During the 1990s a considerable number of houses were built using
methods that haven't withstood the weather conditions in New Zealand. Because
of the problems involving design, choice and installation of materials, these
houses leak when it rains.
Once water or moisture gets behind certain cladding types, if there is no
cavity between the cladding and the framework, the water becomes trapped and
cannot easily escape or evaporate.
From bad to worse:
Untreated timber used for wall framing
In
1998, a
change in the New Zealand standard for timber treatment allowed the use of untreated kiln-dried timber in wall
framing. If this untreated timber framing gets wet, the timber starts
to rot.
Likewise, steel framed buildings and treated timber can also be affected if
they remain wet long enough. This causes, in some cases, extensive damage to
the fabric and
structure of
the house. (See also: Prendos' Timeline).
While most identified leaky homes are in Auckland or the North Island,
respectively, this picture may change in the near future. Symptoms are showing
in Christchurch in the South Island, too. Due to the drier
climate there, the rot is just taking longer to appear on the
surface, according to a reasonable-sounding hypothesis suggested in this
article.
Figures [data: 2008/2009] from the Department of Building and Housing show
6,403 properties nationwide have lodged claims with the Government's
Weathertight Homes Resolution Service. The 223 claims on properties in
Christchurch represent 85 per cent of all claims in the South Island (source: this
article).