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Water resistant (vs waterproof)

Water resistant and waterproof are two levels of moisture protection AS 3740 sets for different wet-area zones. Waterproof stops all water; water resistant holds it back.

By Chalkline. Last updated 26 May 2026. Verified 26 May 2026.

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Water resistant and waterproof are two different levels of moisture protection that the NCC and AS 3740 require in different parts of a wet area. The distinction decides which surfaces need a full membrane and which do not, so it is one of the most useful things to be clear on before tiling.

The distinction

  • Waterproof: stops water completely. A continuous impervious barrier (a membrane) that lets no water through to the substrate behind it. This is full waterproofing.
  • Water resistant: resists water but does not fully stop it. The surface or material holds moisture back well enough that it does no harm to the structure, but some moisture movement is accepted (a water-resistant board, or a sealed junction, rather than a membrane).

In short: waterproof is “no water gets through”; water resistant is “water is held back well enough to do no harm”.

Where each applies

The NCC (via AS 3740 and NCC Specification 26) sets which zones get which. As a rule of thumb for a typical bathroom:

  • Waterproof: the shower floor, including any hob or step-down, and the shower walls up to a set height (not less than 1800 mm above the floor substrate).
  • Water resistant: the rest of the room floor, and wall and floor junctions outside the shower.

The required level can also be driven by the floor material: timber-based floors generally need waterproofing, while concrete and fibre-cement floors may only need to be water resistant.

For a builder

  • Don’t treat the whole room as waterproof. Only the zones the standard names need a membrane; the rest needs water resistance, a different and cheaper requirement.
  • Read it off AS 3740 and the NCC, not habit. The exact zones and heights are in the standard; confirm them for the specific room rather than guessing.
  • It is still a certified trade item. Where waterproofing is required, it is a documented, certified job for a waterproofer, not a paint-on afterthought.

Also known as: water-resistant, water resistant vs waterproof.

See also

Last updated: 2026-05-26. Verified: 2026-05-26. Quarterly review for currency.

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