Orange timber a roughy say experts

The building industry is in turmoil over the use of surface-treated timber - which experts say could rot - in external walls.
Building experts say timber treated with a spray-on boron preservative is being used in external wall framing in place of traditional boron-soaked timber, which safeguards against borer and moisture. The new timber is coded "T1.2" and its distinctive orange coating is dubbed "Agent Orange" within the trade.
While the treated timber is being used in Hawke's Bay it appears to be used correctly, only in internal walls.
Malcolm Hart, who is responsible for the Hastings District Council's building inspectors, said the orange timber was not common in Hawke's Bay.
Council building inspectors had only seen it in a new house once in the last two months, he said. They would stop any building where the orange-coloured timber was being used inappropriately, he said.
Hastings builder Alan Whyte, who is the eastern region representative for the Certified Builders Association of New Zealand said rather than the orange timber, he used the blue-coded H1.2 in external walls and the green H3.1 for the bottom plate.
National MP Nick Smith claimed the timber could have been used in as many as 10,000 homes and apartments.
The Building Industry Authority (BIA) approved the use of boron-sprayed timber in April last year, within six months of a law change reintroducing treatment to boron-soaked H1.2 grading as a requirement for framing timber, after the leaky buildings scandal.
The law change requires "complete sapwood penetration" but the new product is a surface spray which experts claim does not adequately penetrate the wood.
Timber treated this way is widely sold by timber merchants as equivalent to H1.2 grade treated pine, but labelled "keep dry".
Robin Wakeling, a Forest Research Institute scientist and now a consultant on leaky building issues, said the surface spray does not penetrate wood as well as traditional soaking and is liable to wash off if it gets wet.
The T1.2 coded timber was approved as an "alternative solution" under the Building Code, meaning it can be used in the same situations as H1.2 graded timber.
But Certified Builders Association chief executive Gary Shuttleworth said it does not meet the H1.2 treatment standard, which requires complete penetration.
The preservative, marketed as TimberSaver, is manufactured by Wiri-based Osmose NZ.
The company's technical sales manager Terry Smith said the product was subjected to rigorous testing by the old BIA. It was intended for situations where wood would not be continuously damp, including wall linings.
"If it was left wet for a long time it would be susceptible to rot but so would H1.2 timber. As long as it stays dry there's no risk of decay."