Post from Roger Belton on July 12, 2017 at 6:10am
Determinations, specialty timbers and the building code
What do you know about "Determinations"? Well... Determinations are best described as judgements made by MBIE where disputes arise between the Building Consent Authority (BCA) and those undertaking building work. BCA's must accept compliance where the building work is an "Acceptable Solution", such as when using materials complying with the standards referenced in the building code. However, where building work doesn't "fit" within these constraints (such as using materials that are not specified in the standards) the owner has to apply for an "Alternative Solution".
Last year an application was made to Marlborough District Council for specifying NZ grown European oak for flooring, floor joists and beams in the owners dwelling. This was an Alternative Solution because oak is not a species listed in NZS 3602 "Timber and Wood-based Products for Use in Building". MDC rejected the application because they contended that they didn't have enough information on the durability of European oak for use in internal applications.
The owner had to supply a whole lot of information on the natural durability of oak to MDC, for use in a dry internal environment. Now, keep in mind that the natural durability of oak is the stuff of legends and is based on many centuries of use as a structural timber. And yes, this is a true story, MDC declined the consent because they asserted that the applicant didn't supply enough information on durability.
The information supplied included:
- A paper published in the New Zealand Journal of Forestry: “Durability of New Zealand grown timbers”
- Information about oak indicating the timber is classified as “Durable”.
- Email correspondence from a Scion Research scientist saying "results indicate that the heartwood has a durability rating of 2 (durable) in ground contact. The heartwood is generally regarded as durable - very durable in Europe hence there should be no problem with it being used for framing timber or for flooring."
The owner was forced to apply to MBIE for a Determination to sort out this mess. They just wanted to use oak timber in their house!
What was in question was the durability in a dry internal environment. The Determination is eight pages long and is all very official, but concludes that "New Zealand grown European oak in its proposed use as flooring, floor joists, posts and beams in an internal double-height space in the building will meet the requirements of the Building Code with respect to Clause B2 Durability."
Unfortunately, next time a BCA declines an application to use oak for similar applications, the owner will need to go through this process all over again, because this Determination only applies to that one house - Determinations are conducted on a "case-by-case basis".
Is there a solution to this mess, where "alternative" species are relegated to the realm of "Alternative solutions", allowing BCA's to get away with being completely unreasonable? Did you know that laying a blackwood floor currently requires an Alternative Solution and is open for rejection by your local BCA?
We need to make it easier to use specialty timbers in building work where they are well suited. This is why I'm representing Farm Forestry Timbers on the NZS 3602 committee "Timber and Wood-based Products for Use in Building".
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