AS 3740 Explained: What Homeowners Should Know About Wet Area Waterproofing
AS 3740 sets the rules for waterproofing bathrooms, laundries and toilets in Australian homes. Here is a plain-English overview of what it covers.
If you are renovating a bathroom or building a new home, you will probably hear your builder or tiler mention "AS 3740". Here is what it means and why it matters to you.
What is AS 3740?
AS 3740 is the Australian Standard for Waterproofing of domestic wet areas. It is referenced by the National Construction Code (NCC) and sets minimum requirements for the materials, design and installation of waterproofing in rooms such as bathrooms, showers, laundries and toilets in residential buildings.
Waterproof vs water resistant
The standard divides wet areas into zones. Some surfaces — such as shower floors and walls within the shower area — must be waterproof. Others, such as bathroom floors outside the shower, must be at least water resistant. The exact requirements depend on the room layout, the type of shower and whether there is a floor waste.
Key details the standard addresses
- Treatment of wall/floor and wall/wall junctions, including bond breakers
- Floor wastes and puddle flanges
- Pipe and tap penetrations
- Shower hobs, step-downs and waterstops at the shower boundary
- Falls to the floor waste
- Membrane materials, which are classified under AS 4858
Why compliance matters to you
- Durability — compliant detailing is designed to handle building movement and daily water exposure.
- Certification — certifiers and builders need evidence the work meets the standard.
- Insurance and warranty — a certificate supports claims and statutory warranty rights under the NSW Home Building Act 1989.
- Resale — buyers' inspectors often ask for waterproofing certificates.
Questions to ask your waterproofer
- Are you licensed and insured for waterproofing work?
- Which membrane system will you use, and is it certified?
- How will you treat junctions, wastes and penetrations?
- Will you flood test and provide a certificate?
- What warranty do you provide?
Our wet area waterproofing service is installed to AS 3740 with certificates on completion.
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