New rot fears for 10,000 homeowners

Wood mycologist Robin Wakeling with two samples of timber. The one on the left is pink H1.2 timber, the one on the right is the new orange T1.2 timber. Picture / Martin Sykes

The home building industry is in fresh turmoil, with claims that framing timber in thousands of homes built in the past 15 months has not been effectively treated and could rot.

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 timber is coded "T1.2" and its distinctive orange coating is dubbed "Agent Orange" within the trade.

Last night it was claimed that the timber could have been used in as many as 10,000 homes and apartments.

However, the firm which makes the preservative says its product has been rigorously tested.

The Building Industry Authority approved the use of boron-sprayed timber in April last year, within six months of a law change reintroducing treatment to 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".

Scientist Robin Wakeling says the surface spray does not penetrate wood as well as traditional soaking and is liable to wash off if it gets wet. Dr Wakeling, a former Forest Research Institute scientist and now a consultant on leaky building issues, raised concerns before its introduction but says these were ignored by the BIA.

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 says it does not meet the H1.2 treatment standard, which requires complete penetration.

Mr Shuttleworth says there is confusion in the industry between the two similarly identified products.

"It appears builders, even though specifying the higher standard, are receiving timber for exterior framing that does not meet that standard."

A Herald call to an Auckland Placemakers yard confirmed that orange-coated timber was being sold as H1.2 grade framing.

"The bottom line here is that we have a product being either specified or supplied for situations where it is simply not fit for the purpose," Mr Shuttleworth said.

He called for a review of the new products appraisal certification and approval process used by the old BIA, now part of the Department of Building and Housing.
"The last time we had this situation [with untreated kiln dried timber] we ended up with a billion-dollar leaky building problem."

National MP Nick Smith said up to 10,000 homes and apartments may have been built with the T1.2 timber.

"The last thing homeowners need is another unproven, non-compliant timber product that puts their most important asset at risk."

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. Trials showed the preservative was no more leach-prone than conventional H1.2 boron-based treatments.

It was intended for situations where wood would not be continuously damp, including wall linings.

"If it was left wet for a long, 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."

Building Issues Minister Chris Carter said the Department of Building and Housing would investigate and act if the concerns were verified.

Placemakers general manager David Worley said timber merchants relied on the product supplier's advice. "We do not hold ourselves to be experts in the field of timber treatment."

Leaky homes whistleblower Greg O'Sullivan, a building surveyor, wrote to the department on Friday with concerns about the product. He said its sale as the equivalent of H1.2 was misrepresentation - "it's making a mockery of the standard".

Mr O'Sullivan said there were even moves to extend the use of the spray-on product to more hazardous H3 graded timber used outside above ground.

"It's the consumer who will pay," he said.

Different treatments

* These samples of construction pine, held by wood scientist Robin Wakeling (pictured above), are both used for building houses but are treated differently.

* The red H1.2 timber is treated by soaking. The colour shows how the preservative has penetrated through the wood.

* The orange T1.2 timber is treated with a spray-on boron preservative, saving time and money at timber mills.

* Building experts are concerned that the spray-on treatment does not protect wood to the same density as conventional treatment, is prone to leaching and will eventually lead to rot.

* The preservative manufacturer says the approval process involved rigorous testing and the wood is safe provided it is used in appropriate settings.