10 Common Mistakes to Avoid When Waterproofing Internal Wet Areas

A report issued in September 2021, by the Office of the NSW Building Commissioner and Strata Community Association NSW titled ‘Research report on serious defects in recently completed strata buildings across New South Wales’ found: 

• 39% of buildings reported serious defects. 
  • Where a serious defect occurred 63% of the time, it was related to waterproofing. 
  • 23% of buildings surveyed have a waterproofing defect. 
• 53% of serious defects were unresolved.
  • Where resolved, 75% of cases took over 6 months to resolve. 

 In this blog post, we will discuss the most common mistakes that should be avoided when waterproofing internal wet areas, helping you achieve a watertight and durable space, whilst upholding the integrity, safety, and value of the property. 

1. Inadequate Surface Preparation:

One of the most common mistakes is failing to properly prepare the surface before applying waterproofing materials. It is crucial to ensure the surface is clean, sound, dry, and free from dirt, grease, or loose particles. Any existing cracks or holes should be repaired before proceeding with waterproofing. Neglecting this step can compromise the effectiveness of the waterproofing membrane or coating.

2. Incorrect Selection of Waterproofing Membrane:

Choosing the right waterproofing membrane system is crucial for long-term success. Using the wrong type or a poor quality membrane can result in leaks and water damage. It is essential to select a proven and suitable waterproofing membrane specifically designed for internal wet areas. Using the wrong product can lead to ineffective waterproofing and potentially result in water damage to the structure and adjacent spaces. It is also important to ensure the membrane you are using complies with the regulatory requirements as outlined within the NCC (National Construction Code). Waterproofing membranes for internal wet areas must be designed and installed in accordance with AS 3740, and be compliant with AS 4858. Our Product Selector can help guide you to ensure the correct choice of waterproofing membrane. 

3. Improper Application Techniques: 

Even with the right product, improper application can hinder the effectiveness of waterproofing. It is always recommended to follow the supplier's instructions and apply the product correctly. This includes using the appropriate tools, such as brushes or rollers, and ensuring even coverage. Failure to do so can result in weak spots or gaps in the waterproofing layer. Tremco offers great data sheets that can help guide you. 

Image 1: Example of internal wet area waterproofing from https://duram.com.au/duram-applications-2/

4. Lack of Proper Sealing:

Penetrations such as pipes and drains require special attention during waterproofing. Failing to properly detail these penetrations can create potential entry points for water, undermining the effectiveness of the waterproofing system. Using appropriate sealants and techniques to seal all penetrations is crucial for a watertight internal wet area.

5. No slope/fall: 

 A very common mistake often made in wet area waterproofing is not providing a sufficient fall toward a drainage point both at the surface and sub-surface level. Without a proper fall, ponded water can result in unhealthy or dangerous conditions, and have a detrimental impact on the installed membrane system. 

6. Neglecting corners and joints: 

Corners and joints are vulnerable areas where water can easily seep through if not properly waterproofed. It is important that all corners and junctions are appropriately detailed to ensure the performance of the overall waterproofing system. 

7. Rushing the Curing Process: 

To ensure long-term performance, it is critical to allow the membrane to properly cure before the installation of any overburden finishes. Rushing through this process can compromise the integrity of the waterproofing system. It is important to follow the recommended curing time provided by the manufacturer to ensure maximum performance. 

8. Lack of Quality Control:

A common mistake is neglecting quality control during the waterproofing process. Insufficient checks, overlooking details, or rushing through the application can result in overlooked errors and compromised waterproofing. Implementing a thorough quality control process, including an Inspection Test Plan (ITP), completed in real-time and thorough post-completion testing, will mitigate application-related risk and promote longevity and effectiveness for the overall waterproofing system.

Image 2: Example of a good internal wet area application.

9. Failure to Address Underlying Issues: 

Waterproofing is not a standalone solution but rather a preventative measure. If there are underlying issues such as structural defects, plumbing leaks, or inadequate drainage, they must be addressed before applying any waterproofing materials. Failing to identify and rectify these issues can render the waterproofing efforts ineffective. 

10. Lack of Professional Assistance:

Attempting to waterproof internal wet areas without professional guidance can lead to costly mistakes. Consulting with waterproofing experts or hiring experienced contractors ensures that the correct techniques, materials, and procedures are followed. Their expertise can help you avoid common pitfalls and achieve a successful waterproofing outcome.

Waterproofing internal wet areas is a critical aspect of building construction and requires careful attention to detail and adherence to best practices to assist in maintaining the integrity, safety, and value of the property. By avoiding these common mistakes, you can ensure a watertight and durable internal wet area, protecting your investment and maintaining a safe and functional space for years to come. Remember, sufficient surface preparation, correct membrane selection, proper application and detailing, and professional assistance are key factors in achieving successful waterproofing and by doing so, you can enjoy peace of mind knowing that your internal wet areas are effectively protected.

If you have any questions or need project-specific advice, our Specification Team and Technical Representatives are always available to assist you.