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*ARCHIVE* - Changes to Acceptable Solution B2/AS1 - Timber Durability 23 Dec 2003

Important notice
9 March 2004

Today the BIA announced implementation dates and arrangements for the new Acceptable Solution B2/AS1 (Timber durability): The new Acceptable Solution is applicable to any application for a building consent received on or after 1 April 2004 that proposes building according to B2/AS1.

1. For new building consents - 1 April 2004

2. For existing building projects - 31 March 2005

Further information
- BIA Update 23: Two-Stage Implementation for New Timber Treatment Requirements
- Changes to Treated Timber Requirements
A pamphlet published by the BIA on 9 March 2004 which contains important information on timber treatment requirements for people building or renovating.

The confirmed implementation dates listed above differ from the dates indicated in the documents below.

A one-year transition period for those buildings that were consented under the old Acceptable Solution will now apply. This means projects consented before 1 April 2004, based on the Acceptable Solution then in place, have until 31 March 2005 to be completed and for code compliance certificates to be issued based on the old requirements.

Timber durability changes

Proposed Changes to B2/AS1 - Report to Building Industry Authority, November 2003
The report submitted to the BIA on the proposed changes to B2/AS1 (Durability) is available below. The Report contains ten reference documents, available here as individual PDF files. The full media release can be found further down this page.

 Proposed Changes to B2/AS1 - Report to Building Industry Authority, Nov 2003 (PDF 560 Kb)
Help with PDF documents >>

References
 Appendix A: NZS 3602 Comparative Table 1 (90 Kb)
 Appendix B: Definitions (28 Kb)
 Appendix C: B2 Durability Working Group - Members (24 Kb)
 Appendix D: B2 Durability Working Group - Final Minutes (100 Kb)
 Appendix E: B2 Durability Regulatory Impact Statement (108 Kb)

 Attachment 1: BIA Report on B2/AS1 Comments Received (508 Kb)
 Attachment 2: Risk Matrix Approach considering Weathertightness and Durability (476 Kb)
 Attachment 3: Report on E2/AS1 Risk Matrix and WHRS Data (672 Kb)
 Attachment 4: BIA / NZIER Update on Cost Benefit Analysis (328 Kb)
 Attachment 5: Proposed B2 Durability for Publication (208 Kb)

Additional documents
 NZIER Cost Benefit Analysis, June 2003 (B2 and E2) (965 Kb)
 Background to B2 Durability Proposed Changes (213 Kb)
BIA Update 20: Changes to Acceptable Solution B2/AS1 - Timber Durability

Detail of amendments
A PDF version of the amended B2/AS1 is available from Victoria Books in the normal manner by clicking here. Printed and CD Rom versions will be available in January.

B2/AS1 amendment calls up New Zealand Standard 3602 (NZS3602:2003) Timber and Wood-based Products for use in Building), which in turn calls up New Zealand Standard 3640 (NZS3640:2003) Chemical Preservation of Round and Sawn Timber).

NZS 3602 describes what level of timber treatment is required to meet the durability requirements set out in B2/AS1 (i.e., what timber is needed where). This is available for purchase from Standards New Zealand by clicking here.

NZS 3640 is intended for use by treatment plants and sets out the preservative treatment and identification of timber to provide protection from decay and insect attack. The requirements are based on six hazard classes that are described in this Standard. This is available for purchase from Standards New Zealand by clicking here.


Media release 
23 Dec 2003

Higher levels of timber treatment will be required in parts of buildings more at risk from leaking, the Building Industry Authority announced today.

However final changes to its Acceptable Solution [1], that sets out the level of treatment required of timber, are less conservative than the original proposals issued in June, Authority chairman Barry Brown said.

"The changes are more flexible and are based on assessing the risk of moisture causing damage in specific parts of a building and the level of protection needed to manage that risk," Mr Brown said.

"They will require additional treatment levels in some situations, but we are not introducing a requirement that all framing timber is treated as was proposed earlier this year.

"Our focus has been on putting in place a regime that will provide homeowners and users with appropriate protection if a building leaks. We have also taken into account feedback from the timber and building industries during our extensive consultation on this matter."

"This approach is about putting additional protection in place where it is needed. It also means that certain timber products - like untreated kiln dried radiata pine and untreated Douglas fir - can still be extensively used in buildings built to the Acceptable Solution."

Key Points
Key elements of the Acceptable Solution change include:

  • An increase in treatment level from H1 (provides insect only resistance) to H1.2 (insect plus fungal or rot resistance) for:
    • subfloor framing
    • exterior wall framing including parapets (except in certain low risk brick veneer buildings)
    • enclosed framing and structural supports for riskier roof types (like enclosed skillion roofs)
  • An increase in treatment level from H1 to H3.1 for all framing and boundary joists or walls for enclosed decks, balconies and balustrades, and for enclosed flat roofs.
  • Untreated kiln dried radiata and untreated Douglas fir can still be used in a range of situations including:
    • roof framing, trusses and ceiling joists, except certain roof types with a higher risk of leaking and causing damage (like flat roofs)
    • inter-storey floor joists
    • interior wall framing, beams, rafters and joists
    • exterior wall framing in single storey, low risk brick veneer buildings
  • New requirements for colour coding and identification marking of timber will be introduced so that treatment level and treatment type will be more easily identified.
  • The changes apply to all buildings, not just to residential buildings as originally proposed.

The changes have been the subject of an independent cost benefit analysis by the New Zealand Institute of Economic Research. This shows that, when combined with the proposed changes to the external moisture requirements, they will result in a national economic benefit of between $94 million and $1.1 billion over the next 25 years[2].

The BIA estimates the timber treatment changes will add around $500 to the cost of building an average house.

The changes are proposed to take effect from 1 April 2004, subject to feedback from the industry over implementation timing.

Mr Brown said the changes to B2/AS1 were about how a building copes if it leaks.

"Treated timber is a second line of defence. That is, it can resist decay for a period of time while the moisture dries, or it gives you time to discover and fix a leak before too much damage is done."

The changes to B2/AS1 have been developed in tandem with changes to the Acceptable Solution E2/AS1[3] that deals with the way external moisture should be managed in buildings - that is, how water is kept out or coped with by, for example, cladding systems, flashings and wall cavities. E2/AS1 is due to be issued early in 2004.

Contact: Laurie Edwards, Communications Manager, (04) 495 2773 or 027 258 2849.

 

[1] Known as B2/AS1 because it is the Acceptable Solution supporting Clause B2 (Durability) of the New Zealand Building Code.
[2] This assumes that between 1 and 2 percent of houses built in that period would 'fail' or suffer from weathertightness related problems if these changes weren't made.
[3] Known as E2/AS1 because it is the Acceptable Solution supporting Clause E2 (External Moisture) of the New Zealand
Building Code.