The scope of this project was to provide an effective, maintainable, and robust waterproofing solution to a below ground extension and underground garage to a residential home in Suffolk.

Delta Registered Installers, Oaks Damp Proofing Co Ltd along with Delta’s Technical Sales Consultant Paul Callaghan, were appointed as Waterproofing Specialists to undertake the waterproofing design and installation of the waterproofing solution.

Basement extensions provide opportunities for increasing a property’s footprint.  Basement extensions have the potential to enhance living circumstances, from storage to additional bedrooms or pleasurable spaces, such as games rooms, libraries, or swimming pools. All structures, however damp, degraded or contaminated can be retrofitted into a dry, fully functioning habitable space.

Whether retrofitting a waterproofing system or installing a new waterproofing system, BS 8102:2022 protection of below ground structures against water ingress. Code of Practice should always be incorporated into the waterproofing design.

The qualified waterproofing design was to achieve grade-3 level and to incorporate two forms. Combination waterproofing systems (two forms) can offer optimal structural protection against water ingress.  Where a combination of waterproofing protection is being used, the two systems should offer different performance characteristics to mitigate the risk of failure due to a common cause. The compatibility of the different protection types should be assessed in order to minimise the risks and negate the need for remedial measures.

A combination of two forms of waterproofing is preferred when designing a habitable space.


Pre site inspections were carried out along with consultations with the main contractor (Seaman’s Building Contractors), to ensure the waterproofing design not only meets BS 8102:2022 but also the client’s expectations.

The proposed two forms of waterproofing were Type A and C:

  • Type A is defined as ‘barrier protection’. A material is used to offer a barrier to the passage of water.  A barrier protection which physically holds water back on either the positive side of a below ground level structure (externally), the negative sides (internally) or sandwiched into the construction.  Cementitious coatings, bituminous coatings or flexible sheet membranes are categorised within Type A ‘barrier protection’.
  • Type C is defined as “drained protection” and functions by diverting a passage of water away from the structure (which is usually collected into a submersible pump).  A drained cavity system collects and manages any moisture which breaches the integrity of the structure by channelling, collecting, and discharging such free water via a suitable evacuation point. A Type C waterproofing system will not increase or exert water pressure on a structure nor alter the dynamics of a structure.

As the name implies, Type C, Cavity Drained Waterproofing provides a ‘drained protection’. Drained Protection is often required when any earth retaining wall is subject to hydrostatic pressure.

Delta’s Type C membranes are textured, breathable membranes which are installed to the entire inside of a basement.  Delta MS 500 was installed to all wall areas, with Delta MS 20 installed to all floor areas.

Part of this ‘controlled system’ is basement drainage.  Any water ingress which penetrates the basement, is directed into perimeter drainage channels which this then efficiently disperse to a sump pump station.  Once collected in the sump pump chamber, the water is then pumped to a suitable evacuation point.

The incorporation of a new basement slab allowed for easy installation of the Delta Dual V4 Sump Pump and perimeter drainage channel.

To accommodate the underground garage lift pit and any potential surface water run-off from the lightwell an additional Dual V4 packaged pumping station was incorporated into the design.  Underground garages are a unique technology of cars and motor vehicles underground storage, which allows to increase the number of parking spaces in private households and small offices.


Oaks Damp Proofing Co Ltd and Delta’s Technical Team delivered an exceptional waterproofing design and installation for the client, who now has a watertight and guaranteed basement beneath their home.

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