Installing Waterproofing for Underground Structures

Underground structures, such as basements, tunnels, and parking garages, are subjected to significant water pressure due to their proximity to the water table. This constant exposure to moisture can lead to water infiltration and structural issues if not addressed properly. Waterproofing these underground structures is essential to protect them from water damage, mold growth, and potential structural failure. In this article, we will delve into the installation methods for waterproofing underground structures and explore the different techniques used for effective waterproofing.

Why is Waterproofing Underground Structures Important?

Before diving into the installation methods, it is crucial to understand why waterproofing underground structures is so important. Failure to waterproof these structures can result in:

  1. Water infiltration: Without proper waterproofing, water can seep into underground structures through cracks, joints, or porous materials. This infiltration can cause significant damage to the structure and compromise its integrity.

  2. Mold growth and health hazards: Moisture provides an optimal environment for mold growth. Mold not only damages the structure, but it can also pose health risks to individuals who come into contact with it.

  3. Structural instability: Constant exposure to water can weaken the structural elements of underground structures, leading to their potential collapse. The deterioration of reinforcement bars, corrosion of steel, and degradation of concrete are common consequences of water damage.

Now that we understand the importance of waterproofing, let’s explore some of the installation methods used for effective waterproofing.

1. External Waterproofing Membrane

One of the most common methods employed for waterproofing underground structures is the use of an external waterproofing membrane. This method involves the application of a membrane or coating on the exterior side of the structure to prevent water infiltration. The steps involved in this installation method are as follows:

  • Surface preparation: The surface of the structure is thoroughly cleaned and prepared to ensure proper adhesion of the membrane.

  • Application of primer: A primer is applied to the surface to enhance the bonding between the membrane and the structure.

  • Installation of the membrane: The waterproofing membrane is then applied to the prepared surface, typically in multiple layers. The membrane can be made of modified bitumen, PVC, polyurethane, or other suitable materials.

  • Sealing of joints and penetrations: Special attention is given to sealing joints, corners, and any penetrations to ensure a watertight seal.

This installation method creates a strong barrier between the structure and the external environment, effectively preventing water infiltration.

2. Internal Waterproofing System

Another method for waterproofing underground structures is to install an internal waterproofing system. This method involves the installation of a water management system within the structure to control and redirect any water that may infiltrate. The steps involved in this installation method are as follows:

  • Surface preparation: Similar to external waterproofing, the surface needs to be properly prepared before installing the internal waterproofing system.

  • Installation of drainage system: A network of pipes and drainage channels is installed along the interior perimeter of the structure. These channels collect any water that seeps through the walls or floor.

  • Sump pump installation: A sump pump is installed at the lowest point of the structure to collect and discharge the water collected by the drainage system.

  • Waterproofing of walls and floors: The walls and floors are treated with a waterproofing membrane to prevent water from seeping through them.

By implementing an internal waterproofing system, any water that infiltrates the structure is effectively managed and directed away, minimizing the potential for water damage.

3. Injection Waterproofing

Injection waterproofing is a technique used to seal and fill the cracks and voids within the structure to prevent water infiltration. This method involves injecting a waterproofing material into the cracks under pressure, ensuring a complete and tight seal. The steps involved in this installation method are as follows:

  • Identification of cracks: All the cracks and voids within the structure are identified using a thorough inspection.

  • Drilling of injection holes: Injection holes are drilled along the length of the cracks, allowing for the injection of the waterproofing material.

  • Injection of waterproofing material: Once the holes are drilled, the waterproofing material is injected under pressure into the cracks, filling them completely.

  • Monitoring for effectiveness: After the injection, the structure is monitored to ensure that the waterproofing material has effectively sealed the cracks and prevents any water infiltration.

This technique is particularly effective for Repairing existing cracks and preventing further water damage.

Frequently Asked Questions (FAQs)

Q1. How long does the installation of external waterproofing membrane take?
The installation time for an external waterproofing membrane depends on various factors such as the size of the structure, weather conditions, and the materials used. However, it typically takes a few days to complete.

Q2. Can internal waterproofing alone prevent water infiltration?
While internal waterproofing can effectively manage and redirect water, it is recommended to combine it with external waterproofing for optimal protection. This provides a double layer of defense against water infiltration.

Q3. How long does the injection waterproofing last?
The longevity of injection waterproofing depends on various factors such as the quality of the materials used and the structural conditions. However, when installed correctly, injection waterproofing can last for several years.


Waterproofing underground structures is crucial to protect them from water damage, mold growth, and potential structural failure. By using external waterproofing membranes, internal waterproofing systems, and injection waterproofing techniques, these structures can be effectively protected from the damaging effects of water infiltration. Each installation method offers its own benefits and should be chosen based on the specific needs and conditions of the structure. Hire a professional waterproofing Contractor to ensure the proper installation of the chosen method and enjoy a dry and structurally sound underground space.

Cape Town Waterproofing

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