WP104 Waterproofing – Retaining Walls on Slab Edge (Spray Applied)


  1. 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 a minimum of 28 days.
  2. External corners to be waterproofed must be bevelled to ensure a smooth transition of membrane from vertical to horizontal surfaces.


  1. Repair all surface defects on retaining wall masonry surfaces with Aftek Penapatch Structural HB80.

    Aftek Penapatch Structural HB80 is a high strength; high build shrinkage compensated structural repair mortar.

  2. Install a Gunnable Waterstop around all penetrations. The waterstop must be packed in between at least a 50mm cover of Aftek Penapatch Structural HB80.

    Gunnable waterstop products are caulk-grade, single-component swelling pastes used to stop water infiltration through concrete construction joints.

  3. Install an appropriate fillet (bond breaker) to all transitions and pipe penetrations using WPA FC.

    WPA FC is a high-performance, fast-cure, one-component polyurethane sealant.

  4. Apply WPA SB primer to some non-porous surfaces such as PVC and metal pipe penetrations using the 2-cloth method. (The 2-cloth method is carried out as follows: dampen a clean cloth with an appropriate amount of WPA SB primer, and wipe evenly over the non-porous substrate utilizing a rubbing action. With a clean dry cloth, immediately remove all primer residues by implementing a buffing action).

    WPA SB is a fast-drying, solvent-based primer, with exceptional penetrating properties. WPA SB primer is designed to assist in improving adhesion on porous and some non-porous substrates.

  5. Apply WPA 560 or WPA 3460 primer to the substrate being waterproofed.

    WPA 560 is a two-part, water-based epoxy primer, designed as a water and vapour-proof coating under waterproofing membranes.

    WPA 3460 is a single-component primer based on polyether polyol and modified MDI isocyanate.

  6. Apply WPA 3400 membrane to the external side of the retaining wall.

    WPA 3400 is a two-component, 100% solids, rapid curing, spray applied, hybrid polyurea, and elastomeric waterproofing membrane.

  7. If the membrane is required above ground level, Install an appropriate fillet (bond breaker) to all transitions using WPA MS or WPA SPUR.

    WPA MS is a single-component, moisture-cured silane-modified hybrid sealant.

    WPA SPUR is a high-quality, professional, universal, low-modulus sealant based on hybrid technology.

  8. Apply WPA 460 or WPA 560 primer to the substrate with a minimum 150mm overlap onto the WPA 3400 membrane.

    WPA 460 is a two-part, water-based epoxy primer, used to seal concrete and masonry surfaces.

    WPA 560 is a two-part, water-based epoxy primer, designed as a water and vapour-proof coating under waterproofing membranes.

  9. Apply WPA 230UV membrane to the above-ground surface, ensuring that the first coat has completely dried before applying the second coat.

    WPA 230UV is an elastomeric, fibre-reinforced, water-based polyurethane membrane system designed for exposed or under-tile applications.

  10.  Install WPA Drainage Cell on all waterproofed surfaces below ground level.

    WPA Drainage Cell is a two-core drainage sheet consisting of a non-woven geotextile filter layer thermally welded to a water-impermeable, recycled HDPE (High-Density Polyethylene) drainage membrane.

  11.  Install slotted drainage pipe wrapped in geotextile next to the slab edge.
  12.  Cover the drainage pipe with a minimum of 300mm of gravel and cover gravel with an additional geotextile filter layer.
  13.  Backfill with clean material.