For waterproofing retaining walls, external cellar walls, planter boxes, and garden beds, 51 Membrane is a solvent-free bitumen rubber liquid membrane that accommodates substrate movement and withstands continuously damp environments. It forms a flexible barrier with high adhesion over concrete, timber, and weathered bituminous surfaces, and doubles as a protective, anti-corrosive coating for galvanised iron, zincalume, and timber posts.
51 Membrane cures from a charcoal liquid into a durable black elastomeric barrier. With a Class III elongation rating of over 500%, the cured membrane stretches to bridge non-structural cracks and absorb the shifting stresses common in underground masonry and retaining structures. The solvent-free formula is non-toxic and non-flammable, making it safe for confined excavations and basement walls. It can also be mixed directly with sand-cement mortars to form waterproof fillets at wall-and-floor junctions or to level uneven blockwork and old asphalt surfaces before membrane application.
This membrane is compatible with both porous and non-porous building surfaces, including:
Surfaces must be clean, dry, sound, and free from laitance, curing compounds, release agents, and existing loose coatings. Concrete must cure for at least 28 days and cement render/screeds for at least 7 days before application. Prime the prepared area according to the substrate type:
All movement joints, junctions, and transitions must be detailed before applying the main membrane:
No, Gripset 51 is not suitable for applications involving continuous immersion. It is designed for continuously damp environments and external/underground areas, but not constant water submersion.
Gripset 51 is effective on concrete, render, masonry, compressed fibre cement, marine ply, timber, galvanised iron, zincalume, bituminous, asphalt, and polystyrene. All surfaces must be primed according to specific guidelines before application.
Yes, Gripset 51 offers good crack bridging properties. For static cracks between 1mm and 6mm, they must first be cleaned, filled with RLA MAX SMP 25 sealant, and then reinforced with waterproofing bandage or joint tape before membrane application.
A minimum of 1mm dried film thickness is required, achieved by applying at least two coats. This translates to a total minimum coverage of 1.5 litres per square metre, ensuring robust waterproofing performance.
| Application | Key benefit | Primary trades |
|---|---|---|
| Waterproofing retaining walls and underground surfaces | Withstands continuously damp environments and prevents water ingress. | Waterproofers, builders, landscapers |
| Sealing external cellar and basement walls | Provides flexible protection against moisture with high adhesion to masonry. | Waterproofers, builders, renovators |
| Lining planter boxes and garden beds | Protects against water damage and rot in soil-filled conditions. | Landscapers, builders |
| Repairing gutters | Bonds to existing bitumen/asphalt surfaces for efficient repairs. | Roofers, plumbers, maintenance teams |
| Protective coating for timber posts | Guards against corrosion, rot, and salt damp for extended service life. | Fencers, builders, rural contractors |
| Coating galvanised iron and zincalume | Offers protection against corrosion on specific metal surfaces. | Roofers, shed builders, maintenance teams |
| Crack bridging on concrete substrates | Elongation >500% Class III accommodates normal substrate movement, preventing failure. | Waterproofers, concrete repairers |
| High-build mortar applications | Forms waterproof fillets and fills voids when mixed with sand/cement, enhancing system integrity. | Waterproofers, bricklayers, concreters |
Substrates must be clean, sound, smooth and dry; free from dust, oil/grease, wax, laitance, curing agents, release agents, moss/algae, loose coatings and sharp protrusions. Concrete must cure ≥28 days; cement render/screeds ≥7 days. Patch voids, pitting and non-structural cracks with compatible repair mortars.
Grind, shot-blast or abrade to remove weak layers and contaminants; vacuum thoroughly.
Degrease where required, rinse, then allow to dry. Ensure no standing water before priming.
Prime the entire application area before membrane installation.
Dilute Gripset 51 at 1:3 (v/v) with clean water; mix to a smooth, homogeneous consistency. Apply liberally by brush/roller.
Dilute Gripset 51 at 1:1 (v/v) with water and apply, or use Gripset OP Primer as an alternative.
Apply Gripset E60 at 1–2 coats (≈1 L/3 m² per coat) over mineral substrates with residual moisture or subject to rising damp.
Pre-detail all joints, junctions, movement zones, penetrations, drains and cracks before field coating.
Option A: Embed Elastoproof B50 Joint Band into a wet coat of Gripset 51, then fully encapsulate. Corners: use prefabricated Elastoproof corners.
Option B: Apply BRW PF Tape centrally over joints; roll firmly to expel air and creases.
Option C: Tool a continuous fillet using RLA MAX SMP 25 at floor/wall and horizontal/vertical transitions.
Fit Elastoproof Collars into a wet coat; or form flanges with BRW PF Tape; or seal with RLA MAX SMP 25 and reinforce.
Clean, fill with RLA MAX SMP 25, then overlay with Elastoproof B50/BRW PF Tape/RLA Waterproofing Bandage.
Use blends to create fillets, fill voids, level rough asphalt/bitumen, or assist drying/coverage in cooler conditions.
Mortar: 3 parts sand : 1 part cement (by volume). Pre-wet to a workable mortar, then mix 1:1 (Gripset 51 : mortar) with an electric stirrer. Trowel/spatula to thickness.
Use the same 3:1 sand:cement mortar. Pre-wet, then blend 3:1 (Gripset 51 : mortar). Apply by brush/roller at specified coverage.
Apply Gripset 51 by brush or medium nap roller in two coats.
Apply at 750 µm wet film thickness (WFT). Work methodically; maintain uniform coverage.
Recoat after 2–4 hours (at 23 °C, 50% RH). Apply at 750 µm WFT perpendicular to the first coat. Target total DFT ≈1.0 mm (≈1.5 L/m² total).
Clean tools with water while wet. Dried product requires mechanical removal. Store sealed pails out of direct sun at room temperature; avoid freezing.
Record substrate condition, primer used, tape/band details, WFT readings per coat, recoat intervals and weather conditions.
WFT gauge readings logged by area; confirm target DFT ≈1.0 mm and coverage ≈1.5 L/m².
Confirm minimum 5 days before backfill and 10 days before flood testing at 23 °C/50% RH.
Wear safety shoes, overalls, gloves (nitrile rubber recommended for intermittent contact), and safety glasses.
Natural ventilation is adequate under normal use conditions. Ensure good ventilation in confined spaces.
Store in a cool, dry, well-ventilated place, out of direct sunlight, and away from incompatible materials. Keep containers closed and check for leaks. Avoid freezing conditions and cold floors. Best stored at room temperature. Shelf life is 12 months in original unopened packaging. Dispose of material and container according to local regulations.
Proper surface preparation and priming are critical for Gripset 51 to bond correctly and deliver long-term protection.
Surface prep: Surfaces must be clean, sound, smooth, and dry. Remove all loose material, dirt, dust, oil, grease, wax, laitance, and existing coatings. Masonry must be pointed flush. Fill voids, holes, pitted sections, and non-structural cracks. Concrete requires a minimum 28-day cure, and cement render/screeds a 7-day cure.
Primer: Required. For porous/absorbent surfaces, use Gripset 51 diluted 1:3 with water. For damp or moisture-sensitive mineral surfaces (residual moisture >80% RH or 5% moisture content, or subject to rising damp), use Gripset E60 at 1 litre per 3m² per coat.
Surface prep: Ensure surfaces are clean, sound, smooth, and dry. Remove any loose material, dirt, dust, oil, grease, or existing coatings. Timber posts should be free from rot or significant degradation.
Primer: Required. For porous/absorbent surfaces, use Gripset 51 diluted 1:3 with water.
Surface prep: Surfaces must be clean, dry, and free from oil, grease, rust, or other contaminants. Mechanically remove any unsound layers.
Primer: Required. For non-porous/non-absorbent surfaces, use Gripset 51 diluted 1:1 with water. Alternatively, Gripset OP Primer can be used.
Surface prep: Clean surfaces thoroughly, removing loose material, dirt, and any failed aged coatings. Ensure the substrate is sound and dry.
Primer: Required. For non-porous/non-absorbent surfaces, use Gripset 51 diluted 1:1 with water. Alternatively, Gripset OP Primer can be used.
Surface prep: Ensure the surface is clean, dry, and free from dust or contaminants. The polystyrene must be sound and securely fixed.
Primer: Required. For porous/absorbent surfaces, use Gripset 51 diluted 1:3 with water.
| Property | Value |
|---|---|
| Form | Viscous Liquid |
| Colour | Wet: Charcoal, Dry: Black |
| Specific Gravity | 1.15 kg/litre |
| Shore A Hardness (ASTM D2240-97) | 52 |
| Elongation (AS1145.3) | >500% Class III |
| Tensile Strength (AS1145.3) | >2 MPa |
| Water Absorption (AS 3558.1) | 1.6% |
| Water Vapour Transmission (ASTM E96 Desiccant method) | 1.2 g/m²/24 hours |
| Re-coat Time | 2-4 hours |
| Backfilling Time | 5 days |
| Full Cure / Flood Test Time | 10 days |
| Minimum Film Thickness | 1.0 mm (dry) |
| Minimum Coverage | 1.5 litres/m² (total, 2 coats) |
| Shelf Life | 12 months |
Here are some common examples on where Gripset 51 Membrane used by our customers.
