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Waterproofing of Retaining Walls with WPA 880

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Preparation:

  • All surfaces to be waterproofed must be firm, clean, dry, sound and smooth. All grease, oil, wax, curing compounds, loose material, paint and any other contaminants must be removed, masonry surfaces must be pointed flush and surface defects repaired. New concrete must be cured for minimum 28 days.

  • External corners to be waterproofed must be bevelled to ensure a smooth transition of membrane from vertical to horizontal surfaces.

Installation:

  • Repair all surface defects on retaining wall masonry surfaces with Mapefill GP.

  • Mapefill GP is a general purpose non-shrink grout recommended for grouting voids in structural elements.

  • Install a 40mm x 40 mm fillet to the internal corner of wall and footing using Mapegrout T40. Preferably extend fillet to outside edge of footing to prevent pooling of water. Mapegrout T40 is a medium strength (40 MPA), fibre reinforced, thixotropic grout for repairing concrete. Mapegrout T40 can also be used to repair surface defects in masonry building elements.

  • Install a gun-able water stop around all penetrations. The water stop must be packed in between at least a 50 mm cover of Mapegrout T40. Gun-able water stop products are caulk grade (gun-able), single component swelling pastes used to stop water infiltration through concrete construction joints.

  • Apply WPA 560 primer. WPA 560 is a water based 2 part epoxy primer designed as a water and vapour proof coating under water proofing membranes and / or adhesives.

  • Apply WPA 880 Tanking to side and top of retaining wall, ensuring that the first coat has completely dried before applying second coat. WPA 880 Tanking is a chemically modified waterborne flexible waterproof membrane designed for use in demanding external waterproofing applications.

  • Install Newton 408 EcoDrain to all waterproofed surfaces. Newton 408 EcoDrain is a two-core drainage sheet consisting of a non-woven geotextile filter layer, thermally welded to a water impermeable HDPE (High Density Polyethylene) drainage membrane.

  • Install slotted drainage pipe wrapped in Geotextile next to footing and below fillet level.

  • Cover drainage pipe with a minimum of 300 minimum of gravel and surround gravel with additional Geotextile filter.

  • Ensure that membrane which extends above soil fill level is protected from UV damage by selected surface finish or capping material.

  • Backfill soil.