Fosroc Proofex LMT
Two-component, polymer-modified bituminous rubber-emulsion membrane for below-ground waterproofing, intricate detailing and basement curtain protection.
What is it?
A two-component, polymer-modified bituminous (PMB) rubber-emulsion waterproofing material, applied as a thick, seamless, flexible, crack-bridging coating that is part of the Fosroc Proofex below-ground waterproofing family.
Where is it used?
External (curtain) waterproofing of basements, retaining walls, foundations, plinth beams, water tanks and the intricate details that defeat sheet membranes – pipe entries, covings, edges, construction joints and re-entrant corners.
Why use it?
It can be trowel- or brush-applied onto damp (not wet) substrates, forms a jointless monolithic film around complex geometry, bridges shrinkage cracks, is solvent-free, and resists aggressive ground water and a hydrostatic head of up to around 70 m.
How is it applied?
Prime the prepared substrate with Proofex LM/LMT diluted 1:10 with clean water, then power-mix the powder into the liquid and apply by steel float or brush in one or two coats (roughly 3.3-4.0 mm wet per coat), reinforcing covings, edges and penetrations with a second coat plus Proofex LM mesh.
About Fosroc Proofex LMT
Fosroc Proofex LMT is a factory-batched, two-component waterproofing compound built around a polymer-modified bituminous rubber emulsion combined with special hydraulically hardening fillers. In plain terms, it is a liquid-applied bitumen membrane that you mix and trowel on site rather than a torch-on or self-adhesive sheet. It sits within Fosroc’s wider Proofex below-ground waterproofing range and is engineered specifically for the parts of a structure where sheet membranes are awkward or unreliable – around pipe penetrations, internal and external corners, covings, kickers and tight detailing – as well as for continuous basement curtain (external face) waterproofing. Because it cures to a seamless, flexible, rubberised film, it eliminates the laps, welds and edge terminations that are the usual failure points of conventional membranes. The product is solvent-free, which makes it safer to handle in confined basement and tank environments and harmless to ground water. It tolerates damp substrates, resists aggressive salts and weak acids commonly present in Indian soils and ground water, and is fully compatible with the rest of the Proofex system, so it can be used as a stand-alone coating or as the detailing and dressing compound that ties a Proofex sheet or liquid system together. For Space Arc Engineering’s clients across Delhi NCR and pan-India, Proofex LMT is positioned as the specialist’s answer to the leak-prone junctions that decide whether a basement stays dry – applied by trained applicators as part of a complete, warranted Fosroc waterproofing build-up.
The technical insight
The performance of Proofex LMT comes from its chemistry: a bitumen emulsion is modified with elastomeric polymer so the cured film stays flexible and crack-bridging, while hydraulically hardening (cementitious) fillers give it body, early strength and the ability to be built up to a thick, structurally stable layer without slumping on vertical and overhead detail. This places the product in the EN 15814 family of polymer-modified bituminous thick coatings (PMB) for below-ground waterproofing. The two-component format matters – the powder is power-mixed into the liquid to a homogeneous paste with a pot life of roughly 90 minutes at 20 C, so it gains green strength far faster than single-pack bitumen emulsions and can take a hydrostatic head soon after application. A diluted (1:10 with water) coat of the same material serves as the primer, ensuring a chemically identical, fully bonded interface rather than a dissimilar primer that can debond. Typical build-up is one or two coats at about 3.3-4.0 mm wet film, with extreme-loading zones (covings, edges, pipe penetrations) doubled up and reinforced with Proofex LM mesh at 10 mm overlaps. Cure is moisture- and temperature-dependent (about 24 hours at 20 C, 60% RH for a 3.3 mm coat; rain-resistant in about 3 hours), and the system resists a hydrostatic head of up to around 70 m.
Where it is used
- External curtain (positive-side) waterproofing of basement walls, raft soffits and retaining walls
- Waterproofing and dressing of intricate details – pipe entries, sleeves, covings, internal/external corners and re-entrant angles
- Sealing of construction joints, day joints and kickers in below-ground concrete
- Foundation, plinth-beam and footing protection against ground moisture and aggressive ground water
- Below-ground water tanks, sumps and lift pits (positive side)
- Detailing and tie-in compound used alongside Proofex sheet and liquid membranes to complete a continuous Proofex system
- Protection of buried concrete against weak acids, salt solutions and sulphate-bearing soils
Key advantages
- Two-component PMB chemistry that cures to a seamless, flexible, crack-bridging film with no laps or welds
- Can be applied to damp (not wet) substrates – reduces drying-out delays on site
- Trowel and brush application lets it follow complex geometry that sheet membranes cannot
- Solvent-free – safer in confined basements/tanks and harmless to ground water
- Resists aggressive ground water, weak acids and salt solutions found in Indian soils
- Withstands a hydrostatic head of up to around 70 m when correctly built up
- Fast strength gain (pot life ~90 min at 20 C; rain-resistant in ~3 hours) for quicker back-filling programmes
- Fully compatible with the Fosroc Proofex system, enabling a single-source, warrantable build-up
Limitations & considerations
- Two-pack material with a limited pot life (~90 min at 20 C) – must be mixed in workable batches and not retempered once it starts to dry
- Substrate must be clean, sound and damp but not shining-wet, with no standing water on horizontal areas
- Macro-porous or honeycombed concrete needs a scratch-coat first to avoid blistering/bubble formation
- Bituminous chemistry – not intended as a UV-exposed, trafficked or long-term exposed wearing surface; protect and backfill promptly
- Application temperature window of roughly +5 C to +35 C; cure slows markedly in cold/damp conditions
- Coverage and final dry-film thickness depend heavily on substrate porosity and workmanship – dry-film checks are essential
- Reduced shelf life (down to under 6 months) if stored in high heat/humidity, a real risk in Indian summers
- Confirm the exact current grade designation, coverage and certification on the latest local Fosroc TDS before specifying
Selection & best practice
Treat Proofex LMT as a system, not a single coat. Start with sound, profiled concrete free of laitance, sharp arrises and standing water; round off internal corners with a fillet and prepare a scratch-coat on porous or honeycombed areas. Prime every surface with Proofex LMT/LM diluted 1:10 in clean water so the first coat bonds to a chemically identical layer. Power-mix the powder into the liquid to a uniform paste, mix only what can be used inside the ~90-minute pot life, and apply by steel float in even passes to the specified wet-film thickness (about 3.3-4.0 mm), checking with a wet-film gauge. Reinforce all covings, edges and pipe penetrations with a second coat and Proofex LM mesh at 10 mm overlaps. Let each full coat dry (overnight where required) before the next, protect the cured membrane with a board or protection layer before backfilling, and store stock in cool, dry, shaded conditions. Always have it installed by Fosroc-trained applicators – Space Arc Engineering provides specification, site detailing drawings and applicator supervision.
Specifications
| Product type | Two-component, polymer-modified bituminous rubber-emulsion waterproofing material (PMB) |
| Standard / classification | EN 15814 – polymer-modified bituminous thick coatings (PMB) for below-ground waterproofing (Proofex LM family) |
| Components | Liquid (emulsion) + powder (hydraulically hardening filler), supplied pre-batched in one kit |
| Consistency / density | Paste-like when mixed; approx. 1.2 g/cm3 fresh (mixed) |
| Primer | Same material diluted 1:10 with clean water; ~50-80 g/m2 unthinned-equivalent depending on porosity |
| Wet film thickness | Approx. 3.3 mm (one layer, damp/no pressure) up to ~4.0 mm (waterproofing build-up) |
| Coverage | Approx. 1.2 kg/m2 per mm wet film; ~4 kg/m2 single layer, ~8 kg/m2 two-layer build-up (Proofex LM family) |
| Number of coats | One or two even coats by steel float/brush; extreme-load zones (covings, edges, penetrations) applied twice with Proofex LM mesh |
| Pot life | At least ~90 minutes at +20 C (shorter when hotter) |
| Application temperature | Approx. +5 C to +35 C ambient |
| Cure / rain resistance | ~24 h at 20 C/60% RH for 3.3 mm coat; rain-resistant after ~3 h at 20 C/65% RH; full cure 1-3 days |
| Hydrostatic head | Resists up to approx. 70 m head of water when correctly applied |
| Chemical resistance | Resists numerous salt solutions, weak acids and aggressive substances normally present in soil/ground water |
| Shelf life / storage | ~12 months in cool, dry, unopened conditions; reduced (<6 months) at high heat/humidity |
Industry use cases
Residential & commercial basements
Positive-side curtain waterproofing of basement retaining walls and raft soffits, with Proofex LMT dressing every pipe entry, coving and corner to deliver a continuous, leak-free below-ground envelope.
Infrastructure & metro/underground
Detailing and tie-in compound for cut-and-cover structures, underpasses and service ducts where complex penetrations and joints must be sealed alongside the main Proofex sheet/liquid membrane.
Water-retaining & containment structures
Sealing of sumps, lift pits, water tanks and STP/ETP structures where the membrane must resist a standing hydrostatic head and aggressive effluent/ground water.
Industrial & warehouse foundations
Protection of foundations, plinth beams and footings against sulphate- and salt-bearing soils common across Indian industrial sites, extending concrete durability.
High-rise & podium construction
Below-ground and plinth-level detailing on large residential and mixed-use developments, integrated with Fosroc admixtures and joint systems for a single-source waterproofing warranty.
Frequently asked questions
Is Fosroc Proofex LMT a sheet membrane or a liquid-applied coating?
What is Proofex LMT actually made of?
Can it be applied to damp concrete during the monsoon?
How much Proofex LMT do I need, and how thick should it go?
How does Proofex LMT differ from Proofex LM and Proofex 3000?
Does Space Arc supply and apply Proofex LMT in Delhi NCR and pan-India?
How we position Fosroc Proofex LMT
Within the Fosroc Proofex range, Proofex LMT is the two-component bituminous detailing and curtain-waterproofing partner to products like Proofex LM (its close sibling and trowel-grade equivalent) and the Proofex 3000 self-adhesive sheet membrane – typically the sheet handles large flat runs while Proofex LMT seals the penetrations, covings and corners that defeat sheets. It also complements Fosroc’s broader basement strategy alongside the Conplast integral waterproofing admixtures and Nitoseal/Hydrocell joint systems. Against the wider Indian market, Proofex LMT competes with two-component bituminous and acrylic/cementitious membranes such as Sika’s bituminous coatings and SikaProof range, MBCC/Master Builders Solutions (formerly BASF) MasterSeal bituminous and crystalline systems, STP Limited’s bituminous and APP membranes, and Dr. Fixit’s two-component LW+/Newcoat-type basement products. Its differentiators are damp-substrate tolerance, genuinely seamless detailing performance, solvent-free handling and full integration into a single-source Proofex system. Honest caveat: the publicly available Fosroc page confirms the LMT chemistry and uses, while the quantitative figures here are drawn from the matching Proofex LM family TDS – so for tender specification, confirm the exact grade designation, coverage, thickness and certification on the latest India-region Fosroc datasheet, which Space Arc Engineering can provide along with project-specific specification support.
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