Waterproofing A New-Build Basement

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Above: Newton Waterproofing Systems were used to waterproof 193 houses and apartments in a Crest Nicholson housing development in Sunbury-on-Thames. Insert: Newton 403 HydroBond installed to provide Type A (Barrier) protection.

Implications of British Standard 8102 for Waterproofing A New-Build Basement

In deciding the method for waterproofing a new-build basement it is advisable to follow the recommendations within BS 8102:2009 ‘Code of Practice for Protection of Below Ground Structures Against Water From the Ground’. The standard advises on the types of waterproofing available and confirms the performance grade to be achieved:

Types of Waterproofing:

• • Type A (Barrier) protection – A barrier to water ingress is applied to the inner or outer surface of the structure
  • Type B (Structurally Integral) protection – The structure is formed as a watertight construction and requires no additional protection
  • Type C (Drained) protection – Water entering the structure is received by planned cavities or voids and safely removed

Grades of Waterproofing Protection:

• Some water seepage and damp is tolerable depending on the intended use – Car parks, plant rooms etc.
• No water penetration is acceptable. Damp areas are tolerable depending on the end-use – Plant rooms, workshops etc.
• No dampness or water penetration is acceptable – Ventilated residential and commercial areas such as homes, offices, shops etc.

The different grades of waterproofing: What is a dry basement?

Recommendations From BS 8102:2009

Site Investigation Regarding Geology, Hydrogeology and Topography

Where a comprehensive site investigation is not possible, or the results are inconclusive, the designer should design both the structure and the waterproofing of the structure to be able to deal with a full head of hydrostatic water pressure – or in layman’s terms, full saturation of the ground.

It is also important to consider that ground investigations are a snap-shot in time of the ground water levels, and many factors can influence these levels. One such example is a perched water table that only occurs after heavy and prolonged rainfall, or during a water-pipe burst. It is therefore always safer to assume that a full head of water pressure will come to bear at some point, and at Newton, all of our waterproofing specifications are designed to deal with fully saturated ground and full height water levels.

Inclusion of a Waterproofing Specialist as Part of the Design Team

A “Waterproofing Specialist” should be included as a part of the design team so that an integrated waterproofing solution is created. All design decisions made by others that might have an impact on the waterproofing design should be brought to the attention of the waterproofing specialist/designer or installing contractors. Final decisions and any recommendations should be approved by the specialist waterproofing designer/contractor.

Combined Waterproofing Systems

Consideration should be given to combining two or more of the Type A, B and C waterproofing systems, where in a single scenario:

• The likelihood of leaking is high
• The consequences of leakage is unacceptable, or
• Additional vapour checks are necessary for a system where unacceptable water vapour transmission could otherwise occur.
• The decision to use a combined approach of two or more types of waterproofing will always be based up on a risk vs cost calculation. Furthermore, other factors will often dictate the use of a second or third type of waterproofing, such as ground gasses or aggressive agents found within the ground water.

Newton Combination Waterproofing Solutions

When designing the waterproofing for other structural elements that require protection, for example on podium decks, pile caps etc., in all such situations these building elements can be successfully waterproofed using Newton products, often using a combination of systems.

Newton Specialist Basement Waterproofing Contractors

Whether waterproofing a new-build basement or an existing structure, we will always recommend that the preferred waterproofing system be installed by one of our registered contractors.

When involved in the design they are able to offer insured guarantees for both the installation and the design of the waterproofing system, and with most of our contractors having suitable Professional Indemnity, this allows you to delegate the full design liability for the waterproofing aspect of the project to them. Newton Specialist Basement Contractors are able to fulfil the role of waterproofing specialist as suggested by BS 8102:2009 and we see that waterproofing contracts run more smoothly and have fewer issues where one of our NSBC contractors are also the waterproofing design specialist on the design team.