Gripset C-1P

Gripset C-1P is a one-part, fibre-reinforced flexible cementitious waterproofing membrane for positive and negative waterproofing. It is designed for concrete and masonry structures, under-tile areas, basements, retaining walls, pools and water-retaining structures, including applications subject to hydrostatic pressure.

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What it does

Gripset C-1P cures to form a flexible, non-toxic waterproof barrier. It bonds directly to concrete, render, masonry, compressed fibre cement sheeting, plasterboard, and aerated concrete panels. Because it withstands both positive pressure (up to 5 bar) and negative pressure (up to 1.5 bar), it prevents water ingress in deep underground spaces like lift pits and earth shelters where external access is impossible. It is approved to AS 4020 for potable water storage, making it suitable for internal tank linings. The polymer-modified chemistry allows application over damp and green concrete without compromising adhesion, and it is fully compatible with polymer-modified tile adhesives and screeds.

Numbers that matter

• 5 bar positive / 1.5 bar negative resistance: Prevents water penetration under significant hydrostatic pressure on both the internal and external sides of retaining structures.
• 2mm minimum dry film thickness (DFT): The required cured thickness to ensure waterproof integrity, achieved in 2 coats by flat trowel or 3 coats by roller.
• 37% elongation (Class 1, AS1145.3): Provides the flexural capacity and crack-bridging capability (≥0.75mm under ISO13007-5) required to absorb movement across construction junctions and blockwork.
• 10-day immersion window: The necessary cure time at 23°C and 50% RH before water features, tanks, or pools can be safely filled.
• 1-hour pot life: The working window to apply the mixed slurry by brush, roller, or trowel before hydration limits workability.

Limitations

• Do not apply when surface or ambient temperatures are below 5°C or above 35°C, or if rain is imminent.
• Not to be applied over standing water. For vertical surfaces with running or dripping water, leaks must first be stopped with Gripset C-Plug.
• Must not be left as an exposed coating in swimming pools or spas; it must be tiled over.
• When detailing joints and penetrations, note that BRW PF Tape, RLA Max SMP 25, and Butyl Squares are not suitable for immersed applications.

Where to use it

Gripset C-1P is suitable for commercial, industrial, and residential applications on the following substrates and structures:

• Substrates: Concrete, render, masonry, compressed fibre cement sheeting, plasterboard, and aerated concrete panels or blocks.
• Structures: Lift pits, basement walls (both internal and external sides), retaining walls, planter boxes, slab edges, general landscaped areas, feature walls, and water tanks.
• Applications: Waterproofing under tiles and pavers in external wet areas, internal bathrooms and laundries, and sandwich sealing between existing and new concrete toppings.

How to apply

Substrates must be clean, sound, and free of laitance, curing compounds, and contaminants. Grind or abrade structurally unsound layers. Concrete must cure for 28 days and cement render for 7 days before application. Non-porous or burnished concrete surfaces must be mechanically abraded, cleaned, and pre-dampened, or primed with Gripset OP Primer at 1 litre per 10m². Porous mineral substrates must be pre-wetted with a light water mist, leaving no standing or ponding water.

Mix only with an electric stirrer and paddle; do not mix by hand. Always add the dry powder to the water to prevent clumping. Allow the mix to settle for 2 to 3 minutes, then re-stir lightly before application. Apply coats in alternating directions using a wet film gauge to monitor coverage.

• Roller or brush application: Mix 4.2 litres of water per 15kg bag (or 1 part water to 3.5 parts powder). Apply in a minimum of 3 coats to achieve the 2mm minimum DFT. Yields approximately 7m² per bag.
• Trowel application: Mix 3.0 litres of water per 15kg bag (or 1 part water to 5 parts powder). Apply in a minimum of 2 coats using a flat trowel to achieve the 2mm minimum DFT. Yields approximately 5.5m² per bag.

Detailing and system components

All joints, junctions, penetrations, and cracks must be detailed prior to applying the overall membrane:

• Joints and transitions (AS 3740 & AS 4654.1): Bed Elastoproof B50 Joint Band into a 150mm wide wet coat of Gripset C-1P, brush out all air pockets, and encapsulate with a second coat. Alternatively, apply self-adhesive BRW PF Tape centrally over the joint.
• Pipes and penetrations: Fit Elastoproof Collars over the pipe neck into the wet membrane, or create a flange using a cut length of BRW PF Tape. Alternatively, seal the penetration base with a bead of RLA Max SMP 25.
• Static cracks (1mm to 6mm): Fill flush with RLA Max SMP 25 and overlay with RLA Waterproofing Bandage, Elastoproof B50 Joint Band, or BRW PF Tape.
• Tiling and toppings: Tile directly with polymer-modified cement-based adhesives such as Gripset C-Lite, C-Mastic, C-Rubber, or C-Stone. If applying a screed or render topping, incorporate Gripset 11Y as a bonding agent, or use Gripset C-Bed engineered screed.