Waterproofing is a critical aspect of construction that often goes unnoticed but plays a vital role in protecting buildings from long-term damage. Whether safeguarding a roof from heavy rainfall or preventing moisture from seeping into basement walls, effective waterproofing ensures a building’s longevity and structural integrity.
In this post, we’ll explain the step-by-step process of applying waterproofing, the different methods available, and why paying extra attention to certain areas like joints and penetrations is essential. Proper waterproofing isn’t just about avoiding leaks—it’s about extending the life of your construction and avoiding costly repairs down the line.
Let’s get straight to the point.
Waterproofing in construction is essential for protecting buildings from water damage and extending their lifespan. The process involves preparing the surface, choosing the appropriate waterproofing method (cementitious waterproofing, liquid membranes, or bituminous membranes), and applying multiple layers for full protection.
Key areas like joints, corners, and penetrations require extra reinforcement, and a final protective layer is often added to ensure durability. Proper waterproofing prevents leaks, preserves structural integrity, and avoids costly future repairs.
Surface Preparation
Preparing the surface where the material will be applied is the first and arguably most critical step in waterproofing.
Proper surface preparation is key to ensuring strong adhesion and effective long-term waterproofing. A poorly prepared surface can compromise the entire waterproofing system, leading to leaks and failures.
- Cleaning the surface: It is essential to clean the surface thoroughly, removing any dust, dirt, grease, oil, or debris that may hinder the waterproofing material’s adhesion. Contaminants can create a barrier that prevents the material from bonding effectively with the substrate.
- Repairing damage: If the surface has visible damage, such as cracks, holes, or gaps, these should be repaired using an appropriate filler or patching compound. Leaving these imperfections untreated can allow water to seep through and undermine the waterproofing layer.
- Smoothing the surface: An even surface ensures that the waterproofing material can be applied uniformly. Irregularities like bumps or depressions can create weak points in the waterproofing layer, leading to potential leaks.
Important Considerations
- The surface must be completely dry before applying waterproofing materials, as moisture can prevent proper adhesion and lead to failure.
- To ensure the new application bonds effectively with the substrate, existing deteriorating or failing waterproofing layers must be completely removed.
Choosing The Waterproofing Method
Selecting the right waterproofing method is critical for achieving the desired protection.
The choice depends on several factors, such as the area’s location to be treated (e.g., roof, basement, or exterior wall) and the environmental conditions it will face (e.g., heavy rain, extreme temperatures, or groundwater pressure).
Understanding the specific demands of the structure allows for the most appropriate waterproofing technique to be chosen.
- Cementitious waterproofing: This rigid or semi-flexible method is often used in indoor areas with constant moisture, such as bathrooms, kitchens, or basements. It is easy to apply and highly resistant to moisture.
- Liquid waterproofing membrane: This method involves applying a liquid membrane that cures to form a flexible, seamless, and durable layer. It is commonly used on roofs and in irregular-shaped areas, as it easily conforms to surface contours.
- Bituminous coating and membrane: This technique is well-suited for low-slope roofs and foundations. Bitumen creates a highly durable and waterproof barrier, protecting against water intrusion and weathering.
- Polyurethane liquid membrane: This is an ideal solution for flat roofs and areas exposed to extreme weather conditions. Polyurethane is highly elastic and offers excellent resistance to harsh elements.
Applying Primer Layer
Once the surface is fully prepared, a primer is often applied to improve the adhesion of the waterproofing material. Primers help create a strong bond between the surface and the waterproofing layer, essential for long-lasting protection.
Neglecting this step can lead to adhesion issues, especially on porous surfaces.
- Apply an even coat: Using a roller or brush, apply a uniform coat of primer to the entire surface, ensuring it reaches all corners and edges.
- Allow drying time: The primer typically requires a specific drying period before applying the waterproofing material. Following the manufacturer’s drying time recommendations is critical to ensure maximum adhesion.
Application Of Waterproofing Material
After the primer has dried, the chosen waterproofing material is applied according to its specific method.
Each material requires a different technique, whether rolling, spraying, or troweling, to ensure complete coverage and maximum effectiveness. Careful application at this stage is critical for creating a continuous, leak-proof barrier.
For Liquid Waterproofing Membranes
Roll or spray the material: Apply the liquid waterproofing material evenly over the surface, ensuring that thin, consistent layers are built up.
Depending on the material’s viscosity and the size of the area, a roller or spray equipment can be used. Cover all areas thoroughly.
Please pay attention to corners, edges, and other hard-to-reach areas to ensure they are well-coated. These are common areas where leaks can form.
For Bituminous Membranes
Torch-applied or self-adhesive: Bituminous membranes may require heating with a torch during application or may come with a self-adhesive backing. Either method should be applied carefully to avoid gaps or bubbles.
Overlap the seams: Ensure the membrane overlaps adequately to prevent water from seeping between layers. Seams are particularly vulnerable to leaks if not sealed properly.
For Cementitious Waterproofing
Mix with water or additives: To achieve consistency, prepare the cementitious material with water or special additives according to the manufacturer’s instructions.
- Brush or trowel the mixture: Apply the material evenly across the surface using a brush or trowel, ensuring it penetrates any cracks or pores for complete coverage.
Adding Multiple Layers For Full Protection
Waterproofing typically involves applying multiple layers to ensure a durable and effective water barrier. Each layer strengthens the previous one, ensuring the system can withstand normal wear and harsh environmental conditions.
Skipping layers or applying them incorrectly can result in a failed waterproofing system.
- Two coats minimum: Most waterproofing systems recommend applying at least two coats. The first layer provides initial coverage, while the second ensures full protection.
- Drying time: Each coat must dry completely—typically about 24 hours—before applying the next. Rushing this process can cause the layers to weaken.
- Extra coats in high-risk areas: In areas prone to heavy rainfall, groundwater pressure, or extreme weather conditions, additional coats may be necessary to reinforce the waterproofing system.
Reinforcing Weak Areas
Certain areas of a structure are more vulnerable to water penetration, such as corners, joints, and places where pipes or drains penetrate the surface.
These areas often require additional reinforcement to protect them from leaks.
- Using waterproofing tape: Specialised waterproofing tape can be applied to seams, joints, and other weak points to provide extra protection and prevent leaks.
- Installing reinforcing mesh: Reinforcing mesh can be applied between layers of waterproofing material to add strength and flexibility to areas subjected to stress or movement.
- Sealing around penetrations: Flexible waterproofing materials should be used to seal around pipes, drains, and other penetrations, as these areas are common sources of leaks if not properly sealed.
Final Protective Layer
Once the waterproofing material has been applied and fully dried, a final protective layer is often added to ensure long-term durability and protection from external factors.
This layer shields the waterproofing system from mechanical damage, UV rays, and environmental wear and tear.
- Tiles or insulation: In areas like bathrooms and terraces, tiles or insulation boards can be installed to add an extra layer of protection and improve the aesthetic finish.
- Gravel or paving: Gravel or paving stones can protect the waterproofing membrane from direct sunlight and mechanical damage on flat or low-slope roofs.
- Protective coatings: Some waterproofing systems include an additional top coat that provides increased resistance to UV rays, chemicals, and environmental degradation, further extending the system’s lifespan.
Conclusion
Applying waterproofing in construction is a vital step that protects a building from water damage and prolongs its lifespan. The process involves surface preparation, choosing the right method, applying multiple layers, and reinforcing vulnerable areas.
Proper waterproofing is necessary for key parts of a structure, such as roofs, basements, walls, and terraces, each requiring specific materials and techniques. By following the correct waterproofing steps, builders can ensure that the structure remains protected from water infiltration, enhancing durability and preventing costly repairs in the future.
FAQs About Waterproofing
What Are The Types Of Waterproofing?
The most common types of waterproofing are cementitious waterproofing, liquid waterproofing membrane, bituminous membrane, bituminous coating, and polyurethane liquid membrane.
How Is Construction Waterproofing Done?
Typically, building a waterproofing system creates multiple barriers to stop water inflow from entering the structure. Using materials and techniques, this development of multiple layers creates an “envelope” structure around the building.
How Many Coats Are Waterproof?
Two coats are needed, each taking 24 hours to dry. The extra sealant may also be needed once the tiles are down. It’s a job that can take up to four days, so allow plenty of time-waterproofing a kitchen.
Is Tar Good For Waterproofing?
Asphalt-based tar is often used to dampproof basement walls. It is painted on the walls to keep water vapour from moving in and out. However, asphalt-based tar isn’t a true waterproofing material. Applying tar to your basement walls provides a dampproof coating instead of waterproofing.
Where Is Waterproofing Used?
Waterproofing is used for building structures (such as basements, decks, or wet areas), watercraft, canvas, clothing (raincoats or waders), electronic devices and paper packaging (such as cartons for liquids).
