BMT

Waterproofing Materials

1. Introduction

Waterproofing refers to the process of making a structure impervious to the ingress of water under hydrostatic pressure or moisture intrusion. Effective waterproofing enhances durability, service life, and hygiene of buildings, especially in foundations, basements, roofs, and water-retaining structures.

The materials used must form a continuous, durable, and elastic barrier against water penetration without compromising the structural performance.

2. Functions and Importance

• Prevents leakage in basements, terraces, water tanks, and bathrooms.
• Protects reinforcement from corrosion due to moisture exposure.
• Improves durability of concrete and masonry by preventing dampness.
• Reduces maintenance costs and enhances building aesthetics.
• Ensures comfort by maintaining indoor humidity and temperature levels.

3. Classification of Waterproofing Materials

Category	Examples	Typical Applications
Cementitious	Cement-based coatings, crystalline compounds	Water tanks, basements, internal wet areas
Bituminous	Bituminous coatings, membranes, mastic asphalt	Roofs, foundations, retaining walls
Polymer-based (Liquid Membranes)	Acrylic, polyurethane, epoxy coatings	Roofs, balconies, terraces
Sheet Membranes	PVC, HDPE, EPDM, TPO	Roofs, podiums, tunnels
Integral Waterproofing Compounds	Admixtures mixed into concrete	Structural members, tanks
Cementitious Crystalline Compounds	Hydrophilic compounds reacting with water	Concrete structures needing self-sealing
Modern Hybrid Systems	Poly-cementitious, nano-coatings	High-performance structures

4. Cementitious Waterproofing

Description:

• Composed of Portland cement, sand, and additives that improve adhesion and flexibility.
• Easy to apply and economical for internal wet areas where thermal movement is minimal.

Applications:

• Water tanks, basements, swimming pools, lift pits, and toilets.

Advantages:

• Simple mixing and brush application.
• Compatible with damp concrete.
• Good bonding with masonry and RCC.

Limitations:

• Brittle under structural movements.
• Not suitable for exposed or vibrating areas.

Example Products:

• Cementitious slurry coatings, crystalline waterproofing systems (e.g., Xypex, Dr. Fixit crystalline).

5. Bituminous Waterproofing

Description: Derived from bitumen; provides excellent adhesion and flexibility when applied as coatings or membranes.

5.1 Bituminous Coating

• Applied as protective paint or spray on concrete or masonry.
• Acts as a vapor barrier and protective layer for retaining walls or substructures.

5.2 Bituminous Membrane

• Consists of polymer-modified bitumen (SBS, APP) reinforced with polyester or glass fiber.
• Available in torch-applied, self-adhesive, or mechanically fastened forms.

Type	Description	Thickness	Applications
APP (Atactic Polypropylene)	Heat-resistant, suitable for hot climates	3–5 mm	Roofs, terraces
SBS (Styrene-Butadiene-Styrene)	Elastic, suited for cold climates	2–4 mm	Basements, podiums

Advantages:

• Long-lasting and UV-resistant.
• Provides monolithic and flexible membrane.

Limitations:

• Requires skilled application.
• Sensitive to substrate preparation and temperature.

6. Liquid Applied Membranes (Polymer-Based)

Description: Single or multi-component polymer coatings forming a seamless, elastic, waterproof film upon curing.

Type	Base Polymer	Key Features	Typical Use
Acrylic Coating	Water-based acrylic resin	UV-resistant, breathable	Exposed roofs, terraces
Polyurethane (PU)	Two-component, solvent-based	Highly elastic, chemical resistant	Roofs, podium slabs
Epoxy Coating	Epoxy resin + hardener	Hard, durable, low permeability	Industrial floors, water tanks

Advantages:

• Seamless coverage without joints.
• Excellent adhesion and flexibility.
• Quick application by brush, roller, or spray.

Limitations:

• Requires clean and dry substrate.
• UV degradation possible for non-modified polymers.

7. Sheet Membranes

Description: Prefabricated flexible sheets laid over the surface to form a continuous waterproof barrier.

Common Types:

• PVC (Polyvinyl Chloride) – economical, flexible.
• HDPE (High-Density Polyethylene) – durable, puncture resistant.
• EPDM (Ethylene Propylene Diene Monomer) – highly elastic, long-lasting.
• TPO (Thermoplastic Polyolefin) – heat-weldable, UV resistant.

Applications:

• Roofs, tunnels, basements, water-retaining structures.

Installation Methods:

• Loose laid with ballast.
• Fully bonded using adhesives.
• Heat welded (TPO/PVC) or mechanically fastened.

Advantages:

• Uniform thickness and factory-controlled quality.
• High tensile strength and elongation.
• Resistant to roots, chemicals, and punctures.

Limitations:

• Seams must be perfectly joined.
• Skilled installation required.

8. Integral Waterproofing Compounds

Description: Admixtures added directly to concrete during mixing to reduce permeability and improve durability.

Types:

1. Plasticizing Compounds – reduce water demand and improve workability.
2. Pore-blocking Compounds – fill pores and capillaries with fine materials.
3. Hydrophobic Compounds – repel water penetration through capillaries.

Applications:

• Structural concrete in foundations, slabs, tanks, retaining walls.

Advantages:

• No extra layer needed.
• Enhances concrete durability.
• Compatible with standard mixing procedures.

9. Selection of Suitable Waterproofing System

Consideration	Recommended Type
Internal wet areas (toilets, water tanks)	Cementitious coatings
Terraces / Roofs	Acrylic or PU liquid membrane, APP membrane
Basements / Retaining walls	Bituminous membrane or HDPE sheet
Podium slabs / Tunnels	PVC/EPDM sheet or PU coating
Water-retaining structures	Crystalline or integral waterproofing

Key Factors:

• Substrate movement and joint behavior.
• Exposure conditions (UV, chemicals, temperature).
• Accessibility for maintenance.
• Life-cycle cost and ease of application.

10. Methods of Application

A. Surface Preparation

• Remove dust, oil, and laitance.
• Fill cracks and honeycombs with non-shrink mortar.
• Ensure smooth, dry substrate for membranes.

B. Application Procedures

Method	Materials Used	Description
Brush/Trowel Coating	Cementitious, acrylic, epoxy	Apply in 2–3 coats at 90° directions
Spray Coating	PU, bituminous emulsions	Used for large roof or wall areas
Sheet Laying	APP, PVC, HDPE membranes	Overlap by 100 mm; heat-seal or bond
Integral Admixture	Liquid or powder additives	Mixed in concrete during batching

C. Quality Checks

• Check for pinholes and holidays (spark test).
• Conduct water ponding test for 48 hours on flat roofs.
• Ensure overlap joints are sealed and terminated properly.

11. Common Failures and Preventive Measures

Defect	Cause	Prevention
Blistering / Peeling	Trapped moisture or poor adhesion	Proper surface preparation, avoid damp base
Cracking	Rigid coating on moving substrate	Use flexible membranes or elastomeric coatings
Delamination	Weak bonding or contamination	Apply primer, ensure clean surface
Leakage at Joints	Poor overlap or detailing	Seal overlaps and upturns carefully
UV Degradation	Exposure to sunlight	Apply protective screed or reflective coating

12. Relevant IS Codes and Standards

IS Code	Description
IS 2645:2003	Integral waterproofing compounds
IS 13182:1991	Waterproofing by polymer-modified bitumen
IS 1346:1991	Waterproofing of roofs with bitumen felt
IS 3384:1986	Bitumen primer for waterproofing
IS 8887:2004	Bitumen/Polymer modified membranes
IS 3067:1988	Code of practice for waterproofing of roofs
IS 10262:2019	Concrete mix design incorporating admixtures

13. Practical Insights / Site Observations

• Always check surface dryness before applying liquid coatings.
• Maintain membrane overlap ≥ 100 mm for sheet systems.
• Conduct water ponding tests before finishing layers.
• Avoid waterproofing during heavy rain or high humidity.
• Protect completed waterproofing with screed or tiles.

14. Summary

Waterproofing materials play a crucial role in ensuring long-term durability and structural integrity of buildings. The choice of system depends on location, exposure, structural movement, and budget. Modern polymer and crystalline systems provide superior flexibility, adhesion, and self-healing properties compared to traditional coatings.