Duct Tape Beats Sandbags in University of Hull Flood Door Tests

Imagine a front door in a Hull test lab with floodwater coming up against it in 5cm increments. Without any protection the water just pushes right through the gaps in the frame. The engineers then go and put a good width of duct tape around the outside of the door and raise the water again. Almost nothing comes through.

That’s the surprising result of new tests by the University of Hull on behalf of Flood Re (the UK’s flood reinsurance scheme). Correctly applied duct tape on the outside of a domestic door reduced water ingress by 97 to 98% as opposed to an unprotected door.^[1][2] Sandbags, the long established symbol of flood defence, only managed around 70%.^[3]

How the duct tape flood protection tests worked

The experiments were carried out at PFRlab (Hull’s purpose built property flood resilience testing facility) with support from Flood Re and the Environment Agency.^[4] Six common door types were tested at water depths of up to 600mm.^[5] The water level was raised in 5cm increments to a maximum of 60cm and the amount of leakage at each stage was recorded.

For the sandbag test they stacked 54 sandbags with a plastic sheeting between the bags and the door.^[6] Even the weakest tape they tried outperformed that wall of sand, reducing the leakage by 80%.^[7] The best tape was the flood putty tape (the butyl type) which achieved up to 99% reduction in leakage and was as much as ten times more effective than the sandbags under the test conditions.^[8]

The tests revealed a few more useful engineering lessons. A standard outward opening door allowed 74% less water in than an inward opening one.^[9] Tape on the outside of the door was clearly superior to tape on the inside.^[10] With no protection at all, leakage through a standard door could easily reach tens of thousands of litres per hour at 60cm depth.

The real numbers are what make this interesting. It took about 10-20 minutes to tape each door and a roll of duct tape is £10 or less.^[11][12] Jonathan Kassian, Head of Flood Resilience at Flood Re, said it all in one go: “Sandbags are the archetypal flood defence but these tests completely overturn that.”

Why this matters in Hull

Hull knows all about flooding having seen over 8,600 homes and 1,300 businesses flood in 2007.^[13] The researchers are very clear that duct tape is not in any way a substitute for properly designed flood doors and barriers and will not prevent water getting in through the floor, the walls or the drains. It is, however, a quick and cheap first step for a household and one that is backed up by actual measurements rather than just anecdote. If you’re the sort of person who likes the idea of tackling real problems with actual tests and data then our guide on which engineering discipline is right for you is well worth a look.

What comes next

Tape is best for very shallow flooding at the door. Water will still find its way in through airbricks, walls, floors and drains and the temporary barriers are only as good as their installation. The next challenge for the flood engineers is to take results such as this and turn them into clear guidance and better permanent products so that when the water finally goes down the homes can get back to normal much more quickly.

What this means for you

Behind it all are civil and hydraulic engineers who work out how floodwater moves and the forces it exerts on buildings, and laboratory technicians who build and operate the test rigs (e.g. PFRlab). A lot of people in these roles come through a civil engineering degree or a degree apprenticeship and our guide on engineering degrees v degree apprenticeships will explain the difference. The pressure and flow calculations above are straight from the syllabus and that’s why an A-level in Physics is such a useful stepping stone into this type of work.