Do I need to use a Vapour Permeable Membrane??

It has recently come to my attention through Zara D’Cotta from The Healthy Home’s Healthy Buildings Mastermind course that one of Australia’s largest volume builders were not aware that they were required by the current NCC (NCC 2019) to install vapour permeable membranes on some of their projects.

The building code changes every 3 years, sometimes significantly, and it is simply not ok that the people that these changes impact the most (builders, designers, architects and home owners) have no idea about these changes and no way to find out, until someone uncovers an error.

This particular building company believed they had until the next iteration of the NCC was introduced to change to vapour permeable membranes on their walls, so they they have inadvertently been using their standard plastic wrap that they’ve always used across all of their projects.  The potential consequence of this could be that moisture could get trapped in the walls of some of their new homes and mould could grow, affecting the integrity of the structure and the health of the occupants.

The only state that has compulsory CPD for builders is New South Wales.  Why not the other states??  This baffles and frustrates me and many others in this industry. In the absence of compulsory education, it’s up to professionals like me to spread the required information.  So.  If you’re in the residential building game, please listen up.


NCC 2019

If you are building in Climate Zones 6, 7 or 8 – you are required by the current NCC 2019 to install Vapour Permeable Membrane.  See the excerpt below from the Condensation in Buildings Handbook.

In South Australia, climate zone 6 is the hills, down South around Victor Harbour and on Kangaroo Island.  Then of course there’s Victoria, Tasmania and some of Southern NSW.  Be sure to check which climate zone you are building in and don’t risk the mould and condensation!  Check here using the ABCB’s interactive Climate Zone Map where you can search exact addresses.

NCC 2022 Housing Provisions

Looking forward to NCC 2022, the requirements become even more stringent, stipulating that in climate zones 4 and 5, a class 3 membrane must be used and in climate zones 6, 7 and 8, a class 4 membrane must be used.

What is the difference between class 3 and class 4 you ask?  Essentially the class 4 is more permeable than a class 3.  They have different product features but that’s a discussion for another day.  What you need to know right now is that class 4 is more vapour permeable than class 3 and a  house built in a colder climate requires a membrane with a higher vapour permeability classification.  Therefore, you can of course use a class 4 membrane in climate zones 4 and 5 as well.

The table to the right shows the technical information for the different levels of permeance.

If you’re not currently using the right membranes on your projects, I happen to know someone who sells top quality German engineered class 4 vapour permeable membranes, designed to keep your building moisture free and give you peace of mind – gimme a call! 🙂



Jessica Allen  |  0409 404 924  | 

See this link for NCC 2022 Adoption dates in your state.


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