Thumbs up for timber machine

David Dick of Rapaura Timber uses a new strength and stiffness grader to test a beam.
David Dick of Rapaura Timber uses a new strength and stiffness grader to test a beam.

A mill owner has been won over by new machinery that tests the load-bearing ability of timber used in building houses, which has proved to be less costly than he imagined.

Benefits of measuring timber stiffness and strength are outweighing costs, says Graham Sutton, who last month switched on a machine that tests for these qualities at his Rapaura Timber sawmill.

Since January, all load-bearing and structural timber used to build houses must meet New Zealand Building Code stiffness and strength standards.

Mr Sutton admits that for five years he resisted introducing machinery to objectively measure these qualities, because he was confident his staff had the skills to gauge timber quality by eye to the same standard.

However, in the month since his company installed a proof-tester machine he has been convinced it was money well spent.

The setup cost for the stress grader was about $35,000 plus an ongoing licence fee covering a three-monthly visit by an auditor and testing data analysis, Mr Sutton said.

The payback was customers' increased confidence in the quality of timber from the mill, he said.

The image of the industry suffered in a wave of bad publicity around the leaky building syndrome, despite that being a symptom of bad building rather than bad timber.

David Dick, who oversees quality verification at Rapaura Timber admits he had a few nervous moments, testing his skill at assessing timber quality by looking for knots and defects against a machine. However, results confirmed his eye assessments were right on the nail.

The force applied to timber during testing was well beyond what could be expected in a building, Mr Dick said. The 200x75mm beams, which were the specialty of Rapaura Timber, were tested up to 1080kg of pressure and the machine could apply up to 4.5 tonnes.

Auditor Paul Carpenter, of Grade Right in Rotorua, said that was well beyond the strength required as load was shared across timber used in house-framing.

"Every bit of timber doesn't have to be tested," Mr Carpenter said.

"Timber is visually graded then random samples are tested for stiffness and strength."

Mr Carpenter said the pressure came on for stiffness and strength testing when the average age for harvesting radiata pine moved from 40 to 60 years to less than 30 years. That was good for foresters' income but not always for timber quality, he said.

Grade Right also audited timber milled by Flight Timber in Blenheim and the Kaituna Sawmill, west of Renwick.

Rapaura Timber sells all its timber in the top of the South Island.

The Marlborough Express