New Standards in Waterproofing of basements and other below ground structures

Raising standards and protecting home owners

Analysis of defects help to form a view of where the improvements need to be strengthened, to help the industry achieve robust construction that will stand the test of time. In the following piece, Mark Jones – Head of House-Building Standards at NHBC provides insight into the new Chapter 5.4: ‘Waterproofing of basements and other below ground structures’:

“In our experience, it is often a lack of appreciation that even the smallest defect in waterproofing can lead to problems that are both difficult to trace and expensive and disruptive to repair.

The new chapter introduces measures to address this including guidance on design, materials and workmanship.

This video provides an overview of the changes and outlines what you need to do if you are designing and constructing basements or other below ground structures.

The introduction of Chapter 5.4 is a key component in NHBC’s drive to improve basement construction. The industry needs to be getting it right first time, every time.

To develop the Chapter, NHBC initially called upon the valued expertise of their own technical staff. They subsequently set up a task group that enabled them to engage with all areas of the basement industry including builders, designers, manufacturers and regulators.”

Those involved in the steering group: Visqueen

Visqueen 1By setting up the task group and gaining the views of the industry, NHBC have ensured that the new Chapter is practical and robust. Importantly, NHBC have understood and addressed the real concerns of those dealing with waterproofing on a day-to-day basis.

When the technical content was agreed by the task group, the draft document underwent a wider industry consultation in advance of the NHBC standards committee approving the Chapter for publication and implementation.

The first important job of the task group was to define where waterproofing systems are needed, the types of structure usually requiring waterproofing ranges from full basements to situations where the external ground levels are raised to less than 150mm of the internal floor and where normal waterproofing arrangements would not provide suitable performance.

Designing waterproofing for below ground structures is often technically complex and the finished construction would always have high performance demands placed on it. An important part of the Chapter is the introduction of the waterproofing design specialists who should be appointed early in the design phase. They should co-ordinate with the designers of the other parts of the building, making sure that suitable materials and detailing are correct for the situation.

The Chapter provides guidance for the correct application of waterproofing systems such as;

  • Type A: Waterproofing Barriers
  • Type B: Structurally Integral Waterproofing
  • Type C: Drained Cavity Construction

As well as where a combination of two of these systems will be required, Waterproofing systems should be pre-defined and include important ancillary items such as pre-formed joints and junctions. Systems should be independently assessed in accordance with technical requirement R3. Where type C systems rely on pumps, these should include a primary and a secondary pump with backup battery or generator and a suitable alarm to indicate pump failure.

Waterproofing systems should be installed by trained operatives in accordance with the design and manufacturers recommendations. Where ‘Type A’ systems are used, particular care is needed to ensure that surfaces are suitably prepared to receive the waterproofing. Concrete surfaces should have latents removed and masonry surfaces should be smooth with pointed joints.

Completed waterproofing should be protected from on-going works. Detailed guidance about the waterproofing of basements and other below-ground structures can be found in the new Chapter.

To learn more about our market leading technical support service when specifying your next structural water proofing project, contact Visqueen and we’ll help you throughout every stage of your scheme, from specification to installation.

Contact the Visqueen team on 0333 202 6800 or send us your CAD details for review to

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