1. Introduction
Repair & refurbishment waterproofing is required where old slabs or failed membranes cannot be demolished. The challenge is to restore watertightness without replacing the mother slab, often over APP membranes, weak concrete, or multiple patch repairs.
System choice depends on whether the surface can be repaired and prepared for bonding or if it is too weak and requires a loose-laid membrane solution.
2. Key Challenges
- Weak, low-strength concrete → poor adhesion.
- Existing APP/bitumen layers → removal not always possible.
- Uneven slope → ponding issues.
- UV exposure → membranes must be UV-stable.
- Accessibility → live buildings, heritage sites, operational industries.
3. Typical Application Areas
- Old residential & industrial terraces with service constraints
- Failed APP/bituminous overlays.
- Podiums or public buildings under refurbishment.
4. Technology Options Based on Site Constraints
Case 1: Surface Repair Possible → Bonded Membrane Solution
- System: Substrate can be repaired (grinding, screeding, patch repair).
- Technologies:
- 2K Polyurethane Membranes (Hand-applied, ≥2 mm DFT) → seamless, elastomeric, UV-resistant with aliphatic topcoat.
- Polyurea (Spray, ≥2 mm DFT) → high performance for industrial refurbishments (ETP/STP, chemical exposure).
- Advantages:
- Full adhesion to substrate → no water migration risk.
- Seamless application.
- High elongation & crack bridging.
- Constraints:
- Requires substrate prep & curing.
- Higher cost than loose-laid membranes.
Case 2: Surface Cannot Be Repaired → Loose-Laid Membrane Solution
- System: Substrate too weak for adhesion; overlay needed.
- Technologies:
- TPO Membranes (Mechanically Fastened / Ballasted) → UV-stable, weldable seams, long life.
- Advantages:
- Does not rely on substrate strength.
- Fast installation, no curing time.
- Reflective, reduces heat load.
- Constraints:
- Requires ballast, mechanical fixing, or insulation boards.
- Junction & detailing critical to avoid wind uplift.
5. Comparative Table
Criteria | Case 1: Bonded Membranes (PU/Polyurea) | Case 2: Loose-Laid Membranes (TPO) |
Substrate Condition | Sound (repairable) | Weak / cannot be repaired |
Adhesion | Fully bonded | Loose-laid, mechanically fastened |
Crack Bridging | High (PU ≥2 mm, Polyurea ≥3 mm) | Moderate (depends on sheet) |
UV Resistance | PU (with topcoat) / Polyurea (excellent) | Excellent (inherent UV stability) |
Application | Requires substrate prep & skilled team | Faster, factory QA sheet membrane |
Service Life | 10–20 years | 15–20 years |
Best Use | Industrial refurbishments, ETP/STP, tanks, old RCC roofs | Old terraces, PEB retrofits, heritage refurbishments, weak slabs |
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