PU Injection Grouting in Chennai
Quick answerPU injection grouting stops active water leaks by pumping polyurethane resin into a crack or joint under pressure. The resin reacts with water, expands into foam and seals the full depth of the crack. In Chennai it typically costs ₹250 to ₹600 per injection point, and most leaks are stopped the same day.
Why it is in demand in Chennai
Large parts of the city are built on low, formerly marshy ground. In Velachery, Pallikaranai, Madipakkam and Mudichur, and along much of the OMR, the water table is high all year and rises further during the northeast monsoon. Any structure below ground level, such as a basement car park, lift pit, underground sump or retaining wall, then sits in water for months.
Under that pressure, ground water finds every crack, every construction joint and every pipe sleeve. Surface patching with cement fails because the water simply pushes it off. PU injection works the other way round: it uses the water already in the crack to trigger the seal, so it can be done while the leak is running. That is why it is the first response for flooded basements and lift pits after heavy rain.
Signs you need PU injection
- Water dripping or flowing through a visible crack
- Basement walls or floors that weep after rain
- Water collecting in the lift pit
- Leaks at the joint between wall and floor slab
- Seepage around pipes passing through concrete
- Ceiling leaks in a podium or car park below a garden or driveway
- Expansion joints dripping onto parked vehicles
What is actually going wrong
Construction joints are open.
Concrete is poured in stages. Where a new pour meets hardened concrete, the bond is weak unless a waterstop was fitted properly. These joints are the most common leak path in basements.
Failed external membrane.
Concrete is poured in stages. Where a new pour meets hardened concrete, the bond is weak unless a waterstop was fitted properly. These joints are the most common leak path in basements.
Shrinkage and settlement cracks.
Concrete shrinks as it cures, and buildings settle. The resulting cracks may be hair-thin but run through the full wall thickness.
Honeycombed concrete.
Poorly compacted concrete has voids that link up into channels.
In every case, water under pressure is travelling through a defined path. Injection fills that path through its full depth, and that is what makes the repair hold.
Recommended systems
System | Where we use it | Notes |
|---|---|---|
Hydrophobic PU foam resin | Running or gushing leaks | Expands many times on contact with water and stops flow in minutes |
Flexible PU gel or elastomeric resin | Second-stage permanent seal | Stays flexible and tolerates crack movement |
Hydrophilic PU resin | Fine, damp cracks | Swells with moisture for a tight seal |
Steel or aluminium injection packers | All injections | Removed after the resin cures |
Polymer repair mortar | Surface finishing | Closes drill holes and the crack face |
For heavy leaks we use two stages: foam to stop the water, then flexible resin to make the seal permanent.
How we do the work
- Trace the leak.We follow the water back to the crack or joint and mark its full length.
- Drill. Holes are drilled at a 45 degree angle on alternating sides of the crack, to meet it at mid-depth. Spacing is usually 200 to 300 mm.
- Fix packers. Injection packers are set and tightened in each hole.
- Flush. Clean water is injected where required, to clear the crack and wet the surface for the resin.
- Inject.Resin is pumped from the lowest packer upwards, until it shows at the next packer or along the crack face..
- Second pass.Flexible resin is injected for permanent sealing where specified.
- Cure and check.The area is watched until the leak has stopped fully.
- Finish. Packers are removed, holes filled and the surface made good.
A typical crack of a few metres is completed within a day. The space stays usable throughout.
Cost in Chennai
Work | Indicative rate |
|---|---|
PU injection | ₹250 to ₹600 per injection point |
By crack length | ₹250 to ₹450 per running foot |
Basement or lift pit, full treatment | Quoted after survey |
Cost depends on the number of injection points, wall thickness and how much resin the crack takes. A wide crack with strong flow uses more material than a damp hairline.
Frequently asked questions
Can it be done while water is flowing?
Yes. PU resin needs water to react, so active leaks are exactly where it works best.
How long does the repair last?
A properly injected crack stays sealed for many years. Flexible resin copes with the small movements that reopen rigid repairs.
What is the difference between PU and epoxy injection?
PU is flexible and stops water. Epoxy is rigid and restores strength in dry structural cracks. Some repairs need both.
Will you have to break the wall or floor?
No. The work involves only small drilled holes, which are filled afterwards.
Is it safe inside an occupied building?
Yes. The work is low in noise and dust, and the cured resin is inert.
My lift pit floods every monsoon. Can this fix it?
In most cases, yes. We inject the joints and cracks, then coat the pit with a crystalline system.
Is there a warranty?
Yes. A written warranty covers the treated cracks and joints.
Stop the leak today
Call or WhatsApp WATREX with a short video of the leak. We attend urgent basement and lift pit leaks across Chennai.