Waterproofing of Wet Areas: Navigating the Key Changes in AS 3740-2021

In September 2021, research published by the New South Wales government on serious building defects in strata communities found that the most commonly occurring serious defect related to waterproofing, which affected 23% of surveyed buildings (followed by fire safety at 14%). A resolution was only possible in 47% or so of the buildings with significant defects. For homeowners, tenants, and strata managers, serious defects typically resulted in considerable financial and emotional stress, highlighting the importance of a thorough and upto-date understanding of current best practices and the changing regulatory environment. When it comes to waterproofing of domestic wet areas, the 2021 update of the AS 3740 “Waterproofing of wet areas within residential buildings” and the 2022 update of the National Construction Code require careful consideration.

Waterproofing of Wet Areas: Navigating the Key Changes in AS 3740-2021 for Residential Projects discusses the key changes to AS 3740 and how it may affect your next residential project. We provide an overview of AS 3740, including some of the key structural changes in the 2021 update, its relationship with the NCC and the most notable new requirements.

The role of waterproofing is to retain water within the designated wet area and exclude water from non-water-resistant building elements. The 2021 revision was intended to bring AS 3740 in line with current waterproof practices. Accordingly, the structure of AS 3740-2021 has been reorganised under four sections, as follows:

• Section 1. Scope, definitions and other specific normative reference documents.

• Section 2. Design principles that apply to the standard.

• Section 3. Requirements for acceptable materials to be used in the waterproofing of wet areas.

• Section 4. Details for the installation of waterproof and water-resistant materials to be used in domestic wet areas. The revised standard also adds several additional informative appendices, including Appendix C Membrane continuity testing, Appendix D Suggested installation checklist, Appendix E Compatibility, and Appendix F Testing for moisture content in subfloors.

Recently, the NCC 2022 was released, and both Volume One and Volume Two included a full restructure of the provisions as well as a number of revisions for both interior and external waterproofing requirements. Both NCC 2022 Volumes One and Two adopt the updated version of AS 3740-2021. We then consider some potential issues that may arise between the NCC and the updated waterproofing standards. For example, in AS 3740-2021, falls in areas adjacent to the shower have an allowable minimum fall of 1:100, whereas the NCC 2022 Volume Two combined with the Livable Housing Provisions has a minimum of 1:80. We also cover ambiguities relating to leak control flanges, waterproofing membranes and linear drains. Australia’s leading linear drainage manufacturer and supplier, Stormtech is committed to providing the highest quality, expertly tailored drainage solutions for today’s building projects. Boasting an unrivalled depth of experience in linear drainage solutions, Stormtech welcomes questions on product selection, code compliance and fault-free installation.