Water-resistant plasterboard: the wall-only wet-area board
Water-resistant plasterboard (Aquachek, Wetstop) is permitted as a wet-area wall substrate under the NCC, but not on floors, and it still needs a membrane.
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Water-resistant plasterboard is moisture-treated, blue-faced plasterboard (brands Aquachek by Gyprock/CSR and Wetstop by Knauf) permitted as a wet-area wall substrate under NCC 2022 Housing Provisions 10.2.9 (verified 2026-05-10, corpus wet-area substrates). Two things matter most: it is moisture-resistant, not waterproof, so a membrane to AS 3740 still goes over it in shower zones; and it is a wall-only product, not permitted on wet-area floors. Get either of those wrong and it is a rip-out.
What it is
Water-resistant plasterboard has a treated core, face, and back that resist moisture and humidity, giving it dimensional stability as a tile substrate. Both common brands are blue-faced to tell them apart from standard plasterboard, and both comply with the gypsum plasterboard standard AS/NZS 2588 (water-resistant grade) (verified 2026-05-10, corpus):
| Brand | Product | Common thicknesses |
|---|---|---|
| Gyprock (CSR) | Aquachek | 10 mm, 13 mm |
| Knauf | Wetstop | 10 mm, 13 mm |
Where it can and cannot go
| Application | Water-resistant plasterboard |
|---|---|
| Shower recess walls | Permitted (NCC HP 10.2.9); cement sheet also permitted |
| Bathroom and laundry walls | Permitted |
| Wet-area floors | Not permitted (use concrete or compressed sheet) |
| Hob construction | Not permitted (masonry, concrete or AAC) |
It is moisture-resistant, not waterproof: in any shower zone a membrane compliant with AS 3740 must be applied before tiling.
Cut-edge treatment
Under NCC 2022 Housing Provisions 10.2.26, all cut edges of water-resistant plasterboard that may be exposed to water or moisture must be waterproofed, including the bottom edge over a preformed shower base (verified 2026-05-10, corpus). The board’s water resistance is in the sheet; a raw cut edge lets moisture track straight into the core, so seal it with the membrane system’s primer or a compatible sealant before the membrane.
Common defects
- Standard plasterboard used in a shower instead of the water-resistant grade. Detected when the lining softens or the membrane flakes. Rip-out.
- Used on a wet-area floor. Not on the NCC floor-substrate list; compressed fibre-cement sheet or concrete is required on floors.
- Cut edges unsealed. Moisture wicks into the core from the cut edge, bypassing the membrane, and the board swells.
References
- NCC 2022 Housing Provisions Part 10.2, Wet area waterproofing (ABCB) (verified 2026-05-10, corpus)
- Knauf, Wet area solutions (knaufapac.com) (verified 2026-05-10, corpus)
- Gyprock (CSR), Aquachek (gyprock.com.au) (verified 2026-05-10, corpus)
Related
- Plasterboard
- Cement sheet (fibre cement)
- Wet area substrates
- AS 3740: waterproofing of domestic wet areas
See also
Last updated: 2026-05-24. Verified: 2026-05-24. Quarterly review for currency.