Waterproofing of domestic wet areas
Bathroom, ensuite, laundry and shower waterproofing.
Overview
AS 3740 is one of the most-cited standards on a residential job. It sets the minimum waterproofing for wet areas — substrate, membrane extent (full shower enclosure, partial elsewhere), minimum heights up walls, falls to wastes, and treatment of penetrations and junctions.
Key Requirements
- Membrane to full floor of shower enclosure and minimum 150 mm up walls.
- Shower walls fully waterproofed to at least 1800 mm (or to underside of head).
- Falls to floor waste — min 1:80 floor, 1:60 within shower.
- Hob or step-down to contain water within shower.
- Compatible substrate (compressed FC, concrete, masonry — not standard plasterboard in shower).
How it's used in the NCC
Called up by Part 10.2 of the Housing Provisions as the deemed-to-satisfy pathway.
Practical Notes
- Single biggest source of residential insurance claims — get it right.
- Many states require a licensed waterproofer and a certificate of compliance.
- Membrane must be tested for ponding before tiling — don't skip this step.
Where to obtain
The full text of AS 3740 is published by Standards Australia and must be purchased — typical price A$150–400 per part. Always work from the current edition referenced in the NCC, not an older one.