Reinforced concrete is strong, versatile, and widely used in construction—but it isn’t naturally waterproof. Effective waterproofing prevents costly water damage, corrosion, and structural deterioration. In this guide, we’ll explore why waterproofing matters, identify common solutions, and help you select the best waterproofing techniques for your project.

Waterproofing reinforced concrete is essential to protect structures against moisture penetration, rusting steel reinforcement, and concrete degradation. Unprotected concrete absorbs water, causing cracks, weakening strength, and shortening the structure’s lifespan.

Not familiar with what reinforced concrete is or how it works? Start with our overview: What is Reinforced Concrete to understand its composition, strength, and role in modern construction.

Concrete waterproofing is not just about keeping water out—it’s about preserving your structure’s integrity and protecting your investment.

• Enhanced durability against environmental damage.
• Longer lifespan and reduced need for repairs.
• Improved safety by preventing structural failure.

• Structural weakening and reduced lifespan.
• Corrosion of steel reinforcement.
• Increased maintenance costs.
• Potential structural failure in severe cases.

Understanding the causes of deterioration can help you take proactive waterproofing measures:

• Water ingress and hydrostatic pressure: Water entering concrete creates pressure, causing cracks and structural damage.
• Corrosion of steel reinforcement: Moisture corrodes reinforcing steel, leading to expansive rust, cracking, and weakening of concrete.
• Freeze-thaw cycles: Water in concrete expands when freezing, causing fractures.
• Chemical attack: Chlorides, sulphates, and pollutants react with concrete, causing chemical damage.

Curious how concrete compares to other building materials when it comes to durability and water resistance? Read our detailed breakdown: Concrete vs Other Construction Materials.

Concrete waterproofing solutions generally fall into three categories:

• Integral waterproofing (Type B).
• Surface-applied waterproofing (membranes and coatings).
• Joint and penetration waterproofing systems.

For a comprehensive overview of waterproofing solutions tailored to various construction needs, Sika South Africa offers a range of systems, including liquid-applied coatings, sheet membranes, and joint sealing products.​

Integral waterproofing involves adding waterproofing admixtures directly into the concrete mix, creating inherent resistance to moisture.

• Advantages:
  • Long-lasting waterproofing.
  • Reduced maintenance.
  • Seamless protection throughout concrete.
• Applications:
  • Basements, foundations, and retaining walls.

Surface-applied waterproofing provides an external barrier against water penetration.

• Sheet membranes: Durable, pre-fabricated sheets applied directly onto concrete surfaces.
• Torch-on membranes: Asphalt-based waterproofing melted onto the concrete surface for a robust seal.
• Liquid-applied membranes: Polyurethane or epoxy solutions that cure to form flexible, seamless barriers.

A cement-based coating, suitable for areas with limited movement and low water pressure. Economical and easy to apply, but not flexible enough for high-movement joints.

Crystalline waterproofing penetrates concrete pores, forming water-insoluble crystals that block moisture. Ideal for new structures, it provides permanent protection, reducing future maintenance.

Applied topically, this gel forms a water-repellent barrier within concrete pores. It’s particularly effective in existing concrete structures, sealing cracks and preventing further moisture intrusion.

Certain areas of reinforced concrete structures demand special care to ensure complete waterproofing.

Construction joints can be weak points where water easily enters. Special sealants, water bars, and joint tapes ensure effective waterproofing and structural integrity.

Often overlooked, tie-bolt holes from formwork must be sealed with appropriate waterproofing plugs or mortars to prevent leaks.

Services like pipes and cables penetrating concrete can cause leaks. Waterproof these areas using sealing collars, hydrophilic strips, or injectable resins.

• Basement waterproofing: Crucial for underground structures exposed to hydrostatic pressure.
• Roof waterproofing: Protects structures against direct exposure to weather and UV radiation.
• Wet areas (bathrooms/showers): Essential to prevent moisture damage and mould growth.

Selecting the right waterproofing solution depends on several factors:

• Type and location of the structure.
• Expected environmental conditions (e.g., water pressure, climate).
• Budget and lifecycle costs.
• Ease and speed of application.

Careful evaluation helps ensure optimal waterproofing performance for your structure.

Proper waterproofing application requires preparation and skill:

• Surface preparation: Surfaces must be clean, dry, and free of loose debris, contaminants, or laitance.
• Application best practices: Follow manufacturer recommendations closely, apply consistent thickness, and check curing conditions.
• Avoiding common pitfalls: Always inspect for surface cracks and irregularities before applying waterproofing products.

Even well-waterproofed structures require regular inspections:

• Perform routine checks to detect early signs of deterioration.
• Establish a maintenance schedule to ensure long-term waterproofing effectiveness.
• Quickly address minor waterproofing issues to prevent major structural damage.

For a more in-depth look at maintaining reinforced concrete over time, check out our guide on Maintenance and Inspection of Reinforced Concrete Structures.

Waterproofing reinforced concrete is essential to preserving structural integrity, prolonging service life, and protecting your investment. Choosing appropriate waterproofing solutions, ensuring proper application, and regular maintenance significantly reduces the risk of water-related damage and costly repairs.

Taking proactive waterproofing measures today will deliver significant long-term savings and peace of mind for years to come.