Some homes built in the 1990s and early 2000s had design features and installation techniques that put them at high risk of leaking. Where water got behind the cladding, if it was not removed by drainage or ventilation it could lead to mould and rot. Those houses and apartments where water entry has occurred (commonly called leaky buildings) may require significant and expensive remediation to deal with the leaks and subsequent damage. This maintenance guide looks at the design features often associated with leaky buildings, the signs that may indicate that a building is leaking and remediation options. The risks and potential costs involved in weathertight remediation mean that you should seek expert help in assessing a potential problem and in determining the action you want to take. A New Zealand Institute of Building Surveyors (NZIBS) building surveyor can help you assess whether you have a problem and advise on your options.

There is a BRANZ website dedicated to weathertightness and a BRANZ book, Building Basics: Weathertightness (2nd edition).  

Remediation can be expensive. To recover costs, leaky home owners have a range of actions to consider, including negotiation, mediation, adjudication, and (as a last resort) court action.

Be aware that there is a deadline of the end of this year, 2021, for claims to be accepted by the Weathertight Homes Tribunal. The house must have been built (or alterations giving rise to the claim were made to it) before 1 January 2012 and within 10 years of when the claim is brought. If a code compliance certificate was issued, this may be taken as the date the house was built.

The MBIE has good information on its website. 

For five years after 23 July 2011, homeowners could seek help through the Financial Assistance Package where the government and council each paid 25% of the repair cost and the homeowner the remaining 50%. 

The FAP scheme closed to new claimants on 23 July 2016.