The Importance of Selecting the Correct Flood Barrier Solution

Flood risk to the built environment across the UK continues to increase as a result of climate change and more frequent extreme weather events. Both residential and commercial properties are now facing greater exposure to surface water, fluvial and tidal flooding. As a result, flood resilience and resistance measures are becoming an essential consideration in building design, refurbishment and asset management.

Flood barriers are designed to prevent or delay floodwater from entering a building through vulnerable points such as door openings, garages, ventilation systems, service penetrations and basements. By limiting water ingress, appropriately specified systems can significantly reduce internal damage, protect building fabric and contents, and minimise business interruption and displacement of occupants.

Passive and Non-Passive Flood Barriers

Flood protection measures generally fall into two categories: passive and non-passive (active) systems.

Passive flood barriers operate automatically without human intervention. These include automatic flip-up barriers, purpose designed flood resistant external doors, self-closing airbricks and permanent flood walls. Passive systems are particularly appropriate in high-risk areas, locations prone to flash flooding, or where flood warning times are limited and properties may be unoccupied.

Non-passive (active) flood barriers require manual deployment prior to a flood event. Examples include demountable flood screens, removable door boards and, in some cases, temporary sandbagging. While effective in moderate risk areas, their performance is dependent on reliable flood warnings, appropriate storage, maintenance and timely installation.

The choice between passive and non-passive measures should always be informed by a site-specific flood risk assessment.

Risk Based and Site-Specific Specification

The selection and specification of flood resistance measures should align with BS 851188:2019 – Code of practice for flood-resistant and flood-resilient construction. This standard provides guidance on property level protection measures and emphasises the importance of a risk-based approach.

Supporting guidance from the Environment Agency (EA) and CIRIA (Construction Industry Research and Information Association) reinforces that flood mitigation strategies must consider:

The source and type of flooding (fluvial, pluvial, tidal, groundwater)
Predicted flood depth and duration
Available warning time
Building construction type and structural capacity
Occupancy, vulnerability and use of the property

An unsuitable or poorly integrated solution may provide a false sense of security and leave a property vulnerable to significant damage.

The Role of the Building Surveyor

From an RICS and APC competency perspective, Building Surveyors play a key role in assessing flood risk, advising on compliance with relevant standards, and coordinating appropriate remedial solutions. This may involve reviewing Flood Risk Assessments, specifying property level protection measures, advising on maintenance requirements, and ensuring compatibility with existing building fabric.

Correct specification can substantially reduce repair costs, minimise disruption, and enhance the long-term resilience of assets.

At Potter Raper, we provide tailored advice and support to ensure flood protection strategies are proportionate, compliant and aligned with our clients’ specific risk profiles and operational requirements.

Visit our Building Surveying and Technical Design page here.