What Is AS 3740?
AS 3740-2021 is the Australian Standard that governs waterproofing of domestic wet areas. It sets out mandatory requirements for how bathrooms, showers, laundries, and other wet areas must be waterproofed to prevent water damage to building structures. In South Australia, compliance with AS 3740 is required by the National Construction Code (NCC) for all new construction and renovations that involve wet area modifications.
For most Adelaide homeowners, AS 3740 becomes relevant during a bathroom renovation. The standard dictates which surfaces must be waterproofed, the minimum membrane performance requirements, and the testing procedures that must be completed before tiling. Our full AS 3740 guide provides the detailed technical specifications, while this article offers a practical overview.
Key Requirements for Homeowners
The standard requires that all shower floors and walls (to 1800mm or showerhead height) must be waterproofed with a membrane that meets AS 4858. The bathroom floor within 1500mm of a water source must also be waterproofed. Junctions between walls and floors must be reinforced with tape or bandage, and all penetrations (pipes, drains, fixtures) must be sealed.
After application, a flood test must confirm the membrane is watertight before any tiling commences. A waterproofing certificate must be issued by the applicator, and this document should be retained for building compliance records and insurance purposes. Learn more about this documentation in our waterproofing certificate guide.
What Happens If You Do Not Comply?
Non-compliant waterproofing can have serious consequences. If your renovation does not meet AS 3740, your building certifier can refuse to sign off on the work. If a leak occurs and the waterproofing is found to be non-compliant, your home insurance may deny the water damage claim. In multi-unit developments, non-compliant waterproofing in one apartment can damage neighbouring units, creating liability for the owner.
In Adelaide, Consumer and Business Services SA can issue rectification orders for non-compliant building work. The cost of rectifying non-compliant waterproofing — which involves removing tiles, membrane, and screed, then re-doing everything — typically runs 3 to 5 times the cost of doing it correctly the first time.
Questions to Ask Your Waterproofer
Before hiring a waterproofer for your Adelaide bathroom renovation, ask these questions: What membrane system will you use, and does it meet AS 4858? Will you tape and seal all internal corners and penetrations? Will you carry out a flood test? Will you issue a waterproofing compliance certificate? Can you provide references from recent projects? Do you hold a current building work licence with bathroom waterproofing endorsement?
A reputable waterproofer will answer all of these questions confidently and provide documentation at every stage.
Get Compliant Waterproofing Quotes
Our Find a Waterproofer tool connects you with licensed waterproofers who understand AS 3740 compliance requirements. All contractors in our network are verified for licensing and insurance, giving you confidence that your project will meet the standard.
For related information about waterproofing different areas of your home, explore our bathroom waterproofing standards article.