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Waterproofing Retaining Walls (on slab)



  • 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.


  • Prior to installation of concrete slab, install Colphene BSW directly on top of footing, extending a minimum of 300 mm under the slab.Ensure enough product is left so that Colphene BSW can be wrapped 200 mm up the retaining wall once it has been constructed.

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

  • Install a Gunable Waterstop around all penetrations. The waterstop must be packed in between at least a 50 mm cover of Mapegrout T40.

  • Mechanically fix the remaining Colphene BSW to retaining wall, then prime retaining wall, PVC and metal pipes using Soprema Elastocol Stick.

  • Install Colphene 3000 to Retaining Wall.

  • Lap Colphene 3000 onto penetrations, and then flash with Alsan Flashing.

  • Install Aluminium Pressure Seal at top of wall and flash with Sopramastic in order to terminate membrane.

  • Install Newton 408 EcoDrain to all waterproofed surfaces.

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

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

  • Backfill soil.