Fosroc Expoband One
A flexible polyolefin membrane strip bonded over expansion and movement joints to keep water out while the structure keeps moving.
What is it?
An un-reinforced Flexible Polyolefin (FPO) membrane strip that is bonded across an expansion or movement joint to bridge it and block the passage of water.
Where is it used?
Water-retaining and water-excluding structures where joints move: reservoirs, water tanks, basements, retaining walls, tunnels, STPs/ETPs, roof decks and podiums.
Why use it?
It waterproofs a working joint without relying on a sealant to hold a bond across large, repeated movement, so it stays watertight through years of cyclic flexing.
How is it applied?
Bonded either side of the joint onto primed concrete using Nitobond PC40 two-part epoxy adhesive, leaving a free unbonded loop over the joint gap that absorbs movement.
About Fosroc Expoband One
Expoband One is Fosroc’s answer to a problem that catches out a lot of waterproofing on Indian sites: an expansion joint is designed to move, and most gun-grade sealants are asked to both fill that gap and stay bonded to the arris while it opens and closes for the life of the structure. On wide joints, in water-retaining tanks, or where movement is pronounced, that is a hard ask and sealant failure is where leaks usually start. Expoband One takes a different route. It is a strip of un-reinforced Flexible Polyolefin (FPO) membrane that is bonded flat onto the concrete on both sides of the joint, with a deliberate unbonded section left loose over the gap itself. That loop is what accommodates the movement, so the waterproofing element is never being stretched to breaking point at the joint edge.
For engineers and consultants specifying below-ground and water-retaining works across Delhi NCR and the rest of India, that distinction matters. The membrane is chemically inert, resists weathering and UV, and can be laid on dry or damp substrates, which suits real basement and tank conditions rather than laboratory ones. It is supplied in rolls, typically 20 m long in a grey finish, in 1 mm and 2 mm thicknesses and in widths from 100 mm up to a metre, so the strip can be sized to the joint width and the expected movement. Space Arc Engineering supplies Expoband One as an authorised Fosroc distributor and applicator, with the matching Nitobond PC40 epoxy adhesive and on-site guidance so the system is installed the way the manufacturer intends.
The technical insight
The whole system works on separating two jobs that a sealant tries to do at once: sticking to the concrete, and absorbing movement. With Expoband One the bond is made away from the joint. The FPO strip is adhered flat to sound, primed concrete on each shoulder of the joint using Nitobond PC40 two-part epoxy, which develops a strong, permanent grip on the substrate. Directly over the joint gap, a defined width of membrane is left unbonded. When the structure expands and contracts, that free loop simply flexes and unrolls rather than transferring strain into the adhesive line. Because polyolefin is highly flexible and elastic, it can take continuous and pronounced cyclic movement without fatiguing, and because it is a manufactured sheet rather than a site-mixed material, the waterproofing thickness is consistent along the whole run. The material’s chemical inertness is what lets it sit in sewage, effluent and treated-water environments; the UV and weathering resistance is what lets it work on exposed roof and podium joints. In short, the concrete carries the load, the epoxy carries the bond, and the membrane loop carries the movement.
Where it is used
- Expansion and movement joints in water tanks, reservoirs and water treatment structures
- Basement raft and wall joints in below-ground, water-excluding construction
- Joints in retaining walls and box structures subject to water pressure
- Tunnels, subways and cut-and-cover structures
- Sewage treatment plants (STPs) and effluent treatment plants (ETPs) needing chemical-resistant joint sealing
- Roof decks, podiums and terraces where movement joints must stay watertight
- Concrete facades and external walls with pronounced movement joints
- Rehabilitation of leaking or failed joints where a bonded strip is more reliable than resealing
Key advantages
- Handles continuous and pronounced cyclic joint movement without stressing the bond line
- Manufactured membrane gives a consistent, controlled waterproofing thickness along the whole joint
- Chemically inert, so it suits sewage, effluent and treated-water environments
- Good UV and weathering resistance for exposed roof, podium and facade joints
- Can be applied to dry or damp concrete, matching real basement and tank conditions
- Available in 1 mm and 2 mm thicknesses and multiple widths to match joint size and movement
- Well suited to remedial work on joints where a previously applied sealant has failed
- Backed by the matching Nitobond PC40 epoxy as a designed, single-source system
Limitations & considerations
- It is a strip-over-joint system, not a gun-grade filler; narrow perimeter and window joints are better served by a sealant like Nitoseal PU40
- Performance depends heavily on correct surface preparation and full epoxy bond either side of the joint
- The unbonded loop over the joint must be set out correctly for the expected movement, so it needs a competent applicator
- Concrete arrises must be sound and clean; weak, spalled or contaminated substrate will compromise the epoxy bond
- As a surface-bonded strip it is not a substitute for a cast-in waterstop where one is specified for new construction
- Grey membrane finish is functional rather than decorative and is usually covered or screeded where appearance matters
Selection & best practice
Start with the concrete: the bonding zones on each side of the joint must be sound, clean and free of laitance, dust, oil and any old sealant, cutting back to solid concrete at the arris where necessary. Set out the strip so a defined, unbonded length of membrane sits centrally over the joint gap to act as the movement loop, then bond the outer margins flat to primed concrete with Nitobond PC40, working the adhesive to remove air and voids so there are no unbonded pockets along the edges. Choose the width and thickness to suit the joint width and the anticipated movement rather than defaulting to the smallest roll. Because Nitobond PC40 is a two-part epoxy with a temperature-dependent working time, mix only what can be placed within the pot life and plan the day around ambient temperature. Overlap and detail junctions and changes of direction carefully, as these are the common leak points. On water-retaining structures, allow the epoxy to cure fully before flood or hydrostatic testing. Space Arc can provide site demonstration and applicator support to get the first joints detailed correctly.
Specifications
| Product type | Un-reinforced Flexible Polyolefin (FPO) membrane strip system |
| Function | Bonded over expansion / movement joints to prevent passage of water |
| Thickness | 1 mm and 2 mm |
| Width range | 100 mm to 1 m (common India sizes 100 / 150 / 200 mm) |
| Roll length | 20 m (typical) |
| Colour | Grey |
| Bonding adhesive | Nitobond PC40, two-part epoxy adhesive |
| Movement capability | Accommodates continuous and pronounced cyclic movement |
| Substrate condition | Can be applied to dry or damp surfaces |
Industry use cases
Water & wastewater
Expansion joints in reservoirs, water tanks, STPs and ETPs, where chemical inertness and long-term watertightness across moving joints are essential.
Below-ground / basements
Raft and wall movement joints in basements and retaining structures under hydrostatic pressure, where a bonded FPO strip out-performs a resealed joint.
Infrastructure
Tunnels, subways and cut-and-cover box structures needing joints that stay dry through repeated cyclic movement.
Roofs, podiums & facades
Exposed movement joints on decks, podiums and concrete facades where UV and weathering resistance are needed alongside waterproofing.
Repair & rehabilitation
Reinstating watertightness on leaking or failed joints where a surface-bonded membrane strip is more dependable than re-caulking with sealant.
Frequently asked questions
Is Expoband One a polyurethane sealant?
How is it fixed to the concrete?
Can it be used inside water tanks and sewage structures?
What widths and thicknesses are available?
Does the concrete need to be dry before application?
Do you supply it in Delhi NCR and elsewhere in India?
How we position Fosroc Expoband One
Expoband One sits at the heavy-duty end of joint waterproofing: use it where a joint moves significantly and must stay watertight, particularly in water-retaining and below-ground structures. It is a system, so specify it alongside its designed partner, Nitobond PC40 epoxy adhesive, which does the bonding. For the narrower building, perimeter and non-trafficked floor joints where a gun-grade sealant is the right tool, move to Fosroc Nitoseal PU40 (one-part PU) rather than a membrane strip. Where a cast-in solution is preferred on new construction, Fosroc PVC waterstops are the complementary route. Beyond the Fosroc family, Space Arc also supplies expansion-joint and sealant systems from Sika and other brands, so we can match the specification to the joint, the substrate and the exposure rather than forcing one product to do every job.
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