*ARCHIVE* - Weathertightness News - No. 4, Oct 2003

What's inside

  1. Weathertightness post-Hunn - a BIA update
  2. Weathertightness risk areas

Weathertightness post-Hunn - a BIA update

It is now over a year since the release of the BIA-commissioned Hunn Report into Weathertightness. Containing twenty-five recommendations that addressed and aimed to remedy the systemic failures within the building industry that had led to the weathertightness crisis, the Hunn report provided a blueprint for change across the industry.

One of the outcomes of the weathertightness crisis was the expansion of the Government's review of the 1991 Building Act, resulting in the Building Bill that is currently before the Government Administration Select Committee. The BIA has undergone significant strategic realignment in order to prepare for the expanded role indicted by the changes proposed in the Building Bill and has increased its resourcing, work programmes and technical capabilities.

Resolving the weathertightness problem remains a priority for the BIA and a major area of focus - it is accordingly identified as a key work area in our 2003/04 Statement of Intent.

While the BIA has worked to address many of the Hunn recommendations over the past year, the most important progression in this area has been the completion of the BIA's proposed amendments to Building Code Clause B2 Durability and Clause E2 External Moisture. The Authority is currently considering the submissions it received during the public consultation on the proposed changes and hopes to reach a final decision by the end of the year. The conclusion of this review should make a significant contribution to addressing weathertightness problems.

As well as ensuring that future buildings are "designed and built right first time", to meet the Minister of Commerce's challenge, the nature of the weathertightness problem is such that existing cases will continue to manifest themselves over the coming years. There is, therefore, an ongoing need for the industry to be vigilant in identifying weathertightness risk factors.

One area of risk, which formed the basis of a Hunn recommendation, is cantilevered balconies and decks supported by untreated radiata timber. The BIA has been working with TAs to ensure that awareness of this risk is kept to the forefront. To this end, the last issue of Weathertightness News carried a reminder about this risk and featured illustrative information from the BRANZ/BIA Weathertightness poster (Risk area 3 Balustrades/Parapets and Handrails; Risk area 4 Doors and Balconies).

This month, we have chosen to illustrate further examples of risk areas from the BRANZ/BIA poster:

Risk area 1 Complex Roofs
Risk area 2 Deck Barrier/Wall Junctions
Risk area 5 Ground Clearances
Risk area 6 Window Flashings

Of course, as the poster states, the best time to deal with weathertightness is at the design stage, where different options can be considered and changes easily made to plans. It is important for the designer, builder and owner to look at the weathertightness risks associated with the proposed building and reduce these to acceptable levels before building.

For existing building stock, which may incorporate at risk features for weathertightness problems, owners must ensure that the necessary maintenance and inspection is carried out on their properties to ensure that weathertightness problems do not emerge at a later stage.

By being mindful of all aspects of weathertightness risks, we can minimise this problem in New Zealand buildings for good.

Richard Martin
Chief Executive

For further information on the BRANZ weathertightness poster, please contact BRANZ 0900 59090 or www.branz.co.nzExternal website.

Weathertightness risk areas

Complex roofsComplex roofs

Risk area

  • parapet/roof junctions
  • valley heads and terminations
  • ridge, hip and valley intersections
  • roof penetrations (chimneys, pipes)
  • variable or (too) low pitch
  • junctions between roofing and wall cladding materials
  • insufficient flashing cover
  • internal gutters.

Reduce risk

  • simplify roof forms 
  • consider roof form when planning spaces 
  • comply with minimum pitch requirements 
  • flash and slope tops of parapets
  • ensure flashings are wide enough for the roof slope and wind zone
  • exercise caution when considering the use of internal gutters.

Deck barrier/wall junctionsDeck barrier/wall junctions

Risk area

  • vertical and horizontal wall junctions
  • fixing penetrating the cladding
  • no framing to support fixings
  • details not allowing space for construction.

Reduce risk

  • over-or under-flash the junction with a saddle flashing
  • provide defined break between the surfaces
  • providing framing hehind all the fixing points
  • allow space for installation of cladding and other requirements.

Ground clearanceGround clearance

Risk area

  • insufficient level difference between inside floor levels and the ground outside to prevent water entry 
  • cladding too close to, or in contact with, ground or deck 
  • plants preventing building materials from drying 
  • subfloor vents omitted or blocked 
  • soil or landscaping work built up against cladding. 

Reduce risk

  • ensure the Building Code clearance is met at the design stage 
  • lift the bottom edge of cladding to provide clearance and drainage plus allow for maintenance of the bottom edge 
  • trim or remove plants 
  • clear blockages, install additional vents 
  • remove built-up soil or materials.

Window flashingWindow flashing

Risk area

  • relying on sealant instead of flashing
  • cutting head flashings short
  • not using sill tray flashings
  • no stop-ends to sloping or curved head flashings
  • failure to window-joint sealant
  • no air seal between reveal and framing
  • no jamb flashings.

Reduce risk

  • always install head and jamb flashings
  • carry head flashings 30mm past edge of window or side flshings
  • install properly designed stop-ended sill tray flashings and ensure they drain to the outside
  • stop-end all sloping and curved head flashings
  • install air seals zone
  • install jamb flashings.

Legality of BIA Interpretations
Only the courts can issue binding interpretations of the Building Act 1991 and Regulations. Indications and guidelines issued by the Department of Building and Housing, either in Weathertightness News or other communications, are provided with the intention of helping people to understand the legislation. They are, however, offered on a “no-liability” basis, and, in any particular case, those concerned should consult their own legal advisers.

Please copy - copyright waived
Articles in this newsletter may be freely reproduced, in full or in part, in other publications as long as Weathertightness News is acknowledged as the source, including issue number and date. Disclaimers relating to an article must be included.

Editorial enquiries:
Please contact Ryan Nielson, Communications Adviser,
DDI: 04 495 2711 or nielson@bia.govt.nz

Subscriptions and general enquiries:
Weathertightness News is a free, monthly information service. To subscribe contact the Authority by telephone, facsimile or email.

The Authority is a New Zealand Government Crown agency established by the Building Act 1991 to manage the building control system.

0800 242 243
04 471 0794 (tel)
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bia@bia.govt.nz PO Box 11 846
New Zealand

Published by the Department of Building and Housing ISSN 1176-3159. Print run: 11,000