basements or lower ground areas. Electrical installations in flood-prone areas should be raised above anticipated flood levels or protected with isolation switches that can be activated quickly. Airbrick covers should be available to seal ventilation points, and critical plant such as boilers and electrical distribution boards should ideally be located above ground floor level. The building should also have a flood response plan that is shared with all residents, detailing emergency contacts, evacuation routes, and the location of flood protection equipment. Managing agents should review and test these measures annually.
Does buildings insurance cover flood damage for blocks of flats?
Most buildings insurance policies for blocks of flats do cover flood damage, but the extent of cover and the excess applied can vary significantly between insurers. It is essential to check the specific terms of your policy, as some insurers impose high flood excesses or exclude certain types of flood damage such as groundwater ingress. If your block has a history of flooding or is located in a high-risk flood zone, obtaining affordable cover may be more difficult, and the Flood Re scheme may be relevant. Buildings insurance typically covers the cost of drying out, decontamination, and reinstatement of the structure and communal areas, but it may not cover the contents of individual flats or temporary accommodation for residents. Managing agents should ensure the buildings insurance policy is reviewed annually and that adequate flood cover is maintained.
What should a managing agent do before, during and after a flood?
Before a flood, a managing agent should ensure that a flood response plan is in place, that flood protection equipment is maintained and accessible, and that residents know what to do in the event of a flood warning. The agent should register the building for Environment Agency flood alerts and maintain an up-to-date emergency contact list. During a flood, the managing agent should coordinate the deployment of flood barriers, ensure that electricity and gas supplies are isolated where necessary, and liaise with the emergency services. After a flood, the immediate priorities are ensuring structural safety, arranging professional drying and decontamination, and notifying the buildings insurer to begin the claims process. The managing agent should document all damage with photographs and arrange for specialist assessments of the electrical, mechanical, and structural systems before the building is reoccupied.
Who pays for flood resilience measures in a block of flats?
The cost of flood resilience measures in a block of flats is typically funded through the service charge. Under most leases, the freeholder or managing agent is responsible for maintaining and protecting the structure and common parts of the building, and the costs of doing so are recoverable from leaseholders via the service charge. For significant expenditure such as installing permanent flood barriers, sump pump systems, or raising electrical installations, the Section 20 consultation process under the Landlord and Tenant Act 1985 may apply if the cost exceeds the statutory threshold. Leaseholders should be consulted and given the opportunity to comment on proposed works and costs. In some cases, grants or funding may be available from local authorities or the Environment Agency for flood resilience improvements, and managing agents should explore these options before passing the full cost to leaseholders.
What is the Flood Re scheme and does it apply to blocks of flats?
Flood Re is a joint initiative between the UK government and the insurance industry, launched in 2016, designed to make flood insurance more affordable for residential properties at high risk of flooding. It works by allowing participating insurers to pass the flood risk element of a home insurance policy to Flood Re, which then covers the flood risk at a capped premium. However, Flood Re currently applies only to individual household policies and does not cover buildings insurance for blocks of flats. This means that blocks of flats in high-risk flood areas may still face elevated buildings insurance premiums or difficulty obtaining cover. Managing agents and directors of resident management companies should work with specialist insurance brokers to secure the best available terms. The insurance industry has indicated that Flood Re will transition to risk-reflective pricing by 2039, so investing in flood resilience measures now can help reduce future premiums.
Need Help Managing Flood Risk in Your Block?
Whether you need a flood risk assessment for your block, advice on flood resilience measures, help with flood insurance arrangements, or support with emergency response and recovery after a flood event, Block is here to help. Our experienced team manages flood risk and building resilience across hundreds of residential blocks nationwide.