Concrete is strong, durable and widely used, but it is not naturally waterproof. Without the right protection, water ingress can lead to corrosion of reinforcement, freeze-thaw damage, cracking and long-term structural deterioration. That’s why choosing the correct waterproofing method is critical to the performance and lifespan of any concrete structure.
In this article, we’ll, compare the most commonly used waterproofing systems, outlining where each works best and what to consider when specifying a solution.
Liquid-applied waterproofing systems
Liquid-applied waterproofing is one of the most versatile and widely used methods for protecting concrete. These systems are applied as a liquid coating that cures to form a seamless, fully bonded membrane.
Their key advantage is flexibility. Liquid systems can be applied to complex shapes, irregular surfaces and areas with penetrations or detailing that would be difficult to treat with sheet membranes. They also provide excellent adhesion, reducing the risk of water tracking beneath the system.
Liquid-applied waterproofing is commonly used on roofs, podium decks, car parks and internal wet areas. Correct surface preparation and controlled application are essential to ensure consistent thickness and long-term performance.
Sheet and membrane waterproofing
Sheet membranes are pre-manufactured waterproofing layers that are bonded or mechanically fixed to the concrete surface. They offer consistent thickness and predictable performance when correctly installed.
These systems are often specified for large, open areas such as basements, tunnels and foundation slabs. However, detailing around joints, corners and penetrations requires care, as weak points can allow water ingress if not properly sealed.
Sheet membranes can be highly effective but they typically require more space and access for installation, making them less suitable for constrained or retrofit projects.
Cementitious waterproofing
This approach uses cement-based coatings or renders that are applied directly to the concrete surface. These systems are compatible with concrete substrates and relatively straightforward to apply.
They are often used in internal applications such as plant rooms, lift pits and water-retaining structures. Though cementitious systems can be cost-effective, they are generally less flexible than other methods and may be more susceptible to cracking if the structure moves. As a result, cementitious waterproofing is best suited to areas with limited movement and where ongoing access for inspection is available.
Crystalline waterproofing
Crystalline waterproofing works differently to surface-applied systems. Special additives or coatings react with moisture in the concrete to form crystals that grow within the pores and capillaries, blocking water pathways.
This method provides internal waterproofing and can offer long-term protection, even if the surface is damaged. That’s why it’s often used in new construction or for remedial works where external access is limited.
However, crystalline systems rely heavily on correct concrete quality and moisture conditions, and they may not be suitable for all environments or levels of water pressure.
How do you choose the right system?
There is no single “best” waterproofing method for every concrete structure. The right solution depends on several factors, including exposure conditions, water pressure, structural movement, access constraints and whether the project is new build or refurbishment. In many cases, combining systems (such as primary waterproofing with secondary protection) delivers the most robust outcome.
A considered approach to concrete waterproofing
Effective waterproofing is about more than just keeping water out. It protects structural integrity, reduces maintenance costs and extends asset life. By understanding the strengths and limitations of each method, you can make informed decisions that deliver long-term performance and value.
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