Revision of Standard for timberframed buildings NZS 3604 technical committee and review update

Timber-framed buildings, NZS 3604:1999, is the foremost building Standard in New Zealand for the building and construction industry. A 'limited technical review' of NZS 3604 is now underway and the draft revised Standard is planned for public comment release in late 2009. Publication is scheduled by late 2010/early 2011.

The project is in the early stages of draft development and the organisational structure for the project has been broken down into three main areas: a leadership group, a single technical committee (P 3604), and five work groups have been established. The leadership group has held two meetings to date, the technical committee three meetings, and the five work groups are currently working on specific assignments to report to the next P3604 meeting currently planned for June 2009.

In the April issue of Touchstone and Standards magazine, we profiled the leadership group We will profile the work groups in future issues of Touchstone and Standards magazine. Below, we profile the technical committee for 3604.

Introducing the technical committee

The technical committee has been formed in accordance with Standards New Zealand's Standards development guidelines to enable the many different stakeholders to be involved in the NZS 3604 revision process.

'The technical committee is primarily responsible for focusing on and reviewing technical issues surrounding the revision of the Standard, and developing the revised draft,' says Don Bunting, Chair of the technical committee.

The review of the Standard will reflect the needs of industry, changes in materials and industry practice, and changes in related Standards including those setting requirements for loadings. It will also incorporate content on bracings and durability.

Overall, the leadership group and the technical committee agree that there is a need for a limited technical review of the NZS 3604 (see below for more information). The value of the Standard to the sector is that NZS 3604 provides an Acceptable Solution in the Compliance Documents of the New Zealand Building Code. This means designs and plans in accordance with NZS 3604 are deemed to comply with the New Zealand Building Code and must be accepted by Building Consent Authorities. This provides the sector with the most cost effective, efficient way for designing, building, and inspecting a house, which meets the performance requirements of the New Zealand Building Code.

The technical committee includes 22 industry representatives, nominated for their expertise in areas directly related to the revision of NZS 3604.

Representatives on the technical committee

Nominating organisation

Technical committee member

Architectural Designers New Zealand Inc.

Colin Hill

Building Officials' Institute of New Zealand

Colin Clench

Building Research Association

Eddie Bruce

Building Research Association

Roger Shelton

Cement and Concrete Association New Zealand

David Barnard

Certified Builders' Association New Zealand

Richard Merrifield

Construction Information Limited

Don Bunting – Chair

Department of Building and Housing

Graeme Lawrance

Design Association of New Zealand Inc

Allan Walters

Douglas Fir Association

Scott Gibbons

Frame and Truss Manufacturing Association New Zealand

Mark John Ash

Institute of Professional Engineers New Zealand

Ernest Lapish

Institute of Professional Engineers New Zealand

Ian Garrett

New Zealand Building Industry Federation of New Zealand Inc.

Stephen Walker

New Zealand Institute of Architects

Michael Middlebrook

New Zealand Institute of Building Surveyors Inc.

Hans Gerlich

New Zealand Metal Roofing Manufacturers Inc.

Stuart Hayman

New Zealand Timber Industry Federation Inc.

Bruce Anderson

Registered Master Builders' Federation

Jamie O'Leary

Scion Research

Douglas Gaunt

Window Association of New Zealand Inc.

John Yolland

Wood Processors' Association of New Zealand

Warwick Banks

Key decisions/recommendations made to date

Standards New Zealand notified key stakeholders about the revision in 2008 and sought feedback. From the comments made, the technical committee has begun implementing changes needed in the draft Standard.

  1. The revision of NZS 3604 is to proceed as a 'Limited Technical Review' according to the following scope:
    • AS/NZS 1170 Structural design actions – the loadings Standard – is referenced in the Compliance Documents to the New Zealand Building Code effective 1 December 2008. NZS 3604 needs to be updated to reflect AS/NZS 1170.
    • Section 11. The building envelope, roof, and wall cladding The majority of this section has been superseded by the compliance document E2/AS1 External Moisture. This section will be removed. Not all of section 11 has been superseded by E2/AS1. NZS 3604 should maintain the content that has not been duplicated in E2/AS1 or other Standards until such time that it is.
    • Section 4. Durability
      This section needs to be brought into line with the recent changes to the Building Code and other Standards, in particular the maps and recent product developments. Some of the information is out of date, while other parts are incomplete.
    • Section 5. Bracing design
      The content is appropriate; however there are a number of problems with readability and some areas are too open for interpretation, which has the potential for inconsistency among building consent authorities. The committee will need to consider usability and the appropriateness of worked examples, and so on. Subfloor bracing needs to be re-evaluated as there have been many complaints about this.
    • Section 10. Roof framing
      The biggest issue concerns the design process, now roof trusses are designed and manufactured by producers.  There are also other issues where the information is out of date and does not reflect current practice.
    • Indexing and referencing, tables, diagrams, worked examples, and so on
      All the feedback received suggested that the Standard has a good order and flow, however there is an opportunity to improve the indexing, referencing, and the usability and clarity of the diagrams and tables.
  2. E2/AS1 is to be revised; The Department of Building and Housing will be running this project in parallel with the revision of NZS 3604.
  3. Section 11 is to be removed from NZS 3604. Any items that are currently in NZS 3604 and not covered in E2/AS1 will be incorporated into E2/AS1, for example, brick veneer cladding.
  4. Section 4 Durability is to cover structural issues only. All areas to do with the building envelope or weather-tightness are to be removed because they are now referenced in E2/AS1.
  5. Section 19 Statutory information is no longer relevant and is to be removed.
  6. Foreword is to be reviewed and updated. A draft has been tabled for discussion by the technical committee.
  7. Several recommendations have been made by the loadings work group on AS/NZS 1170 including reviewing the soils determination process and soils classification, adding an extra high wind zone classification of 55 metres per second to NZS 3604, including re-clarification of the wind zone and seismic maps to be adjusted to include reference points identifying where the zones start and finish. This is work in progress.
  8. The durability work group has identified key issues including re-clarifying the corrosion zone maps for sea spray zones, reviewing fastener treatments for higher weight galvanising, including identifying clauses 4.5, 4.6, 4.7, 4.9, 4.10, and tables 4.4 & 4.5 for deletion, among others.
  9. The bracing work group is well advanced. It has made several recommendations to the technical committee, and is currently reviewing section 5 on bracing design, for relevant clause, table, and figure changes.
  10. The roof framing and design appearance and clarity work groups have identified the key issues for consideration and are in the early stages of developing their recommendations to be put to the technical committee.

For more information, please email, or call 04 495 0934.

Published in building.