# Shower & Wet Area Waterproofing (NCC 2025)

What the NCC makes you waterproof in a bathroom — shower walls to 1800 mm, the shower floor, and the 150 mm rule at baths and basins — plus where AS 3740 fits.

- Canonical HTML: https://www.chippy.tools/building-codes/au/wet-areas/waterproofing-requirements/
- Publisher: Chippy Tools
- Updated: 2026-09-06
- Market: au
- Code edition / reference: NCC 2025
- References: HP 10.2


## The requirement

Inside the shower, the walls must be waterproof up to at least **1800 mm** above the floor. So must the shower floor, the junctions and any penetrations. The fixture detail matters. **Inserted baths need waterproof walls** to at least **150 mm above the lip**, plus shelf and junction treatment. Other bath and basin splash zones may need water-resistant surfaces (clauses 10.2.4–10.2.5).

Water is the thing that wrecks a bathroom. So the rule book, the National Construction Code (NCC), says which parts of a wet area you have to seal, and how well. There are two levels of sealing:

- **Waterproof** means a full barrier that water cannot get through. That is your membrane.
- **Water-resistant** means the surface stands up to water. It is not a sealed barrier.

The NCC asks for waterproof in the wettest spots. Water-resistant covers the splash zones. Here is where each one goes.

**Inside the shower (clause 10.2.2).** This is the wettest part of the house. Nearly all of it must be waterproof.

| Part of the shower                                           | What’s required (NCC 2025) |
|--------------------------------------------------------------|----------------------------|
| The shower floor, including any hob or step-down             | **Waterproof**             |
| The shower walls, up to at least **1800 mm** above the floor | **Waterproof**             |
| Wall junctions and joints                                    | **Waterproof**             |
| Wall-to-floor junctions                                      | **Waterproof**             |
| Any penetrations (tap, waste, mixer)                         | **Waterproof**             |

The **1800 mm** wall height is set by the NCC itself, not by any standard. That is the number to build to inside the shower.

**Diagram labels:** 1; 2; ≥ 150 mm; ≥ 1800 mm

NCC 2025 Housing Provisions 10.2

1. 1 shower floor
2. 2 basin / bath

**Outside the shower (clauses 10.2.3 and 10.2.5).** Out here the rules ease off. They also change with what you are building on.

- Floors only need to be water-resistant on a concrete or fibre-cement substrate. On a timber-based substrate, like particleboard or plywood, the floor must be fully waterproof. The material under your feet decides it.
- Check the bath type first. Inserted baths need waterproof walls to at least 150 mm above the lip, waterproof adjoining shelves and the specified joints.
- Other bath and basin splash zones have water-resistant surface rules. Check the 75 mm distance and 150 mm height rules for that fixture.

There is no single wall height for the whole room. It depends on what the wall sits next to. Build to 1800 mm inside the shower. Check the bath or basin detail for its height, surface and joint rules. Check the complete room detail too.

**Check the edition and state.** National NCC 2025 clause 10.2.1 requires a waterproofing system. Clauses 10.2.6 onward set system, material and construction details. The older AS 3740 alternative wording is not the national text of 10.2.1. South Australia has a variation with that option. Read the adopted provisions and the specified system together.

## On site — what to waterproof

A quick run-through before you start rolling membrane:

1. **Shower floor.** Waterproof the whole floor. Don’t forget the hob or step-down.
2. **Shower walls.** Waterproof up to at least 1800 mm off the floor.
3. **Junctions.** Waterproof the shower wall junctions and joints. Do every wall-to-floor junction too. Follow the specified flashing detail.
4. **Penetrations.** Seal around the waste, taps and mixer.
5. **The floor outside the shower.** Waterproof it over a timber-based substrate. Water-resistant is enough over concrete or fibre-cement.
6. **Walls beside a bath, basin or sink.** Check clauses 10.2.4–10.2.5. Inserted baths need waterproof treatment, not just a water-resistant surface.
7. **Membrane.** Follow the maker’s instructions, and AS 3740 if you are on that path. The product’s own specs come from the maker, not the code. That covers coats, cure time and primer.

## Related

- Part of the [NCC rules for Australian chippies](https://www.chippy.tools/building-codes/au/ncc-for-chippies/). That is the pillar page, with the state-by-state adoption tracker.
- Building the room around it? See [NCC minimum ceiling heights](https://www.chippy.tools/building-codes/au/rooms/minimum-ceiling-heights/). It covers the 2.1 m rule for bathrooms and laundries.
- Setting out the wet-area floor falls and drainage is a plumbing job. Check with your plumber and the relevant plumbing standard.

## Sources

- **NCC 2025, ABCB Housing Provisions Standard, Part 10.2 “Wet area waterproofing” (clauses 10.2.1–10.2.32)** — what must be waterproof vs water-resistant, the 1800 mm shower-wall height, the junction and flashing details, the 150 mm/75 mm rule at baths and basins, and the timber-vs-concrete floor split. Confirm at [NCC Part 10.2](https://ncc.abcb.gov.au/editions/ncc-2025/adopted/housing-provisions/10-health-and-amenity/part-102-wet-area-waterproofing). *(Confirmed against the NCC 2025 Housing Provisions Standard, verified 2026-07-28.)*
- **AS 3740 “Waterproofing of domestic wet areas”** — check the edition and the adopted provision that calls it up. Its use is not a blanket alternative under the national NCC 2025 clause 10.2.1.


## State variations

These states apply requirements that differ from the national provisions for this rule.

- Queensland Announced HP 10.2
  
  Current code: NCC 2022
  
  Queensland does not require a floor waste in a Class 1 bathroom or laundry — only in shower areas (10.2.14). Where one is installed, QDC MP 4.5 relaxes the fall to 1:100–1:80 (national range is 1:80–1:50), and allows a linear drain, a 10 mm weir or full overflow protection instead of grading the floor at all.
  
  [Queensland building codes →](https://www.chippy.tools/building-codes/au/qld/) [Official source →](https://www.housing.qld.gov.au/__data/assets/pdf_file/0025/73627/qdcmp4-5-pending-LivableDwellingsGradingFloorWastes.pdf) Verified 2026-08-06

Content adapted from the National Construction Code 2022, provided by the Australian Building Codes Board under the CC BY 4.0 licence.

This page is general information for tradespeople and is not compliance, engineering or legal advice. Requirements are subject to state and territory variations and adoption timing. Always confirm requirements with your building certifier and relevant state authority.


## Frequently asked questions

### How high do you have to waterproof a shower wall?

Inside the shower, the walls must be waterproof up to at least 1800 mm above the floor. That height is set by the NCC itself. The shower floor, any hob or step-down, the wall and floor junctions, and any penetrations must all be waterproof too.

### Do the walls next to a bath or basin need waterproofing?

Bath details differ. Inserted baths need waterproof walls to at least 150 mm above the lip, plus the specified shelf and junction treatment. Other bath and basin splash zones may require water-resistant surfaces. Use clauses 10.2.4 and 10.2.5 for the exact fixture detail.

### Does the bathroom floor outside the shower need waterproofing?

It depends on what's under it. On a concrete or fibre-cement substrate the floor only has to be water-resistant. On a timber-based substrate, like particleboard or plywood, the floor must be fully waterproof.

### Do I have to follow AS 3740?

Check the adopted edition and state variation. Do not assume the NCC 2022 wording still applies. The national NCC 2025 Part 10.2 sets system and material requirements. A South Australian variation retains an AS 3740 construction option.

### What's the difference between waterproof and water-resistant?

Waterproof means a full barrier that water can't get through. That's your membrane. Water-resistant means the surface stands up to water but isn't a sealed barrier. The NCC asks for waterproof in the wettest spots, like the shower and timber floors. Water-resistant covers the splash zones, like walls near a bath or basin.