MC-Bauchemie Nafuflex DB
MC-Bauchemie’s thermoplastic elastomer joint tape that keeps structural waterproofing watertight exactly where the structure moves.
What is it?
A 1.5 mm thick thermoplastic elastomer (TPE) strip with a polypropylene-fleece bonding edge, supplied as 30 m rolls in two widths — DB 230 (230 mm) and DB 300 (300 mm) — used to bridge and waterproof structural joints and cracks.
Where is it used?
Construction/cold joints, movement joints and cracks in basements, retaining walls, water-retaining structures, lift pits, tunnels and other below-grade or wet structures carrying an MC-Bauchemie structural waterproofing (tanking) system.
Why use it?
It stays flexible from -30°C to +90°C, resists more than 3 bar of positive water pressure, tolerates dilute acids, bases and saline exposure, and its unbonded centre section absorbs joint movement instead of tearing at the seal line.
How is it applied?
The fleece edges are bonded to a dry, prepared substrate with MC-DUR 1280 SA epoxy adhesive spread roughly 2-3 mm thick, leaving the centre strip free to flex; seams and laps are joined by hot-air welding at 350°C rather than simply overlapped.
About MC-Bauchemie Nafuflex DB
Nafuflex DB is MC-Bauchemie’s dedicated strip for the part of a waterproofing job that membranes alone can’t handle: the joint. Basement rafts, retaining walls and water tanks all have construction joints, day joints and the odd shrinkage crack — exactly where a monolithic membrane is most likely to lose continuity. It’s a thermoplastic elastomer (TPE) tape with a polypropylene-fleece bonding edge on each side; the fleece takes the adhesive bond while the centre stays free-floating, so the strip can stretch and flex with structural movement instead of pulling away from the substrate.
On Space Arc’s Delhi NCR and pan-India sites, Nafuflex DB is specified as part of a full structural tanking package with MC-DUR 1280 SA epoxy adhesive and MC-Bauchemie’s polymer-modified bituminous coatings, which it’s formulated to bond and pair with. It ships as 30 m rolls in two widths, DB 230 and DB 300, so the strip can be sized to expected joint movement rather than defaulting to one universal size. Because installation is entirely surface-bonded and hot-air welded, it works as well on retrofit and leak-repair jobs on existing concrete as it does on fresh pours.
The technical insight
The detail worth knowing before specifying is the split between bonded and free width. On DB 230, only 110 mm of the 230 mm strip is meant to carry adhesive; the rest stays unbonded so it can move independently of the joint faces. Gluing the full width down — a common site shortcut for a flatter finish — turns a movement-tolerant tape into a rigid strip that cracks or debonds at the first real joint movement. The adhesive is also specified by name: MC-DUR 1280 SA is formulated to bond to both the TPE/fleece and marginally damp concrete, which a generic epoxy hasn’t been tested to do. Joints between strip runs should be hot-air welded at 350°C, not just lapped — a weld is monolithic, a lap is only as strong as its adhesive bond.
Where it is used
- Construction and day joints in basement rafts and retaining walls under a tanking system
- Movement joints in UG water tanks, STP/ETP tanks and swimming pools
- Cold joints between existing and new concrete in retrofit and extension work
- Sealing over shrinkage or structural cracks found during a waterproofing survey
- Lift pits and sumps sitting below the water table
- Segmental and construction joints in tunnels, underpasses and box culverts
- Podium and basement retaining wall joints exposed to backfill moisture
- Joints in ETP/effluent containment structures needing dilute acid and base resistance
Key advantages
- Fleece-edge bonding with a free-floating centre absorbs joint movement instead of tearing the seal
- Hot-air welded seams give a continuous, monolithic run rather than a taped lap joint
- Resists more than 3 bar of positive water pressure, enough for typical below-grade heads
- Wide -30°C to +90°C service range copes with Indian slab temperatures and hot bitumen overlays
- Resists dilute acids, bases and saline exposure — useful on ETP/STP and coastal sites
- Formulated to pair with MC-Bauchemie’s bituminous coatings and expert proof tanking range
- Two roll widths (230 mm/300 mm) let you match the strip to actual joint movement
- Fully surface-applied, so it works on retrofit and repair jobs, not only fresh pours
Limitations & considerations
- Is a surface-bonded tape, not a cast-in PVC waterstop — needs access to both faces of the joint
- Needs substrate moisture ≤6% (CM method) and pull-off strength ≥1.5 N/mm²; shortcuts show up as bond-line leaks
- Hot-air welding needs a trained applicator — scorched or under-fused seams are a real risk otherwise
- Locked to MC-DUR 1280 SA; substituting a generic epoxy risks the bond and voids the system warranty
- Needs protection from UV and mechanical damage until covered by screed, backfill or coating
- Published data sits under MC-Bauchemie’s own DIN-referenced tests, not a separate IS test report
Selection & best practice
Treat substrate prep as non-negotiable — confirm residual moisture is at or below 6% (CM method) and pull-off strength is at least 1.5 N/mm² before the strip goes down, and level the concrete with an MC-DUR epoxy mortar first if roughness exceeds 1.5 mm. Keep adhesive strictly within the coating width (110 mm on DB 230, 180 mm on DB 300) and never bond the free centre section; roller every bonded edge by hand to chase out trapped air. For any seam or junction, insist on a hot-air weld at 350°C rather than a taped lap, and ask an unfamiliar applicator to demonstrate a test weld on scrap material first. On wide joints, install the strip looped in an Ω (omega) shape for slack, and protect the finished run from UV and site traffic until the next layer — screed, backfill or bituminous coating — goes on.
Specifications
| Type of product | Thermoplastic elastomer (TPE) with polypropylene fleece |
| Available widths | DB 230: 230 mm / DB 300: 300 mm |
| Coating (bonded) width | 110 mm (DB 230) / 180 mm (DB 300) |
| Total thickness | 1.5 mm |
| Breaking load, lateral | 61 N/15 mm (both variants) |
| Extension at break, lateral | 490% |
| Breaking load, longitudinal | 142 N/15 mm (DB 230) / 167 N/15 mm (DB 300) |
| Resistance to water pressure | > 3 bar |
| Temperature resistance / Pack | -30°C to +90°C; supplied as 30 m rolls |
Industry use cases
Residential high-rise, Delhi NCR
Basement raft-to-wall construction joints sealed under a full tanking system before backfill.
Commercial / institutional
Movement joints in an underground water storage tank sealed against sustained hydrostatic head.
Industrial
ETP/STP tank joints where saline and dilute chemical exposure ruled out a standard bituminous joint tape.
Retrofit / leak repair
Existing lift pit joint re-sealed from the accessible face after recurring seepage.
Infrastructure
Segmental joints in an underpass/box culvert waterproofed as part of the below-grade tanking package.
Frequently asked questions
Is Nafuflex DB the same thing as a PVC waterstop?
Can I use a different adhesive if MC-DUR 1280 SA isn’t on site?
Which width should I order, DB 230 or DB 300?
Can it be applied during the monsoon or on a damp substrate?
Does the joint need to be perfectly flat first?
Can it be tiled or screeded over right after installation?
How we position MC-Bauchemie Nafuflex DB
Within Space Arc’s MC-Bauchemie range, Nafuflex DB is the joint-detailing piece of a structural waterproofing system rather than a standalone product — it’s installed with MC-DUR 1280 SA epoxy adhesive and sits alongside MC-Bauchemie’s polymer-modified bituminous coatings and expert proof tanking range, so specifying it typically means specifying the adhesive and field coating together as one warrantable system. Where a joint is being formed in a fresh pour and the sequence allows it, Fosroc’s Supercast PVC Waterstop is a genuine alternative worth pricing against it — embedded directly in the concrete rather than surface-bonded, which some site teams prefer for straightforward new-pour construction joints. For retrofit joints, cracks found after the structure is cast, or any joint accessible from only one face, Nafuflex DB stays the more practical of the two.
Fosroc Supercast PVC Waterstop — Specify Fosroc Supercast PVC Waterstop instead when the joint is being formed in a fresh pour and the sequence allows a cast-in strip — Nafuflex DB remains the better fit for retrofit joints, cracks found after casting, or any joint accessible from only one face.
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