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Waterproofing
Elastomeric Coatings
Using Elastomeric Coatings for Waterproofing Crack-Bridging
You can ignore them, but sooner or later, they will make their presence felt. Cracks. They are one of the most common and most misunderstood problems in Indian buildings. They appear on roofs, external walls, and around window frames, often returning within months of being repaired with conventional fillers. The reason is simple. Standard fillers are rigid. Cracks move. Elastomeric coatings solve this problem by staying flexible after curing, stretching and recovering with the crack as it moves without losing their waterproofing integrity. This guide covers what elastomeric waterproofing is, how it works, where to use it, and how to apply it correctly.
IN THIS ARTICLE
What Causes Cracks and Seepage in Walls
What Are Elastomeric Coatings?
How Elastomeric Coatings Bridge Cracks
Where Elastomeric Waterproofing Works Best
Best Elastomeric Coatings and Products
How to Apply Elastomeric Coatings
Repairing Cracks Before Waterproofing
What Causes Cracks and Seepage in Walls
Before we get to fixing them, let's understand what causes cracks. It’s essential to choose the right waterproofing solution.
- Thermal movement: concrete, brick, and plaster expand in heat and contract in cold. This daily and seasonal movement creates stress that eventually produces cracks, particularly at junctions between different materials.
Structural settlement: buildings settle over time, especially in the first few years after construction. Differential settlement produces cracks at predictable locations.
Shrinkage cracks: concrete and plaster shrink as they cure. If curing is not properly managed, shrinkage cracks appear across flat surfaces.
Corrosion of embedded steel: when steel reinforcement within a concrete structure corrodes, the expanding rust creates internal pressure that causes the concrete to crack and spall.
- Inadequate expansion joints: buildings without adequate movement joints concentrate thermal and structural movement stress at unpredictable points, producing cracks in unexpected locations.
What Are Elastomeric Coatings?
Elastomeric coatings are polymer-based waterproofing products that remain flexible after curing. Unlike rigid waterproofing compounds or standard paints that crack when the substrate beneath them moves, elastomeric coatings can elongate significantly, often 100 to 300% of their original dimension, and return to their original shape when the stress is released.
This elastomeric property is what enables them to bridge cracks and continue waterproofing even as the underlying crack opens and closes with temperature and structural movement. Elastomeric waterproofing is available in both liquid-applied and sheet membrane forms, with liquid-applied systems being the most commonly used for roofs, terraces, and external walls in India.
How Elastomeric Coatings Bridge Cracks
The crack-bridging capability of an elastomeric coating depends on its elongation, film thickness, and the quality of its bond to the substrate.
- Elongation value: expressed as a percentage, this indicates how far the coating can stretch before breaking. Most quality elastomeric waterproofing products used in India have elongation values between 100 and 300%.
Film thickness: A thicker applied film has a greater absolute stretch capacity. This is why coverage rate matters in elastomeric waterproofing. Applying too thinly reduces the practical crack bridging capacity of the system.
Substrate adhesion: an elastomeric coating can only bridge a crack if it is well bonded to the surface on either side of it. Poor adhesion causes the coating to peel rather than stretch.
- Recovery: quality elastomeric coatings recover their original shape after stretching. This recovery property is what allows them to continue waterproofing through repeated cycles of crack opening and closing over many years.
Where Elastomeric Waterproofing Works Best
Roofs and Terraces
Roofs and terraces are the primary application for elastomeric roof coating in India, and the area where the crack-bridging property provides the most value.
Flat concrete roofs develop hairline cracks from thermal movement that become active water entry points during the monsoon. An elastomeric roof coating applied at the correct film thickness bridges these cracks and prevents water ingress even as the cracks continue to move.
Elastomeric roofing systems are particularly effective on roofs that show a pattern of fine cracks across the surface without any individual crack being large enough to fill conventionally.
The UV resistance of quality elastomeric roof coatings allows them to perform on exposed roof surfaces for 5 to 10 years without significant degradation.
Asian Paints SmartCare offers elastomeric roof coating products formulated for the specific UV and rainfall conditions of Indian climates.
External Concrete Walls
External concrete and masonry walls experience thermal movement and develop hairline cracks that allow rain to penetrate the wall thickness.
An elastomeric coating applied to an external wall provides a flexible, breathable waterproofing layer that bridges hairline cracks and prevents rain penetration while allowing moisture vapour to escape from within the wall.
Elastomeric waterproofing on external walls is particularly effective where the wall surface shows a pattern of fine shrinkage or thermal cracks that are too numerous to fill individually.
The elastic roof coating or wall coating must be applied at the correct coverage rate and in a minimum of two coats to achieve the film thickness needed for effective crack bridging.
Humid and Rainy Climates
In regions with high annual rainfall, coastal humidity, and extreme monsoon intensity, elastomeric waterproofing provides specific advantages over rigid coating systems.
The flexibility of elastomeric coatings accommodates the greater thermal movement experienced in regions with wide temperature swings between summer and monsoon seasons
Elastomeric roofing systems with high elongation values maintain their waterproofing integrity under the sustained hydrostatic pressure of heavy monsoon rainfall better than rigid coatings
In coastal regions, elastomeric coatings provide a protective layer that resists salt penetration as well as water ingress
Best Elastomeric Coatings and Products
Whenever you do it, we ensure you do it right. Choosing the right elastomeric waterproofing product for the application and exposure conditions determines the long-term performance of the system.
- Asian Paints SmartCare Damp Proof Ultra: a premium elastomeric waterproofing product for roofs and terraces with high elongation, strong UV resistance, and excellent crack bridging capability
Elastomeric exterior wall coatings: formulated for vertical surfaces with breathable, crack-bridging properties. Available from Asian Paints in a range of colours for direct application as a finished exterior coat.
- Elastomeric roofing systems with fibreglass reinforcement: the highest performance elastomeric waterproofing option for roofs and terraces with active cracking or a history of waterproofing failure. The fibreglass mesh embedded in the first coat of the elastomeric coating significantly increases the crack-bridging capacity of the finished system.
How to Apply Elastomeric Coatings
Surface Preparation
Surface preparation is the most important step in any elastomeric waterproofing application.
- Remove all dust, loose material, algae, moss, and any existing coating that is not sound and well-adhered
- Repair all cracks wider than 0.3mm with a flexible polyurethane crack sealant before applying the elastomeric coating. Hairline cracks under 0.3mm can be bridged directly without prior filling.
Allow the surface to dry fully. Most elastomeric waterproofing products require a dry substrate for proper adhesion and curing.
Apply an appropriate primer before the elastomeric coating. The primer improves adhesion and ensures the elastomeric coating is applied at a uniform film thickness.
Applying Over Existing Coatings
Elastomeric waterproofing can be applied over existing coatings provided the existing coating is sound and well-adhered.
Test the adhesion of the existing coating by pressing adhesive tape firmly onto the surface and pulling it off sharply. If the coating comes away, the existing coating must be removed before elastomeric waterproofing is applied.
If the existing coating is sound, clean the surface thoroughly, apply a bonding primer, and apply the elastomeric coating system over the top.
Always apply elastomeric waterproofing to joints, edges, and penetrations with a strip of reinforcing mesh regardless of whether the application is to a new or existing surface.
Repairing Cracks Before Waterproofing
Not all cracks can be bridged by elastomeric coatings alone. Understanding which cracks require prior repair determines the long-term performance of the waterproofing system.
Cracks under 0.3mm: bridge directly with elastomeric waterproofing applied at the correct film thickness. No prior filing required.
Cracks between 0.3mm and 2mm: fill with flexible polyurethane sealant, cure, and then apply elastomeric waterproofing over the filled crack with a reinforcing mesh strip embedded in the first coat.
Cracks over 2mm or active structural cracks: these require structural assessment and repair before any elastomeric waterproofing is applied. Elastomeric coatings are not a substitute for structural repair.
Are Elastomeric Coatings Enough Alone?
It’s not a simple yes or no answer. For most hairline cracking applications on roofs and external walls, a correctly applied elastomeric waterproofing system is sufficient as a standalone waterproofing solution. However, there are situations where elastomeric coatings alone are not the complete answer.
Below-ground applications: basement and foundation waterproofing require products that resist sustained hydrostatic pressure from groundwater. A specialist product rated for the expected water pressure should always be specified.
Active structural cracks: elastomeric coatings bridge cracks that move within their elongation range. A crack that moves beyond the elongation capacity of the elastic roof coating or wall coating will cause it to rupture. Large active cracks require structural repair before elastomeric waterproofing is applied.
- New construction: on new construction where significant structural settlement is still expected, a more robust membrane system may be more appropriate for the first waterproofing application.
Elastomeric Waterproofing for Long-Lasting Crack Bridging
That said, elastomeric coatings are among the most effective waterproofing solutions available for Indian buildings. They accommodate the thermal movement that rigid coatings cannot, bridge the hairline cracking that conventional fillers cannot keep up with, and provide durable, long-lasting protection on roofs, terraces, and external walls. Asian Paints SmartCare offers a complete range of elastomeric waterproofing products for every application. Visit your nearest Asian Paints dealer or contact the Asian Paints Safe Painting Service for a professional assessment and the right elastomeric waterproofing solution for your building.
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