Why We Investigate First - And What DEFRA's New Research Says About That

FPS Environmental | May 2026

Defra has just published two substantial documents on Property Flood Resilience: an Evidence Synthesis and Gap Analysis Final Report and an accompanying Evidence Compendium, completed December 2025. We’ve read them carefully. And while they cover a lot of ground on awareness, uptake, costs and data gaps, the thread that runs most clearly through both is one we’ve built our practice around: understanding a site, not just measuring it.

Investigation first.

The original PFR model – and the one that much of the industry has built itself around – typically starts with someone visiting a property, assessing what products might fit, and specifying accordingly. It’s measure-led. Someone comes, has a look, and recommends a flood door or a set of barriers.

At FPS Environmental, that’s not where we start.

We investigate how sites behave. How water moves across them, through them, and around them. How drainage is performing. What the levels and constraints are. Where water is actually coming from and why it’s ending up where it is. That investigative understanding isn’t background context – it is the work. It directly informs everything we go on to do, whether that’s supporting a planning application, designing a solution, or understanding an existing flooding problem that nobody has managed to get to the bottom of.

The Defra report identifies this gap in the sector precisely. It notes that the majority of the UK PFR evidence base is “theoretical and conceptually based,” and that there is “limited technical evidence on what PFR measures work, in what context, and why.” It flags that resistance measures “can worsen damage if overtopped” – meaning a poorly understood specification isn’t just ineffective, it can actively make things worse. And it’s frank about the risk of surveyors recommending what they know and sell, rather than what the property actually needs.

That’s can happen when you start with the product rather than the problem.

Complex properties need more than a product visit

We’re typically appointed on complex properties. Properties where the flood pathway is unclear, or where there are multiple potential sources – fluvial, surface water, groundwater, or combinations of all three. Properties where the building itself is part of the problem: structural vulnerabilities, repointing that’s let water in for years, site alterations and configurations that nobody has fully accounted for.

On properties like these, the range of considerations goes well beyond what a standard PFR survey is designed to address.

Structural integrity and waterproofing

Before recommending any barrier system, we look at the structure itself. The height barriers need to achieve. How the building fabric performs under hydrostatic pressure. Whether repointing is needed and what specification is appropriate. Whether waterproofing to walls, floors or below-ground structures is part of the answer. A flood door is only as good as the wall it’s set into.

Flood walls and permanent engineered defences

When water volumes or levels mean that demountable barriers or property-level products aren’t viable, the conversation moves into alternative considerations, a different set of consents, design requirements and responsibilities. Flood walls and permanent defences typically require permits or consents, and they almost always need a compensatory flood storage analysis: if you’re displacing water, you have to account for where it goes. This is engineering analysis, not a product specification exercise.

Backflow

One of the most commonly overlooked flood pathways, particularly on properties served by older combined sewer systems. Water entering through drainage connections – floor drains, toilets, inspection chambers – can bypass every external barrier you install. Understanding whether backflow is a factor requires knowledge of the drainage system, not just the building envelope.

When keeping the water out isn’t the answer

Sometimes it isn’t viable. Water depths, building configuration, or the sheer impracticality of achieving a sealed perimeter mean that resistance measures alone can’t do the job. In those cases the right answer is recoverability design – accepting that water will enter and designing to minimise damage and maximise recovery speed. That’s a valid and often more cost-effective route, but it requires honest assessment of what’s achievable, not optimism about what a product might do.

When the problem is bigger than the property

Where surface water is the primary issue – and particularly on sites where flooding is affecting multiple properties, a school, a community facility, or a commercial estate – we think the right question isn’t just “how do we keep water out of this building?” It’s “why is this water here, and can we do anything about that, can the risk be reduced?”

Case study

Which is exactly what we did on a commercial site in Leicestershire – investigating not just the property but the wider flood risk, and considering what could actually be done to reduce it. See also our Flood Risk Assessment services in Leicestershire.

That’s the territory of our Flood Investigation and Management Strategy service. We look at the catchment. We assess whether drainage improvements would make a meaningful difference. We consider whether a SuDS scheme is viable – and increasingly, we’re designing SuDS schemes that carry additional value beyond flood management. On school sites, for instance, a well-designed SuDS scheme isn’t just drainage infrastructure – it can become part of the curriculum. Planting, biodiversity habitat, pond ecology, insect surveys. Flood resilience and environmental education in the same scheme.

That kind of thinking doesn’t come out of a product catalogue. It comes out of understanding how water behaves across a landscape and being willing to look for the most intelligent response to it.

Where PFR products do have a place – and our sister company

Property-level flood resilience products absolutely have their place. Flood barriers, demountable door barriers, air brick covers, non-return valves, pumping systems – these are legitimate and valuable tools when properly specified for the right situation. The Defra research confirms their cost-effectiveness in appropriate scenarios, with the average cost-benefit ratio from Defra’s own grant scheme evaluation coming in at £4.80 saved for every £1 spent.

But availability and accessibility matter. Flood events don’t give much warning. The value of a well-specified set of flood barriers depends entirely on them being to hand, in good condition, and deployable when needed.

That’s where our sister company, Flood Protection Solutions Ltd, comes in. While FPS Environmental are the investigative and design engineers, Flood Protection Solutions exists to make the right products available – ensuring that where barriers, pumps and flood protection equipment are the answer, they can actually be sourced and deployed when it counts.

Two distinct roles. Both necessary.

FPS Environmental was created to make engineering expertise and forensic investigation available – over and above what standard PFR can offer. It’s good to see that the Defra research is arriving at the same conclusion.

Our survey work – and where it sits in the wider picture

Our Flood Survey is our entry-level service for property-level PFR assessment, and it reflects the approach above: investigation-led, not product-led. But it sits within a much broader range of services.

For properties going through the planning process, our Flood Risk Assessments provide the technical documentation needed to support planning permission for development – addressing flood risk to and from a site, sequential and exception testing, drainage strategy, and the full technical picture that local planning authorities and the Environment Agency need to see.

At the other end of the scale, our investigation and management strategy work analyses flooding as forensic engineering.

The common thread across all of it is the same: understand the site first. Let that understanding drive the recommendation.

What the Defra research is really saying

The reports are honest about the state of the PFR sector: uptake has been slower than hoped, evidence is fragmented, technical standards are patchy, and quality of installation varies enormously. They call for accredited assessors, standardised approaches, better data, and more rigorous technical oversight.

We’d add one thing to that list: a clearer distinction between PFR as a product-fitting exercise and PFR as an engineering problem. The former has its place. But for complex sites, for persistent flooding, for properties where previous attempts haven’t worked – you need the latter.

That’s what we do.

Download the full Defra reports: