Fosroc Proofex LM
Seamless, solvent-free two-component bituminous-rubber membrane for waterproofing below-ground structures and intricate details — applied by trowel to damp or dry substrates.
What is it?
A two-component, solvent-free bituminous-rubber emulsion with hydraulically hardening fillers that cures into a seamless, flexible, crack-bridging waterproofing membrane.
Where is it used?
External (positive-side) waterproofing of basements, retaining walls, foundations, tanking and below-ground structures, and the detailing of pipe entries, covings, fillets and penetrations.
Why use it?
Forms a jointless elastic membrane that resists hydrostatic head up to 70 m, can be applied to damp surfaces, contains no solvents and is harmless to groundwater — ideal for tricky details where sheet membranes are hard to dress.
How is it applied?
The primed substrate is coated by steel float/trowel in one or two even layers (typically ~4 kg/m2 at 3.3 mm), with a second pass at edges, covings and penetrations.
About Fosroc Proofex LM
Fosroc Proofex LM is a two-component bituminous-rubber emulsion incorporating special hydraulically hardening fillers, formulated as a liquid-applied (cold-applied) waterproofing membrane for below-ground concrete and masonry. Unlike sheet membranes that must be cut, lapped and torched, Proofex LM is float-applied as a thick paste that cures into a seamless, monolithic, elastic skin — making it especially well suited to the intricate geometry where most below-ground leaks actually originate: pipe penetrations, service entries, covings, fillets, kickers and re-entrant corners. In the Fosroc Proofex family it functions as the liquid detailing and tanking companion to the loose-laid and bonded sheet systems (Proofex 3000, Proofex Torchseal, Proofex Engage), allowing a contractor to keep one compatible waterproofing system across both flat runs and complex junctions. Because it is solvent-free and water-based, it is environmentally friendly, low-odour and harmless to groundwater, and — significantly for Indian site conditions — it can be applied to damp (though not running-wet) substrates, reducing weather-window pressure during and after the monsoon. For Delhi-NCR and Pan-India projects, Space Arc Engineering supplies Proofex LM as an authorised Fosroc distributor and applicator, with on-site method guidance to ensure priming, layer thickness and curing are executed correctly.
The technical insight
Chemically, Proofex LM is a polymer-modified (rubberised) bitumen emulsion combined with a reactive powder component containing hydraulically hardening (cement-type) fillers. When the two components are blended, the powder both stiffens the paste so it holds thickness on vertical and overhead details without slumping, and chemically sets via hydration — so the membrane builds early strength and rain resistance rather than relying purely on slow water evaporation. This is why it gains rain resistance in about 3 hours and substantially cures in roughly 24 hours (at 20 C, ~60% RH, 3.3 mm), and why it tolerates damp substrates that would defeat a pure solvent-based bitumen paint. The hydraulic set also explains the relatively short pot life (~90 minutes at 20 C) — once the powder is wetted the reaction has started, so material must be used promptly and not re-tempered with extra water. The cured film is elastic and crack-bridging, accommodating minor substrate movement and shrinkage cracking, and is rated to resist a hydrostatic head of up to 70 m, placing it firmly in the tanking class rather than mere damp-proofing. It has been tested in accordance with DIN 18195 parts 4-6 (the German below-ground waterproofing code), MPA Dortmund certificate No. P-22 1356 8 96-1.
Where it is used
- External (positive-side) tanking of basements, lift pits, retaining walls and foundation walls below grade
- Waterproofing and detailing of pipe entries, service penetrations and conduit sleeves through below-ground concrete
- Forming and sealing covings, fillets and re-entrant corners at wall-to-slab junctions
- Sealing kickers, construction joints and complex geometry where sheet membranes are difficult to dress
- Detailing and patching around projections in conjunction with Proofex sheet membrane systems
- Waterproofing of underground tanks, sumps and structures subject to ground-water pressure
- Protection of buried concrete against aggressive (sulphate/chloride-bearing) groundwater
Key advantages
- Seamless, jointless membrane — no laps, welds or torching, eliminating the weak points where sheet systems leak
- Resists a high hydrostatic head (up to 70 m), suiting deep basements and high water-table sites
- Can be applied to damp substrates, widening the workable window in humid and post-monsoon conditions
- Solvent-free and water-based — low odour, environmentally friendly and harmless to groundwater
- Flexible and crack-bridging, accommodating minor structural movement and shrinkage cracks
- Float/trowel application builds thickness easily on covings, fillets and vertical details without slumping
- Hydraulically hardening fillers give early rain resistance (~3 h) and faster effective cure
- Part of the integrated Fosroc Proofex system, so it is fully compatible with Proofex sheet membranes for hybrid detailing
Limitations & considerations
- Two-component mix with a short pot life (~90 minutes at 20 C) — only mix what can be used within the working time
- Bitumen-based, so it is a positive-side / external membrane and is not UV-stable for permanent above-ground exposure; it must be covered, backfilled or protected
- Substrate must be primed first (one part Proofex LM diluted with ten parts clean water) before the waterproofing layer
- Applied to damp but not running-wet or ponding-water surfaces; standing water and active leaks must be stopped first
- Performance depends on achieving the specified film thickness (~3.3 mm / ~4 kg/m2) and a second pass at high-stress details
- Application temperature is limited (approx. 5 C to 35 C); avoid application in rain or onto frozen/frosted substrates
- As a bituminous product it is not intended as a finished trafficable or decorative surface; it requires protection boarding/screed before backfill
Selection & best practice
Prepare a sound, clean substrate free of laitance, oil and loose material, and round off sharp internal/external corners with a coving fillet. Prime all surfaces by brushing on Proofex LM diluted 1 part to 10 parts clean water and allow it to dry. Mix the two components mechanically to a uniform, lump-free paste and apply by steel float in even layers to achieve the specified thickness (about 4 kg/m2 at 3.3 mm), giving a second coat at covings, edges and pipe penetrations where loading is highest. Mix only the quantity usable within the ~90-minute pot life and do not add extra water to re-soften set material. Protect the freshly applied membrane from rain for at least the first few hours, allow proper cure (~24 h at 20 C before loading), and install protection board/screed prior to backfilling. On critical or deep-basement projects, engage Space Arc Engineering’s applicators to validate primer, wet-film thickness and the overall Proofex system build-up.
Specifications
| Product type | Two-component bituminous-rubber emulsion with hydraulically hardening fillers (liquid-applied membrane) |
| Chemical base | Polymer/rubber-modified bitumen emulsion (solvent-free, water-based) |
| Hydrostatic head resistance | Up to 70 m |
| Consumption / coverage | Approx. 4 kg/m2 at 3.3 mm layer thickness |
| Number of coats | One or two even layers; two at covings, edges and penetrations |
| Primer | 1 part Proofex LM diluted with 10 parts clean water, applied by brush |
| Pot life | Approx. 90 minutes at +20 C |
| Application temperature | Approx. 5 C to 35 C |
| Rain resistance | After approx. 3 hours at 20 C / 65% RH |
| Cure | Approx. 24 hours at 20 C, ~60% RH, 3.3 mm coating |
| Application method | Steel float / trowel (cold-applied) |
| Substrate | Concrete and masonry; may be applied to damp (not running-wet) surfaces |
| Standards / test | Tested to DIN 18195 parts 4-6; MPA Dortmund cert. No. P-22 1356 8 96-1 |
| Pack size | 28 kg two-component kit |
Industry use cases
Residential & commercial basements
Positive-side tanking of basement and retaining walls, with Proofex LM dressing the pipe entries, covings and wall-slab junctions that sheet membranes struggle to seal.
Metro, tunnels & infrastructure
Detailing and waterproofing of penetrations, construction joints and complex geometry in below-ground RCC structures subject to high water tables.
Water-retaining & sewage structures
External waterproofing of underground tanks, sumps and pits against ground-water pressure and aggressive groundwater.
Lift pits & deep foundations
Seamless tanking of lift pits and deep foundation elements where hydrostatic head and intricate detailing demand a jointless liquid membrane.
Industrial & plant foundations
Protecting buried concrete around equipment foundations and service ducts from moisture ingress and sulphate/chloride-bearing soils.
Frequently asked questions
What exactly is Fosroc Proofex LM?
How much hydrostatic pressure can Proofex LM withstand?
What is the coverage and how thick should it be?
Does the surface need priming, and can it be applied to damp concrete?
What is the pot life and cure time?
How does Proofex LM differ from Proofex sheet membranes?
How we position Fosroc Proofex LM
Within the Fosroc range, Proofex LM is the liquid-applied detailing and tanking member of the Proofex below-ground waterproofing family. It complements the sheet membranes — loose-laid Proofex 3000, torch-applied Proofex Torchseal, and the cast-in Proofex Engage HDPE system — by sealing the penetrations, covings and complex junctions those sheets cannot easily dress; on most projects the two are specified together. For positive-side detailing it also sits alongside Fosroc’s crystalline and cementitious options (such as the Brushbond and Renderoc/Conplast families) where a rigid coating is preferred over an elastic bituminous one. Compared with competing liquid below-ground systems, Proofex LM competes with Sika’s bituminous and elastic tanking coatings (e.g. the Igolflex/SikaProof range), MBS (MYK Schomburg) AQUAFIN/COMBIDIC bituminous-thick-coating products, Dr. Fixit’s Newcoat/Pidiproof tanking and detailing solutions, and STP Limited’s bituminous membranes and coatings. Its distinguishing strengths are the high 70 m hydrostatic-head rating, solvent-free composition, damp-surface tolerance and the integration benefit of staying within one Fosroc-approved system end to end. Space Arc Engineering, as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, supplies Proofex LM with system-level guidance so the membrane, primer and protection are specified and installed as a complete, warrantable build-up.
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