Sheet, liquid, bentonite — expert guidance from Sydney’s approved waterproofing specialists.
A waterproofing membrane is a thin, continuous barrier applied to a structure to prevent water ingress. In Sydney, where heavy summer storms and ageing concrete are facts of life, choosing the right membrane is the difference between a dry building and a costly water damage claim.
At Econyc we have installed waterproofing membranes on hundreds of residential and commercial projects across Sydney — from Parramatta basements to CBD podium decks. This guide explains every major membrane type, where each performs best, and how to choose correctly.
Factory-controlled thickness for large flat roofs, podium decks, and below-slab applications. Heat-welded seams for a uniform, inspectable membrane to AS 4654.2.
Seamless elastic film applied by brush or roller. Perfect for balconies, wet areas, and complex geometry with penetrations, drains, and wall-floor junctions.
CETCO Voltex and Tremco Paraseal — self-sealing panels for blind-side retaining walls, below-slab, and basement waterproofing. Econyc is an approved applicator for both.
Waterproofing membranes fall into three families: sheet-applied, liquid-applied, and cementitious / crystalline. A fourth specialist category — bentonite clay systems — is used almost exclusively for below-grade applications like retaining walls and basement blind-side waterproofing.
Sheet membranes are factory-manufactured rolls — typically 2–4 mm thick — of bituminous, PVC, TPO, or HDPE material. Ideal for large flat roofs, podium decks, and below-slab applications where uniform, inspectable thickness is essential. Seams are heat-welded or cold-adhesive bonded; penetrations require purpose-made collars.
Best for: Large flat roofs and podium decks (AS 4654.2). Below-slab and retaining wall applications where the membrane is protected by drainage board or structural fill before concrete is poured.
Applied by brush, roller, or spray as a wet fluid that cures to a seamless, elastic film. Common chemistries include polyurethane, acrylic, polyurea, and rubberised bitumen. The seamless nature makes them ideal for complex geometry — balconies, wet areas, drains, and penetrations.
Minimum DFT: 1.0 mm for internal wet areas (AS 3740), 1.5 mm for external exposure (AS 4654.1). Econyc verifies DFT with calibrated wet film gauges on every job.
Cement-polymer slurries trowelled or brushed directly onto concrete. They handle negative-side water pressure — water pushing from outside in — that would delaminate sheet or liquid membranes applied to the positive face. Crystalline products (Xypex, Kryton) self-seal cracks up to 0.4 mm by forming insoluble crystals in the concrete matrix.
Sodium bentonite panels (CETCO Voltex, Tremco Paraseal) swell on contact with water to form an impermeable barrier. Econyc is an approved applicator for both products. Used for blind-side waterproofing, below-slab applications, and retaining walls under heavy groundwater pressure.
| Application | Recommended Membrane | Standard |
|---|---|---|
| Internal wet area / bathroom | Liquid polyurethane or acrylic | AS 3740 |
| Balcony / terrace (trafficable) | Liquid polyurethane + screed | AS 4654.2 |
| Flat roof (non-trafficable) | Sheet bituminous or liquid polyurea | AS 4654.1 |
| Basement — new build (positive) | Sheet or liquid + drainage cell | AS 3600 |
| Basement — retrofitted (negative) | Bentonite panel or crystalline | AS 3600 |
| Retaining wall (below grade) | Bentonite sheet (Voltex / Paraseal) | AS 4678 |
| Water-retaining structure | Crystalline admixture + cementitious | AS 3735 |
Insufficient DFT: The single most common failure. Econyc specifies DFT in every quote and inspects mid-installation with calibrated gauges. Missed terminations: Every installation uses purpose-made termination bars and flashing at wall junctions and penetrations. Wrong product for substrate movement: We match elongation at break to the substrate’s expected movement range before specifying any membrane.
Prices vary with substrate condition, access, required thickness, and penetration complexity. Contact Econyc for a fixed-price site-specific quote.
Free site inspection · Fixed-price quote · 10-year workmanship warranty