About Dr. Fixit Polybar Plus

Dr. Fixit Polybar Plus is Pidilite’s hydrophilic waterstop strip — a red, synthetic-rubber bar cast into the joint between two concrete pours and left inert until water reaches it. On contact with groundwater or seepage, the strip absorbs moisture and expands, pressing into the microscopic gaps a cold joint always has and closing the seepage path from the inside out. It isn’t a membrane, coating or injection grout; it’s a mechanical barrier that lives permanently inside the concrete section, sitting exactly at the plane where two separate pours meet — the point every other waterproofing system finds hardest to protect.

Indian basements, rafts, retaining walls, tanks and pile caps are almost never poured in one continuous go — shuttering limits, ready-mix logistics and monsoon scheduling force multi-stage pours, and every stage break is a cold joint. Polybar Plus is built for that reality: it goes in during the rebar-and-shuttering stage of the first pour, is nailed or glued along the joint line, and waits under cover until the next lift locks it in place. Space Arc Engineering, an authorised Dr. Fixit distributor and applicator across Delhi NCR, supplies Polybar Plus with its recommended fixing adhesive, Feviseal HY300, and plans the joint layout — cover, laps and protection between pours — before the rebar cage goes in, which is where most site failures with swellable bars actually start.

The technical insight

Polybar Plus works by osmotic swelling, not adhesion or mechanical clamping. Its chloroprene-rubber matrix is compounded with a hydrophilic filler that draws in water and expands the strip’s cross-section — Pidilite’s 14-day immersion test records a 300% unrestrained volume increase in plain water and a still-substantial 150% in 3% salt water, which matters on sites near the coast or with saline subsoil. That expansion only becomes useful when it is restrained: the strip has to be locked between two concrete faces with a minimum of 80 mm cover on each side, so the swelling pressure pushes sideways into the joint rather than outward into open air. This is also why the product is explicitly ruled out for expansion or isolation joints — a hydrophilic bar can seal a gap that opens once and then stays static, but it cannot cycle open-close-open the way a genuine movement joint does; that job belongs to a PVC or dumbbell-type waterstop instead.

Where it is used

• Horizontal and vertical construction (cold) joints in cast-in-situ RCC
• Kicker joints at the base of retaining walls and shear walls
• Pile cap joints and raft-to-wall construction joints in foundations
• Diaphragm wall joints in basements and deep excavations
• Pipe, conduit and sleeve entries through concrete walls and slabs
• Underground water tank (UGT) floor-to-wall construction joints
• STP/WTP tankage and sump pit construction joints
• Basement and podium slab pours executed in multiple stages

Key advantages

• Fast to fix on site — glued with Feviseal HY300 or nailed at roughly 300 mm centres, no curing wait before the next pour
• Retains its swelling capacity through repeated wet-dry cycles instead of degrading after the first wetting
• Still expands 150% in 3% salt water, so it keeps working in saline or brackish groundwater sites
• Rated to a 6 bar hydrostatic head, enough for most basement and deep-foundation water tables
• Functions across a wide service range, -30°C to +60°C, so weather extremes don’t affect the installed bar
• Self-forms into the actual shape of a crack or void around the joint rather than relying on a perfectly straight seal
• Supplied in two cross-sections (20×10 mm and 20×5 mm) to match joint width and available cover
• One product covers construction joints, kicker joints, pile caps and pipe entries — fewer separate SKUs for the site store

Limitations & considerations

• Not for expansion or isolation joints — no allowance for cyclic movement, only for a joint that closes once and stays put
• Needs a minimum 80 mm concrete cover on each side; it cannot be specified in thin walls or slabs
• Must stay dry, or only briefly damp, until the second pour locks it in — a strip left exposed to monsoon rain or curing water for days can swell prematurely and lose its seal
• Treats only the joint line itself; it is not a substitute for a membrane or coating system on the rest of the wall or slab
• Performance depends on correct fixing — centring, the 300 mm nailing pitch, 20 mm side-laps — a rushed installation is the usual cause of joint leakage, not the product
• Pidilite’s own data sheet flags up to 5% variation in the quoted swelling and hardness figures depending on water quality and test conditions

Selection & best practice

Specifications

Industry use cases

How we position Dr. Fixit Polybar Plus

Within the Dr. Fixit range, Polybar Plus is a specialist joint product, not a stand-alone waterproofing system — it is meant to be specified alongside a field waterproofing membrane (Dr. Fixit Raincoat or Pidiproof LW+ for the slab and wall area) and its own fixing adhesive, Feviseal HY300, which Space Arc stocks as a matched pair. Where a joint calls for a co-extruded strip with a documented higher swell ratio for critical or high-value works, Fosroc’s Hydrotite is a genuine, widely specified alternative technology built on the same swellable principle, and Space Arc can quote either brand against the same joint. Where the joint is a true expansion or isolation joint rather than a static construction joint, neither swellable bar is the right call — a centre-bulb PVC waterstop such as Sika Waterbar is the correct specification, and our technical team flags that distinction at the design-review stage rather than let a swellable bar go into a moving joint by default.

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