The cheapest flood defence could be hiding in your toolbox

Behind every flood alert is the question of what comes next. Even when we know water is coming, what can we actually do about it? New research from the University of Hull offers a much simpler (and cheaper) answer than most people assume.

It isn’t uncommon to hear “flood mitigation” and think of something expensive and slow: capital budgets, major retrofits, long lead times and ongoing maintenance costs. When that’s the assumption, a flood alert can feel like bad news you can’t do anything about.

But lab tests published during Flood Action Week show that ordinary tape, applied in good time, outperforms sandbags, stopping almost all floodwater from getting through a door.

Researchers at the University of Hull’s Property Flood Resilience lab tested low-cost temporary measures on six commonly used door types, simulating flood depths of up to 600mm. The tests replicated the type of low-level flooding seen in Hull in 2007, when more than 8,600 homes and 1,300 businesses were damaged.

Flexible synthetic rubber tape  on the outside of a door - 99%

Duct tape  on the outside of a door - 97-98% 

Lowest-performing tape tested  on the outside of the door - 80% 

Sandbags  on the outside of the door - 70% 

Reduction in leakage compared with an unprotected door. Source: University of Hull (https://doi.org/10.5281/zenodo.23220942)

The research, commissioned by Flood Re, found that all four tapes tested (synthetic rubber, duct, aluminium and yellow plastic) kept out more water than sandbags. Tape is also cheaper, lighter, and easier to store and dispose of, whereas sandbags can become contaminated and begin to rot.

Further findings showed that tape applied to the outside of a door worked significantly better than tape applied to the inside, and that a standard outward-opening door leaked 74% less than an inward-opening one, even before any protection was added.

Tape isn’t a substitute for permanent flood resilience measures, but it offers a simple, affordable extra line of defence that can be put into place quickly.

The University of Hull focused its research on low-level flooding, at depths of up to 600mm. Deeper or faster-moving water may call for more robust protection. The wider lesson is that well-chosen, low-cost measures can cut losses, but only if there’s enough warning to deploy them in time.

Why this changes the “so what?” of an alert

When a flood is coming, the limiting factor is rarely equipment but is time. A roll of tape, like most flood defences, is only useful if someone knows to use it before water reaches the door.

That’s the gap property-level alerts close. Surface water flooding can develop quickly, and the Environment Agency estimates 4.6 million properties in England are at risk from it – a 43% increase on its previous assessment years before.

Low-depth flooding is exactly the kind of event where simple measures make the biggest difference. Combine an early, property-specific forecast with a roll of tape, and a flood alert stops being bad news and becomes a plan.

What to do when an alert arrives

A short, rehearsed checklist can make the difference between a prevented loss and a costly claim. When an alert comes in:

1. Tape the outside of doors. Seal along the bottom and up the sides, where water is most likely to get in. Synthetic rubber tape performed best, but everyday duct tape still cut leakage by 97-98%.
2. Don’t forget other entry points. Air bricks, vents and gaps around pipes can all let water in.
3. Move valuables and essentials up. Raise stock, equipment, documents and electricals off the floor where you can.
4. Fit any temporary barriers already on site. The University of Hull’s tests found that their performance ranged from full protection to failure, depending on the installer’s skill and how well the barrier fitted the doorway, so you should practise fitting them in advance.

None of this works without preparation. Keep tape, a torch, gloves and any other flood kit somewhere easy to reach, so no time is lost when the alert arrives.

In 2021, surface water flooding damaged ten bungalows owned by Southern Housing in Chatham, Kent, at a cost of around £1 million. After this event Southern Housing started using Previsico’s early alerts and when the same area faced another severe event in 2023, a Previsico alert gave the team 12 hours to prepare. Acting on their flood plan, they deployed defences in time and prevented 100% of flood impacts to the at-risk homes.

Rehearsal is key. Previsico clients can review past flood events in the Flood Intel Platform to see how water behaved at their sites, and then build their drills around real scenarios.

What it means for insurers, brokers and asset holders

The barrier to acting on an alert is lower than many people think, and the action doesn’t need a budget line. A flood action plan built around low-cost measures can be agreed in days.

For insurers, alerts paired with simple, practical guidance give policyholders a clear way to act, and give claims and risk teams early sight of where losses are likely to concentrate. Brokers can add real value by helping clients turn that guidance into a plan before the next event.

Asset holders can keep a flood kit at each higher-risk site, name who’s responsible for deploying it, and rehearse the response with little cost or disruption.

This matters because planning is where the gap is. Previsico’s State of Flood Resilience Report 2026 found that only 8% of respondents have flood action plans across all locations, down from 30% in 2025.

The University of Hull’s research will also inform Flood Performance Certificates, due to be piloted before the end of 2026, which will give owners and insurers a standard rating of a property’s flood resilience. Cheap, simple and verifiable measures could count.

Act before it costs you

A flood alert is only as valuable as what you can do with it. The University of Hull’s research shows that what you can do is often much simpler than you might think.

The question is whether you’ll know in time to use it.

To see what property-level warnings up to 48 hours ahead would mean for your site, request a demo.