Gripset 51 Solvent Free Bitumen Rubber Membrane

Gripset 51 is a solvent-free bitumen-rubber liquid membrane for underground and protected external waterproofing. It combines flexible sealing with adhesion to a broad range of building surfaces and is particularly suited to retaining walls, basement walls, planter boxes, gutters and protective coating work.

Why choose Gripset 51? This bitumen-rubber membrane is intended for protected underground walls, planter boxes, gutters and compatible timber or metal coatings—not permanently exposed roof decks or immersed tanks. For pools or water tanks, compare Gripset 2P or Gripset C-1P.

How it works

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, non-flammable formulation is well suited to the protected waterproofing and coating applications for which Gripset 51 is designed. 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.

Numbers that matter

• >500% elongation (AS1145.3): Class III high elasticity to handle structural movement and settling in underground walls without tearing.
• 1.5 litres/m² total coverage: Minimum application rate applied in two coats (750 microns wet film thickness per coat) to achieve the required 1.0mm dry film thickness.
• 2 to 4 hours recoat time: Efficient turnaround window at 23°C and 50% relative humidity to complete the two-coat system in a single day.
• 5 days to backfill: Required curing window before soil or drainage cell can be placed against the treated retaining wall or basement exterior.
• 10-day flood-test window: Allow about 10 days before flood testing under standard drying conditions.

Where to use it

This membrane is compatible with both porous and non-porous building surfaces, including:

• Concrete, cement render, masonry, and concrete blockwork.
• Compressed fibre cement sheeting.
• Marine ply, timber sheeting, and underground timber posts.
• Galvanised iron and zincalume (excluding raw steel).
• Existing bituminous and asphalt substrates, ideal for repairing failed, aged coatings.
• Polystyrene.

Limitations

• UV exposure: Surface crazing may occur when exposed to long-term UV light; protect or cover the membrane for permanent external exposure.
• Direct finishes: Do not apply tiles, renders, screeds, paints, or other surface finishes directly over the cured membrane.
• Traffic: Not to be used as a trafficable coating.
• Immersion: Not suitable for continuously immersed applications such as pools or water tanks.
• Incompatible substrates: Do not apply over glass or glazed surfaces.
• Moisture limits: Gripset 51 is not a negative-hydrostatic-pressure waterproofing solution. Damp substrates require a properly specified and compatible moisture-management system. Do not apply when rain is imminent.
• Application limits: Do not apply when surface temperatures are below 5°C or above 35°C.
• Joint restrictions: Not designed to function as a sealant for expansion or control joints.

Substrate preparation and priming

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:

• Porous substrates: Apply 51 Membrane diluted 1:3 with clean water by volume, brushing or rolling it liberally over the surface.
• Non-porous substrates: Apply 51 Membrane diluted 1:1 with clean water by volume, or prime using Gripset OP Primer.
• Damp mineral substrates: Where residual moisture is present, a compatible moisture-barrier treatment may be required before coating. Negative hydrostatic pressure calls for a separately specified waterproofing system.

System detailing

All movement joints, junctions, and transitions must be detailed before applying the main membrane:

• Bond breakers: Install Elastoproof B50 Joint Band into a wet 150mm wide strip of 51 Membrane, smoothing out creases before encapsulating with the second coat. Alternatively, apply self-adhesive BRW PF Tape centrally over the joint, or tool a fillet of RLA Max SMP 25 sealant at the junction.
• Penetrations and flanges: Fit Elastoproof Collars over pipe necks and bed them into wet membrane, seal the perimeter with RLA Max SMP 25, or detail with BRW PF Tape.
• Static cracks (1mm to 6mm): Clean, fill flush with RLA Max SMP 25 sealant, and overlay with RLA Waterproofing Bandage, Elastoproof B50 Joint Band, or BRW PF Tape.