AS 3740 is the Australian Standard that governs waterproofing in all domestic wet areas, and it is the single most important document in the Australian waterproofing industry. Referenced directly by the National Construction Code, AS 3740-2021 applies to every bathroom, shower, laundry, and wet area in every home and residential building across Australia. Understanding this standard helps you ensure your waterproofing project meets the minimum legal requirements and protects your property for the long term. We connect you with licensed waterproofers who know AS 3740-2021 inside out and deliver compliant work on every job.
What AS 3740-2021 Covers
AS 3740-2021 specifies the requirements for waterproofing domestic wet areas including bathrooms, showers, laundries, toilets, balconies, decks over habitable spaces, and any area that contains a floor waste or is subject to water exposure. The standard defines precisely where waterproofing membranes must be applied, to what height on walls, what materials and methods are acceptable, and how the completed work must be tested and inspected. It is the mandatory reference standard for all wet area waterproofing in residential buildings across Australia and forms the basis for building certifier assessments during construction and renovation projects.
Shower Waterproofing Requirements Under AS 3740
Shower recesses have the most stringent waterproofing requirements under AS 3740-2021. Shower walls must be waterproofed to a minimum height of 1800 millimetres above the finished floor level, or to the ceiling height in the case of stepless or hobless showers. The shower floor must be fully waterproofed with the membrane extending under the shower screen and connecting to all wall membranes without gaps. Shower hobs must have a minimum 75 millimetre upstand that is fully wrapped by the membrane. All joints between walls and floors must incorporate bond breakers to accommodate structural movement without cracking the membrane.
Bathroom Floor and Wall Requirements
Bathroom floors that contain a floor waste must be fully waterproofed across the entire floor area under AS 3740-2021. The membrane must extend a minimum of 150 millimetres up all walls surrounding the bathroom floor. In areas adjacent to baths and basins, specific requirements apply depending on the fixture configuration. The membrane must continue under door thresholds and transition smoothly to adjoining areas without creating gaps where water could escape. These requirements ensure that any water reaching the floor is contained within the waterproofed zone and directed to the floor waste rather than escaping into the building structure.
Laundry and Toilet Waterproofing Requirements
Laundries that contain a floor waste must be waterproofed to the same standard as bathroom floors under AS 3740-2021, with the full floor membrane and 150 millimetre wall upstands. Laundries without floor wastes may not require waterproofing under the standard, though some state regulations and building certifiers require it regardless. Toilets with floor wastes must also be waterproofed. The standard acknowledges that these areas typically have less water exposure than showers and bathrooms but still require protection where floor wastes are present because the waste itself creates a penetration through the floor that must be sealed.
Balcony and External Wet Area Requirements
AS 3740-2021 extends its requirements to balconies and external wet areas that are located above habitable spaces. These areas must be waterproofed with membrane systems that can withstand outdoor conditions including UV exposure and thermal movement. The standard requires adequate falls to drainage, membrane coverage of the full floor area and all upstands, and proper detailing at all penetrations and terminations. Balcony waterproofing must be inspected before tiling or paving is installed. The 2021 update provided additional clarity on external wet area requirements, particularly for hobless balcony thresholds that connect to interior spaces.
Membrane Material and Performance Requirements
AS 3740-2021 specifies that waterproofing membranes must comply with relevant material standards and be fit for purpose in their intended application. Membranes must be able to bridge cracks in the substrate, resist hydrostatic pressure, and maintain their integrity over the expected lifespan of the installation. The standard recognises both liquid-applied and sheet membrane systems, provided they meet the required performance criteria. Products must be applied at the thickness specified by the manufacturer, and the completed membrane must pass visual inspection for continuity, coverage, and adhesion before any tiling or covering work begins.
Inspection and Testing Requirements
One of the most important aspects of AS 3740-2021 is its requirement for waterproofing to be inspected before it is covered by tiles or other finishes. The building certifier or their appointed inspector must verify that the membrane has been applied correctly, covers all required areas to the specified heights, and shows no defects before giving approval for tiling to commence. Flood testing, where the waterproofed area is filled with water and left to stand for a specified period, is used to verify watertightness in shower bases and bathroom floors. These inspections are your assurance that the waterproofing has been done properly.
Recent Changes in the 2021 Update
The 2021 update to AS 3740 introduced several important changes that affect how waterproofing is specified and installed. The standard clarified requirements for stepless and hobless shower designs that have become increasingly popular in modern bathrooms. It updated provisions for external wet areas and balcony thresholds, addressing design trends that create new waterproofing challenges. Material requirements and testing protocols were also updated to reflect advances in membrane technology. Licensed waterproofers stay current with these changes through ongoing professional development and ensure every job they complete meets the latest version of the standard.
Consequences of Non-Compliance With AS 3740
Non-compliance with AS 3740-2021 carries serious consequences for homeowners, builders, and waterproofers alike. Building certifiers will refuse to sign off on work that does not meet the standard, preventing progress on construction or renovation projects. Non-compliant waterproofing that is discovered during a property sale can delay or collapse the transaction. Insurance claims related to water damage may be denied if the waterproofing was not installed to the standard. In Queensland, performing waterproofing work that does not comply with AS 3740 can result in QBCC disciplinary action against the licensed contractor, including fines and licence suspension.
How AS 3740 Interacts With the NCC and QBCC
AS 3740-2021 is referenced by the National Construction Code as a deemed-to-satisfy solution for wet area waterproofing. This means that complying with AS 3740 is the accepted standard path to meeting NCC performance requirements. In Queensland, the QBCC requires that waterproofing work be performed by appropriately licensed contractors who deliver work compliant with AS 3740 and issue proper documentation. The QBCC provides consumer protection through the Home Warranty Scheme and investigates complaints about defective waterproofing work. This regulatory framework ensures homeowners have recourse if waterproofing fails to meet the standard.
Work With AS 3740-Compliant Licensed Waterproofers
Every wet area in your home must meet AS 3740-2021, and the only way to be confident in compliance is to engage a licensed waterproofer who understands the standard thoroughly and applies it on every job. We connect you with QBCC licensed waterproofers in Brisbane who deliver compliant, certified waterproofing and provide proper documentation including waterproofing certificates for your records. Do not risk non-compliant work that could create legal, financial, and structural problems down the track. Request your free quotes today and get matched with a waterproofer who gets it right the first time.
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