# Wet Area Waterproofing (NZ E3/AS1)

The E3/AS1 numbers for a NZ bathroom — 1800 mm up a shower wall, a 150 mm upstand at baths and basins, and how far the impervious floor has to reach.

- Canonical HTML: https://www.chippy.tools/building-codes/nz/wet-areas/waterproofing-requirements/
- Publisher: Chippy Tools
- Updated: 2026-09-06
- Market: nz
- Code edition / reference: NZBC E3/AS1 (2nd ed., Amendment 7, effective 5 November 2020)
- References: NZ E3


## The requirement

In a shower, the waterproof wall lining must reach **1800 mm** above the shower floor. If **50 mm** above the shower rose is higher, go to that instead. Walls at a bath, basin, tub or sink need a **150 mm** upstand. That’s **E3/AS1**, Paragraph 3.3.1 “Showers” and Paragraph 3.2.2 “Joints between fixtures and wall linings”.

E3/AS1 is the Acceptable Solution for Building Code clause E3 “Internal Moisture”. It’s the recipe most bathrooms are built to. The code word for waterproof here is “impervious”: water cannot get through the surface. The height you need depends on what sits under the wall, not one number for the whole room.

| Where                                        | What’s required (E3/AS1)                                                                                 |
|----------------------------------------------|----------------------------------------------------------------------------------------------------------|
| **Shower walls**                             | Impervious lining up to the **higher of 1800 mm above the shower floor, or 50 mm above the shower rose** |
| **Shower floor**                             | Impervious floor or floor finish, the full extent of the enclosure                                       |
| **No shower enclosure** (open shower)        | Impervious floor extends at least a **1500 mm horizontal radius** from the shower rose                   |
| **Walls next to a bath, basin, tub or sink** | Impervious lining with a **150 mm minimum** upstand, sides and back, sealed to the fixture               |

Inside the shower, seal the top edge of the lining to the wall behind it. Or run the lining all the way up to the ceiling. That stops condensation getting in behind it. Holes for tapware, mixers and roses must be waterproofed too. Use a proprietary flange or sealant. You still need access to service them.

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

NZBC E3/AS1

1. 1 shower floor
2. 2 basin / bath

## The rest of the floor

Outside the shower, E3/AS1 still guards every spot where water can get behind a lining or under a floor finish:

- Floor-to-wall junctions. Where a floor covering meets a wall, you need at least **75 mm** of water-resistant wall lining above the junction. Cove or seal the floor covering at the join. Vinyl gets coved up the wall in one run. Tiles get coved or sealed at the edge.
- Open-plan wet areas. No wall between the wet fixtures and the rest of the room? Then the impervious floor must run at least **1.5 m** out from every sanitary fixture or appliance.
- Fixture-to-floor joints. Where a bath, basin, tub or sink sits on an impervious floor finish, seal the joint between the base of the fixture and the floor.

## AS1 is one path, not the only one

Clause E3 itself is performance-based. It asks for impervious, easily cleaned surfaces, but names no height. E3/AS1 is the Acceptable Solution: the recipe MBIE writes. A council treats work built to it as meeting the code. A designer can propose an Alternative Solution instead. E3/VM1 gives no specific verification method. The figures above are the AS1 path.

## On site — what to waterproof

1. Shower walls. Lining up to the higher of **1800 mm** above the floor or **50 mm** above the rose. Seal the top edge.
2. Shower floor. Impervious across the whole enclosure. No enclosure? Go out to a **1500 mm** radius from the rose.
3. Bath, basin, tub and sink walls. A **150 mm** minimum upstand, sides and back, sealed to the fixture.
4. Floor-wall junctions elsewhere. At least **75 mm** of water-resistant lining above the join. Cove or seal the floor covering at the edge.
5. Open-plan wet areas. No wall to hold the water? The impervious floor runs **1.5 m** out from every sanitary fixture.
6. Penetrations. Waterproof the tapware, mixer and rose holes with a proprietary flange or sealant. Leave access for servicing.

## Related

- Part of the [New Zealand Building Code hub](https://www.chippy.tools/building-codes/nz/). The national framework and the checks for your project.
- Building the room around it? See [NZ minimum ceiling heights](https://www.chippy.tools/building-codes/nz/rooms/minimum-ceiling-heights/). It covers what the Building Code does and doesn’t set for a bathroom ceiling.
- Setting out the wet-area floor falls and floor waste is a plumbing job. Check with your plumber and NZBC Clause G13 Foul Water.

## Sources

- **NZ Building Code Acceptable Solution E3/AS1 (2nd edition, Amendment 7, effective 5 November 2020), Paragraph 3.3.1 “Showers,” Paragraph 3.3.1.1 “Shower floor materials,” Paragraph 3.2.2 “Joints between fixtures and wall linings,” Paragraph 2.1.1 “Containment,” and Paragraph 3.1.1 “Floors”** — the 1800 mm / 50 mm shower-wall height, the 1500 mm shower- floor radius, the 150 mm fixture upstand, the 75 mm floor-junction lining, and the 1.5 m open-plan floor extent. Free official PDF via [building.govt.nz](https://www.building.govt.nz/assets/Uploads/building-code-compliance/e-moisture/e3-internal-moisture/asvm/e3-internal-moisture-2nd-edition-amendment7.pdf). *(Confirmed by direct text extraction from the official MBIE PDF, verified 2026-07-31.)*
- **Acceptable Solution vs compulsory path:** E3/AS1 is a **deemed-to-comply** route for Building Code clause **E3 Internal Moisture**, not the only legal way to comply. A designer can propose an Alternative Solution instead. E3/VM1 gives no specific verification method. Always check the current amendment on [building.govt.nz](https://www.building.govt.nz/) before you sign off on a job.


Sourced from the New Zealand Building Code, © Crown copyright, reused under NZGOAL / Creative Commons Attribution.

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 in New Zealand?

Under E3/AS1, the impervious shower wall lining must reach 1800 mm above the shower floor, or 50 mm above the shower rose, whichever is higher. Seal the top edge of the lining to the wall behind it, or run it to the ceiling, so condensation can't get behind.

### Does the wall next to a bath or basin need waterproofing too?

Yes, at a lower height. Where impervious wall lining meets a bath, basin, tub or sink, E3/AS1 sets a 150 mm minimum upstand on the sides and the back, sealed to the fixture. That's a splash zone, not a full shower wall.

### Does the shower floor need waterproofing?

Yes. Every shower space needs an impervious floor and impervious wall linings. No shower enclosure at all, so no wall, screen, door or curtain? Then the impervious floor must extend at least a 1500 mm horizontal radius from the shower rose.

### What about the rest of the bathroom floor?

Where a floor covering meets a wall, E3/AS1 asks for at least 75 mm of water-resistant wall lining above the junction, with the covering coved or sealed at the join. In an open-plan wet area with no separating walls, the impervious floor must extend at least 1.5 m from every sanitary fixture or appliance.

### Do I have to follow E3/AS1?

No. E3/AS1 is one Acceptable Solution. An Alternative Solution may be proposed. E3/VM1 provides no specific verification method. Check the approved design and current national provisions.