Waterproofing

At Collective Consult, we understand the critical importance of ensuring robust waterproofing solutions in construction. With the latest updates in the National Construction Code (NCC) Housing Provisions and AS 3740-2021, it’s essential to navigate these standards effectively to prevent costly building defects.

Authority of NCC (A4G2)

Section A4G2 of the NCC 2022 is a crucial clause to note. It establishes that any conflicts between the NCC, including the ABCB Housing Provisions, and a primary referenced document like AS 3740-2021 are to be resolved in favour of the NCC. This provision ensures that the NCC’s standards take precedence, providing a clear guideline for compliance in all construction projects.

Waterproofing: The Largest Cost in Building Defects

Waterproofing failures are the leading cause of serious building defects in Australia. At Collective Consult, we have observed that waterproofing accounts for a significant percentage of defects, particularly in Class 1 and Class 2 buildings. The financial burden of rectifying these defects is substantial, with Owners Corporations expending substantial amounts on repairs. Proper waterproofing is not just a regulatory requirement; it’s a critical aspect of cost-effective building management.

Definitions: Waterproof vs. Water-Resistant

Understanding the distinction between “waterproof” and “water-resistant” is vital for proper application:

• NCC Definitions:
  • Waterproof: The property of a material that does not allow water to penetrate through it.
  • Water-resistant: The property of a system or material that restricts water movement and will not degrade under conditions of water.
• AS 3740-2021 Definitions:
  • Waterproof: The property of a material that does not allow moisture to penetrate through it.
  • Water-resistant: The property of a system or material that restricts moisture movement and will not degrade under conditions of moisture.

While the terms are similar, the use of “moisture” instead of “water” in AS 3740-2021 can lead to interpretational differences.

Materials and Substrates

Choosing the right materials and substrates is crucial for effective waterproofing:

• NCC Housing Provisions:
  • Stainless steel
  • Flexible waterproof sheet flooring with waterproof joints
  • Membranes complying with AS/NZS 4858
  • Waterproof sealant
• AS 3740-2021:
  • Includes additional materials like copper, glass, and PVC, offering more flexibility and options in construction design.

Fall to Floor Wastes and Risk Categories

Both the NCC and AS 3740-2021 specify the importance of proper falls to floor wastes to ensure effective drainage:

• NCC Requirements:
  • A minimum fall of 1:80 to floor wastes in shower areas.
  • Clear categorisation of wet areas based on risk levels, with stringent measures for high-risk zones (e.g., enclosed shower areas).
• AS 3740-2021:
  • Similar fall requirements with detailed provisions for different configurations.

These guidelines help in determining the extent of waterproofing needed for various areas, ensuring that high-risk zones are adequately protected.

Conclusion

By adhering to the key differences between the NCC Housing Provisions 10.2 and AS 3740-2021, builders and developers can ensure compliance with the most authoritative standards. This approach not only minimises the risk of defects but also helps in managing construction costs effectively. At Collective Consult, we prioritise waterproofing in all our projects to avoid the significant financial and structural repercussions of water damage.

If you need further insights or customised waterproofing solutions for your projects, feel free to reach out to Collective Consult. We’re here to ensure your construction projects stand the test of time.

Resources

1. ‘2023 Strate Defects Survey Report – New South Wales government (November 2023)
2. NCC National Construction Code 2019
3. NCC 2022 Volume One
4. NCC 2022 Volume Two
5. NCC 2022 Volume Three
6. ABCB Housing Provisions Standard 2022
7. AS 3740-2021 Waterproofing of domestic wet areas
8. https://ncc.abcb.gov.au/news/2022/new-livable-housing-design-requirements