About Fosroc Proofex LM Spray

Fosroc Proofex LM Spray is a spray-applied member of Fosroc’s long-established Proofex LM family of liquid-applied below-ground waterproofing membranes. It is a two-component product combining a bituminous rubber emulsion with a hydraulically hardening cementitious powder; once the two parts are combined and applied, the membrane cures through both evaporation of water and hydration of the powder, producing a tough, seamless, elastomeric film that bonds intimately to the concrete or masonry substrate. The “LM” denotes Liquid Membrane, and the “Spray” designation reflects that this grade is formulated to be projected onto the structure with spray equipment rather than applied solely by trowel or brush. For a contractor in Delhi NCR or anywhere across India, the single biggest practical advantage of the spray version is speed: large basement raft slabs, deep retaining walls and the complex geometry of lift pits and pile caps can be coated far faster, and far more uniformly, than with a hand-applied system, while still achieving a continuous joint-free barrier. Because it is a cold-applied liquid system, there is no torching, no naked flame and no need for the lapping, welding and detailing that sheet-membrane systems demand. The cured membrane remains flexible and crack-bridging, so it accommodates the minor shrinkage and settlement movement that is unavoidable in cast in-situ concrete. It tolerates damp (though not running-wet) substrates, which is invaluable in below-ground work where surfaces rarely dry out fully, and it resists the chlorides, sulphates and other aggressive salts commonly present in Indian ground water and made-up soils. It also functions as a radon barrier where soil gas ingress is a design concern. In short, Proofex LM Spray is positioned for projects where a robust, flexible, seamless below-ground membrane is needed and where productivity on large or intricate areas matters.

The technical insight

The defining chemistry here is the marriage of a polymer-modified bitumen emulsion with a hydraulically setting (cementitious) filler. This dual-cure mechanism is what separates Proofex LM-type membranes from ordinary single-pack bitumen paints. The emulsion phase delivers the elastomeric, crack-bridging flexibility, while the cementitious component drives a chemical set that lets the membrane build film thickness rapidly, gain early water resistance and tolerate application onto damp concrete – something solvent or water-based single-component coatings struggle with. The base Proofex LM has a published pot life of roughly 90 minutes at +20C, is rain-resistant after about 3 hours at +20C/65% RH, and develops a substantial film (the trowel grade builds around 3.3 mm at approximately 4 kg/m2), which is why these membranes resist high hydrostatic heads. The standard Proofex LM is type-tested to DIN 18195 parts 4 to 6 (the German below-ground waterproofing standard), giving consultants a recognised performance benchmark. The Spray grade shares this thinking but is rheologically tuned so that the mixed material atomises and builds correctly through spray plant; spray-specific consumption and the exact two-component mix ratio should always be confirmed against the current project-specific Technical Data Sheet for the LM Spray grade rather than assumed from the trowel grade, since film build per pass and total coats differ with equipment and design head. For Indian specifiers, the practical takeaways are: design the membrane thickness to the hydrostatic head, prime correctly, reinforce stress points with Proofex LM Mesh, and protect the cured film before backfilling.

Where it is used

• External (positive-side) waterproofing of basement retaining walls and raft foundations
• Below-ground tanking of foundations, pile caps and ground beams
• Lift pits, sumps and below-ground machine pits subject to hydrostatic pressure
• Waterproofing of intricate details – pipe penetrations, service entries, covings and internal/external angles
• Radon and soil-gas barrier beneath and around occupied below-ground spaces
• Protection of buried concrete against aggressive (chloride/sulphate-bearing) ground water
• Tunnels, culverts and other below-grade civil structures requiring a seamless flexible membrane
• Tank and reservoir external faces where a flexible bituminous barrier is specified

Key advantages

• Spray application gives high productivity on large rafts, walls and irregular geometry
• Seamless and monolithic – no joints, laps or welds to fail, unlike sheet membranes
• Flexible and crack-bridging, accommodating shrinkage and minor structural movement
• Can be applied to damp (not running-wet) substrates typical of below-ground work
• Cold-applied with no torching or naked flame – safer on confined sites
• Resists hydrostatic head of up to 30 metres (LM Spray grade, per Fosroc)
• Resistant to aggressive ground water – chlorides, sulphates and other ground salts
• Functions as a radon / soil-gas barrier
• Two-component reactive cure builds film and gains water resistance relatively quickly
• Compatible with and integrates into the wider Proofex waterproofing system

Limitations & considerations

• Requires spray plant and a trained applicator – not a simple brush-on DIY product
• Substrate must be sound, clean and primed; bond fails on dusty, friable or contaminated concrete
• Tolerates damp but not running water or standing water during application
• Two-component product has a limited pot life once mixed (base LM approx. 90 min at 20C), so mixing must be batched to working rate
• Cured membrane needs mechanical protection (protection board / screed) before backfilling or trafficking
• It is a positive-side / external membrane – not intended as a structural negative-side internal coating against high heads
• Application is temperature- and humidity-sensitive; cold or wet weather extends cure and delays rain resistance
• Exact spray consumption, coat build and mix ratio must be taken from the current project-specific TDS, not assumed

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Proofex LM Spray

Proofex LM Spray sits in Fosroc’s below-ground liquid-membrane range as the spray-applied, high-productivity option for tanking large or intricate underground structures, complementing the trowel-applied Proofex LM, the Proofex LMT and Proofex LM 1K Poly grades. Within a full Fosroc specification it typically works alongside Proofex primers, Proofex LM Mesh for detailing, and Fosroc joint products such as Hydrotite/Supercast waterstops and Nitoseal/Thioflex sealants, with Conbextra grouts and Renderoc repair mortars used in substrate preparation. As an alternative liquid system, contractors may also consider the cementitious-acrylic Brushbond range where a brush/roller crystalline-type coating suffices. Compared with the broader market, credible alternatives Indian specifiers weigh include Sika’s spray and liquid-applied membranes (e.g. SikaProof and Sikalastic ranges), MBS (MYK) below-ground membranes, Dr. Fixit’s Newcoat/Torchshield and liquid-applied systems from Pidilite, and STP Limited’s bituminous and APP membrane systems. Proofex LM Spray’s strongest case is on projects needing a seamless, flexible, damp-tolerant bituminous membrane that can be sprayed quickly over big rafts and complex geometry while integrating into a documented Fosroc system; where a thin crystalline coat or a fully bonded HDPE pre-applied membrane (e.g. Proofex Engage) is the design intent, those alternatives may be more appropriate. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering can advise on grade selection, supply genuine material, and support specification against the relevant standards and hydrostatic head.

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