Is it time for waterproofing & flooding to work together?

No doubt many of our members will have seen the horrific news coming from New York last week where at least nine people tragically died, eight of whom were residents trapped in basement apartments as a result of flash flooding form Storm Ida.

I will not pretend for a second that the events of London and New York are directly comparable. America certainly has more extreme and volatile weather than the UK for a start. Both London and New York have a large number of basement flats and whilst London has its share of poor housing, it is estimated that New York has some 50,000 illegal basement flats which are very poor quality housing and don’t meet the relevant safety codes.

Despite the differences, some of the images coming out of New York were eerily similar to those from London just a few weeks prior. Flooded underground stations being a particularly common theme with both events being accredited to the ‘new world of extreme weather’.

Thoughts & experiences from PCA members…

Last month I wrote about the horrific flooding events in London (Flooding: Do we need to change our approach to Basement Design?), asking the question:

“given that most will now acknowledge that the threat of global warming and more extreme weather is accepted as a proven reality, should we be giving this more consideration in our waterproofing designs?”

We also asked PCA members the same question at a recent Structural Waterproof Group meeting. I have since taken the opportunity to speak to many waterproofing specialists in the sector and discuss their thoughts and experiences following the recent flood events and how it had impacted them.

Unsurprisingly, many reported a number of call outs in the days following reports of flooded basements. Thankfully, every PCA member I have spoken to on the topic said that not one of the basements they have waterproofed was compromised or impacted by failed waterproofing.

What considerations should we be giving?


Drainage seemed to be one of the most significant considerations. Consideration should be given to avoid soakaways that become full due to the saturated ground, and not accept any more water. A number of horror stories were mentioned where pumps had been connected to soil stacks and had resulted in sewerage entering high end basements.


Another common theme for concern was thresholds into light wells. A modern desire for level thresholds for improved accessibility, particularly in newer properties, means there is little to no resistance to water ingress through penetrations. In one scenario, the glazing did resist water ingress until the water built up to approximately 1.5m against a window and then ultimately the weight of the water became to much and the glazing gave in!

Caveats to protect you

A number of you indicated that you have caveats within your T&C ‘s to protect you against the possibility of flood water coming over the top of a waterproofing system. Clearly, this acknowledges the possibility of an issue – why protect yourself against it? But it also seems that the events of the last few weeks have given much of our industry food for thought.

Guidance documents

What about guidance? Well the ‘waterproofers bible’, BS 8102, is currently being revised with a proposed new title: ‘Code of practice for protection of below ground structures against water ingress’. A change from water from the ground. Is this a suggestion that consideration of all sources of water should be given?

Waterproofing & Flooding Sectors working together?

So should we now start giving more consideration to how we can stop water coming not just through a waterproofing system, but how we can stop it getting through other areas of penetrations too? Then we need to start asking questions about how comparable flood systems are to waterproofing systems…? Could this be an area that requires the collective thought of both sectors…?

At the end of the day, as specialist PCA members, we are looking to provide our clients with dry basements. They do not want to be stood knee deep in water, regardless of whether that water came from the ground, or over the top, or through the door…

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