Importance of waterproofing design specialists highlighted in building warranty technical manual changes

Waterproofing design specialist

Building warranty providers, LABCW and NHBC, have recently updated their technical manuals with further changes to their requirements when it comes to basement waterproofing following the release of the latest British Standard for below ground waterproofing (BS8102:2022), last year.

Both LABCW and NHBC highlight the responsibilities of the design team and reiterate the importance of a qualified waterproofing designer (preferably CSSW) being appointed at a very early stage.

Functional requirements have been substantially revised and include a requirement that the developer provides a waterproofing design and specification, (including a site investigation report), 8 weeks before the commencement of the basement. 3 1

This is to ensure that the specific site conditions have been considered and the design is planned in advance; evidencing that all risks are catered for in the proposal.

These new changes to the requirements of basement waterproofing underline that standards are improving, and warranty providers are more convinced of the merits of having accredited and qualified waterproofing specialists involved where anything is built below ground.

Guaranteed waterproofing design & installation

As waterproofing design specialists, we hold the industry recognised CSSW qualification for individuals involved in designing waterproofing systems for structures below ground level.

In addition:


  • We can demonstrate competence in all aspects of structural waterproofing (and we have over 25 years of waterproofing experience)
  • We are a member of The Property Care Association and the structural waterproofing group
  • Our waterproofing surveyors have attained the Certified Surveyor in Structural Waterproofing (CSSW) qualification
  • Our waterproofing surveyors have an on-going commitment to continual skills development and actively participate in the PCA’s Continuing Professional Development (CPD) scheme
  • We hold professional indemnity insurance which specifically covers us for waterproofing design


By using RTC to specify your waterproofing system, you are complying with recognised guidance, ensuring the system is compliant with BS 8102:2022 and will meet the needs of your building warranty provider. As approved specialists, we are also able to give you the option of a genuine Insurance Backed Guarantees (IBG) for the waterproofing system; usually also a requirement of the building warranty provider.

What happens if you don’t use a waterproofing design specialist?

If you’re an architect or structural engineer, unless you have a specific waterproofing qualification, by designing the waterproofing yourself, you are going against the British Standard guidance. This makes you liable for any errors or failures, in some cases, even if the failure is due to bad workmanship by the installer, if you didn’t consider the ability to repair the waterproofing in this event. It’s now also highly likely your own PI insurance won’t include cover for waterproofing design. Picture1

Some waterproofing product manufacturers will offer ‘standard details’ or even specific assistance with waterproofing design on individual projects. However, this is very unlikely to extend to them taking design liability, so your neck is still on the line and you need to tread carefully.

Remember, BS 8102:2022 states:

“A waterproofing specialist should be appointed as part of the design team so that an integrated waterproofing solution is created.”

More specifically it recommends:

“If the RIBA Stages are used, a waterproofing specialist should be appointed before the technical design stage (STAGE 3) at the latest.”

BS 8102:2022 ‘The Code Of Practice For Protection of Below Ground Structures Against Water Ingress’

Some of the changes to the standard are subtle and some can be contentious. The most important change in our view is the title. Previously, BS 8102 specifically mentioned ‘water from the ground’. As you can see from the title above, it is now concerned with protection against ‘water ingress’. A small change, but it means the waterproofing designer may be liable for water ingress caused by localised flooding or a burst mains water pipe for example. Is this considered in your design? Basement waterproofing

Some other previously agreed methods such as sandwiched waterproofing are now not allowed, so previous specifications may not now be appropriate. There is now almost always a requirement to use two different forms of waterproofing and this is reiterated in both the NHBC & LABCW technical manuals.

Remember, design liability should be placed with the experts. That’s us by the way…

To have a look at our accreditations, please click here.

To have a look at our qualifications, please click here.

To read the LABCW technical manual version 11, please click here.

For any queries on our services, or to book a survey, please contact us.

Our staff will work closely with you from survey stage, right through to the successful completion of the contract.