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A-03 External Waterproofing of Block Walls

external waterproofing of block walls

Newton Waterproofing Index Score

This solution has the capability of achieving an NWI score of 3.0, by employing 1 form of waterproofing (Type A – Barrier Protection) to prevent ground water passing through to the structural elements of the building.

Newton Waterproofing Index 1.1 - 3.0

Recommendations & Standards

Although a ‘Type A’ waterproofing membrane provides a form of waterproofing, it should be understood that the risk of water ingress due to installation defect is reasonably high and so, as advised with BS 8102:2009, consideration should be given to the use of combined protection where the risk of water ingress or dampness is unacceptable.

Contingency planning for dealing with any localised defects or system failure that arise should be included as part of the overall water-resisting design for the structure and the issue of repair-ability should be taken into account and the feasibility of remedial measures assessed. Consider re-usable injection waterbar systems and internal ‘Type C’ waterproofing.

For more information about NWI scores and how they can help with your project design, read our page explaining the Newton Waterproofing Index and how it works.

Type A – Provide a Complete and Continuous Waterproof Barrier to the External Surface


Install Newton 403 HydroBond below the slab. Newton 403 HydroBond is a high-performance composite sheet membrane featuring a locking fleece and a polymer hydrophilic coating.

Type B – Prevent Water Ingress Through the Construction Joints and Service Penetrations

Fit Newton 301 Easyproof to the reinforcement steel so that after concrete placement, the waterbar is fully embedded within the two adjoining elements. Then install the high-grade, hydrophilic Newton 315 Polymer-Waterbar at the centre dimension of joints to provide the most protection to the key critical construction joint.

Please note: Whilst this specification utilises Type B waterproofing products as described above, concrete underpinning does not and cannot qualify as a Type B form of waterproofing due to the number of construction joints and, as a result, the increased risk of water ingress.

Type A – Continue the Complete Waterproof Barrier to the External Walls

Linking from the Newton 403 HydroBond below the raft, continue the waterproofing externally by applying the Newton HydroBond System to the external face of the retaining walls using Newton 108 HydroBond-LM, a spray-applied liquid membrane that cures almost immediately, or Newton 109-LM, a hand applied version used where it is logistically difficult to use a spray machine.

Further Information

To improve the NWI score and provide a Grade 3 environment install the Newton CDM System as per Newton Solution AC-03.

For more information regarding this specification, or to find a specification suitable for your project, please fill out the form below or email our Technical Team at tech@newtonwaterproofing.co.uk.

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