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Wet-area waterproofing: what the NCC asks for

Editions covered: NCC 2022 (current in most states), NCC 2025 (WA, VIC, ACT), NCC 2019 noted · Last reviewed 22 October 2026

Bathrooms, laundries and WCs fail in the same few spots: the shower floor, the wall junctions, the tap holes and the drain. This guide sets out what the NCC requires in each of those spots for houses (Class 1 and 10 buildings). Every point comes with the clause, so you can check it against your plans or show it to your certifier.

Which edition? NCC 2022 still applies in NSW, QLD, SA, TAS and the NT. NCC 2025 applies in WA, VIC and the ACT from 1 May 2026. Which edition applies to a job depends on the permit dates and the state transition rules, so check with your certifier. The wet-area numbers below are the same in both editions unless we note a difference.

Where the rules are

  • NCC 2022 Volume Two H4P1: the performance requirement for wet areas.
  • H4D2 and H4D3: the deemed-to-satisfy routes. You can follow AS 3740 (the NCC 2022 references the 2021 edition) together with the falls rule in Housing Provisions 10.2.12. Or you can follow ABCB Housing Provisions Part 10.2 (10.2.1 to 10.2.32) in full.
  • AS 3740:2021 Waterproofing of domestic wet areas: we cite this Standard by name only and don't reproduce it. Ask the app for the clause that fits your detail.

Key requirements

  1. Every wet area needs a waterproofing system. Each element has to be either waterproof or water resistant, depending on where it sits (HP 10.2.1, 10.2.6). The materials that count as each are listed in 10.2.8 to 10.2.10.
  2. Shower area (HP 10.2.2(1)):
    • The floor is waterproof, including any hob or step-down.
    • The walls are waterproof to at least 1800 mm above the floor substrate.
    • Wall junctions are waterproof for 40 mm either side.
    • Wall/floor junctions and all penetrations are waterproof.
    • A preformed shower base needs all of this except the floor treatment (10.2.2(2)).
    • NCC 2019 difference: under 2019 Table 3.8.1.1, the shower walls only had to be water resistant to 1800 mm. Only the lower section had to be waterproof.
  3. Floor outside the shower (HP 10.2.3):
    • Concrete and fibre-cement floors need to be water resistant.
    • Timber, particleboard and plywood floors need to be waterproof.
    • The wall/floor junction is waterproof. Where a flashing is used, its horizontal leg is at least 40 mm.
  4. Baths and spas (HP 10.2.4):
    • Where the vessel is within 75 mm of a wall, the wall is water resistant to 150 mm above it.
    • Horizontal tap and spout holes are waterproof.
    • An inserted bath needs a waterproof shelf with a waterstop under the lip.
  5. Laundries, WCs and basins (HP 10.2.5):
    • Laundry and WC floors are water resistant.
    • A WC with a handheld bidet spray steps up to a waterproof floor, plus wall treatment within a 900 mm radius of the spray outlet.
  6. Falls (HP 10.2.12): where there is a floor waste, the floor plane falls to it at no flatter than 1:80 and no steeper than 1:50. This applies on both deemed-to-satisfy routes.
  7. Shower type (HP 10.2.14 to 10.2.18): every shower has a floor waste plus one of the following:
    • A step-down of at least 25 mm.
    • A hob of masonry, concrete, AAC or extruded polyurethane foam. Timber hobs are not allowed (10.2.16).
    • A level threshold with a waterstop finishing at least 5 mm above the finished floor (10.2.17).
    • For an unenclosed shower, a waterstop at least 1500 mm from the shower rose (10.2.18).
    • NCC 2025 difference: 10.2.14 is reworded to list the preformed shower base as an option for enclosed showers.
  8. Penetrations (HP 10.2.23):
    • Seal taps and nozzles with sealant, a proprietary flange, or both.
    • It must be possible to remove the tap spindle without damaging the seal.
    • Waterproof any screw fixings and niches.
  9. Flashings at junctions (HP 10.2.24): perimeter flashings have a vertical leg at least 25 mm above the finished floor (except across doorways) and a horizontal leg at least 50 mm wide.
  10. Drain connection (HP 10.2.29): the membrane stops at or in a drainage flange so the connection is waterproof. The floor waste must be tall enough to suit the tile and bed thickness.
  11. Livable housing: in a Class 1a dwelling, one bathroom and one toilet may also have to meet the ABCB Livable Housing Design Standard. That can override hob and step-down options (H4D3 note). Part H8 doesn't apply in NSW (NSW Part H8).

How the states differ

  • South Australia: SA 10.2.1 replaces the national wet-area clause.
    • Work must also follow AS 3740.
    • The wall behind washing-machine taps is water resistant from the floor to 75 mm above and 75 mm either side of the taps.
    • Kitchen and bar sinks set into a bench get water-resistant junctions within 150 mm, and waterproof tap holes in horizontal surfaces.
    • SA 10.2.33 requires a wet-area floor containing a vessel to be graded to a floor waste, with exceptions for vessels that have built-in overflow protection. The falls follow 10.2.12.
    • SA building work stays on NCC 2022 until 1 May 2027.
  • New South Wales: no wet-area variation, and NCC 2022 applies until 1 May 2027. Part H8 (livable housing) doesn't apply.
  • Western Australia, Victoria and the ACT: on NCC 2025. Part 10.2 carries the same key numbers. 10.2.9 (fibre-cement sheet) and 10.2.14 were clarified.
  • Queensland, Tasmania and the NT: no variation to Part 10.2 in the Housing Provisions schedules, and NCC 2022 applies. Tasmania briefly started NCC 2025 but went back to NCC 2022 from 5 June 2026.

Ask the app

Upload a photo of your shower set-down or membrane, or ask:

  • "Is waterproofing required in a laundry under NCC 2022?"
  • "How high does the shower wall membrane need to go?"
  • "What fall does a bathroom floor need to the waste?"
  • "Can I build a shower hob out of timber?"
  • "Does a kitchen sink need waterproofing in South Australia?"

Ask a waterproofing question · Tiling · Plumbing · Builder

Related checklists

This is general guidance, not a compliance check. Always check your approved plans and the edition that applies to your permit, and confirm details with your certifier or building surveyor.

Based on content from the National Construction Code 2022 and 2025 (NCC Volume Two and the ABCB Housing Provisions), provided by the Australian Building Codes Board under the CC BY 4.0 licence. The ABCB does not endorse this guide. The standards the NCC references are cited and explained in our own words, not reproduced.