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Report: Pathways to Building Code compliance for farm-totara timber

June 2016
Dean Satchell
Sustainable Forest Solutions

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Treegrower Article

The author wishes to acknowledge the support from the organisations and individuals that have enabled this project to be undertaken. These include; the Ministry for Primary Industries (through the Sustainable Farming Fund), Tane’s Tree Trust and the New Zealand Farm-Forestry Association, (including the Indigenous Forestry Section), the Northland Totara Working Group members Paul Quinlan and David Bergin for assistance in finalising this report, Michael Hayes & Geoff Cookson, for their time and donated sample boards of timber for testing, and saw-miller, Shane Hyde, for his time and the use of his band-saw in re-sizing some of the timber samples. The time and input from Robin Curtis, CEO of NZ Sustainable Forest Products, is also acknowledged and much appreciated.
In producing this report, reasonable care has been taken regarding the accuracy of the information presented. However, no guarantee as to the truth, accuracy or validity of any of the comments, implications, recommendations, findings or conclusions are made by the author, the Northland Totara Working Group, Tane’s Tree Trust, or any other party. Therefore, neither the authors, nor any of the supporting organisations, shall not be liable for, or accept any responsibility for, any loss, damage or liability incurred as a result of direct or indirect result of any reliance by any person upon information or opinions or recommendations expressed in this work. Users of any of this information, whether contained or inferred, in or arising from this report do so at their own risk.

Pathways to Building Code compliance for farm-totara timber

Building Code compliance is essential for developing timber markets for any tree species. Therefore, understanding the labyrinth of the regulatory framework and knowing how and what to do in order to achieve such compliance is a necessary step. This has been the focus of a recent Tane’s Tree Trust project for farm-totara.

Totara is a prominent feature of many Northland landscapes. Because it is relatively unpalatable to grazing stock, 'farm-totara' regenerates so prolifically that many pastoral landowners have regarded it as a weed. However, over the last century or more, substantial areas of second-growth totara-dominated forests have developed on private land in the region.

The Northland Totara Working Group sees an opportunity to develop a regional industry based on the sustainable management of totara as a specialty timber. Establishing a functioning supply-chain linking the resource to markets is required. However, at present, lack of compliance with the NZ Building Code is a significant restraint that needs addressing.

Why do we need code compliance?

Market potential for farm-totara timber would be significantly improved by complying with New Zealand’s performance-based Building Code. A range of products and applications hold the promise of market demand but these are not currently given consideration because they are not code-compliant. Code compliance requires evidence of structural and/or durability performance, even for such low-risk  uses as interior linings - an issue requiring industry to give immediate consideration to.

The path to compliance would require research and testing, particularly into levels of durability, followed by submissions advocating for inclusion into compliance documents, based on the evidence obtained. The broader issue, one which producers of farm-totara are currently facing, is the need to properly understand and quantify the physical properties of the timber and to get the necessary research done to produce the required evidence.

Pathway to code compliance

A pathway of research and actions to achieve code compliance of farm-totara timber with the New Zealand Building Code is set out in the recommendations of the full report.

Durability performance is a key compliance issue and the Building Code gives guidance for expected service life of different building components. These vary from only 5 years for interior linings to 50 years for structural components that are not easily replaced. Durability performance of farm-totara interior linings is well proven and not requiring testing. However, other farm-totara products that require testing for levels of durability, including structural timber, exterior cladding, exterior joinery and decking.  Durability performance of structural elements would need to be compared to H1.2 treated radiata pine and untreated Douglas fir, both being code-compliant under different circumstances. Exterior cladding and decking should be both tested in service, for evidence of meeting the 15 year durability performance required, along with accelerated decay testing to compare natural durability of farm-totara with H3.1 radiata for cladding and H3.2 radiata for decking.

A mechanism for change

The NZ Farm Forestry Association (NZFFA) has representation at various Ministry of Business, Innovation and Employment (MBIE) and Standards NZ-led committees looking at changes to the Building Code. This representation is essential for minor forestry species with special properties such as natural durability. A seat at the table ensures those interests are served, but this needs to be backed by evidence of code-compliance.

Timber properties that offer natural durability or are unfavourable for chemical impregnation, or induce processing and/or drying issues all contribute to decisions on product mix options. Because there is a limited knowledge-base on timber properties of farm-totara , selection of pathways would mean testing wood properties to ascertain appropriate products, while simultaneously determining code-compliance. Therefore it is suggested that two visual grades for farm-totara, based on timber colour, should be tested for durability in all applications. These are “heartwood + intermediate wood” and “intermediate wood + sapwood”. Until more is understood about relative durability of farm-totara in relation to tree age and radial position in tree, such differentiation based on colour, although presumptive, is based on industry experience regarding the likelihood of significant differences in durability performance that would lead to commercial products suitable for purpose.

Results from a well-planned and targeted testing programme would provide the evidence required to submit to MBIE for inclusion of farm-totara in compliance documents such as NZS 3602 Durability as an 'Acceptable Solution'. This means that Building Consent Authorities (BCA's) cannot question the suitability of the timber for the application. This outcome would allow architects and designers to specify farm-totara timber without hesitation for applications requiring code-compliance.

Incentive for developing regional-based industry

Preliminary studies confirm farm-totara is potentially a high-quality native timber with strong market interest. Removing the uncertainty around Building Code compliance, particularly relating to durability performance, is likely to have an immediate and significant impact on market demand and greatly increase the potential value of the resource to land-owners. This is also likely to stimulate greater interest in management of the substantial resource of farm-totara, not only in Northland, but also in many other regions of New Zealand where totara is naturally regenerating on private land. Of course industry would need to take advantage of this opportunity and develop markets, but interest is increasing in doing just this for a range of locally grown specialty timbers.

This work has been funded by the Ministry for Primary Industries’ Sustainable Farming Fund with cofounding from the NZ Farm Forestry Association and Tane’s Tree Trust. The full report is available for download on the NZFFA and TTT websites.


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