Waterproofing is the one trade in a bathroom where you cannot see whether the job was done properly. It gets covered in tiles the next day, and you find out five years later when the skirting in the hallway starts lifting.
So this is worth understanding even if you are never going to hold a roller. Knowing what should happen is how you tell whether it did.
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Where the rules actually live
The structure trips up a lot of people, including some builders, because it changed meaningfully in 2022.
That gives you two legitimate compliance routes rather than one. Clause H4D3 of NCC Volume Two requires compliance with 10.2.1 to 10.2.6 of the ABCB Housing Provisions, and then either AS 3740 together with clause 10.2.12, or clauses 10.2.7 to 10.2.32 of the Housing Provisions.
The trap inside the AS 3740 route
Here is the nuance almost nobody gets right. If you take the AS 3740 path, you still cannot use AS 3740's material requirements. The Housing Provisions material clauses still apply, because clause 10.2.6 calls up 10.2.8 and 10.2.9.
So "we're doing it to AS 3740" is not a complete answer. It is half an answer, and the materials still have to satisfy the code. If a waterproofer says that sentence and nothing else, ask a follow-up.
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Which edition applies to your job
This matters in 2026 more than it has for years, because the country is mid-transition and your state may not be where you assume.
NCC 2022 Amendment 2 was adopted by states and territories from 29 July 2025, superseding Amendment 1. Then NCC 2025 arrived on top of that.
South Australia split the difference, taking the plumbing code from 1 May 2026 and the building code from 1 May 2027. If you are renovating in Adelaide, that distinction is genuinely relevant to which rules your plumber and your builder are each working to.
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The practical instruction is simple. Ask your building surveyor or certifier which edition applies to your approval, and do not assume the latest published version is the one in force where you live.
What has to be waterproofed
The core requirements, in plain terms.
|
Area |
Requirement |
Note |
|---|---|---|
|
Shower floor |
Waterproofed |
Clause 10.2.2(a), no exceptions |
|
Shower walls |
Waterproofed to 1800mm |
Raised in NCC 2022, previously lower |
|
Unenclosed shower extent |
1500mm radius from the rose |
Measured from the rose, not the screen |
|
Floor outside shower |
Per clause 10.2.3 |
Water resistant rather than fully waterproof |
|
Shower area falls |
Between 1 in 80 and 1 in 50 |
There is a maximum as well as a minimum |
|
Bath and wall junction |
Detailed junction required |
The code points to AS 3740 here specifically |
The 1800mm shower wall height is the change that catches people comparing against an older bathroom. If your reference point is a renovation done a decade ago, the bar has moved. Our shower range and wastes are specified with the current requirements in mind.
Spot fixing, and why it fails
Strictly this is tiling rather than waterproofing, but it sits right on top of the membrane and it is the defect people photograph most often.
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Spot fixing means dabbing adhesive in blobs rather than using a notched trowel to get full coverage across the back of the tile. It is faster and it leaves voids behind the tile.
Those voids matter in a wet area for three reasons. Water that gets through the grout sits in them. The tile has no support, so it cracks under point load. And the drummy sound when you tap it is how an inspector finds it years later.
If you suspect it
Tap across the tiles with a knuckle or a coin. A solid tile sounds dull. A spot-fixed tile sounds hollow, and once you hear the difference you cannot unhear it. Consistent hollowness across a wall is a coverage problem rather than one bad tile.
Worth knowing on the remedy side. Work that was never built to standard is a defect rather than a wear-and-tear warranty claim, and that is a different conversation with a builder. It is also a conversation worth having with your state building regulator rather than only with the builder who did it.
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Details that decide whether it holds
Membranes rarely fail across the middle of a floor. They fail at junctions and terminations.
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Bond breakers at the junctions. Required at wall to wall, wall to floor and hob to wall junctions, and at movement joints where the membrane is bonded to the substrate.
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Substrate moisture checked first. Residual moisture stops the membrane curing or causes early failure.
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Multiple thin coats, not one thick one. A thick coat skins over and traps air, which becomes pinholes.
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Clean, dry, dust-free, no protrusions. Poor preparation is the main cause of pinholing and poor adhesion.
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Waterstop flush with finished floor level. The membrane must terminate bonded to it for continuity.
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Perimeter flashings at floor level openings. These divert moisture away from dry areas.
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Compatible system components. Primers, sealants, membranes and overlays must suit each other.
That last point sounds like fine print and is not. Mixing a sealant from one system with a membrane from another is a genuine failure mode, because the two can simply refuse to bond. Buy the system, not the cheapest of each part.
The inspection you should insist on
One request changes your odds more than anything else here.
Ask for a visual inspection of the membrane before any tiling starts, and ask for photographs. The point is to check pinholes, dry film thickness, the adequacy of fillets and transitions, bonding, vertical termination heights and the location of the waterstop.
This is the last moment the work is visible. Once tiles go on, verifying it means destroying it. Any competent waterproofer will expect the request and most will have the photos already, because it protects them as much as you.
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Who is licensed to do it
Varies by state, and worth checking rather than assuming your tiler is covered.
In Queensland, waterproofing is its own licence category under the QBCC. Elsewhere it may sit within a broader licence or be handled through accreditation schemes.
Either way, ask who is doing it, what their licence or accreditation is, and what documentation you will receive. Our trade range is the starting point if you are specifying for a job. Also check that the products are appropriate for the application, and look for WaterMark certification on plumbing products, which confirms they have been assessed as fit for purpose and authorised for use.
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The short version
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NCC 2022 brought construction details back into the code, with AS 3740 as an option.
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Clause H4D3 requires 10.2.1 to 10.2.6, plus either AS 3740 with 10.2.12, or 10.2.7 to 10.2.32.
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Taking the AS 3740 route does not exempt you from the code's material requirements.
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NCC 2022 Amendment 2 applied from 29 July 2025.
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NCC 2025 was published 1 May 2026 and adoption varies by state.
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Victoria, the ACT and Western Australia adopted from 1 May 2026.
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New South Wales, Queensland and Tasmania take it up from 1 May 2027.
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South Australia took the plumbing code in 2026 and the building code in 2027.
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Shower walls must now be waterproofed to 1800mm.
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An unenclosed shower extends 1500mm in radius from the rose.
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Shower falls must sit between 1 in 80 and 1 in 50.
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Spot fixing leaves voids and is a defect rather than a warranty matter.
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Bond breakers are required at wall, floor and hob junctions.
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Apply multiple thin coats on a clean, dry, moisture-checked substrate.
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Insist on a photographed visual inspection before tiling.
Waterproofing is cheap relative to the rest of a bathroom and catastrophic when it fails, which makes it the worst possible place to accept the lowest quote. If you are planning an Adelaide bathroom and want to get the sequence right, book a showroom appointment and we will talk it through.
