RLA 2 Part Cementitious Waterproofing Membrane

RLA 2 Part is a two-part flexible cementitious waterproofing membrane based on fast-setting high-alumina cement and a high-solids acrylic liquid. It is designed as an under-tile Class II system for balconies, roofs, wet areas and selected swimming-pool applications with strong adhesion to concrete, screeds and fibre-cement substrates.

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How it works

This two-component membrane cures to form a Class II flexible barrier with 214% elongation. It is independently tested to AS4858 and AS 4654.1 for internal and external wet areas, allowing a single product to span across interior shower trays, exterior facade walls, and fully submerged environments. The cured tan film provides an exceptionally stable keying surface for direct fixing of tiles using polymer-modified adhesives, or for laying sand-cement screeds. It is also tested to AS 4020 for contact with potable drinking water, making it suitable for concrete retention tanks and storage facilities.

Numbers that matter

• 1.2mm minimum dry film thickness (DFT): Achieved by applying a minimum of two coats at 0.75mm wet film thickness (WFT) per coat, ensuring reliable barrier performance under tiles or toppings.
• 1.5 litres/m² minimum coverage: The minimum required application rate across two coats to meet certified waterproofing thickness standards. One 40kg kit covers approximately 23m².
• 24-hour tile window: Allows tiling or screed application to commence just 24 hours after membrane application under standard conditions (23°C and 50% RH).
• 7-day full cure: The required curing window before filling ponds, pools, or water features for continuous immersion.
• 1-hour pot life: The working window of the mixed material at 23°C before it begins to set in the pail.

Where to use it

Suitable for installation over the following structurally sound and prepared substrates:

• Concrete (cured for at least 28 days)
• Cement render and sand-cement screeds (cured for at least 7 days)
• Compressed fibre cement sheeting and plasterboard
• Masonry and brickwork (pointed flush)

Required priming systems

The membrane must be applied over primed surfaces. Match the primer to the substrate condition:

• Porous and absorbent surfaces: Apply 1 to 2 coats of RLA Porous Primer at 1 litre per 8m² per coat.
• Non-porous surfaces: Apply 1 coat of RLA Non Porous Primer at 1 litre per 8 to 10m².
• Damp substrates or residual moisture: Where testing shows >80% RH (ASTM F2170) or >5% moisture content (ASTM F2659), apply 1 to 2 coats of RLA Moisture Seal barrier at 1 litre per 4m² per coat.

Joint detailing and system components

Different joint-sealing and bondbreaker options apply depending on whether the installation is dry, wet, or fully immersed:

• Immersed applications (pools, ponds, tanks): Must use Elastoproof Joint Band and Corners embedded in the wet first coat for bondbreaker transitions. Use Elastoproof Collars for pipes and penetrations.
• Non-immersed applications (bathrooms, balconies, facades): May use BRW PF Tape for bondbreakers, joints, and penetrations. RLA Max SMP 25 can be used to seal leak control flanges, penetrations, and to fill static cracks from 1mm up to 6mm flush before coating.

Limitations

• Do not apply when ambient or surface temperatures are below 5°C or above 35°C.
• Do not apply if rain is falling or imminent.
• Not suitable as a final trafficable wearing finish.
• Must not be left exposed in swimming pools or spas; the membrane must be tiled over.
• Do not use in areas subject to negative hydrostatic pressure.
• Do not mix the powder and liquid components by hand; an electric stirrer with a paddle mix attachment is required.