Weather tightness has become an important issue
in New Zealand. The Claddings Institute of New Zealand has been
making its members aware of these problems and, in 2000, undertook
a study tour to the USA and Canada.
Summary of findings fo the New Zealand Industry Study
Tour to the USA and Canada, November 5-10, 2000
Study tour participants:
- Brad Ridoutt, Manager Built Environment Programme,
- Dale Knox, Systems Design Engineer, James Hardie
- Guy Cavanagh, Marketing Engineer, Carter Holt Harvey;
- Kevin Golding, Manager-Future, Winstone Wallboards;
- Philip O'Sullivan, President, Claddings Institute
of New Zealand;
- Rosemarie Knight, Development Executive, Winstone
- Wayne Sharman, General Manager Science and Engineering,
Early last century, New Zealand's residential architecture
and construction was influenced greatly by North America. Timber
is an abundant resource in both regions and remains the predominant
structural material used in housing today.
Since the mid-1980s the range and complexity of cladding
materials have flourished allowing a freedom of style and architecture
that has changed our residential landscape.
However many of these recent buildings have weathertightness
problems. New Zealand's pattern is strikingly similar to reported
failures in North America.
A forum was held on weathertightness to help create
a greater industry awareness of building leakage. The study tour
was one of the outcomes. The tour focused on the PATH Conference
on Duarbility and Diaster Mitigation in Housing, held in Madison,
Wisconsin, and a visit to Vancouver, Canada on the return leg. This
coincided with a meeting of BERC, a reserach consortium that leads
weathertightness research at present. Three of the New Zealand group
were able to attend that meeting.
Summary of findings
Scientific research is needed to better understand
the building envelope and its role with moisture.
Such understanding will eventually lead to a rational
approach for the development and design of exterior wall systems.
Technology is best transferred from research agenices
to industry by creating useful tools for design and understanding.
Education is necessary for all levels and parts of
Even with improved codes, the implementation through
the design, approval and construction phases will be an elusive
In order to bring about successful outcomes, co-ordinated
government agency and industry initiatives are best.
While timber framing is the predominant structural
form in housing, it is being challenged by its perceived poor performance
during hurricanes and because of reported termite and decay problems.
New Zealand can directly benefit from North American
initiatives by monitoring programmes, using their knowledge and
adapting this to our needs.
Problem analysis - The North
US$250 billion industry with 1.6 million new home built
each year. 90% are woodframed.
29% of recent houses have problems with 6% considered
serious. 90% of surveyed problems are due to rainwater leaks.
The population is increasing most rapidly in durability
and disaster prone areas.
The size and complexity of houses are increasing.
Floor levels are too close to the ground.
Loss of roof eaves
Inappropriate use of vapour barriers
Omission of flashings and abuse of sealants
Abuse of claddings by other trades and poor construction
English is a second language for many workers.
Multitude of opinions. Science is still evolving and
there is a lack of good research.
Condensation within concealed spaces of airconditioned
buildings eg. on the underside of floors in subfloor spaces.
Stiffening of buildings from monolithic claddings can
generate earthquake damage.
Problem analysis - Canada
Residential construction is stretched to allow cheaper
low-rise condominiums on expensive inner suburban land.
800 three to four-storey condominium complexes were
built in Vancouver between 1980 and 1995 with over half of these
experiencing water leakage. It is estimated that 50,000 units are
affected. Repair costs range from C$35,000 to C$40,000 per condominium
unit that have a value of around C$150,000.
Condominiums are often owned by retired people on fixed
incomes. They are used as their own homes or sources of income.
Some emergency loans are now available.
The builders' home warranty scheme has collapsed.
Buildings are sometimes repaired more than once.
Condominiums are difficult to sell unless the cladding
has been replaced, irrespective of damage. Repaired buildings are
readily identified by exposed flashings at each flood level.
Leakage problems are also present in highrise buildings.
Given the level of public awareness it is surprising
that nothing is being done to rectify problems in attached and detached
Consumers expect industry to get it right.
Cheap and inappropriate construction, while seemingly
lowering building costs, merely allows land values to rise often
to unrealistic levels.
Increased consumer awareness promotes change.
Claddings are vulnerable to owner abuse - blocking
vents and rains, inappropriate alterations and poor maintenance.
All buildings leak.
More rain means more rain control is needed.
Moisture penetration is deceptive in its apparent simplicity.
The building envelope must have drying potential.
Greater building complexity leads to lower building
The envelope is a climate transition zone that can
provide ideal micro-ecological niches for destructive organisms.
The creation of energy efficent buildings has resulted
in tight, cold and unforgiving claddings.
Poor indoor air quality is not related to external
leakage. It is due to high occupant density, excessive moisture
from internal sources, inadequate ventilation and excessive subfloor
Buildings are chaotic structures, created in a chaotic
manner and occupied by chaotic people. Accurate prediction is not
There must be robustness and a margin of safety in
the way we build.
Educating the public requires lots of time and money.
In the short term industry-based solutions are required.
A common language for weathertightness is needed -
simple terms that convey meaning and understanding.
To educate, first we must have knowledge, then we must
educate the educators.
Problems can become institutionalised where unreasoned
behaviour is not only accepted, it is difficult to change.
Most failures are due to poor implementation, often
arising from simple mistakes.
Inspecting quality into building does not work.
Quality comes from personal traits such as knowledge,
pride, care and attention to detail.