MC-Bauchemie Nafuflex 2K-05
Two-component polymer-modified bituminous thick coating (PMBC) for seamless, crack-bridging waterproofing of below-grade structures in contact with soil.
What is it?
A two-component polymer-modified bituminous thick coating (PMBC) from MC-Bauchemie Germany, supplied as a matched liquid bitumen emulsion plus a reactive powder that speeds up drying.
Where is it used?
On the earth-facing (positive) side of foundations, basement walls, floor slabs, retaining walls, lift pits and earth-covered roofs — anywhere a structure sits in contact with soil.
Why use it?
It forms one seamless, jointless, permanently flexible membrane that bridges shrinkage cracks and copes with everything from soil moisture to 3 m of pressing groundwater, all classified under DIN 18533.
How is it applied?
Prime the substrate, round off fillets, then apply two fresh-in-fresh coats by trowel or airless/screw pump — embedding Nafuflex GRID 25 NF reinforcing mesh at corners and penetrations.
About MC-Bauchemie Nafuflex 2K-05
MC-Bauchemie Nafuflex 2K-05 sits in the German manufacturer’s flagship structural-waterproofing range: the polymer-modified bituminous thick coatings, or PMBCs, that European specifiers reach for when a below-grade concrete structure has to stay dry for its whole service life. Unlike the rigid cementitious slurries that get brushed onto the inside of a tank, Nafuflex is a thick, spreadable bitumen system applied to the outer, earth-facing face — the side the water actually pushes against. Component A is a solvent-free bitumen emulsion; Component B is a fine reactive powder that pulls the mix together and drives out water faster, so the membrane skins over and resists rain sooner. Mixed on site, the two build into a jointless film several millimetres thick that follows every protrusion, light shaft and angled joint without a single lap or weld.\n\nFor Indian projects, the appeal is reliability under real ground conditions. The system is engineered and classified to DIN 18533 — the German structural-waterproofing standard that ties the specification directly to the water load the building will face — and to DIN EN 15814, the European PMBC product standard. That means a basement raft dealing only with damp soil and one submerged 3 m deep in the water table are treated as different design cases, each with its own minimum built-up thickness. Nafuflex 2K-05 is solvent-free and eco-friendly, carries cryoscopic additives that let it be applied and stored in cold weather (down to about -5 degrees C), and is even used as a radon barrier in Europe. As MC-Bauchemie’s authorised distributor and applicator across Delhi NCR and Pan-India, Space Arc supplies the material together with its matched Nafuflex ancillaries and on-site guidance.
The technical insight
A PMBC waterproofs by drying, not by curing chemically, and that is the whole design logic behind the two-component format. The water held in the bitumen emulsion has to evaporate before the film develops its final watertight, elastic character — so anything that speeds safe water loss makes the system more robust on a live site. That is what Component B does: the reactive powder binds part of the mix water and accelerates through-drying, which is why the 2K grade sets faster and shrugs off early rain far better than a single-component coating, and why it works even when ambient temperatures are low. The flexibility that lets the membrane bridge substrate cracks comes from the polymer modification of the bitumen; because the film is applied several millimetres thick and reinforced with Nafuflex GRID 25 NF mesh at the high-movement zones — wall-to-slab fillets, pipe penetrations, corners — small shrinkage and settlement cracks in the concrete open beneath an intact, elastic skin rather than tearing it. Getting the specified wet layer thickness is therefore the single most important thing on site: too thin and the dried membrane falls short of the DIN 18533 class it was chosen for, which is why MC-Bauchemie supplies a layer-thickness gauge and a wet-film recording form for every job.
Where it is used
- Positive-side (external) tanking of basement walls and foundation slabs in contact with soil
- Waterproofing below-grade structures against soil moisture and non-pressing water (DIN 18533 W1.1-E / W1.2-E)
- Waterproofing against moderate pressing groundwater up to 3 m submersion depth (W2.1-E)
- Waterproofing of earth-covered roofs and podium/planter decks (W3-E)
- Splash-water and plinth zone protection at wall footings where capillary damp rises (W4-E)
- Sealing of retaining walls, lift pits and buried utility shafts before backfilling
- Bonding of insulation, drainage and protection panels (e.g. Nafuflex SD) to the finished membrane
- Radon-barrier waterproofing of ground-contact slabs and walls in affected regions
Key advantages
- Seamless and jointless — one continuous membrane with no laps, welds or overlaps to fail
- Genuinely flexible with efficient crack-bridging over the movement the polymer bitumen can accommodate
- Two-component format dries and resists rain faster than 1K coatings, even at low temperatures
- Solvent-free and eco-friendly, with good environmental and workplace compatibility
- Suitable for both hand application by trowel and high-output machine spraying (airless, peristaltic, screw pump)
- Cryoscopic additives allow cold-weather working and storage down to about -5 degrees C
- Classified across the full DIN 18533 water-load range (W1.1-E to W4-E) so one product family covers most below-grade cases
- Backed by matched Nafuflex ancillaries — primer, mesh, fillet mortar, joint tape and protection panels — as a single coordinated system
Limitations & considerations
- It is a positive-side (external) tanking product, applied to the earth-facing face before backfill — it is not a negative-side or internal water-retaining lining
- PMBC cross-section sealing / damp-proof course is no longer permitted in many jurisdictions; use a flexible mineral slurry (e.g. MC-Proof 101 HS) for the DPC detail
- Waterproofs only by drying — it must fully through-dry before backfilling, panelling or overplastering; rain, frost or snow on a fresh coat can destroy it
- The dried bituminous membrane must be permanently protected from point and line loads with protection/drainage panels before the pit is refilled
- Render or plaster applied directly onto the bituminous coating can crack — the plinth zone needs a mineral waterproofing mortar beneath the render
- Achieving the DIN 18533 minimum dry-layer thickness for the chosen water class is essential; under-application quietly downgrades performance
Selection & best practice
Start with a frost-free, sound, load-bearing substrate cleaned of release agents, dust, laitance and loose particles; chamfer sharp edges and fill voids or joints deeper than 5 mm with Nafuquick barrier mortar, rounding all wall-to-slab fillets. Prime with Nafuflex GIP (diluted per the datasheet) so absorbent or dusty concrete does not rob the coating of water — spray application can skip the separate primer coat. Mix the two components for at least 3 minutes until completely lump-free. Apply in two fresh-in-fresh layers by trowel or machine, building up to the minimum dry-layer thickness for your DIN 18533 water class (3 mm for soil moisture / splash-water cases such as W1.1-E, W1.2-E and W4-E; 4 mm for pressing water up to 3 m in W2.1-E and for earth-covered roofs in W3-E), and embed Nafuflex GRID 25 NF mesh in the first layer at fillets, corners and pipe penetrations with 10 cm overlaps. Check the wet-film thickness as you go using the Nafuflex gauge and MC-Bauchemie’s recording form — each reinforced layer is measured separately. Protect the fresh coat from sun, rain and frost, let it through-dry fully (verify on a coated reference sample), then bond Nafuflex SD protection/drainage panels over the whole area before backfilling the pit in layers no thicker than 0.3 m.
Specifications
| Product type | Two-component polymer-modified bituminous thick coating (PMBC) |
| Components | Component A: bitumen emulsion (liquid) | Component B: reactive powder (accelerates drying) |
| Product standard | DIN EN 15814 (PMBC for waterproofing) |
| Design / application standard | DIN 18533 — structural waterproofing of components in contact with soil |
| Water-load classes covered | W1.1-E, W1.2-E, W2.1-E, W3-E, W4-E |
| Min. dry-layer thickness (soil moisture / splash water — W1.1-E, W1.2-E, W4-E) | 3 mm |
| Min. dry-layer thickness (pressing water ≤3 m — W2.1-E; earth-covered roof — W3-E) | 4 mm |
| Application methods | Trowel (hand) or machine spray — airless, peristaltic or screw pump |
| Cold-weather storage / working | Solvent-free; cryoscopic additives allow storage down to approx. -5 °C |
Industry use cases
Residential & Commercial Basements
External tanking of raft slabs and retaining walls before backfill, matched to the DIN 18533 water class the plot’s water table demands.
Infrastructure & Underground Utilities
Waterproofing of lift pits, buried service shafts and inspection chambers where a seamless, machine-sprayable membrane speeds large-area coverage.
Podium & Landscape Decks
Earth-covered roofs, planter boxes and podium slabs (W3-E) sealed as a continuous flexible membrane beneath the growing medium and protection layers.
Industrial & Plinth Protection
Splash-water and rising-damp protection at wall footings and plinths (W4-E), coordinated with a mineral slurry for the render-line and DPC detail.
Frequently asked questions
Is Nafuflex 2K-05 a cementitious slurry or a bituminous coating?
Which side of the wall does it go on — inside or outside?
How thick does the membrane need to be?
Can it be spray-applied for large basements?
How long before I can backfill the excavation?
Do I need any other products with it?
How we position MC-Bauchemie Nafuflex 2K-05
Within the MC-Bauchemie Nafuflex family, choose by application method and speed: Nafuflex Basic 1 (1K, high-yield trowel grade) or Basic 2 (2K, fast-drying all-rounder) for hand application; Easy Tech 1/2 for peristaltic and screw-pump spraying; and Profi Tech 1/2 for airless spraying over long hose runs on large sites. For subsequent waterproofing or wider cracks, Nafuflex High Performance bridges cracks up to 3 mm and stays flexible below freezing. Every job also draws on the Nafuflex ancillaries — GIP primer, GRID 25 NF mesh, Nafuquick fillet mortar, MC-FastTape and Nafuflex SD panels — plus a mineral slurry such as MC-Proof 101 HS for the plinth and DPC line. Where a specifier wants a membrane that cures rather than dries — so it will not soften in extreme heat and can be laid on horizontal decks and inspection pits — Space Arc also carries Fosroc’s polyurethane tanking membranes as an alternative.
Fosroc Nitoproof 600 — Specify this single-component pitch-modified polyurethane instead when you want a moisture-cured membrane that will not soften at high temperatures and suits horizontal decks, inspection pits and aggressive-groundwater tanking, rather than a dry-to-cure bituminous PMBC.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.