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New Zealand building code

marcjb | Posted in GBA Pro Help on

Help! I’m a retired builder from Canada now living in NZ. The last work I did was on a new residential build here, not as contractor but just to do carpentry. Unbelievable to me, there is no air barrier prescribed in the code and there was none on this brand new house. I put in my two cents worth and the builder agreed with me but nothing was done.

Here’s the thing. NZ has a severe housing shortage. The new government is rolling out a program called KiwiBuild, a multi-billion dollar work programme set to deliver 100,000 homes for first home buyers over the next decade. That’s 100,000 new homes with no air barrier.

I’ve tried contacting the NZ Green Building Council and Branz (BRANZ is an independent and impartial research, testing, consulting and information company providing services and resources for the building industry. Our two main areas of activity are research and investigation in the construction and design of buildings and the environment, and the transfer of knowledge in these areas.) with my concerns. No response. It seems there’s nothing I can do as an individual.

So now I think that it’ll take an organisation like GBA to get a response from someone in NZ who might be able to do something about the code here.  Are you good folks here at GBA willing to give this some thought? Cheers,


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  1. Expert Member

    I know nothing about their codes, but a quick Google search seems to show they do seem to include requirements for an air barrier.

    1. marcjb | | #2

      Thanks Malcolm, that's nice to see but it's still not a requirement, i.e. prescribed by the code, which is the point. If builders are not required to include an air barrier then they won't.

  2. GBA Editor
    Martin Holladay | | #3

    For what it's worth, I wrote an article in 2002 for Energy Design Update called "Leaky Homes Plague New Zealand." (See the pdf file attached below.)

    The article focused on wet-wall disasters. My article quoted an official report on the crisis published by a committee called the "Overview Group on Weathertightness."

    Here's what I wrote: "...Other factors contributing to the crisis, according to the report, were a lack of attention by designers to weathertightness details, inadequate building inspection by local officials, and deficiencies in New Zealand’s building code. For example, the report criticizes elements of the code that permit the use of caulk as an acceptable weatherproof detail for exterior joints.

    "Among the report’s findings: 'There has been much evidence of a general lack of understanding of the importance of, and in some cases even the need for, flashings at junctions and penetrations (even at windows and doors). Their use can be often minimal and in the worst cases non-existent. ... Generally, New Zealand lacks science and technology based courses at tertiary level. There are few if any recognized Bachelor of Building, Construction Studies or Building Surveying courses available.' "

  3. marcjb | | #4

    Thanks Martin. So do you think there's anything further that can be done?

  4. GBA Editor
    Martin Holladay | | #5

    I'm not sure if you want to address this problem on the job-site level or the national level.

    On the job-site level, the first step is to let the builder know that the New Zealand building code may, indeed, have air barrier requirements (assuming Malcolm is right).

    On the national level, you've raised a political question rather than a building science question. I'm not a political consultant. It's hard enough to move the code enforcement needle in the U.S., where I have some understanding of the players and lobbying going on. I have zero experience with the political scene in New Zealand.

    1. marcjb | | #6

      Just saw this now Martin, I didn't get notified for some reason. Thanks for responding. It requires a code change or addition so I guess it's political. If you look at Malcolm's link it's a "detail solution" offered by BRANZ but it's not part of the code. They also say that "In most New Zealand domestic buildings, the internal plasterboard linings provide this general air barrier." This doesn't meet the airtight drywall approach that you've written about.

      By the way, another odd thing here is unvented attics. There's no venting in the soffits and none in the roofs. Metal ridge caps have a flexible membrane along each side that seals to the roofing...

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