Scientists challenge another wood coat

Scientists' concerns about a second wood preservative raise fresh worries about the way new products can enter the house-building market.

The preservative, marketed as Framecoat Blue and Framecoat Green, is being reviewed after scientists queried whether it met the New Zealand Standard for timber treatment.

Concerns include whether it underwent durability testing before launch and whether the inclusion of a vegetable oil lessens its active ingredient's effectiveness.

With a Government inquiry already underway into spray-on preservative TimberSaver, the latest issue underlines industry unease about the approval system for new preservatives, the reliability of "independent" testing and manufacturers' ability to change formulations.

The Framecoat products, like TimberSaver, entered the market last year after the reintroduction of treated framing timber following the leaky homes scandal.

Manufacturer Koppers Arch claimed the active ingredient in Framecoat Blue met the New Zealand standard for H1.2 graded timber, used for external framing which might get wet. Framecoat Green met requirements for H3.1 wood, exposed to the weather above ground.

Standards NZ marketing general manager Grant Thomas says the scientific concerns included a lack of evidence of durability testing and whether the addition of linseed oil could reduce the effectiveness of the active ingredient.

The Department of Building and Housing asked Koppers Arch in February to do more testing after the technical committee aired doubts.

Koppers Arch said the company stood by the enhancement but further testing was underway to satisfy the New Zealand authorities.

But the issue highlights potential loopholes in the appraisal of new building products, with Standards NZ, the Department of Building and Housing and Branz (the Building Research Association) all in the mix.

Mr Thomas said Standards NZ set standards but had no role in approving products."It's entirely up to manufacturers to claim compliance themselves or have independent certifiers audit their systems."

Preliminary results of the TimberSaver inquiry are expected next week.