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Keeping the moisture out: Important NCC Updates for Australian Builders

Keeping the moisture out

Building regulations in Australia are shifting with adoption of the NCC 2025 progressively across Australia.

If you’re working in south eastern parts of the country, there are some critical changes you need to know about condensation management and moisture control.

Whether you’re a builder, architect, or developer, staying compliant means understanding how the National Construction Code (NCC) is making significant improvements towards on moisture control. Here is a breakdown of the latest updates and what they mean for your next project—especially if you’re using Weathertex.

Make sure to visit your jurisdiction’s website for more information

Mandatory wall cavities in

south eastern areas

For the first time, wall cavities are no longer just best practice, they are a legal requirement in cooler Australian climates. Under HP Clause 10.8.1 (External Wall Construction), drained and ventilated cavities are now mandatory across three climate zones.

Zone 6

Melbourne & surrounds

Sydney & surrounds

Hunter region

Northern Rivers hinterland

Zone 7

Regional Victoria

NSW tablelands

Tasmania

Zone 8

Alpine regions – NSW, ACT, TAS & VIC

Not sure which zone your project falls in? The ABCB maintains an interactive climate map to help you verify.

The 12mm Rule

For Climate Zones 6-8, the Deemed-to-Satisfy (DtS) minimum cavity depth is now set at 12mm. This applies to most external wall cladding systems

Weathertex 9.5mm Cavity Batten Compliance

Weathertex continues to maintain its approved CodeMark Performance Solution, allowing builders to continue to use the 9.5mm cavity batten despite the general 12mm DtS requirement.

Vapour permeance: Class 4 is here to stay

There has been plenty of industry discussion about membrane classifications, but for Weathertex users, it remains business as usual. The NCC continues to emphasise the use of Class 4 vapour permeable membranes, allowing buildings to breathe while keeping rain out.

Weathertex continue to specify Class 4 membranes as per Section 1.4.6 of the Weathertex installation manual in Climate Zones 2 to 8. For Climate Zone 1, continue to seek advice from your preferred membrane manufacturer.

Expanded scope: it’s not just houses anymore

Perhaps the most significant shift in the updated code is where these condensation rules now apply. Previously focused largely on residential houses and apartments, the updated Part F8 of Volume One extends requirements to a broader range of building classes.

Class 1 & 2

Houses & Apartments

Class 2

Multi-Residential

New – Class 3

Hotels,motels,hostels

New – Class 9c

Aged-Care facilities

If you are currently working on hospitality or aged-care projects in the relevant climate zones, these requirements now apply directly to your builds. You can find out more information on PCD 2025 – Condensation mitigation

The NCC 2025 has made significant improvements to moisture control. Builders and specifiers continuing to use Weathertex in accordance with our guidelines will remain compliant.

Remember to verify your Climate Zone and consult the ABCB for guidance.

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Keeping the moisture out: Important NCC Updates for Australian Builders