If positive side accessible: pre-applied HDPE for rafts/retaining walls or SBS/PU for unconfined faces. If only negative side: grid drill NRV 300–500 mm c/c, inject PU (hydrophilic for running water, hydrophobic for damp), then apply breathable cementitious/osmotic coat; crystalline as base densifier.
LQ-BASEMENT
Map joints, cracks, honeycombs → install NRV packers at 300–500 mm c/c → inject PU grout (hydrophilic for running leaks, hydrophobic for damp) until flow at next nozzle → apply breathable cementitious/osmotic coat; crystalline slurry base where dampness persists.
Confirm no active flow post-injection; record grout take. Negative-side coat continuous with no pinholes. Adhesion ≥1.0 MPa where applicable. 24–72 hr compartment/fill test as relevant.
Includes retaining walls, rafts, water tanks, STP/ETP; consolidated into Basement Leakages canonical record.
Summary
Basement leakages in India are widespread due to workmanship gaps, weak joint detailing, and the assumption that basements will leak. Typical failure points are the raft base under high water pressure, raft–retaining wall starters, construction joints along retaining walls, and tie-rod penetrations where PVC sleeves do not bond well with concrete. In occupied basements, the positive side is inaccessible, so remediation is performed from the negative side.
Symptoms
- Damp bands or active seepage lines along construction joints and wall–slab junctions
- Water ingress at tie-rod points and honeycombed zones
- Persistent damp patches after rains or when dewatering is paused
Probable causes
- High hydrostatic head acting on the raft base
- Weak or unsealed raft–wall starter joint
- Poorly prepared or unsealed construction/cold joints along retaining walls
- Tie-rod sleeve to concrete interface not watertight
- Honeycombs and discontinuities providing leak paths
Standard remedy overview (negative-side approach)
Because the external face is not accessible in service, adopt a two-step negative-side repair strategy:
1) Stop the leak at source
- Map the leakage zone. Drill a grid of NRV packers at 300–500 mm centers within the source radius.
- Inject suitable grout based on the condition:
- Running water: PU hydrophilic foam (rapid expansion with water)
- Heavy flow with limited water contact: PU hydrophobic (with accelerator)
- Seepage/micro-porosity: Vinyl acrylate
- Structural crack: Low-viscosity epoxy
- Continue injection until grout emerges at adjacent packers to confirm coverage.
2) Apply a negative-side protective membrane
- After active leakage is arrested, apply a cementitious breathable coating designed to resist negative water pressure over the treated area, including joints and junctions. Use crystalline or 2K cementitious systems per specification.
Note: Perimeter drain channels discharging to a sump are a common retrofit practice, but they normalize leakage and increase operational burden. Aim for watertightness by eliminating leak paths and then providing a continuous negative-side barrier.
Recommended technologies
- Injection grouts: PU hydrophilic, PU hydrophobic, vinyl acrylate, epoxy (structural)
- Negative-side coatings: Crystalline slurry, 2K elastomeric cementitious membrane
- Protection and detailing: Fillets at junctions, chase terminations, geotextile reinforcement where specified
Quick SOP
1) Investigate and mark all joints, tie-rod lines, cracks, and honeycombs. Determine active vs. damp seepage.
2) Drill NRV grid 300–500 mm c/c across mapped zones. Inject appropriate grout until emergence at the next nozzle.
3) Remove or seal packers. Fair and prepare the surface. Form 20×20 mm fillets at wall–slab junctions.
4) Apply specified negative-side coating:
- Crystalline slurry: 2 coats on SSD substrate with moist curing
- 2K cementitious: Crosswise coats to target DFT with reinforcement at corners and joints
5) Reinstate terminations and details. Document with photos and logs.
Decision guide
- Active running leaks at joints or tie rods → PU hydrophilic injection first → follow with negative-side cementitious
- Slow seepage through porous zones/honeycombs → Vinyl acrylate injection → negative-side cementitious
- Structural cracks that must transfer load → Epoxy injection → negative-side cementitious on top as needed
- Confined areas with widespread seepage and no access outside → Full NRV grid + staged injections → continuous negative-side coating
- Prefer fully bonded systems at the build stage to prevent lateral migration under high water tables. For retrofits, the above negative-side method restores dryness without normalizing leaks via sump channels.
Acceptance criteria
Video Masterclass
Masterclass: Basement Leakages — Coming soon
Disclaimer
Conix is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.