*ARCHIVE* - Weathertightness - preliminary report 20 May 2002

The Building Industry Authority appointed Weathertightness Overview Group has given a preliminary verbal report to the BIA into the increasing incidence of water damage to some modern residential dwellings.

The verbal report provided sufficient evidence for the Authority to initiate immediate action, Chief Executive Bill Porteous said following the BIA meeting on 10 May. However, the Overview Group will continue to investigate the problem.

He said the report found the causes of the problem were complex and the culmination of a range of factors.

"However, we know the consequences are very real for those affected and we need to act now."

The Authority will take the following steps:

• Organise a forum of industry leaders to impress on them the "multiple cause" nature of the problem and to develop an industry-wide response.
• Review the Building Code clauses and related documents that concern durability and external moisture, including issuing for public consultation by 31 August new draft clauses and technical documents based on a more traditional approach to weathertightness.
• Require the Overview Group to complete the next stage of its report by 31 July including:
  • Developing research briefs to further investigate the nature and extent of the problem
  • Providing further commentary on the causes of the problem and recommendations for further action
  • Recommending a means of monitoring the on-going investigation and implementation of the Overview Group's recommendations.

Dr Porteous said the Authority will also develop a communications programme to ensure the public and the industry are fully informed of the issue and action taken.

He said it was important to stress the problem had multiple causes and it was critical the industry worked together to achieve a lasting solution.

The BIA Weathertightness Overview Group members are: Don Hunn (chair), former State Services Commission chief executive; Ian Bond, civil engineer; and David Kernohan, architect.

Summary of the BIA Overview Group's preliminary findings

Overview Group members are: Don Hunn (chair), former State Services Commission chief executive; Ian Bond, civil engineer and David Kernohan, architect.

• Although a small percentage, a growing number of new housing constructions are showing signs of water damage
• It is not possible at this stage to fully determine the extent and nature of the problem
• Dwellings typically affected are upmarket houses and multi-unit apartments in the medium price range
• Both building types typically use monolithic cladding systems in a style that commonly uses complex roof forms; no eaves; internal and external balconies; and often flush windows and doors with inadequate or no flashings
• The problem is systemic - that is caused by the confluence of a range of factors including:
  • Town planning criteria relating to plot ratio and yard distances that inadvertently lead to particular building solutions or contribute to the choice of housing style
  • Imperatives of cost and speed (cutting corners)
  • Changes in responsibilities and relationships of designers and builders
  • Variable application of professional and trade skills and good judgements. There has been some anecdotal comment about an identifiable decline in the levels of skills in various trades on site
  • Changes in on-site structures and responsibilities (sub-trades)
  • Emphasis among product manufacturers on product rather than building system
  • Lack of effective supervision/inspection practices
  • Lack of emphasis and detailed attention to weathertightness in compliance documents compared to, say, structural integrity.
• Two fundamentals of construction were being by-passed in some instances. These are:
  • A traditional "belt and braces" approach to construction, which accepted that water will penetrate the exterior of a building at some time
  • therefore a backup was required.
  • A lack or misuse of flashings at junctions and penetrations.

Preliminary report in full Word Doc [DOC 40 KB, 5 pages]