Hi there,
Welcome to Episode 16 of ‘Waterproofing Wisdom’ – our monthly email. In this email I cover:
- Technical – The hidden risks of placing structural waterproofing design within the engineer’s scope
- Recruitment – we’re looking for a Practice Director, if you know of anyone please do pass this on
- Waterproofing Risk Review – we’ve created an app for assessing basement waterproofing risks.
I think this content will be especially relevant to Project Managers and Architects.
You can watch the short 5-minute video below, or read on for the highlights.
Introduction
In this episode, I reflect on a major project failure I was tasked to review as an expert witness, where a critical design error—stemming from a lack of specialist knowledge—led to serious consequences. It highlights the dangers of relying on generalist engineering teams for specialist waterproofing tasks.
I also touch on more common challenges I see regularly: misjudged risk assessments, incorrect grading within basements, and a general lack of future-proofing in designs.
Waterproofing Wisdom
These are avoidable issues, and the NHBC’s guidance is clear—waterproofing design should be led by qualified professionals, ideally those with CSSW credentials and inclusion on the PCA’s Waterproofing Design Specialist Register.
Closing Comments
At CLW, our team bring both the technical qualifications and the hands-on experience to get waterproofing design right from the outset.
Involving Specialist Waterproofing Consultants early can prevent costly errors later.
If your projects involve below-ground structures or you’re simply looking to reduce design risk, I’d be happy to discuss how we can support you.
Many thanks,
Ben Hickman
Technical Director
CSSW London Waterproofing
0207 458 4073
info@cssw.london
Well hello, and welcome to another episode of ‘Waterproofing Wisdom’. My name is Ben, I am the Technical Director of CLW, and this time, I wanted to talk about ‘The Hidden Risks of placing Structural Waterproofing Design in the Structural Engineer’s scope’. I wanted to give you an example from many years ago – and I cannot go into details – but I was an expert witness for a project that went very badly wrong in the Middle East.
After many hundreds of hours of reviewing and understanding what had happened, what went wrong, what it came down to most extremely was a water bar. And the water bar had been designed and drawn by a Structural Engineer from a major waterproofing – sorry – a major general engineering consultancy which no longer exists. This water bar had been taken to the underside, and up the sides, and then over the top of culvert. These culverts were fairly long and they had to have some movement joints in them, hence the water bars on the movement joints and unfortunately this Structural Engineer was a Structural Engineer, and not a Waterproofing Specialist, and he took that water bar under the culverts, up the sides and over the top. The problem with all of that is that this water bar on top of a culvert is never going to work and a lot of people within the waterproofing industry would know that very quickly, but unfortunately this was a generalist engineer. The issue being that if you invert this, turn it upside down, the air can’t get out from between these fingers or ribs and that means that the concrete can’t get in, and what you end up with is a lot of voids -and once that’s underwater, a lot of water can come in.
That’s a very extreme example, more common sort of things that we would see is just, poor understanding of risk assessment, poor assessment of what grade is really needed where within a basement, more nuanced things where an engineer thinks about hydraulic gradient in terms of where is the water table now, whereas we would think about where could it be in the future…some of those sorts of things. I guess I would want to articulate that a Structural Engineer in reality is unlikely to be a qualified waterproofing person, and – I’ve taken this from NHBC’s Technical Manual – and here it will talk about ‘the Waterproofing Design Specialist should be appointed early’, and it should be somebody who has got, for example, a CSSW qualification or better yet, and on the scale of the projects that we work on, it really should be somebody who is on the waterproofing design specialist register, that’s held by the PCA. That is somebody who has been through the training, been through the qualification to get the CSSW, and then later gone through a peer review process looking at two of their example projects. And that is something that we would have at CLW, and lots of other specialists within the industry would have but it’s very unlikely that if you go to one of the major engineering consultancies the person doing any of the waterproofing design is unlikely to have that qualification, or indeed anything similar, and whilst they are extremely well qualified and will be a Chartered Engineer, that’s not the same as being a Chartered Engineer and having done a deep dive on this and being examined on this, and then being peer reviewed on Structural Waterproofing.
So, my appeal is to a) Structural Engineers, saying – do not take something on if it is not your area of expertise, or, if you are going to do that, take on some sub-consultancy advice. Or, if you are a major developer, and your project has a big waterproofing component in a basement, come to somebody like ourselves. With that comes the niche expertise and the qualification.
I do a lot of expert witness work, so I am always learning from mistakes, and seeing what goes wrong, and trying to correct for that. Also I guess I would really encourage you to recognise the value – although we might cost however many tens of thousands of pounds, how much of that do you recoup through better tender processes where the main contractor isn’t doing some risk mitigation, and adding in a percentage for uncertainty.
So, there is my episode of Waterproofing Wisdom, if you ever want to get in touch and talk about basement waterproofing, please do, I would love to hear from you!
Thank you.