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Timber performance

Applications and products

Building with timber

Sustainable future

Resources

Learning centre

Standards and Codes

The Building Act 2004 sets out the legislation on building standards and procedures that affect the construction, alteration, maintenance and also demolition of new and existing building in New Zealand.

The Building Regulations contain the mandatory Building Code that defines the minimum performance standards that any building must meet. These cover requirements such as fire safety, access, healthy environment, moisture control, durability.

The Department of Building and Housing (DBH) manages the system that regulates building work and monitors its effectiveness. The DBH publishes Compliance documents which prescribe one method of how to comply with specific requirements of the NZ Building Code.These are known as Acceptable Solutions, they are conservative by nature as they are deemed to comply in all situations throughout NZ.

These can describe the use of particular building methods or building materials, e.g. the preservative treatment needed to meet durability requirements under an end-use situation.

Sometimes products, systems or methods may not fit within the Compliance documents so acceptance by Building Consent Authorities (BCA’s) as being Code compliant requires Certification or an independent assessment as an Alternative Solution by an independent third party organisation.

Untreated and preservative treated timber, with a few exceptions are included in New Zealand Standards, e.g. NZS3602:2003 Timber and wood-based products for use in building (available from Standards NZ),  and are recognised as being Acceptable Solutions within the context of the NZ Building Code.

NB: The code has changed as of April 2011 to use H1.2 for Timber Treatment for enclosed framing.

Read the brochure Pink is Tough here.

Standards

Standards are prepared to provide and define specifications for the required properties and applications of timber and wood-based products. There are also standards that define test methods, and provide requirements for treatment plant site design and operations.

Some standards relevant to timber use in construction are solely New Zealand standards while others are joint Australian/New Zealand standards. The latter are particularly relevant to exporters of processed timber products to Australia.

Standards are issued after consultation and consideration of research results and history of use by a committee comprised of representatives of relevant industry groups and independent experts. All new standards and major amendments are issued for public comment before publication, ensuring a wide range of consumers, end-users and manufacturers have access to input in their development.

NZS 3640:2003

The preservation of timber and roundwood in New Zealand is covered by NZS 3640:2003 Chemical Preservation of Round and Sawn Timber, plus subsequent amendments.

Specifications for preservative treatment for other wood products; reconstituted wood-based products, plywood, laminated veneer lumber (LVL) and glue-laminated timber products, are contained in AS/NZS 1604:2005 Parts 2 to 5.

The wood preservative standards are organised as specifications for treatment of timber to be used in specific “Hazard Classes” – a series of biological hazards for different end-use situations.

Specifications include the approved treatment chemicals, their minimum penetration into the wood and the preservative retention (minimum concentration of the active ingredient within the penetrated zone).

In New Zealand, the NZS 3640 treatment standards for H1.1 and H1.2 apply to all species but H2, H3.1, H3.2, H4. H5 and H6 apply only to radiata pine.

For all the hazard classes to be applied to other species, it must be first demonstrated by a timber treater that they can meet the penetration/retention specification for the species in question.

NB: The code has changed as of April 2011 to use H1.2 for Timber Treatment for enclosed framing. Read the brochure Pink is Tough – H1.2 Frames it Right.

NZS 3602:2003

NZS 3602:2003 Timber and wood-based products for use in building is a particularly important standard for both untreated and preservative-treated timber as it is directly referenced in the New Zealand Building Code Compliance document on Durability B2/AS1.

The minimum performance for timber products is assigned to 5, 15 and 50 year categories. The timber products include radiata pine, douglas-fir and other species, plywood, laminated products and other wood-based products.

Protection is achieved by a low moisture content (typically < 18%) in-service or by a preservative treatment. Information incorporated into New Zealand standards is developed by an expert committee using consensus-based process that allows public to provide input.

The Committee that developed NZS 3602:2003 also considered available research and a history of use on wood species in New Zealand end-use situations.

NB: The code has changed as of April 2011 to use H1.2 for Timber Treatment for enclosed framing. Read the brochure Pink is Tough – H1.2 Frames it Right

View the NZ Hazard Class & timber treatment summary table

Treated timber

NB: The code has changed as of April 2011 to use H1.2 for Timber Treatment for enclosed framing. Read the brochure Pink is Tough – H1.2 Frames it Right.

The standard NZS 3640:2003 Chemical Preservation of Round and sawn timber (or AS/NZS 1604 series where applicable to other wood products) describes the approved chemical actives and the minimum concentrations – retained in the wood after treatment (the retention) – required to meet each hazard class specification.

Six Hazard classes are used to describe the service exposure conditions in relation to the biological hazard in the PDF table below.

Hazard classes (.pdf) 

Treatment solutions

The standard NZS 3640:2003 Chemical Preservation of Round and sawn timber gives the specification for the approved actives only.

These actives and the concentration (retention) approved for each hazard class are summarised in the following PDF table.

Approved actives and concentrations for each hazard class in NZS 3640  (.pdf)

Note: the above .pdf is not yet up-to-date with the latest single hazard class changes, so compare with NZ Hazard Class & Timber Treatment Summary Table and Pink is Tough – H1.2 Frames it Right brochure