*ARCHIVE* - BIA Update No. 20 - Changes to Acceptable Solution B2/AS1 - Timber Durability 23 Dec 2003

Today the BIA announced implementation arrangements for Acceptable Solution B2/AS1 (Timber durability):

1. For new building consents - 1 April 2004

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.

2. For existing building projects - 31 March 2005

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.

Further information:
BIA Update 23: Two-Stage Implementation for New Timber Treatment Requirements
PDFChanges to Treated Timber Requirements (PDF 51 Kb)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 differ from the dates indicated below.

The Building Industry Authority has announced final changes to Acceptable Solution B2/AS1, concerning timber treatment levels.

Chairman Barry Brown said the changes are less conservative than the original proposals issued in June, but do require increased treatment levels in some framing situations more at risk from water damage, particularly caused by leaking.

"The changes are risk informed and require appropriate levels of protection needed to manage the risk of moisture contact in differing building elements or components," 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."

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

The changes will apply to all buildings, not just residential constructions as originally proposed.

They include new requirements for colour coding and identification marking of timber so that treatment level and treatment type will be more easily identified.

Summary of Changes

Changes to Hazard Classes

  • H1 Hazard Class will be split into H1.1 and H1.2 to differentiate between insect only protection (H1.1) and insect protection plus a degree of protection against fungal decay (H1.2)
  • The H3 Hazard Class will be split into H3.1 and H3.2 to resolve concerns about the durability of LOSP
  • H3.1 will contain H3 LOSP
  • H3.2 will contain H3 CCA, ACQ, copper napthenate and copper azole
  • H3.1 treated timber will cease to be acceptable in the construction of the structure of timber decks and balconies.

Changes to Minimum Treatment Requirements

Building Element* Current Minimum Treatment
New** Minimum Treatment
  • Roof framing, trusses and ceiling joists
  • Interior wall framing, including bottom plates
  • Exterior wall framing in low risk, single storey masonry veneer buildings
  • Untreated kiln dried radiata pine
  • Untreated Douglas fir
  • H1 treated, planer gauged radiata pine***
No practical change
  • Exterior wall framing and parapets in all but low risk, single storey masonry veneer buildings
  • Enclosed framing within skillion roofs^^
  • Untreated kiln dried radiata pine
  • Untreated Douglas fir
  • H1 treated, planer gauged radiata pine^
  • H1.2
  • Subfloor framing
  • Untreated Douglas fir
  • H1 treated, planer gauged radiata pine
  • H1.2
  • Enclosed framing within flat roofs
  • Framing for enclosed decks and balconies
  • Framing within enclosed balustrades

Standard unclear, but in practice the following have been typically used:

  • Untreated kiln dried radiata pine
  • Untreated Douglas fir
    H1 treated radiata pine^
  • H3.1
  • Piles and other structural in ground material
  • H5
No change

* Summary of major elements only
** Takes effect from 1 April 2004, subject to final industry feedback
^ A range of other minor timbers are permitted
^^ A pitched roof where the ceiling lining is parallel and close to the roof cladding

Changes to Identification Requirements
In order to help ensure the right timber is used in the right situation, the Acceptable Solution will introduce changes to the way treated timber will be identified. These are:

  • In addition to the existing requirement that the treatment level of timber is branded on its end, there must be a unique numbering system that identifies the treatment type.
  • A requirement that framing timber is coloured at the time of treatment to identify treatment levels.

Detail of Amendments

A BIA paper detailing amendments to B2/AS1 is available by clicking here.

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.

To view further background information on the changes to B2/AS1 please click here.

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.

Impact on Consenting and Code Compliance Certificates

Changes to Acceptable Solutions are not retrospective. If a council has granted a building consent or code compliance certificate before 1 April 2004, the consent or certificate will remain valid.

We have introduced the 1 April 2004 date for two reasons. It provides industry with an opportunity to address supply chain issues. Secondly it provides a reasonable opportunity for existing construction jobs to be completed and signed off prior to the changes taking effect.

However, from 1 April 2004, if a building consent has been granted but no code compliance certificate has been issued, councils may apply the new Acceptable Solution when considering whether to grant certification. Councils must have reasonable grounds that a building complies with the Building Code in order to issue a code compliance certificate.

This means builders and designers should take the changes to the Acceptable Solution into account in regards to current building projects.

Our strong advice to councils is that they clearly inform customers applying for building consents of the changes to the Acceptable Solution and the implications for their building project. The BIA will formally provide additional information to councils on that matter as early as possible in 2004, to facilitate the provision of useful consumer advice.

If a building does not comply with the Acceptable Solution, it may still comply with the Building Code as an Alternative Solution. The building is just not automatically deemed to comply. Councils must consider these buildings on their individual merits and determine whether they will meet the performance requirements of the Building Code. Councils must have reasonable grounds that a building complies with the Building Code in order to issue a code compliance certificate.

It should also be noted that there are three months before the changes come into effect. This change has been widely anticipated since at least the publication of the Hunn report more than 12 months ago. The BIA clearly signaled a need for increased timber treatment requirements when it published proposed changes to B2/AS1 in June 2003.