A concrete box formed of reinforced concrete walls supported from a reinforced concrete raft foundation is the most common and preferred design where some or all of the structure is earth retained. If not waterproofed, the concrete structure is at risk of allowing water ingress where the concrete “isn’t”, through fine cracks, the construction joints/day work joints or through poorly compacted concrete. The use of an external, fully bonded membrane completely surrounding the structure can be a very effective means of preventing water ingress through joints and minor defects within the concrete.
Cracks within the concrete that are greater than the designed crack widths due to poor concrete compaction or insufficient steel reinforcing.
Cracks of 0.3mm and above are not deemed to be self-healing and the structure could suffer from slight water seepage.
Water seepage to the inner surface of the structure that may not be acceptable for the required habitable grade
Construction joints within the concrete due to raft size or complexity. Horizontal joint at the base of walls where supported by the raft, either with or without kicker.
Water seepage that could pressurise the internal finishes leading to severe impact on the internal habitable space.
Fully Isolating the Concrete Structure from Ground Water
Newton 403 HydroBond is a high performance composite sheet membrane that features a locking fleece to one side and a polymer hydrophilic coating to the other. When placed below the new raft, and to permanent formwork, the fibres of the fleece inner core are encapsulated into the concrete, forming a close and intimate bond. The membrane has excellent peel adhesion qualities and thus prevents water from tracking and the membrane from dropping away from the underside of the slab due to settlement. Newton 403 HydroBond has the ability to self-heal small holes due to the hydrophilic coating which expands when in contact with water. Where the formwork is removed, the walls are sprayed with Newton 108 HydroBond-LM a very flexible rubber membrane, overlapping the 403 HydroBond by 150mm at the toe and terminating to the DPC detailing at ground level, to fully envelop the structure with a continuous membrane, isolating the structure from ground water. Where it is not possible to spray Newton 108 HydroBond-LM due to space or other constraints, Newton 109-LM should be applied by brush or roller. This is a Type A Waterproofing System to BS 8102:2009.
Waterproofing the Construction Joints
Where construction joints to the concrete raft and concrete walls are unavoidable, Newton 303 PolyProof hydrophilic waterbar is placed midway within the joint and expands when in contact with water to seal joints against water ingress. The high polymer content of Newton 303 PolyProof ensures that the waterbar remains stable even when resisting high heads of water pressure over many cycles of use. At the compressed horizontal kicker joint, Newton 312 BentoProof waterbar is placed midway within the joint and expands when in contact with water to seal joints against water ingress. The bentonite rubber slightly emulsifies to seal further into the joint and into any surface inconsistencies between the two concrete faces to further seal against water ingress. At kicker-less horizontal joints, Newton 301 EasyProof, a metal waterbar, is fixed within the steel reinforcement and becomes buried equidistantly within the concrete of the walls and raft as a permanent barrier to water passing through the joint. Its textured surface bonds to the concrete to further emphasise the already torturous path to water.
This is a Type B Waterproofing Solution to BS 8102:2009.
The Newton HydroBondTM System fully isolates the concrete structure from ground water, preventing water ingress through non-structural cracks, minor defects and planned construction joints. Used in conjunction with Newton 303 PolyProof, Newton 312 BentoProof and Newton 301 EasyProof waterbars to further waterproof the joints, the most likely places for water ingress, the result is an effective, resilient and coordinated strategy that seals the structure against ground water. The above specification is accepted by the NHBC and fully conforms to NHBC Chapter 5.4 as Type A and Type B waterproofing.
Depending on the end use and habitable grade of the structure, the designer may decide that two or even three forms of waterproofing are required. A further form of waterproofing can be added to the design with the inclusion of Newton System 500, an internal cavity drain membrane system. Please see Newton Specification Sheet AC135 (for a Type C solution). If the structure was correctly designed and formed of reinforced concrete to BS EN 1992 (Eurocode 2) and of sufficient mass and quality to resist heads of water pressure as required by BS 8102: 2009, and the construction joints are correctly waterproofed as indicated above, the structure itself is recognised as being a Type B, integrally waterproof structure.