Cementitious Chemical Pressure Grouting in Chennai
Quick answerCementitious pressure grouting pumps a cement-based grout, mixed with a non-shrink waterproofing compound, into porous concrete through nozzles fixed in a grid. The grout fills hidden voids and honeycombs, so water has no path through the slab or wall. In Chennai it typically starts at about ₹75 per sq ft of treated area.
Why porous concrete is a Chennai problem
Good concrete is dense. Much of what gets built is not. In Chennai, slabs are often poured in high heat, and concrete that stiffens quickly is harder to compact. If the vibrator misses a section, or the mix was too dry, pockets of loosely bound stone are left inside. These honeycombs are plastered over and forgotten.
The first few monsoons find them. During long wet spells in November and December, water that soaks into the roof moves through these voids and appears as broad damp patches below, often with no crack in sight. Owners repaint, the patch returns the next year, and nobody can point to where the water is entering.
Pressure grouting is the answer to that kind of leak: widespread, slow and without a single obvious source.
Signs you need pressure grouting
- Large damp areas on a ceiling rather than a single drip point
- Dampness that appears days after rain and lingers
- Leaks along the joint between an old slab and a new extension
- Visible honeycombing where plaster has come off
- Seepage along beam-slab or wall-slab junctions
- Hollow sounds when the slab surface is tapped
- Leaks that came back after a surface coating
- Bathroom or balcony slabs seeping across a wide area
What is actually going wrong
Honeycombs and voids.
Poor compaction leaves air pockets and unbonded aggregate inside the concrete.
Segregation at the bottom of walls and columns.
Concrete dropped from height separates, leaving a weak, stony layer at the base.
Cold joints.
When concrete is placed against a section that has already set, the two do not fuse. Extensions and staged pours always have them.
Porous mix.
Too much water in the mix leaves a network of fine capillaries once it dries.
A coating on top can bridge these for a while. Grouting fixes the concrete itself, which is why the two are usually done together: grout first, then membrane.
Recommended systems
Material | Purpose | Notes |
|---|---|---|
Ordinary Portland cement slurry | Main grout body | Mixed to a flowing consistency |
Non-shrink expanding grout admixture | Stops the grout shrinking as it sets | Keeps voids fully filled |
Integral waterproofing compound or polymer | Makes the grout itself water-resistant | Dosed as per manufacturer |
Micro-fine cement | Fine voids and tight cracks | Penetrates where ordinary cement cannot |
Aluminium or PVC grouting nozzles | Injection points | Fixed with quick-setting mortar |
Polymer repair mortar | Sealing nozzle holes and surface defects | Finished flush |
Cementitious grout suits voids and porous zones. For a fine crack with running water, PU injection is the better tool, and for a structural crack, epoxy. We choose after seeing the fault.
How we do the work
- Survey.We tap-test the surface, mark hollow and damp zones and decide the grid.
- Drill.Holes are drilled in a grid, commonly 0.5 to 1 metre apart, and closer along joints. Depth is kept to about half the slab thickness to stay clear of the reinforcement.
- Fix nozzles.Nozzles are set in each hole and sealed with quick-setting mortar.
- Flush.Clean water is passed through to wash out dust and show which holes are connected.
- Mix.Cement, admixture and water are mixed in measured proportions.
- Grout.The grout is pumped at controlled pressure, typically 2 to 3 kg per sq cm, until the nozzle refuses more or grout appears at the next one.
- Seal.Nozzles are cut off after the grout sets and the holes are filled.
- Cure. The treated area is kept damp for several days.
- Coat.A waterproof membrane is applied over the surface where specified.
A 500 sq ft slab is usually grouted in two to three days, plus curing.
Cost in Chennai
Work | Indicative rate |
|---|---|
Cementitious pressure grouting | From about ₹75 per sq ft of treated area |
Membrane coating over the grouted area | ₹40 to ₹180 per sq ft, by system |
Grouting along joints only | Quoted per nozzle or per running foot |
The final cost depends on how much grout the concrete takes. Heavily honeycombed sections consume more material, and we report consumption per nozzle on completion.
Frequently asked questions
How is this different from PU or epoxy injection?
Cement grout fills voids and porous areas across a wide zone at lower cost. PU seals individual leaking cracks. Epoxy restores strength in structural cracks.
Will drilling weaken my slab?
No. The holes are small, kept clear of the steel and filled solid afterwards.
Can it be done from below?
Yes. Where the top is not accessible, such as under a neighbour's floor, we can grout from the ceiling side.
Is grouting alone enough?
For minor seepage, sometimes. On roofs and wet areas we recommend a membrane over it for full protection.
Does it work on old buildings?
Yes. It is often the most economical way to restore old slabs without breaking them.
How soon will the dampness go?
The leak stops once the grout sets. The concrete may take a few weeks to dry completely.
Is there a warranty?
Yes. A written warranty is issued for the treated area.