Leaky homes crisis

The leaky homes crisis is an ongoing construction and legal crisis in New Zealand concerning a number of timber framed buildings constructed from 1994 to 2004 that suffered from weather-tightness problems. The problem was primarily related to the decay of timber framing which, in extreme cases, made buildings structurally unsound. Some buildings became unhealthy to live in due to moulds and spores developing within the damp timber framing. The repairs and replacement costs that may have been avoided were estimated in 2009 to be approximately $11.3 billion.

The Building Act 1991, which came into effect about 1994, changed building controls from a prescriptive system to a more self-regulated regime. In addition, the Government dropped the apprentice training system for builders and the related building trades. Some developers and builders knowingly or carelessly constructed buildings with numerous faults and short-cuts. An architectural design trend towards Mediterranean-style houses with complex roofs, plastered exterior walls, internal decks and small or no eaves also factored in.

Some local authorities were later found to have issued Building Consents based on insufficient documentation, failed to carry out inspection of the work during construction, and issued code completion certificates for buildings which were later found to have leaking problems. Consequently some councils now share significant financial responsibilities with the builders (which in many cases have closed or otherwise removed themselves from liability) and the owners. Court cases have generally assigned around one third of the financial responsibility to local authorities. A 2013 Supreme Court case involving the Auckland City Council extended the liability of local bodies.

There are many reasons that some buildings from the 1990s were leaky. A major one was the increase in the use of cladding systems such as fibre cement sheet and EIPS (Externally Insulated Plaster System) that relied on a paint finish as the primary defence against water ingress. This system is very similar to Exterior insulation finishing system (or EIFS). Such cladding systems typically allowed for little construction or thermal movement so that fine cracks that appeared insignificant, and would have been relatively insignificant in traditional claddings such as weatherboard, allowed continuous ingress of moisture into the framing. These causes, combined with the reduced air movement through the prevalence of sheet cladding or sheet insulating materials for the monolithic look cladding, resulted in very damp conditions which are ideal for rot. A further exacerbating factor that resulted in more significant damage from the leaks, was the change to the New Zealand Standard for Timber Treatment in 1995, allowing the use of untreated Pinus radiata timber for wall framing. As this timber has little natural resistance to rot when wet, damage occurs more quickly.

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